+# Permission is hereby granted, free of charge, to any person obtaining a
+# copy of this software and associated documentation files (the "Software"),
+# to deal in the Software without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish, distribute, sublicense,
+# and/or sell copies of the Software, and to permit persons to whom the
+# Software is furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+
=head1 NAME
collectd-python - Documentation of collectd's C<python plugin>
Python-script every time you want to read a value with the C<exec plugin> (see
L<collectd-exec(5)>) and provides a lot more functionality, too.
-Currently only python2 is supported and at least version 2.3 is required.
+At least python I<version 2.3> is required.
=head1 CONFIGURATION
Loads the Python plugin I<Plugin>. Unlike most other LoadPlugin lines, this one
should be a block containing the line "Globals true". This will cause collectd
to export the name of all objects in the python interpreter for all plugins to
-see. If you don't do this or your platform does not support it, the embeded
-interpreter will start anywa but you won't be able to load certain python
+see. If you don't do this or your platform does not support it, the embedded
+interpreter will start anyway but you won't be able to load certain python
modules, e.g. "time".
=item B<Encoding> I<Name>
-The default encoding for unicode objects you pass to collectd. If you obmit
-this option it will default to B<ascii> on python2 and B<utf-8> on python3.
-This is hardcoded in python and will ignore everything else, including your
+The default encoding for Unicode objects you pass to collectd. If you omit this
+option it will default to B<ascii> on I<Python 2> and B<utf-8> on I<Python 3>.
+This is hardcoded in Python and will ignore everything else, including your
locale.
=item B<ModulePath> I<Name>
Appends I<Name> to B<sys.path>. You won't be able to import any scripts you
-wrote unless they are located in one of the directuries in this list. Please
-note that it only has effect on plugins loaded after this option.
+wrote unless they are located in one of the directories in this list. Please
+note that it only has effect on plugins loaded after this option. You can
+use multiple B<ModulePath> lines to add more than one directory.
=item B<LogTraces> I<bool>
=item B<Interactive> I<bool>
-This option will causethe module to launch an interactive python interpreter
+This option will cause the module to launch an interactive python interpreter
that reads from and writes to the terminal. Note that collectd will terminate
right after starting up if you try to run it as a daemon while this option is
enabled to make sure to start collectd with the B<-f> option.
This interactive session will behave slightly differently from a daemonized
collectd script as well as from a normal python interpreter:
-1. collectd will try to import the B<readline> module to give you a decent
-way of entering your commmands. The daemonized collectd won't do that.
-2. collectd will block SIGINT. Pressing Ctrl+C will usually cause collectd to
-shut down. This would be problematic in an interactive session, therefore this
-signal will be blocked. You can still use it to interrupt syscalls like sleep
-and pause but it won't generate a KeyboardInterrupt exception either.
-To quit collectd send EOF (press Ctrl+D at the beginning of a new line).
+=over 4
+
+=item
+
+B<1.> collectd will try to import the B<readline> module to give you a decent
+way of entering your commands. The daemonized collectd won't do that.
+
+=item
+
+B<2.> collectd will block I<SIGINT>. Pressing I<Ctrl+C> will usually cause
+collectd to shut down. This would be problematic in an interactive session,
+therefore this signal will be blocked. You can still use it to interrupt
+syscalls like sleep and pause but it won't generate a I<KeyboardInterrupt>
+exception either.
+
+To quit collectd send I<EOF> (press I<Ctrl+D> at the beginning of a new line).
+
+=item
+
+B<3.> collectd handles I<SIGCHLD>. This means that python won't be able to
+determine the return code of spawned processes with system(), popen() and
+subprocess. This will result in python not using external programs like less
+to display help texts. You can override this behavior with the B<PAGER>
+environment variable, e.g. I<export PAGER=less> before starting collectd.
+Depending on your version of python this might or might not result in an
+B<OSError> exception which can be ignored.
+
+If you really need to spawn new processes from python you can register an init
+callback and reset the action for SIGCHLD to the default behavior. Please note
+that this I<will> break the exec plugin. Do not even load the exec plugin if
+you intend to do this!
