collectd.conf(5): Fix a POD error.

[collectd.git] / src / collectd.conf.pod

=head1 NAME

collectd.conf - Configuration for the system statistics collection daemon B<collectd>

=head1 SYNOPSIS

  BaseDir "/path/to/data/"
  PIDFile "/path/to/pidfile/collectd.pid"
  Server  "123.123.123.123" 12345

  LoadPlugin cpu
  LoadPlugin load
  LoadPlugin ping

  <Plugin ping>
    Host "example.org"
    Host "provider.net"
  </Plugin>

=head1 DESCRIPTION

This config file controls how the system statistics collection daemon
B<collectd> behaves. The most significant option is B<LoadPlugin>, which
controls which plugins to load. These plugins ultimately define collectd's
behavior.

The syntax of this config file is similar to the config file of the famous
B<Apache Webserver>. Each line contains either a key-value-pair or a
section-start or -end. Empty lines and everything after the hash-symbol `#' is
ignored. Values are either string, enclosed in double-quotes,
(floating-point-)numbers or a boolean expression, i.E<nbsp>e. either B<true> or
B<false>. String containing of only alphanumeric characters and underscores do
not need to be quoted. Lines may be wrapped by using `\' as the last character
before the newline. This allows long lines to be split into multiple lines.
Quoted strings may be wrapped as well. However, those are treated special in
that whitespace at the beginning of the following lines will be ignored, which
allows for nicely indenting the wrapped lines.

The configuration is read and processed in order, i.E<nbsp>e. from top to
bottom. So the plugins are loaded in the order listed in this config file. It
is a good idea to load any logging plugins first in order to catch messages
from plugins during configuration. Also, the C<LoadPlugin> option B<must> occur
B<before> the C<E<lt>Plugin ...E<gt>> block.

=head1 GLOBAL OPTIONS

=over 4

=item B<BaseDir> I<Directory>

Sets the base directory. This is the directory beneath all RRD-files are
created. Possibly more subdirectories are created. This is also the working
directory for the daemon.

=item B<LoadPlugin> I<Plugin>

Loads the plugin I<Plugin>. There must be at least one such line or B<collectd>
will be mostly useless.

=item B<Include> I<Path>

If I<Path> points to a file, includes that file. If I<Path> points to a
directory, recursively includes all files within that directory and its
subdirectories. If the C<wordexp> function is available on your system,
shell-like wildcards are expanded before files are included. This means you can
use statements like the following:

  Include "/etc/collectd.d/*.conf"

If more than one files are included by a single B<Include> option, the files
will be included in lexicographical order (as defined by the C<strcmp>
function). Thus, you can e.E<nbsp>g. use numbered prefixes to specify the
order in which the files are loaded.

To prevent loops and shooting yourself in the foot in interesting ways the
nesting is limited to a depth of 8E<nbsp>levels, which should be sufficient for
most uses. Since symlinks are followed it is still possible to crash the daemon
by looping symlinks. In our opinion significant stupidity should result in an
appropriate amount of pain.

It is no problem to have a block like C<E<lt>Plugin fooE<gt>> in more than one
file, but you cannot include files from within blocks.

=item B<PIDFile> I<File>

Sets where to write the PID file to. This file is overwritten when it exists
and deleted when the program is stopped. Some init-scripts might override this
setting using the B<-P> command-line option.

=item B<PluginDir> I<Directory>

Path to the plugins (shared objects) of collectd.

=item B<TypesDB> I<File> [I<File> ...]

Set one or more files that contain the data-set descriptions. See
L<types.db(5)> for a description of the format of this file.

=item B<Interval> I<Seconds>

Configures the interval in which to query the read plugins. Obviously smaller
values lead to a higher system load produced by collectd, while higher values
lead to more coarse statistics.

=item B<ReadThreads> I<Num>

Number of threads to start for reading plugins. The default value is B<5>, but
you may want to increase this if you have more than five plugins that take a
long time to read. Mostly those are plugin that do network-IO. Setting this to
a value higher than the number of plugins you've loaded is totally useless.

=item B<Hostname> I<Name>

Sets the hostname that identifies a host. If you omit this setting, the
hostname will be determinded using the L<gethostname(2)> system call.

=item B<FQDNLookup> B<true|false>

If B<Hostname> is determined automatically this setting controls whether or not
the daemon should try to figure out the "fully qualified domain name", FQDN.
This is done using a lookup of the name returned by C<gethostname>.

Using this feature (i.E<nbsp>e. setting this option to B<true>) is recommended.
However, to preserve backwards compatibility the default is set to B<false>.
The sample config file that is installed with C<makeE<nbsp>install> includes a
line which sets this option, though, so that default installations will have
this setting enabled.

=back

=head1 PLUGIN OPTIONS

Some plugins may register own options. These options must be enclosed in a
C<Plugin>-Section. Which options exist depends on the plugin used. Some plugins
require external configuration, too. The C<apache plugin>, for example,
required C<mod_status> to be configured in the webserver you're going to
collect data from. These plugins are listed below as well, even if they don't
require any configuration within collectd's configfile.

A list of all plugins and a short summary for each plugin can be found in the
F<README> file shipped with the sourcecode and hopefully binary packets as
well.

=head2 Plugin C<apache>

To configure the C<apache>-plugin you first need to configure the Apache
webserver correctly. The Apache-plugin C<mod_status> needs to be loaded and
working and the C<ExtendedStatus> directive needs to be B<enabled>. You can use
the following snipped to base your Apache config upon:

  ExtendedStatus on
  <IfModule mod_status.c>
    <Location /mod_status>
      SetHandler server-status
    </Location>
  </IfModule>

Since its C<mod_status> module is very similar to Apache's, B<lighttpd> is
also supported. It introduces a new field, called C<BusyServers>, to count the
number of currently connected clients. This field is also supported.

The following options are accepted by the C<apache>-plugin:

=over 4

=item B<URL> I<http://host/mod_status?auto>

Sets the URL of the C<mod_status> output. This needs to be the output generated
by C<ExtendedStatus on> and it needs to be the machine readable output
generated by appending the C<?auto> argument.

=item B<User> I<Username>

Optional user name needed for authentication.

=item B<Password> I<Password>

Optional password needed for authentication.

=item B<VerifyPeer> B<true|false>

Enable or disable peer SSL certificate verification. See
L<http://curl.haxx.se/docs/sslcerts.html> for details. Enabled by default.

=item B<VerifyHost> B<true|false>

Enable or disable peer host name verification. If enabled, the plugin checks
if the C<Common Name> or a C<Subject Alternate Name> field of the SSL
certificate matches the host name provided by the B<URL> option. If this
identity check fails, the connection is aborted. Obviously, only works when
connecting to a SSL enabled server. Enabled by default.

=item B<CACert> I<File>

File that holds one or more SSL certificates. If you want to use HTTPS you will
possibly need this option. What CA certificates come bundled with C<libcurl>
and are checked by default depends on the distribution you use.

=back

=head2 Plugin C<apcups>

=over 4

=item B<Host> I<Hostname>

Hostname of the host running B<apcupsd>. Defaults to B<localhost>. Please note
that IPv6 support has been disabled unless someone can confirm or decline that
B<apcupsd> can handle it.

=item B<Port> I<Port>

TCP-Port to connect to. Defaults to B<3551>.

=back

=head2 Plugin C<ascent>

This plugin collects information about an Ascent server, a free server for the
"World of Warcraft" game. This plugin gathers the information by fetching the
XML status page using C<libcurl> and parses it using C<libxml2>.

The configuration options are the same as for the C<apache> plugin above:

=over 4

=item B<URL> I<http://localhost/ascent/status/>

Sets the URL of the XML status output.

=item B<User> I<Username>

Optional user name needed for authentication.

=item B<Password> I<Password>

Optional password needed for authentication.

=item B<VerifyPeer> B<true|false>

Enable or disable peer SSL certificate verification. See
L<http://curl.haxx.se/docs/sslcerts.html> for details. Enabled by default.

=item B<VerifyHost> B<true|false>

Enable or disable peer host name verification. If enabled, the plugin checks
if the C<Common Name> or a C<Subject Alternate Name> field of the SSL
certificate matches the host name provided by the B<URL> option. If this
identity check fails, the connection is aborted. Obviously, only works when
connecting to a SSL enabled server. Enabled by default.

=item B<CACert> I<File>

File that holds one or more SSL certificates. If you want to use HTTPS you will
possibly need this option. What CA certificates come bundled with C<libcurl>
and are checked by default depends on the distribution you use.

=back

=head2 Plugin C<cpufreq>

This plugin doesn't have any options. It reads
F</sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq> (for the first CPU
installed) to get the current CPU frequency. If this file does not exist make
sure B<cpufreqd> (L<http://cpufreqd.sourceforge.net/>) or a similar tool is
installed and an "cpu governor" (that's a kernel module) is loaded.

=head2 Plugin C<csv>

=over 4

=item B<DataDir> I<Directory>

Set the directory to store CSV-files under. Per default CSV-files are generated
beneath the daemon's working directory, i.E<nbsp>e. the B<BaseDir>.

=item B<StoreRates> B<true|false>

If set to B<true>, convert counter values to rates. If set to B<false> (the
default) counter values are stored as is, i.E<nbsp>e. as an increasing integer
number.

=back

=head2 Plugin C<dbi>

This plugin uses the "B<dbi>" library (L<http://libdbi.sourceforge.net/>) to
connect to various databases, execute SQL statements and read back the results.
You can configure how each column is to be interpreted and the plugin will
generate one data set from each row returned according to these rules.

Because the plugin is very generic, the configuration is a little more complex
than those of other plugins. It usually looks something like this:

  <Plugin dbi>
    <Query "out_of_stock">
      Statement "SELECT category, COUNT(*) AS value FROM products WHERE in_stock = 0 GROUP BY category"
      Type "gauge"
      InstancesFrom "category"
      ValuesFrom "value"
    </Query>
    <Database "product_information">
      Driver "mysql"
      DriverOption "host" "localhost"
      DriverOption "username" "collectd"
      DriverOption "password" "aZo6daiw"
      DriverOption "dbname" "prod_info"
      SelectDB "prod_info"
      Query "out_of_stock"
    </Database>
  </Plugin>

The configuration above defines one query and one database. The query is then
linked to the database with the B<Query> option I<within> the
B<E<lt>DatabaseE<gt>> block. You can have any number of queries and databases
and you can also use the B<Include> statement to split up the configuration
file in multiple, smaller files. However, the B<E<lt>QueryE<gt>> block I<must>
precede the B<E<lt>DatabaseE<gt>> blocks, because the file is interpreted from
top to bottom!

The following is a complete list of options:

=head3 B<Query> blocks

Query blocks define SQL statements and how the returned data should be
interpreted. They are identified by the name that is given in the opening line
of the block. Thus the name needs to be unique. Other than that, the name is
not used in collectd.

=over 4

=item B<Statement> I<SQL>

Sets the statement that should be executed on the server. This is B<not>
interpreted by collectd, but simply passed to the database server. Therefore,
the SQL dialect that's used depends on the server collectd is connected to.

The query has to return at least two columns, one for the instance and one
value. You cannot omit the instance, even if the statement is guaranteed to
always return exactly one line. In that case, you can usually specify something
like this:

  Statement "SELECT \"instance\", COUNT(*) AS value FROM table"

(That works with MySQL but may not be valid SQL according to the spec. If you
use a more strict database server, you may have to select from a dummy table or
something.)

=item B<Type> I<Type>

The B<type> that's used for each line returned. See L<types.db(5)> for more
details on how types are defined. In short: A type is a predefined layout of
data and the number of values and type of values has to match the type
definition.

If you specify "temperature" here, you need exactly one gauge column. If you
specify "if_octets", you will need two counter columns. See the B<ValuesFrom>
setting below.

=item B<InstancesFrom> I<column0> [I<column1> ...]

Specifies the columns whose values will be used to create the "TypeInstance"
for each row. You need to specify at least one column for each query. If you
specify more than one column, the value of all columns will be join together
with the hyphen as separation character.

The plugin itself does not check whether or not all built instances are
different. It's your responsibility to assure that each is unique.

=item B<ValuesFrom> I<column0> [I<column1> ...]

Names the columns whose content is used as the actual data for the data sets
that are dispatched to the daemon. How many such columns you need is determined
by the B<Type> setting above. If you specify too many or not enough columns,
the plugin will complain about that and no data will be submitted to the
daemon.

The actual data type in the columns is not that important. The plugin will
automatically cast the values to the right type if it know how to do that. So
it should be able to handle integer an floating point types, as well as strings
(if they include a number at the beginning).

=back

=head3 B<Database> blocks

Database blocks define a connection to a database and which queries should be
sent to that database. Since the used "dbi" library can handle a wide variety
of databases, the configuration is very generic. If in doubt, refer to libdbi's
documentationE<nbsp>- we stick as close to the terminology used there.

Each database needs a "name" as string argument in the starting tag of the
block. This name will be used as "PluginInstance" in the values submitted to
the daemon. Other than that, that name is not used.

=over 4

=item B<Driver> I<Driver>

Specifies the driver to use to connect to the database. In many cases those
drivers are named after the database they can connect to, but this is not a
technical necessity. These drivers are sometimes referred to as "DBD",
B<D>ataB<B>ase B<D>river, and some distributions ship them in separate
packages. Drivers for the "dbi" library are developed by the B<libdbi-drivers>
project at L<http://libdbi-drivers.sourceforge.net/>.

You need to give the driver name as expected by the "dbi" library here. You
should be able to find that in the documentation for each driver. If you
mistype the driver name, the plugin will dump a list of all known driver names
to the log.

=item B<DriverOption> I<Key> I<Value>

Sets driver-specific options. What option a driver supports can be found in the
documentation for each driver, somewhere at
L<http://libdbi-drivers.sourceforge.net/>. However, the options "host",
"username", "password", and "dbname" seem to be deE<nbsp>facto standards.

Unfortunately, drivers are not too keen to report errors when an unknown option
is passed to them, so invalid settings here may go unnoticed. This is not the
plugin's fault, it will report errors if it gets them from the libraryE<nbsp>/
the driver. If a driver complains about an option, the plugin will dump a
complete list of all options understood by that driver to the log.

=item B<SelectDB> I<Database>

In some cases, the database name you connect with is not the database name you
want to use for querying data. If this option is set, the plugin will "select"
(switch to) that database after the connection is established.

=item B<Query> I<QueryName>

Associates the query named I<QueryName> with this database connection. The
query needs to be defined I<before> this statement, i.E<nbsp>e. all query
blocks you want to refer to must be placed above the database block you want to
refer to them from.

=back

=head2 Plugin C<df>

=over 4

=item B<Device> I<Device>

Select partitions based on the devicename.

=item B<MountPoint> I<Directory>

Select partitions based on the mountpoint.

=item B<FSType> I<FSType>

Select partitions based on the filesystem type.

=item B<IgnoreSelected> I<true>|I<false>

Invert the selection: If set to true, all partitions B<except> the ones that
match any one of the criteria are collected. By default only selected
partitions are collected if a selection is made. If no selection is configured
at all, B<all> partitions are selected.

=back

=head2 Plugin C<disk>

The C<disk> plugin collects information about the usage of physical disks and
logical disks (partitions). Values collected are the number of octets written
to and read from a disk or partition, the number of read/write operations
issued to the disk and a rather complex "time" it took for these commands to be
issued.

Using the following two options you can ignore some disks or configure the
collection only of specific disks.

=over 4

=item B<Disk> I<Name>

Select the disk I<Name>. Whether it is collected or ignored depends on the
B<IgnoreSelected> setting, see below. As with other plugins that use the
daemon's ignorelist functionality, a string that starts and ends with a slash
is interpreted as a regular expression. Examples:

  Disk "sdd"
  Disk "/hda[34]/"

=item B<IgnoreSelected> B<true>|B<false>

Sets whether selected disks, i.E<nbsp>e. the ones matches by any of the B<Disk>
statements, are ignored or if all other disks are ignored. The behavior
(hopefully) is intuitive: If no B<Disk> option is configured, all disks are
collected. If at least one B<Disk> option is given and no B<IgnoreSelected> or
set to B<false>, B<only> matching disks will be collected. If B<IgnoreSelected>
is set to B<true>, all disks are collected B<except> the ones matched.

=back

=head2 Plugin C<dns>

=over 4

=item B<Interface> I<Interface>

The dns plugin uses B<libpcap> to capture dns traffic and analyses it. This
option sets the interface that should be used. If this option is not set, or
set to "any", the plugin will try to get packets from B<all> interfaces. This
may not work on certain platforms, such as MacE<nbsp>OSE<nbsp>X.

=item B<IgnoreSource> I<IP-address>

Ignore packets that originate from this address.

=back

=head2 Plugin C<email>

=over 4

=item B<SocketFile> I<Path>

Sets the socket-file which is to be created.

=item B<SocketGroup> I<Group>

If running as root change the group of the UNIX-socket after it has been
created. Defaults to B<collectd>.

=item B<SocketPerms> I<Permissions>

Change the file permissions of the UNIX-socket after it has been created. The
permissions must be given as a numeric, octal value as you would pass to
L<chmod(1)>. Defaults to B<0770>.

=item B<MaxConns> I<Number>

Sets the maximum number of connections that can be handled in parallel. Since
this many threads will be started immediately setting this to a very high
value will waste valuable resources. Defaults to B<5> and will be forced to be
at most B<16384> to prevent typos and dumb mistakes.

=back

=head2 Plugin C<exec>

Please make sure to read L<collectd-exec(5)> before using this plugin. It
contains valuable information on when the executable is executed and the
output that is expected from it.

=over 4

=item B<Exec> I<User>[:[I<Group>]] I<Executable> [I<E<lt>argE<gt>> [I<E<lt>argE<gt>> ...]]

=item B<NotificationExec> I<User>[:[I<Group>]] I<Executable> [I<E<lt>argE<gt>> [I<E<lt>argE<gt>> ...]]

Execute the executable I<Executable> as user I<User>. If the user name is
followed by a colon and a group name, the effective group is set to that group.
The real group and saved-set group will be set to the default group of that
user. If no group is given the effective group ID will be the same as the real
group ID.

Please note that in order to change the user and/or group the daemon needs
superuser privileges. If the daemon is run as an unprivileged user you must
specify the same user/group here. If the daemon is run with superuser
privileges, you must supply a non-root user here.

The executable may be followed by optional arguments that are passed to the
program. Please note that due to the configuration parsing numbers and boolean
values may be changed. If you want to be absolutely sure that something is
passed as-is please enclose it in quotes.

The B<Exec> and B<NotificationExec> statements change the semantics of the
programs executed, i.E<nbsp>e. the data passed to them and the response
expected from them. This is documented in great detail in L<collectd-exec(5)>.

=back

=head2 Plugin C<filecount>

The C<filecount> plugin counts the number of files in a certain directory (and
its subdirectories) and their combined size. The configuration is very straight
forward:

  <Plugin "filecount">
    <Directory "/var/qmail/queue/mess">
      Instance "qmail-message"
    </Directory>
    <Directory "/var/qmail/queue/todo">
      Instance "qmail-todo"
    </Directory>
    <Directory "/var/lib/php5">
      Instance "php5-sessions"
      Name "sess_*"
    </Directory>
  </Plugin>

The example above counts the number of files in QMail's queue directories and
the number of PHP5 sessions. Jfiy: The "todo" queue holds the messages that
QMail has not yet looked at, the "message" queue holds the messages that were
classified into "local" and "remote".

As you can see, the configuration consists of one or more C<Directory> blocks,
each of which specifies a directory in which to count the files. Within those
blocks, the following options are recognized:

=over 4

=item B<Instance> I<Instance>

Sets the plugin instance to I<Instance>. That instance name must be unique, but
it's your responsibility, the plugin doesn't check for that. If not given, the
instance is set to the directory name with all slashes replaced by underscores
and all leading underscores removed.

=item B<Name> I<Pattern>

Only count files that match I<Pattern>, where I<Pattern> is a shell-like
wildcard as understood by L<fnmatch(3)>. Only the B<filename> is checked
against the pattern, not the entire path. In case this makes it easier for you:
This option has been named after the B<-name> parameter to L<find(1)>.

=item B<MTime> I<Age>

Count only files of a specific age: If I<Age> is greater than zero, only files
that haven't been touched in the last I<Age> seconds are counted. If I<Age> is
a negative number, this is inversed. For example, if B<-60> is specified, only
files that have been modified in the last minute will be counted.

The number can also be followed by a "multiplier" to easily specify a larger
timespan. When given in this notation, the argument must in quoted, i.E<nbsp>e.
must be passed as string. So the B<-60> could also be written as B<"-1m"> (one
minute). Valid multipliers are C<s> (second), C<m> (minute), C<h> (hour), C<d>
(day), C<w> (week), and C<y> (year). There is no "month" multiplier. You can
also specify fractional numbers, e.E<nbsp>g. B<"0.5d"> is identical to
B<"12h">.

=item B<Size> I<Size>

Count only files of a specific size. When I<Size> is a positive number, only
files that are at least this big are counted. If I<Size> is a negative number,
this is inversed, i.E<nbsp>e. only files smaller than the absolute value of
I<Size> are counted.