+
+There is an example script located in B<contrib/python/getsigchld.py> to do
+this. If you import this from I<collectd.conf> SIGCHLD will be handled
+normally and spawning processes from python will work as intended.
+
+=back
=item E<lt>B<Module> I<Name>E<gt> block
This block may be used to pass on configuration settings to a Python module.
-The configuration is converted into an instance of the B<Config> class which
-is passed to the registered configuration callback. See below for details about
+The configuration is converted into an instance of the B<Config> class which is
+passed to the registered configuration callback. See below for details about
the B<Config> class and how to register callbacks.
The I<name> identifies the callback.
=back
+=head1 STRINGS
+
+There are a lot of places where strings are send from collectd to python and
+from python to collectd. How exactly this works depends on wheather byte or
+unicode strings or python2 or python3 are used.
+
+Python2 has I<str>, which is just bytes, and I<unicode>. Python3 has I<str>,
+which is a unicode object, and I<bytes>.
+
+When passing strings from python to collectd all of these object are supported
+in all places, however I<str> should be used if possible. These strings must
+not contain a NUL byte. Ignoring this will result in a I<TypeError> exception.
+If a byte string was used it will be used as is by collectd. If a unicode
+object was used it will be encoded using the default encoding (see above). If
+this is not possible python will raise a I<UnicodeEncodeError> exception.
+
+Wenn passing strings from collectd to python the behavior depends on the
+python version used. Python2 will always receive a I<str> object. Python3 will
+usually receive a I<str> object as well, however the original string will be
+decoded to unicode using the default encoding. If this fails because the
+string is not a valid sequence for this encoding a I<bytes> object will be
+returned instead.
+
=head1 WRITING YOUR OWN PLUGINS
Writing your own plugins is quite simple. collectd manages plugins by means of
Any function (except log functions) may set throw an exception in case of any
errors. The exception will be passed on to the user using collectd's logging
-mechanism. If a log callback throws an exception it will be printed to stderr
-instead.
+mechanism. If a log callback throws an exception it will be printed to standard
+error instead.
See the documentation of the various B<register_> methods in the section
"FUNCTIONS" below for the number and types of arguments passed to each
The following complex types are used to pass values between the Python plugin
and collectd:
+=head2 Signed
+
+The Signed class is just a long. It has all its methods and behaves exactly
+like any other long object. It is used to indicate if an integer was or should
+be stored as a signed or unsigned integer object.
+
+ class Signed(long)
+
+This is a long by another name. Use it in meta data dicts
+to choose the way it is stored in the meta data.
+
+=head2 Unsigned
+
+The Unsigned class is just a long. It has all its methods and behaves exactly
+like any other long object. It is used to indicate if an integer was or should
+be stored as a signed or unsigned integer object.
+
+ class Unsigned(long)
+
+This is a long by another name. Use it in meta data dicts
+to choose the way it is stored in the meta data.
+
=head2 Config
-The Config class is an object which keeps the informations provided in the
+The Config class is an object which keeps the information provided in the
configuration file. The sequence of children keeps one entry for each
configuration option. Each such entry is another Config instance, which
may nest further if nested blocks are used.
Data descriptors defined here:
=over 4
-
+
=item parent
This represents the parent of this node. On the root node
of the config tree it will be None.
-
+
=item key
-This is the keyword of this item, ie the first word of any given line in the
+This is the keyword of this item, i.e. the first word of any given line in the
config file. It will always be a string.
-
+
=item values
-This is a tuple (which might be empty) of all value, ie words following the
+This is a tuple (which might be empty) of all value, i.e. words following the
keyword in any given line in the config file.
-Every item in this tuple will be either a string or a float or a bool,
+Every item in this tuple will be either a string or a float or a boolean,
depending on the contents of the configuration file.
-
+
=item children
This is a tuple of child nodes. For most nodes this will be empty. If this node
=over 4
=item B<dispatch>([type][, values][, plugin_instance][, type_instance][, plugin][, host][, time][, interval]) -> None.
-
+
Dispatch this instance to the collectd process. The object has members for each
of the possible arguments for this method. For a detailed explanation of these
parameters see the member of the same same.
source. This value has to be a positive integer, so you can't submit more than
one value per second. If this member is set to a non-positive value, the
default value as specified in the config file will be used (default: 10).