As with the B<MTime> option, a "multiplier" may be added. For a detailed
description see above. Valid multipliers here are C<b> (byte), C<k> (kilobyte),
C<m> (megabyte), C<g> (gigabyte), C<t> (terabyte), and C<p> (petabyte). Please
note that there are 1000 bytes in a kilobyte, not 1024.

=item B<Recursive> I<true>|I<false>

Controls whether or not to recurse into subdirectories. Enabled by default.

=back

=head2 Plugin C<filter_pcre>

This plugin allows you to filter and rewrite value lists based on
Perl-compatible regular expressions whose syntax and semantics are as close as
possible to those of the Perl 5 language. See L<pcre(3)> for details.

  <Plugin filter_pcre>
    <RegEx>
      Host "^mail\d+$"
      Plugin "^tcpconns$"
      TypeInstance "^SYN_"

      Action NoWrite
    </RegEx>

    <RegEx>
      Plugin "^sensors$"
      PluginInstance "^Some Weird Sensor Chip Name Prefix"

      SubstitutePluginInstance "foo"
    </RegEx>
  </Plugin>

The configuration consists of one or more C<RegEx> blocks, each of which
specifies a regular expression identifying a set of value lists and how to
handle successful matches. A value list keeps the values of a single data-set
and is identified by the tuple (host, plugin, plugin instance, type, type
instance). The plugin and type instances are optional components. If they are
missing they are treated as empty strings. Within those blocks, the following
options are recognized:

=over 4

=item B<Host> I<regex>

=item B<Plugin> I<regex>

=item B<PluginInstance> I<regex>

=item B<Type> I<regex>

=item B<TypeInstance> I<regex>

Specifies the regular expression for each component of the identifier. If any
of these options is missing it is interpreted as a pattern which matches any
string. All five components of a value list have to match the appropriate
regular expression to trigger the specified action.

=item B<Action> I<NoWrite>|I<NoThresholdCheck>|I<Ignore>

Specify how to handle successful matches:

=over 4

=item B<NoWrite>

Do not send the value list to any output (a.k.a. write) plugins.

=item B<NoThresholdCheck>

Skip threshold checking for this value list.

=item B<Ignore>

Completely ignore this value list.

=back

Two or more actions may be combined by specifying multiple B<Action> options.

=item B<SubstituteHost> I<replacement>

=item B<SubstitutePlugin> I<replacement>

=item B<SubstitutePluginInstance> I<replacement>

=item B<SubstituteType> I<replacement>

=item B<SubstituteTypeInstance> I<replacement>

Upon a successful match, the matching substring will be replaced by the
specified I<replacement> text. These options require that an appropriate regex
has been specified before, e.E<nbsp>g. B<SubstituteHost> requires that the
B<Host> option has been specified before.

B<Note>: It is not recommended to modify the type unless you really know what
you are doing. The type is used to identify the data-set definition of the
dispatched values.

=back

=head2 Plugin C<hddtemp>

To get values from B<hddtemp> collectd connects to B<localhost> (127.0.0.1),
port B<7634/tcp>. The B<Host> and B<Port> options can be used to change these
default values, see below. C<hddtemp> has to be running to work correctly. If
C<hddtemp> is not running timeouts may appear which may interfere with other
statistics..

The B<hddtemp> homepage can be found at
L<http://www.guzu.net/linux/hddtemp.php>.

=over 4

=item B<Host> I<Hostname>

Hostname to connect to. Defaults to B<127.0.0.1>.

=item B<Port> I<Port>

TCP-Port to connect to. Defaults to B<7634>.

=item B<TranslateDevicename> I<true>|I<false>

If enabled, translate the disk names to major/minor device numbers
(e.E<nbsp>g. "8-0" for /dev/sda). For backwards compatibility this defaults to
I<true> but it's recommended to disable it as it will probably be removed in
the next major version.

=back

=head2 Plugin C<interface>

=over 4

=item B<Interface> I<Interface>

Select this interface. By default these interfaces will then be collected. For
a more detailed description see B<IgnoreSelected> below.

=item B<IgnoreSelected> I<true>|I<false>

If no configuration if given, the B<traffic>-plugin will collect data from
all interfaces. This may not be practical, especially for loopback- and
similar interfaces. Thus, you can use the B<Interface>-option to pick the
interfaces you're interested in. Sometimes, however, it's easier/preferred
to collect all interfaces I<except> a few ones. This option enables you to
do that: By setting B<IgnoreSelected> to I<true> the effect of
B<Interface> is inverted: All selected interfaces are ignored and all
other interfaces are collected.

=back

=head2 Plugin C<ipmi>

=over 4

=item B<Sensor> I<Sensor>

Selects sensors to collect or to ignore, depending on B<IgnoreSelected>.

=item B<IgnoreSelected> I<true>|I<false>

If no configuration if given, the B<ipmi> plugin will collect data from all
sensors found of type "temperature", "voltage", "current" and "fanspeed".
This option enables you to do that: By setting B<IgnoreSelected> to I<true>
the effect of B<Sensor> is inverted: All selected sensors are ignored and
all other sensors are collected.

=item B<NotifySensorAdd> I<true>|I<false>

If a sensor appears after initialization time of a minute a notification
is sent.

=item B<NotifySensorRemove> I<true>|I<false>

If a sensor disappears a notification is sent.

=item B<NotifySensorNotPresent> I<true>|I<false>

If you have for example dual power supply and one of them is (un)plugged then
a notification is sent.

=back

=head2 Plugin C<iptables>

=over 4

=item B<Chain> I<Table> I<Chain> [I<Comment|Number> [I<Name>]]

Select the rules to count. If only I<Table> and I<Chain> are given, this plugin
will collect the counters of all rules which have a comment-match. The comment
is then used as type-instance.

If I<Comment> or I<Number> is given, only the rule with the matching comment or
the I<n>th rule will be collected. Again, the comment (or the number) will be
used as the type-instance.

If I<Name> is supplied, it will be used as the type-instance instead of the
comment or the number.

=back

=head2 Plugin C<irq>

=over 4

=item B<Irq> I<Irq>

Select this irq. By default these irqs will then be collected. For a more
detailed description see B<IgnoreSelected> below.

=item B<IgnoreSelected> I<true>|I<false>

If no configuration if given, the B<irq>-plugin will collect data from all
irqs. This may not be practical, especially if no interrupts happen. Thus, you
can use the B<Irq>-option to pick the interrupt you're interested in.
Sometimes, however, it's easier/preferred to collect all interrupts I<except> a
few ones. This option enables you to do that: By setting B<IgnoreSelected> to
I<true> the effect of B<Irq> is inverted: All selected interrupts are ignored
and all other interrupts are collected.

=back

=head2 Plugin C<libvirt>

This plugin allows CPU, disk and network load to be collected for virtualized
guests on the machine. This means that these characteristics can be collected
for guest systems without installing any software on them - collectd only runs
on the hosting system. The statistics are collected through libvirt
(L<http://libvirt.org/>).

Only I<Connection> is required.

=over 4

=item B<Connection> I<uri>

Connect to the hypervisor given by I<uri>. For example if using Xen use:

 Connection "xen:///"

Details which URIs allowed are given at L<http://libvirt.org/uri.html>.

=item B<RefreshInterval> I<seconds>

Refresh the list of domains and devices every I<seconds>. The default is 60
seconds. Setting this to be the same or smaller than the I<Interval> will cause
the list of domains and devices to be refreshed on every iteration.

Refreshing the devices in particular is quite a costly operation, so if your
virtualization setup is static you might consider increasing this. If this
option is set to 0, refreshing is disabled completely.

=item B<Domain> I<name>

=item B<BlockDevice> I<name:dev>

=item B<InterfaceDevice> I<name:dev>

=item B<IgnoreSelected> I<true>|I<false>

Select which domains and devices are collected.

If I<IgnoreSelected> is not given or I<false> then only the listed domains and
disk/network devices are collected.

If I<IgnoreSelected> is I<true> then the test is reversed and the listed
domains and disk/network devices are ignored, while the rest are collected.

The domain name and device names may use a regular expression, if the name is
surrounded by I</.../> and collectd was compiled with support for regexps.

The default is to collect statistics for all domains and all their devices.

Example:

 BlockDevice "/:hdb/"
 IgnoreSelected "true"

Ignore all I<hdb> devices on any domain, but other block devices (eg. I<hda>)
will be collected.

=item B<HostnameFormat> B<name|uuid|hostname|...>

When the libvirt plugin logs data, it sets the hostname of the collected data
according to this setting. The default is to use the guest name as provided by
the hypervisor, which is equal to setting B<name>.

B<uuid> means use the guest's UUID. This is useful if you want to track the
same guest across migrations.

B<hostname> means to use the global B<Hostname> setting, which is probably not
useful on its own because all guests will appear to have the same name.

You can also specify combinations of these fields. For example B<name uuid>
means to concatenate the guest name and UUID (with a literal colon character
between, thus I<"foo:1234-1234-1234-1234">).

=back

=head2 Plugin C<logfile>

=over 4

=item B<LogLevel> B<debug|info|notice|warning|err>

Sets the log-level. If, for example, set to B<notice>, then all events with
severity B<notice>, B<warning>, or B<err> will be written to the logfile.

Please note that B<debug> is only available if collectd has been compiled with
debugging support.

=item B<File> I<File>

Sets the file to write log messages to. The special strings B<stdout> and
B<stderr> can be used to write to the standard output and standard error
channels, respectively. This, of course, only makes much sense when collectd is
running in foreground- or non-daemon-mode.

=item B<Timestamp> B<true>|B<false>

Prefix all lines printed by the current time. Defaults to B<true>.

=back

=head2 Plugin C<mbmon>

The C<mbmon plugin> uses mbmon to retrieve temperature, voltage, etc.

Be default collectd connects to B<localhost> (127.0.0.1), port B<411/tcp>. The
B<Host> and B<Port> options can be used to change these values, see below.
C<mbmon> has to be running to work correctly. If C<mbmon> is not running
timeouts may appear which may interfere with other statistics..

C<mbmon> must be run with the -r option ("print TAG and Value format");
Debian's F</etc/init.d/mbmon> script already does this, other people
will need to ensure that this is the case.

=over 4

=item B<Host> I<Hostname>

Hostname to connect to. Defaults to B<127.0.0.1>.

=item B<Port> I<Port>

TCP-Port to connect to. Defaults to B<411>.

=back

=head2 Plugin C<memcached>

The C<memcached plugin> connects to a memcached server and queries statistics
about cache utilization, memory and bandwidth used.
L<http://www.danga.com/memcached/>

=over 4

=item B<Host> I<Hostname>

Hostname to connect to. Defaults to B<127.0.0.1>.

=item B<Port> I<Port>

TCP-Port to connect to. Defaults to B<11211>.

=back

=head2 Plugin C<mysql>

The C<mysql plugin> requires B<mysqlclient> to be installed. It connects to the
database when started and keeps the connection up as long as possible. When the
connection is interrupted for whatever reason it will try to re-connect. The
plugin will complaint loudly in case anything goes wrong.

This plugin issues C<SHOW STATUS> and evaluates C<Bytes_{received,sent}>,
C<Com_*> and C<Handler_*> which correspond to F<mysql_octets.rrd>,
F<mysql_commands-*.rrd> and F<mysql_handler-*.rrd>. Also, the values of
C<Qcache_*> are put in F<mysql_qcache.rrd> and values of C<Threads_*> are put
in F<mysql_threads.rrd>. Please refer to the B<MySQL reference manual>,
I<5.2.4. Server Status Variables> for an explanation of these values.

Use the following options to configure the plugin:

=over 4

=item B<Host> I<Hostname>

Hostname of the database server. Defaults to B<localhost>.

=item B<User> I<Username>

Username to use when connecting to the database.

=item B<Password> I<Password>

Password needed to log into the database.

=item B<Database> I<Database>

Select this database. Defaults to I<no database> which is a perfectly reasonable
option for what this plugin does.

=item B<Port> I<Port>

TCP-port to connect to. The port must be specified in its numeric form, but it
must be passed as a string nonetheless. For example:

  Port "3306"

If B<Host> is set to B<localhost> (the default), this setting has no effect.
See the documentation for the C<mysql_real_connect> function for details.

=item B<Socket> I<Socket>

Specifies the path to the UNIX domain socket of the MySQL server. This option
only has any effect, if B<Host> is set to B<localhost> (the default).
Otherwise, use the B<Port> option above. See the documentation for the
C<mysql_real_connect> function for details.

=back

=head2 Plugin C<netlink>

The C<netlink> plugin uses a netlink socket to query the Linux kernel about
statistics of various interface and routing aspects.

=over 4

=item B<Interface> I<Interface>

=item B<VerboseInterface> I<Interface>

Instruct the plugin to collect interface statistics. This is basically the same
as the statistics provided by the C<interface> plugin (see above) but
potentially much more detailed.

When configuring with B<Interface> only the basic statistics will be collected,
namely octets, packets, and errors. These statistics are collected by
the C<interface> plugin, too, so using both at the same time is no benefit.

When configured with B<VerboseInterface> all counters B<except> the basic ones,
so that no data needs to be collected twice if you use the C<interface> plugin.
This includes dropped packets, received multicast packets, collisions and a
whole zoo of differentiated RX and TX errors. You can try the following command
to get an idea of what awaits you:

  ip -s -s link list

If I<Interface> is B<All>, all interfaces will be selected.

=item B<QDisc> I<Interface> [I<QDisc>]

=item B<Class> I<Interface> [I<Class>]

=item B<Filter> I<Interface> [I<Filter>]

Collect the octets and packets that pass a certain qdisc, class or filter.

QDiscs and classes are identified by their type and handle (or classid).
Filters don't necessarily have a handle, therefore the parent's handle is used.
The notation used in collectd differs from that used in tc(1) in that it
doesn't skip the major or minor number if it's zero and doesn't print special
ids by their name. So, for example, a qdisc may be identified by
C<pfifo_fast-1:0> even though the minor number of B<all> qdiscs is zero and
thus not displayed by tc(1).

If B<QDisc>, B<Class>, or B<Filter> is given without the second argument,
i.E<nbsp>.e. without an identifier, all qdiscs, classes, or filters that are
associated with that interface will be collected.

Since a filter itself doesn't necessarily have a handle, the parent's handle is
used. This may lead to problems when more than one filter is attached to a
qdisc or class. This isn't nice, but we don't know how this could be done any
better. If you have a idea, please don't hesitate to tell us.

As with the B<Interface> option you can specify B<All> as the interface,
meaning all interfaces.

Here are some examples to help you understand the above text more easily:

  <Plugin netlink>
    VerboseInterface "All"
    QDisc "eth0" "pfifo_fast-1:0"
    QDisc "ppp0"
    Class "ppp0" "htb-1:10"
    Filter "ppp0" "u32-1:0"
  </Plugin>

=item B<IgnoreSelected>

The behaviour is the same as with all other similar plugins: If nothing is
selected at all, everything is collected. If some things are selected using the
options described above, only these statistics are collected. If you set
B<IgnoreSelected> to B<true>, this behavior is inverted, i.E<nbsp>e. the
specified statistics will not be collected.

=back

=head2 Plugin C<network>

=over 4

=item B<Listen> I<Host> [I<Port>]

=item B<Server> I<Host> [I<Port>]

The B<Server> statement sets the server to send datagrams B<to>.  The statement
may occur multiple times to send each datagram to multiple destinations.

The B<Listen> statement sets the interfaces to bind to. When multiple
statements are found the daemon will bind to multiple interfaces.

The argument I<Host> may be a hostname, an IPv4 address or an IPv6 address. If
the argument is a multicast address the daemon will join that multicast group.

If no B<Listen> statement is found the server tries join both, the default IPv6
multicast group and the default IPv4 multicast group. If no B<Server> statement
is found the client will try to send data to the IPv6 multicast group first. If
that fails the client will try the IPv4 multicast group.

The default IPv6 multicast group is C<ff18::efc0:4a42>. The default IPv4
multicast group is C<239.192.74.66>.

The optional I<Port> argument sets the port to use. It can either be given
using a numeric port number or a service name. If the argument is omitted the
default port B<25826> is assumed.

=item B<TimeToLive> I<1-255>

Set the time-to-live of sent packets. This applies to all, unicast and
multicast, and IPv4 and IPv6 packets. The default is to not change this value.
That means that multicast packets will be sent with a TTL of C<1> (one) on most
operating systems.

=item B<Forward> I<true|false>

If set to I<true>, write packets that were received via the network plugin to
the sending sockets. This should only be activated when the B<Listen>- and
B<Server>-statements differ. Otherwise packets may be send multiple times to
the same multicast group. While this results in more network traffic than
necessary it's not a huge problem since the plugin has a duplicate detection,
so the values will not loop.

=item B<CacheFlush> I<Seconds>

For each host/plugin/type combination the C<network plugin> caches the time of
the last value being sent or received. Every I<Seconds> seconds the plugin
searches and removes all entries that are older than I<Seconds> seconds, thus
freeing the unused memory again. Since this process is somewhat expensive and
normally doesn't do much, this value should not be too small. The default is
1800 seconds, but setting this to 86400 seconds (one day) will not do much harm
either.

=back

=head2 Plugin C<nginx>

This plugin collects the number of connections and requests handled by the
C<nginx daemon> (speak: engineE<nbsp>X), a HTTP and mail server/proxy. It
queries the page provided by the C<ngx_http_stub_status_module> module, which
isn't compiled by default. Please refer to
L<http://wiki.codemongers.com/NginxStubStatusModule> for more information on
how to compile and configure nginx and this module.

The following options are accepted by the C<nginx plugin>:

=over 4

=item B<URL> I<http://host/nginx_status>

Sets the URL of the C<ngx_http_stub_status_module> output.

=item B<User> I<Username>

Optional user name needed for authentication.

=item B<Password> I<Password>

Optional password needed for authentication.

=item B<VerifyPeer> B<true|false>

Enable or disable peer SSL certificate verification. See
L<http://curl.haxx.se/docs/sslcerts.html> for details. Enabled by default.

=item B<VerifyHost> B<true|false>

Enable or disable peer host name verification. If enabled, the plugin checks
if the C<Common Name> or a C<Subject Alternate Name> field of the SSL
certificate matches the host name provided by the B<URL> option. If this
identity check fails, the connection is aborted. Obviously, only works when
connecting to a SSL enabled server. Enabled by default.

=item B<CACert> I<File>

File that holds one or more SSL certificates. If you want to use HTTPS you will
possibly need this option. What CA certificates come bundled with C<libcurl>
and are checked by default depends on the distribution you use.

=back

=head2 Plugin C<notify_desktop>

This plugin sends a desktop notification to a notification daemon, as defined
in the Desktop Notification Specification. To actually display the
notifications, B<notification-daemon> is required and B<collectd> has to be
able to access the X server.

The Desktop Notification Specification can be found at
L<http://www.galago-project.org/specs/notification/>.

=over 4

=item B<OkayTimeout> I<timeout>

=item B<WarningTimeout> I<timeout>

=item B<FailureTimeout> I<timeout>

Set the I<timeout>, in milliseconds, after which to expire the notification
for C<OKAY>, C<WARNING> and C<FAILURE> severities respectively. If zero has
been specified, the displayed notification will not be closed at all - the
user has to do so herself. These options default to 5000. If a negative number
has been specified, the default is used as well.

=back

=head2 Plugin C<ntpd>

=over 4

=item B<Host> I<Hostname>

Hostname of the host running B<ntpd>. Defaults to B<localhost>.

=item B<Port> I<Port>

UDP-Port to connect to. Defaults to B<123>.

=item B<ReverseLookups> B<true>|B<false>

Sets wether or not to perform reverse lookups on peers. Since the name or
IP-address may be used in a filename it is recommended to disable reverse
lookups. The default is to do reverse lookups to preserve backwards
compatibility, though.

=back

=head2 Plugin C<nut>

=over 4

=item B<UPS> I<upsname>B<@>I<hostname>[B<:>I<port>]

Add a UPS to collect data from. The format is identical to the one accepted by
L<upsc(8)>.

=back

=head2 Plugin C<onewire>

B<EXPERIMENTAL!> See notes below.

The C<onewire> plugin uses the B<owcapi> library from the B<owfs> project
L<http://owfs.org/> to read sensors connected via the onewire bus.

Currently only temperature sensors (sensors with the family code C<10>,
e.E<nbsp>g. DS1820, DS18S20, DS1920) can be read. If you have other sensors you
would like to have included, please send a sort request to the mailing list.

Hubs (the DS2409 chips) are working, but read the note, why this plugin is
experimental, below.

=over 4

=item B<Device> I<Device>

Sets the device to read the values from. This can either be a "real" hardware
device, such as a serial port or an USB port, or the address of the
L<owserver(1)> socket, usually B<localhost:4304>.

Though the documentation claims to automatically recognize the given address
format, with versionE<nbsp>2.7p4 we had to specify the type explicitly. So
with that version, the following configuration worked for us:

  <Plugin onewire>
    Device "-s localhost:4304"
  </Plugin>

This directive is B<required> and does not have a default value.

=item B<Sensor> I<Sensor>

Selects sensors to collect or to ignore, depending on B<IgnoreSelected>, see
below. Sensors are specified without the family byte at the beginning, to you'd
use C<F10FCA000800>, and B<not> include the leading C<10.> family byte and
point.