-
+
If you submit values more often than the specified interval, the average will
be used. If you submit less values, your graphs will have gaps.
exception will be raised. If the content of the sequence is not a number, a
I<TypeError> exception will be raised.
+=item meta
+
+These are the meta data for this Value object.
+It has to be a dictionary of numbers, strings or bools. All keys must be
+strings. I<int> and <long> objects will be dispatched as signed integers unless
+they are between 2**63 and 2**64-1, which will result in a unsigned integer.
+You can force one of these storage classes by using the classes
+B<collectd.Signed> and B<collectd.Unsigned>. A meta object received by a write
+callback will always contain B<Signed> or B<Unsigned> objects.
+
=back
=head2 Notification
A notification is an object defining the severity and message of the status
message as well as an identification of a data instance by means of the members
-of PluginData on which it is based.
+of I<PluginData> on which it is based.
class Notification(PluginData)
The Notification class is a wrapper around the collectd notification.
=over 4
=item B<dispatch>([type][, values][, plugin_instance][, type_instance][, plugin][, host][, time][, interval]) -> None. Dispatch a value list.
-
+
Dispatch this instance to the collectd process. The object has members for each
of the possible arguments for this method. For a detailed explanation of these
parameters see the member of the same same.
-
+
If you do not submit a parameter the value saved in its member will be
submitted. If you do provide a parameter it will be used instead, without
altering the member.
=item
I<data> is an optional object that will be passed back to the callback function
-every time it is called. If you obmit this parameter no object is passed back
-to your callback, not even None.
+every time it is called. If you omit this parameter no object is passed back to
+your callback, not even None.
=item
=item register_flush
-Like B<register_config> is important for this callbavk because it determines
+Like B<register_config> is important for this callback because it determines
what flush requests the plugin will receive.
The arguments passed are I<timeout> and I<identifier>. I<timeout> indicates
end.
If this callback throws an exception it will B<not> be logged. It will just be
-printed to sys.stderr which usually means silently ignored.
+printed to B<sys.stderr> which usually means silently ignored.
=item register_notification
=item B<unregister_*>(I<identifier>) -> None
Removes a callback or data-set from collectd's internal list of callback
-functions. Every register_* function has an unregister_* function. I<identifier>
-is either the string that was returned by the register function or a callback
-function. The identifier will be constructed in the same way as for the
-register functions.
+functions. Every I<register_*> function has an I<unregister_*> function.
+I<identifier> is either the string that was returned by the register function
+or a callback function. The identifier will be constructed in the same way as
+for the register functions.
=item B<flush>(I<plugin[, I<timeout>][, I<identifier>]) -> None
=item
-This plugin is not compatible with python3. Trying to complie it with python3
-will fail because of the ways string, unicode and bytearray bahavior was
-changed.
-
-Not all aspects of the collectd API are accessable from python. This includes
-but is not limited to meta-data, filters and data sets.
+Not all aspects of the collectd API are accessible from python. This includes
+but is not limited to filters and data sets.
=back
=head1 AUTHOR
-The C<python plugin> has been written by Sebastian Harl
-E<lt>shE<nbsp>atE<nbsp>tokkee.orgE<gt>.
+The C<python plugin> has been written by
+Sven Trenkel E<lt>collectdE<nbsp>atE<nbsp>semidefinite.deE<gt>.
-This manpage has been written by Florian Forster
-E<lt>octoE<nbsp>atE<nbsp>verplant.orgE<gt> and Sebastian Harl
-E<lt>shE<nbsp>atE<nbsp>tokkee.orgE<gt>.
+This manpage has been written by Sven Trenkel
+E<lt>collectdE<nbsp>atE<nbsp>semidefinite.deE<gt>.
+It is based on the L<collectd-perl(5)> manual page by
+Florian Forster E<lt>octoE<nbsp>atE<nbsp>verplant.orgE<gt> and
+Sebastian Harl E<lt>shE<nbsp>atE<nbsp>tokkee.orgE<gt>.
=cut
-
projects / collectd.git / blobdiff