=item B<IgnoreSelected> I<true>|I<false>

If no configuration if given, the B<onewire> plugin will collect data from all
sensors found. This may not be practical, especially if sensors are added and
removed regularly. Sometimes, however, it's easier/preferred to collect only
specific sensors or all sensors I<except> a few specified ones. This option
enables you to do that: By setting B<IgnoreSelected> to I<true> the effect of
B<Sensor> is inverted: All selected interfaces are ignored and all other
interfaces are collected.

=back

B<EXPERIMENTAL!> The C<onewire> plugin is experimental, because it doesn't yet
work with big setups. It works with one sensor being attached to one
controller, but as soon as you throw in a couple more senors and maybe a hub
or two, reading all values will take more than ten seconds (the default
interval). We will probably add some separate thread for reading the sensors
and some cache or something like that, but it's not done yet. We will try to
maintain backwards compatibility in the future, but we can't probmise. So in
short: If it works for you: Great! But kaap in mind that the config I<might>
change, though this is unlikely. Oh, and if you want to help improving this
plugin, just send a short notice to the mailing list. ThanksE<nbsp>:)

=head2 Plugin C<oracle>

The "oracle" plugin uses the Oracle® Call Interface (OCI) to connect to an
Oracle® Database and lets you execute SQL statements there. It is very similar
to the "dbi" plugin, because it was written around the same time. See the "dbi"
plugin's documentation above for details.

  <Plugin oracle>
    <Query "out_of_stock">
      Statement "SELECT category, COUNT(*) AS value FROM products WHERE in_stock = 0 GROUP BY category"
      Type "gauge"
      InstancesFrom "category"
      ValuesFrom "value"
    </Query>
    <Database "product_information">
      ConnectID "db01"
      Username "oracle"
      Password "secret"
      Query "out_of_stock"
    </Database>
  </Plugin>

=head3 B<Query> blocks

The Query blocks are handled identically to the Query blocks of the "dbi"
plugin. Please see its documentation above for details on how to specify
queries.

=head3 B<Database> blocks

Database blocks define a connection to a database and which queries should be
sent to that database. Each database needs a "name" as string argument in the
starting tag of the block. This name will be used as "PluginInstance" in the
values submitted to the daemon. Other than that, that name is not used.

=over 4

=item B<ConnectID> I<ID>

Defines the "database alias" or "service name" to connect to. Usually, these
names are defined in the file named C<$ORACLE_HOME/network/admin/tnsnames.ora>.

=item B<Username> I<Username>

Username used for authentication.

=item B<Password> I<Password>

Password used for authentication.

=item B<Query> I<QueryName>

Associates the query named I<QueryName> with this database connection. The
query needs to be defined I<before> this statement, i.E<nbsp>e. all query
blocks you want to refer to must be placed above the database block you want to
refer to them from.

=back

=head2 Plugin C<perl>

This plugin embeds a Perl-interpreter into collectd and provides an interface
to collectd's plugin system. See L<collectd-perl(5)> for its documentation.

=head2 Plugin C<ping>

=over 4

=item B<Host> I<IP-address>

Host to ping periodically. This option may be repeated several times to ping
multiple hosts.

=item B<TTL> I<0-255>

Sets the Time-To-Live of generated ICMP packets.

=back

=head2 Plugin C<postgresql>

The C<postgresql> plugin queries statistics from PostgreSQL databases. It
keeps a persistent connection to all configured databases and tries to
reconnect if the connection has been interrupted. A database is configured by
specifying a B<Database> block as described below. The default statistics are
collected from PostgreSQL's B<statistics collector> which thus has to be
enabled for this plugin to work correctly. This should usually be the case by
default. See the section "The Statistics Collector" of the B<PostgreSQL
Documentation> for details.

By specifying custom database queries using a B<Query> block as described
below, you may collect any data that is available from some PostgreSQL
database. This way, you are able to access statistics of external daemons
which are available in a PostgreSQL database or use future or special
statistics provided by PostgreSQL without the need to upgrade your collectd
installation.

The B<PostgreSQL Documentation> manual can be found at
L<http://www.postgresql.org/docs/manuals/>.

  <Plugin postgresql>
    <Query magic>
      Query "SELECT magic, spells FROM wizard WHERE host = $1;"
      Param hostname
      Column gauge magic
      Column counter spells
    </Query>

    <Database foo>
      Host "hostname"
      Port "5432"
      User "username"
      Password "secret"
      SSLMode "prefer"
      KRBSrvName "kerberos_service_name"
      Query magic
    </Database>
    <Database bar>
      Service "service_name"
    </Database>
  </Plugin>

The B<Query> block defines one database query which may later be used by a
database definition. It accepts a single mandatory argument which specifies
the name of the query. The names of all queries have to be unique. The
following configuration options are available to define the query:

=over 4

=item B<Query> I<sql query>

Specify the I<sql query> which the plugin should execute. The string may
contain the tokens B<$1>, B<$2>, etc. which are used to reference the first,
second, etc. parameter. The value of the parameters is specified by the
B<Param> configuration option - see below for details. To include a literal
B<$> character followed by a number, surround it with single quotes (B<'>).

Any SQL command which may return data (such as C<SELECT> or C<SHOW>) is
allowed. Note, however, that only a single command may be used. Semicolons are
allowed as long as a single non-empty command has been specified only.

=item B<Param> I<hostname>|I<database>|I<username>

Specify the parameters which should be passed to the SQL query. The parameters
are referred to in the SQL query as B<$1>, B<$2>, etc. in the same order as
they appear in the configuration file. The value of the parameter is
determined depending on the value of the B<Param> option as follows:

=over 4

=item I<hostname>

The configured hostname of the database connection. If a UNIX domain socket is
used, the parameter expands to "localhost".

=item I<database>

The name of the database of the current connection.

=item I<username>

The username used to connect to the database.

=back

Please note that parameters are only supported by PostgreSQL's protocol
version 3 and above which was introduced in version 7.4 of PostgreSQL.

=item B<Column> I<type> [I<type instance>]

Specify the I<type> and optional I<type instance> used to dispatch the value
of each result column. Detailed information about types and their
configuration can be found in L<types.db(5)>. The number and order of the
B<Column> options has to match the columns of the query result.

=item B<MinPGVersion> I<version>

=item B<MaxPGVersion> I<version>

Specify the minimum or maximum version of PostgreSQL that this query should be
used with. Some statistics might only be available with certain versions of
PostgreSQL. This allows you to specify multiple queries with the same name but
which apply to different versions, thus allowing you to use the same
configuration in a heterogeneous environment.

The I<version> has to be specified as the concatenation of the major, minor
and patch-level versions, each represented as two-decimal-digit numbers. For
example, version 8.2.3 will become 80203.

=back

The following predefined queries are available (the definitions can be found
in the F<postgresql_default.conf> file which, by default, is available at
C<I<prefix>/share/collectd/>):

=over 4

=item B<backends>

This query collects the number of backends, i.E<nbsp>e. the number of
connected clients.

=item B<transactions>

This query collects the numbers of committed and rolled-back transactions of
the user tables.

=item B<queries>

This query collects the numbers of various table modifications (i.E<nbsp>e.
insertions, updates, deletions) of the user tables.

=item B<query_plans>

This query collects the numbers of various table scans and returned tuples of
the user tables.

=item B<table_states>

This query collects the numbers of live and dead rows in the user tables.

=item B<disk_io>

This query collects disk block access counts for user tables.

=item B<disk_usage>

This query collects the on-disk size of the database in bytes.

=back

The B<Database> block defines one PostgreSQL database for which to collect
statistics. It accepts a single mandatory argument which specifies the
database name. None of the other options are required. PostgreSQL will use
default values as documented in the section "CONNECTING TO A DATABASE" in the
L<psql(1)> manpage. However, be aware that those defaults may be influenced by
the user collectd is run as and special environment variables. See the manpage
for details.

=over 4

=item B<Host> I<hostname>

Specify the hostname or IP of the PostgreSQL server to connect to. If the
value begins with a slash, it is interpreted as the directory name in which to
look for the UNIX domain socket.

This option is also used to determine the hostname that is associated with a
collected data set. If it has been omitted or either begins with with a slash
or equals B<localhost> it will be replaced with the global hostname definition
of collectd. Any other value will be passed literally to collectd when
dispatching values. Also see the global B<Hostname> and B<FQDNLookup> options.

=item B<Port> I<port>

Specify the TCP port or the local UNIX domain socket file extension of the
server.

=item B<User> I<username>

Specify the username to be used when connecting to the server.

=item B<Password> I<password>

Specify the password to be used when connecting to the server.

=item B<SSLMode> I<disable>|I<allow>|I<prefer>|I<require>

Specify whether to use an SSL connection when contacting the server. The
following modes are supported:

=over 4

=item I<disable>

Do not use SSL at all.

=item I<allow>

First, try to connect without using SSL. If that fails, try using SSL.

=item I<prefer> (default)

First, try to connect using SSL. If that fails, try without using SSL.

=item I<require>

Use SSL only.

=back

=item B<KRBSrvName> I<kerberos_service_name>

Specify the Kerberos service name to use when authenticating with Kerberos 5
or GSSAPI. See the sections "Kerberos authentication" and "GSSAPI" of the
B<PostgreSQL Documentation> for details.

=item B<Service> I<service_name>

Specify the PostgreSQL service name to use for additional parameters. That
service has to be defined in F<pg_service.conf> and holds additional
connection parameters. See the section "The Connection Service File" in the
B<PostgreSQL Documentation> for details.

=item B<Query> I<query>

Specify a I<query> which should be executed for the database connection. This
may be any of the predefined or user-defined queries. If no such option is
given, it defaults to "backends", "transactions", "queries", "query_plans",
"table_states", "disk_io" and "disk_usage". Else, the specified queries are
used only.

=back

=head2 Plugin C<powerdns>

The C<powerdns> plugin queries statistics from an authoritative PowerDNS
nameserver and/or a PowerDNS recursor. Since both offer a wide variety of
values, many of which are probably meaningless to most users, but may be useful
for some. So you may chose which values to collect, but if you don't, some
reasonable defaults will be collected.

  <Plugin "powerdns">
    <Server "server_name">
      Collect "latency"
      Collect "udp-answers" "udp-queries"
      Socket "/var/run/pdns.controlsocket"
    </Server>
    <Recursor "recursor_name">
      Collect "questions"
      Collect "cache-hits" "cache-misses"
      Socket "/var/run/pdns_recursor.controlsocket"
    </Recursor>
    LocalSocket "/opt/collectd/var/run/collectd-powerdns"
  </Plugin>

=over 4

=item B<Server> and B<Recursor> block

The B<Server> block defines one authoritative server to query, the B<Recursor>
does the same for an recursing server. The possible options in both blocks are
the same, though. The argument defines a name for the serverE<nbsp>/ recursor
and is required.

=over 4

=item B<Collect> I<Field>

Using the B<Collect> statement you can select which values to collect. Here,
you specify the name of the values as used by the PowerDNS servers, e.E<nbsp>g.
C<dlg-only-drops>, C<answers10-100>.

The method of getting the values differs for B<Server> and B<Recursor> blocks:
When querying the server a C<SHOW *> command is issued in any case, because
that's the only way of getting multiple values out of the server at once.
collectd then picks out the values you have selected. When querying the
recursor, a command is generated to query exactly these values. So if you
specify invalid fields when querying the recursor, a syntax error may be
returned by the daemon and collectd may not collect any values at all.

If no B<Collect> statement is given, the following B<Server> values will be
collected:

=over 4

=item latency

=item packetcache-hit

=item packetcache-miss

=item packetcache-size

=item query-cache-hit

=item query-cache-miss

=item recursing-answers

=item recursing-questions

=item tcp-answers

=item tcp-queries

=item udp-answers

=item udp-queries

=back

The following B<Recursor> values will be collected by default:

=over 4

=item noerror-answers

=item nxdomain-answers

=item servfail-answers

=item sys-msec

=item user-msec

=item qa-latency

=item cache-entries

=item cache-hits

=item cache-misses

=item questions

=back

Please note that up to that point collectd doesn't know what values are
available on the server and values that are added do not need a change of the
mechanism so far. However, the values must be mapped to collectd's naming
scheme, which is done using a lookup table that lists all known values. If
values are added in the future and collectd does not know about them, you will
get an error much like this:

  powerdns plugin: submit: Not found in lookup table: foobar = 42

In this case please file a bug report with the collectd team.

=item B<Socket> I<Path>

Configures the path to the UNIX domain socket to be used when connecting to the
daemon. By default C<${localstatedir}/run/pdns.controlsocket> will be used for
an authoritative server and C<${localstatedir}/run/pdns_recursor.controlsocket>
will be used for the recursor.

=back

=item B<LocalSocket> I<Path>

Querying the recursor is done using UDP. When using UDP over UNIX domain
sockets, the client socket needs a name in the file system, too. You can set
this local name to I<Path> using the B<LocalSocket> option. The default is
C<I<prefix>/var/run/collectd-powerdns>.

=back

=head2 Plugin C<processes>

=over 4

=item B<Process> I<Name>

Select more detailed statistics of processes matching this name. The statistics
collected for these selected processes are size of the resident segment size
(RSS), user- and system-time used, number of processes and number of threads,
and minor and major pagefaults.

=back

=head2 Plugin C<rrdcached>

The C<rrdcached> plugin uses the RRDTool accelerator daemon, L<rrdcached(1)>,
to store values to RRD files in an efficient manner. The combination of the
C<rrdcached> B<plugin> and the C<rrdcached> B<daemon> is very similar to the
way the C<rrdtool> plugin works (see below). The added abstraction layer
provides a number of benefits, though: Because the cache is not within
C<collectd> anymore, it does not need to be flushed when C<collectd> is to be
restarted. This results in much shorter (if any) gaps in graphs, especially
under heavy load. Also, the C<rrdtool> command line utility is aware of the
daemon so that it can flush values to disk automatically when needed. This
allows to integrate automated flushing of values into graphing solutions much
more easily.

There are disadvantages, though: The daemon may reside on a different host, so
it may not be possible for C<collectd> to create the appropriate RRD files
anymore. And even if C<rrdcached> runs on the same host, it may run in a
different base directory, so relative paths may do weird stuff if you're not
careful.

So the B<recommended configuration> is to let C<collectd> and C<rrdcached> run
on the same host, communicating via a UNIX domain socket. The B<DataDir>
setting should be set to an absolute path, so that a changed base directory
does not result in RRD files being createdE<nbsp>/ expected in the wrong place.

=over 4

=item B<DaemonAddress> I<Address>

Address of the daemon as understood by the C<rrdc_connect> function of the RRD
library. See L<rrdcached(1)> for details. Example:

  <Plugin "rrdcached">
    DaemonAddress "unix:/var/run/rrdcached.sock"
  </Plugin>

=item B<DataDir> I<Directory>

Set the base directory in which the RRD files reside. If this is a relative
path, it is relative to the working base directory of the C<rrdcached> daemon!
Use of an absolute path is recommended.

=item B<CreateFiles> B<true>|B<false>

Enables or disables the creation of RRD files. If the daemon is not running
locally, or B<DataDir> is set to a relative path, this will not work as
expected. Default is B<true>.

=back

=head2 Plugin C<rrdtool>

You can use the settings B<StepSize>, B<HeartBeat>, B<RRARows>, and B<XFF> to
fine-tune your RRD-files. Please read L<rrdcreate(1)> if you encounter problems
using these settings. If you don't want to dive into the depths of RRDTool, you
can safely ignore these settings.

=over 4

=item B<DataDir> I<Directory>

Set the directory to store RRD-files under. Per default RRD-files are generated
beneath the daemon's working directory, i.E<nbsp>e. the B<BaseDir>.

=item B<StepSize> I<Seconds>

B<Force> the stepsize of newly created RRD-files. Ideally (and per default)
this setting is unset and the stepsize is set to the interval in which the data
is collected. Do not use this option unless you absolutely have to for some
reason. Setting this option may cause problems with the C<snmp plugin>, the
C<exec plugin> or when the daemon is set up to receive data from other hosts.

=item B<HeartBeat> I<Seconds>

B<Force> the heartbeat of newly created RRD-files. This setting should be unset
in which case the heartbeat is set to twice the B<StepSize> which should equal
the interval in which data is collected. Do not set this option unless you have
a very good reason to do so.

=item B<RRARows> I<NumRows>

The C<rrdtool plugin> calculates the number of PDPs per CDP based on the
B<StepSize>, this setting and a timespan. This plugin creates RRD-files with
three times five RRAs, i. e. five RRAs with the CFs B<MIN>, B<AVERAGE>, and
B<MAX>. The five RRAs are optimized for graphs covering one hour, one day, one
week, one month, and one year.

So for each timespan, it calculates how many PDPs need to be consolidated into
one CDP by calculating:
  number of PDPs = timespan / (stepsize * rrarows)

Bottom line is, set this no smaller than the width of you graphs in pixels. The
default is 1200.

=item B<RRATimespan> I<Seconds>

Adds an RRA-timespan, given in seconds. Use this option multiple times to have
more then one RRA. If this option is never used, the built-in default of (3600,
86400, 604800, 2678400, 31622400) is used.

For more information on how RRA-sizes are calculated see B<RRARows> above.

=item B<XFF> I<Factor>

Set the "XFiles Factor". The default is 0.1. If unsure, don't set this option.

=item B<CacheFlush> I<Seconds>

When the C<rrdtool> plugin uses a cache (by setting B<CacheTimeout>, see below)
it writes all values for a certain RRD-file if the oldest value is older than
(or equal to) the number of seconds specified. If some RRD-file is not updated
anymore for some reason (the computer was shut down, the network is broken,
etc.) some values may still be in the cache. If B<CacheFlush> is set, then the
entire cache is searched for entries older than B<CacheTimeout> seconds and
written to disk every I<Seconds> seconds. Since this is kind of expensive and
does nothing under normal circumstances, this value should not be too small.
900 seconds might be a good value, though setting this to 7200 seconds doesn't
normally do much harm either.

=item B<CacheTimeout> I<Seconds>

If this option is set to a value greater than zero, the C<rrdtool plugin> will
save values in a cache, as described above. Writing multiple values at once
reduces IO-operations and thus lessens the load produced by updating the files.
The trade off is that the graphs kind of "drag behind" and that more memory is
used.

=item B<WritesPerSecond> B<Updates>

When collecting many statistics with collectd and the C<rrdtool> plugin, you
will run serious performance problems. The B<CacheFlush> setting and the
internal update queue assert that collectd continues to work just fine even
under heavy load, but the system may become very unresponsive and slow. This is
a problem especially if you create graphs from the RRD files on the same
machine, for example using the C<graph.cgi> script included in the
C<contrib/collection3/> directory.

This setting is designed for very large setups. Setting this option to a value
between 25 and 80 updates per second, depending on your hardware, will leave
the server responsive enough to draw graphs even while all the cached values
are written to disk. Flushed values, i.E<nbsp>e. values that are forced to disk
by the B<FLUSH> command, are B<not> effected by this limit. They are still
written as fast as possible, so that web frontends have up to date data when
generating graphs.

For example: If you have 100,000 RRD files and set B<WritesPerSecond> to 30
updates per second, writing all values to disk will take approximately
56E<nbsp>minutes. Together with the flushing ability that's integrated into
"collection3" you'll end up with a responsive and fast system, up to date
graphs and basically a "backup" of your values every hour.

=back

=head2 Plugin C<sensors>

The C<sensors plugin> uses B<lm_sensors> to retrieve sensor-values. This means
that all the needed modules have to be loaded and lm_sensors has to be
configured (most likely by editing F</etc/sensors.conf>. Read
L<sensors.conf(5)> for details.

The B<lm_sensors> homepage can be found at
L<http://secure.netroedge.com/~lm78/>.

=over 4

=item B<Sensor> I<chip-bus-address/type-feature>

Selects the name of the sensor which you want to collect or ignore, depending
on the B<IgnoreSelected> below. For example, the option "B<Sensor>
I<it8712-isa-0290/voltage-in1>" will cause collectd to gather data for the
voltage sensor I<in1> of the I<it8712> on the isa bus at the address 0290.

=item B<IgnoreSelected> I<true>|I<false>

If no configuration if given, the B<sensors>-plugin will collect data from all
sensors. This may not be practical, especially for uninteresting sensors.
Thus, you can use the B<Sensor>-option to pick the sensors you're interested
in. Sometimes, however, it's easier/preferred to collect all sensors I<except> a
few ones. This option enables you to do that: By setting B<IgnoreSelected> to
I<true> the effect of B<Sensor> is inverted: All selected sensors are ignored
and all other sensors are collected.

=back

=head2 Plugin C<snmp>

Since the configuration of the C<snmp plugin> is a little more complicated than
other plugins, its documentation has been moved to an own manpage,
L<collectd-snmp(5)>. Please see there for details.

=head2 Plugin C<syslog>

=over 4

=item B<LogLevel> B<debug|info|notice|warning|err>

Sets the log-level. If, for example, set to B<notice>, then all events with
severity B<notice>, B<warning>, or B<err> will be submitted to the
syslog-daemon.

Please note that B<debug> is only available if collectd has been compiled with
debugging support.

=back

=head2 Plugin C<tail>

The C<tail plugin> plugins follows logfiles, just like L<tail(1)> does, parses
each line and dispatches found values. What is matched can be configured by the
user using (extended) regular expressions, as described in L<regex(7)>.

  <Plugin "tail">
    <File "/var/log/exim4/mainlog">
      Instance "exim"
      <Match>
        Regex "S=([1-9][0-9]*)"
        DSType "CounterAdd"
        Type "ipt_bytes"
        Instance "total"
      </Match>
      <Match>
        Regex "\\<R=local_user\\>"
        DSType "CounterInc"
        Type "counter"
        Instance "local_user"
      </Match>
    </File>
  </Plugin>

The config consists of one or more B<File> blocks, each of which configures one
logfile to parse. Within each B<File> block, there are one or more B<Match>
blocks, which configure a regular expression to search for.

The B<Instance> option in the B<File> block may be used to set the plugin
instance. So in the above example the plugin name C<tail-foo> would be used.
This plugin instance is for all B<Match> blocks that B<follow> it, until the
next B<Instance> option. This way you can extract several plugin instances from
one logfile, handy when parsing syslog and the like.

Each B<Match> block has the following options to describe how the match should
be performed:

=over 4

=item B<Regex> I<regex>

Sets the regular expression to use for matching against a line. The first
subexpression has to match something that can be turned into a number by
L<strtoll(3)> or L<strtod(3)>, depending on the value of C<CounterAdd>, see
below. Because B<extended> regular expressions are used, you do not need to use
backslashes for subexpressions! If in doubt, please consult L<regex(7)>. Due to
collectd's config parsing you need to escape backslashes, though. So if you
want to match literal parentheses you need to do the following:

  Regex "SPAM \\(Score: (-?[0-9]+\\.[0-9]+)\\)"

=item B<DSType> I<Type>

Sets how the values are cumulated. I<Type> is one of:

=over 4

=item B<GaugeAverage>

Calculate the average.

=item B<GaugeMin>

Use the smallest number only.

=item B<GaugeMax>

Use the greatest number only.

=item B<GaugeLast>

Use the last number found.

=item B<CounterSet>

The matched number is a counter. Simply sets the internal counter to this
value.

=item B<CounterAdd>

Add the matched value to the internal counter.

=item B<CounterInc>

Increase the internal counter by one. This B<DSType> is the only one that does
not use the matched subexpression, but simply counts the number of matched
lines. Thus, you may use a regular expression without submatch in this case.

=back

As you'd expect the B<Gauge*> types interpret the submatch as a floating point
number, using L<strtod(3)>. The B<CounterSet> and B<CounterAdd> interpret the
submatch as an integer using L<strtoll(3)>. B<CounterInc> does not use the
submatch at all and it may be omitted in this case.

=item B<Type> I<Type>

Sets the type used to dispatch this value. Detailed information about types and
their configuration can be found in L<types.db(5)>.

=item B<Instance> I<TypeInstance>

This optional setting sets the type instance to use.

=back

=head2 Plugin C<teamspeak2>

The C<teamspeak2 plugin> connects to the query port of a teamspeak2 server and
polls interesting global and virtual server data. The plugin can query only one
physical server but unlimited virtual servers. You can use the following
options to configure it:

=over 4

=item B<Host> I<hostname/ip>

The hostname or ip which identifies the physical server.
Default: 127.0.0.1

=item B<Port> I<port>

The query port of the physical server. This needs to be a string.
Default: "51234"

=item B<Server> I<port>

This option has to be added once for every virtual server the plugin should
query. If you want to query the virtual server on port 8767 this is what the
option would look like:

  Server "8767"

This option, although numeric, needs to be a string, i.E<nbsp>e. you B<must>
use quotes around it! If no such statement is given only global information
will be collected.

=back

=head2 Plugin C<tcpconns>

The C<tcpconns plugin> counts the number of currently established TCP
connections based on the local port and/or the remote port. Since there may be
a lot of connections the default if to count all connections with a local port,
for which a listening socket is opened. You can use the following options to
fine-tune the ports you are interested in:

=over 4

=item B<ListeningPorts> I<true>|I<false>

If this option is set to I<true>, statistics for all local ports for which a
listening socket exists are collected. The default depends on B<LocalPort> and
B<RemotePort> (see below): If no port at all is specifically selected, the
default is to collect listening ports. If specific ports (no matter if local or
remote ports) are selected, this option defaults to I<false>, i.E<nbsp>e. only
the selected ports will be collected unless this option is set to I<true>
specifically.

=item B<LocalPort> I<Port>

Count the connections to a specific local port. This can be used to see how
many connections are handled by a specific daemon, e.E<nbsp>g. the mailserver.
You have to specify the port in numeric form, so for the mailserver example
you'd need to set B<25>.

=item B<RemotePort> I<Port>

Count the connections to a specific remote port. This is useful to see how
much a remote service is used. This is most useful if you want to know how many
connections a local service has opened to remote services, e.E<nbsp>g. how many
connections a mail server or news server has to other mail or news servers, or
how many connections a web proxy holds to web servers. You have to give the
port in numeric form.

=back

=head2 Plugin C<thermal>

=over 4

=item B<ForceUseProcfs> I<true>|I<false>

By default, the C<thermal> plugin tries to read the statistics from the Linux
C<sysfs> interface. If that is not available, the plugin falls back to the
C<procfs> interface. By setting this option to I<true>, you can force the
plugin to use the latter. This option defaults to I<false>.

=item B<Device> I<Device>

Selects the name of the thermal device that you want to collect or ignore,
depending on the value of the B<IgnoreSelected> option. This option may be
used multiple times to specify a list of devices.

=item B<IgnoreSelected> I<true>|I<false>

Invert the selection: If set to true, all devices B<except> the ones that
match the device names specified by the B<Device> option are collected. By
default only selected devices are collected if a selection is made. If no
selection is configured at all, B<all> devices are selected.

=back

=head2 Plugin C<unixsock>

=over 4

=item B<SocketFile> I<Path>

Sets the socket-file which is to be created.

=item B<SocketGroup> I<Group>

If running as root change the group of the UNIX-socket after it has been
created. Defaults to B<collectd>.

=item B<SocketPerms> I<Permissions>

Change the file permissions of the UNIX-socket after it has been created. The
permissions must be given as a numeric, octal value as you would pass to
L<chmod(1)>. Defaults to B<0770>.

=back

=head2 Plugin C<uuid>

This plugin, if loaded, causes the Hostname to be taken from the machine's
UUID. The UUID is a universally unique designation for the machine, usually
taken from the machine's BIOS. This is most useful if the machine is running in
a virtual environment such as Xen, in which case the UUID is preserved across
shutdowns and migration.

The following methods are used to find the machine's UUID, in order:

=over 4

=item

Check I</etc/uuid> (or I<UUIDFile>).

=item

Check for UUID from HAL (L<http://www.freedesktop.org/wiki/Software/hal>) if
present.

=item

Check for UUID from C<dmidecode> / SMBIOS.

=item

Check for UUID from Xen hypervisor.

=back

If no UUID can be found then the hostname is not modified.

=over 4

=item B<UUIDFile> I<Path>

Take the UUID from the given file (default I</etc/uuid>).

=back

=head2 Plugin C<vmem>

The C<vmem> plugin collects information about the usage of virtual memory.
Since the statistics provided by the Linux kernel are very detailed, they are
collected very detailed. However, to get all the details, you have to switch
them on manually. Most people just want an overview over, such as the number of
pages read from swap space.

=over 4

=item B<Verbose> B<true>|B<false>

Enables verbose collection of information. This will start collecting page
"actions", e.E<nbsp>g. page allocations, (de)activations, steals and so on.
Part of these statistics are collected on a "per zone" basis.

=back

=head2 Plugin C<vserver>

This plugin doesn't have any options. B<VServer> support is only available for
Linux. It cannot yet be found in a vanilla kernel, though. To make use of this
plugin you need a kernel that has B<VServer> support built in, i.E<nbsp>e. you
need to apply the patches and compile your own kernel, which will then provide
the F</proc/virtual> filesystem that is required by this plugin.

The B<VServer> homepage can be found at L<http://linux-vserver.org/>.

=head1 THRESHOLD CONFIGURATION

Starting with version C<4.3.0> collectd has support for B<monitoring>. By that
we mean that the values are not only stored or sent somewhere, but that they
are judged and, if a problem is recognized, acted upon. The only action
collectd takes itself is to generate and dispatch a "notification". Plugins can
register to receive notifications and perform appropriate further actions.

Since systems and what you expect them to do differ a lot, you can configure
B<thresholds> for your values freely. This gives you a lot of flexibility but
also a lot of responsibility.

Every time a value is out of range a notification is dispatched. This means
that the idle percentage of your CPU needs to be less then the configured
threshold only once for a notification to be generated. There's no such thing
as a moving average or similar - at least not now.

Also, all values that match a threshold are considered to be relevant or
"interesting". As a consequence collectd will issue a notification if they are
not received for twice the last timeout of the values. If, for example, some
hosts sends it's CPU statistics to the server every 60 seconds, a notification
will be dispatched after about 120 seconds. It may take a little longer because
the timeout is checked only once each B<Interval> on the server.

When a value comes within range again or is received after it was missing, an
"OKAY-notification" is dispatched.

Here is a configuration example to get you started. Read below for more
information.

 <Threshold>
   <Type "foo">
     WarningMin    0.00
     WarningMax 1000.00
     FailureMin    0.00
     FailureMax 1200.00
     Invert false
     Instance "bar"
   </Type>

   <Plugin "interface">
     Instance "eth0"
     <Type "if_octets">
       FailureMax 10000000
       DataSource "rx"
     </Type>
   </Plugin>

   <Host "hostname">
     <Type "cpu">
       Instance "idle"
       FailureMin 10
     </Type>

     <Plugin "memory">
       <Type "memory">
         Instance "cached"
         WarningMin 100000000
       </Type>
     </Plugin>
   </Host>
 </Threshold>

There are basically two types of configuration statements: The C<Host>,
C<Plugin>, and C<Type> blocks select the value for which a threshold should be
configured. The C<Plugin> and C<Type> blocks may be specified further using the
C<Instance> option. You can combine the block by nesting the blocks, though
they must be nested in the above order, i.E<nbsp>e. C<Host> may contain either
C<Plugin> and C<Type> blocks, C<Plugin> may only contain C<Type> blocks and
C<Type> may not contain other blocks. If multiple blocks apply to the same
value the most specific block is used.

The other statements specify the threshold to configure. They B<must> be
included in a C<Type> block. Currently the following statements are recognized:

=over 4

=item B<FailureMax> I<Value>

=item B<WarningMax> I<Value>

Sets the upper bound of acceptable values. If unset defaults to positive
infinity. If a value is greater than B<FailureMax> a B<FAILURE> notification
will be created. If the value is greater than B<WarningMax> but less than (or
equal to) B<FailureMax> a B<WARNING> notification will be created.

=item B<FailureMin> I<Value>

=item B<WarningMin> I<Value>

Sets the lower bound of acceptable values. If unset defaults to negative
infinity. If a value is less than B<FailureMin> a B<FAILURE> notification will
be created. If the value is less than B<WarningMin> but greater than (or equal
to) B<FailureMin> a B<WARNING> notification will be created.

=item B<DataSource> I<DSName>

Some data sets have more than one "data source". Interesting examples are the
C<if_octets> data set, which has received (C<rx>) and sent (C<tx>) bytes and
the C<disk_ops> data set, which holds C<read> and C<write> operations. The
system load data set, C<load>, even has three data sources: C<shortterm>,
C<midterm>, and C<longterm>.

Normally, all data sources are checked against a configured threshold. If this
is undesirable, or if you want to specify different limits for each data
source, you can use the B<DataSource> option to have a threshold apply only to
one data source.

=item B<Invert> B<true>|B<false>

If set to B<true> the range of acceptable values is inverted, i.E<nbsp>e.
values between B<FailureMin> and B<FailureMax> (B<WarningMin> and
B<WarningMax>) are not okay. Defaults to B<false>.

=item B<Persist> B<true>|B<false>

Sets how often notifications are generated. If set to B<true> one notification
will be generated for each value that is out of the acceptable range. If set to
B<false> (the default) then a notification is only generated if a value is out
of range but the previous value was okay.

This applies to missing values, too: If set to B<true> a notification about a
missing value is generated once every B<Interval> seconds. If set to B<false>
only one such notification is generated until the value appears again.

=back

=head1 FILTER CONFIGURATION

TODO: Update this entire section once development is done.

Starting with collectd 4.6 there is a powerful filtering infrastructure
implemented in the daemon. The concept has mostly been copied from I<iptables>,
the packet filter infrastructure for Linux. We'll use a similar terminology, so
that users that are familiar with iptables feel right at home.

=head2 Terminology

The most important terms are:

=over 4

=item B<Match>

A I<match> is a criteria to select specific values. Examples are, of course, the
name of the value or it's current value.

=item B<Target>

A I<target> is some action that is to be performed with data. Such actions
could, for example, be to change part of the value's identifier or to ignore
the value completely. Built-in functions are B<write> and B<stop>, see below.

Some targets, for example the built-in B<stop> target, signal that processing
of a value should be stopped. In that case processing of the current chain will
be aborted.

=item B<Rule>

The combination of any number of matches and at least one target is called a
I<rule>. The target actions will be performed for all values for which B<all>
matches apply. If the rule does not have any matches associated with it, the
target action will be performed for all values.

If any target returns the stop condition, the processing will stop right away.
This means that any targets following the current one will not be called after
the stop condition has been returned.

=item B<Chain>

A I<chain> is a list of rules and possibly default targets. The rules are tried
in order and if one matches, the associated target will be called. If a value
is handled by a rule, it depends on the target whether or not any subsequent
rules are considered or if traversal of the chain is aborted. After all rules
have been checked and no target returned the stop condition, the default
targets will be executed.

=back

=head2 General structure

The following shows the resulting structure:

 +---------+
 ! Chain   !
 +---------+
      !
      V
 +---------+  +---------+  +---------+  +---------+
 ! Rule    !->! Match   !->! Match   !->! Target  !
 +---------+  +---------+  +---------+  +---------+
      !
      V
 +---------+  +---------+  +---------+
 ! Rule    !->! Target  !->! Target  !
 +---------+  +---------+  +---------+
      !
      V
      :
      :
      !
      V
 +---------+  +---------+  +---------+
 ! Rule    !->! Match   !->! Target  !
 +---------+  +---------+  +---------+
      !
      V
 +---------+
 ! Default !
 ! Target  !
 +---------+

=head2 Synopsis

The configuration reflects this structure directly:

 <Chain "main">
   <Rule "ignore_mysql_show">
     <Match "regex">
       Plugin "^mysql$"
       Type "^mysql_command$"
       TypeInstance "^show_"
     </Match>
     <Target "stop">
     </Target>
   </Rule>
   <Target "write">
     Plugin "rrdtool"
   </Target>
 </Chain>

The above configuration example will ignore all values where the plugin field
is "mysql", the type is "mysql_command" and the type instance begins with
"show_". All other values will be sent to the "rrdtool" write plugin via the
default target of the chain.

=head2 List of configuration options

=over 4

=item B<Chain> I<Name>

Adds a new chain with a certain name. This name can be used to refer to a
specific chain, for example to jump to it.

Within the B<Chain> block, there can be B<Rule> blocks and B<Target> blocks.

=item B<Rule> [I<Name>]

Adds a new rule to the current chain. The name of the rule is optional and
currently has no meaning for the daemon.

Within the B<Rule> block, there may be any number of B<Match> blocks and there
must be at least one B<Target> block.

=item B<Match> I<Name>

Adds a match to a B<Rule> block. The name specifies what kind of match should
be performed. Available matches depend on the plugins that have been loaded.

The arguments inside the B<Match> block are passed to the plugin implementing
the match, so which arguments are valid here depends on the plugin being used.
If you do not need any to pass any arguments to a match, you can use the
shorter syntax:

 Match "foobar"

Which is equivalent to:

 <Match "foobar">
 </Match>

=item B<Target> I<Name>

Add a target to a rule or a default target to a chain. The name specifies what
kind of target is to be added. Which targets are available depends on the
plugins being loaded.

The arguments inside the B<Target> block are passed to the plugin implementing
the target, so which arguments are valid here depends on the plugin being used.
If you do not need any to pass any arguments to a target, you can use the
shorter syntax:

 Target "stop"

This is the same as writing:

 <Target "stop">
 </Target>

=back

=head2 Built-in targets 

The following targets are built into the core daemon and therefore need no
plugins to be loaded:

=over 4

=item B<return>

Signals the "return" condition. This causes the current chain to stop
processing the value and returns control to the calling chain. The calling
chain will continue processing targets and rules just after the B<jump> target
(see below). This is very similar to the B<RETURN> target of iptables, see
L<iptables(8)>.

This target does not have any options.

Example:

 Target "return"

=item B<stop>

Signals the "stop" condition, causing processing of the value to be aborted
immediately. This is similar to the B<DROP> target of iptables, see
L<iptables(8)>.

This target does not have any options.

Example:

 Target "stop"

=item B<write>

Sends the value to write plugins.

Available options:

=over 4

=item B<Plugin> I<Name>

Name of the write plugin to which the data should be sent. This option may be
given multiple times to send the data to more than one write plugin.

=back

If no plugin is explicitly specified, the values will be sent to all available
write plugins.

Example:

 <Target "write">
   Plugin "rrdtool"
 </Target>

=item B<jump>

Starts processing the rules of another chain. If the end of that chain is
reached, or a stop condition is encountered, processing will continue right
after the B<jump> target, i.E<nbsp>e. with the next target or the next rule.
This is similar to the B<-j> command line option of iptables, see
L<iptables(8)>.

Available options:

=over 4

=item B<Chain> I<Name>

Jumps to the chain I<Name>. This argument is required and may appear only once.

=back

Example:

 <Target "jump">
   Chain "foobar"
 </Target>

=back

=head2 Available matches

=over 4

=item B<regex>

Matches a value using regular expressions.

Available options:

=over 4

=item B<Host> I<Regex>

=item B<Plugin> I<Regex>

=item B<PluginInstance> I<Regex>

=item B<Type> I<Regex>

=item B<TypeInstance> I<Regex>

Match values where the given regular expressions match the various fields of
the identifier of a value. If multiple regular expressions are given, B<all>
regexen must match for a value to match.

=back

Example:

 <Match "regex">
   Host "customer[0-9]+"
   Plugin "^foobar$"
 </Match>

=item B<value>

Matches the actual value of data sources against given minimumE<nbsp>/ maximum
values. If a data-set consists of more than one data-source, all data-sources
must match the specified ranges for a positive match.

Available options:

=over 4

=item B<Min> I<Value>

Sets the smallest value which still results in a match. If unset, behaves like
negative infinity.

=item B<Max> I<Value>

Sets the largest value which still results in a match. If unset, behaves like
positive infinity.

=item B<Invert> B<true>|B<false>

Inverts the selection. If the B<Min> and B<Max> settings result in a match,
no-match is returned and vice versa.

=back

Either B<Min> or B<Max>, but not both, may be unset.

Example:

 # Match all values smaller than or equal to 100.
 <Match "value">
   Max 100
 </Match>

=back

=head2 Available targets

=over 4

=item B<set>

Sets part of the identifier of a value to a given string.

Available options:

=over 4

=item B<Host> I<String>

=item B<Plugin> I<String>

=item B<PluginInstance> I<String>

=item B<TypeInstance> I<String>

Set the appropriate field to the given string. The strings for plugin instance
and type instance may be empty, the strings for host and plugin may not be
empty. It's currently not possible to set the type of a value this way.

=back

Example:

 <Target "set">
   PluginInstance "coretemp"
   TypeInstance "core3"
 </Target>

=back

=head2 Backwards compatibility

If you use collectd with an old configuration, i.E<nbsp>e. one without a
B<Chain> block, it will behave as it used to. This is equivalent to the
following configuration:

 <Chain "main">
   Target "write"
 </Chain>

If you specify a B<Chain> block anywhere, the B<write> target will not be added
anywhere and you will have to make sure that it is called where appropriate. We
suggest to add the above snippet as default target to your main chain.

TODO: Notifications will be implemented using chains, too. Describe that here!

=head2 Examples

Ignore all values, where the hostname does not contain a dot, i.E<nbsp>e. can't
be an FQDN.

 <Chain "main">
   <Rule "no_fqdn">
     <Match "regex">
       Host "^[^\.]*$"
     </Match>
     Target "stop"
   </Rule>
   Target "write"
 </Chain>

=head1 SEE ALSO

L<collectd(1)>,
L<collectd-exec(5)>,
L<collectd-perl(5)>,
L<collectd-unixsock(5)>,
L<types.db(5)>,
L<hddtemp(8)>,
L<iptables(8)>,
L<kstat(3KSTAT)>,
L<mbmon(1)>,
L<pcre(3)>,
L<psql(1)>,
L<rrdtool(1)>,
L<sensors(1)>

=head1 AUTHOR

Florian Forster E<lt>octo@verplant.orgE<gt>

=cut