Merge branch 'pull/collectd-4.1' into collectd-4.1

[collectd.git] / src / collectd-snmp.pod

diff --git a/src/collectd-snmp.pod b/src/collectd-snmp.pod
index 22d6e37..00d41e5 100644 (file)
--- a/src/collectd-snmp.pod
+++ b/src/collectd-snmp.pod
@@ -31,7 +31,7 @@ collectd-snmp - Documentation of collectd's C<snmp plugin>
       Version 1
       Community "community_string"
       Collect "std_traffic"
       Version 1
       Community "community_string"
       Collect "std_traffic"

-      Inverval 120
+      Interval 120

     </Host>
     <Host "some.server.mydomain.org">
       Address "192.168.0.42"
     </Host>
     <Host "some.server.mydomain.org">
       Address "192.168.0.42"


@@ -56,11 +56,18 @@ internal format and dispatches them. Depending on the write plugins you have
 loaded they may be written to disk or submitted to another instance or
 whatever you configured.
 
 loaded they may be written to disk or submitted to another instance or
 whatever you configured.
 

+Because querying a host via SNMP may produce a timeout multiple threads are
+used to query hosts in parallel. Depending on the number of hosts between one
+and ten threads are used.
+

 =head1 CONFIGURATION
 
 Since the aim of the C<snmp plugin> is to provide a generic interface to SNMP,
 it's configuration is not trivial and may take some time.
 
 =head1 CONFIGURATION
 
 Since the aim of the C<snmp plugin> is to provide a generic interface to SNMP,
 it's configuration is not trivial and may take some time.
 

+Since the C<Net-SNMP> library is used you can use all the environment variables
+that are interpreted by that package. See L<snmpcmd(1)> for more details.
+

 There are two types of blocks that can be contained in the
 C<E<lt>PluginE<nbsp>snmpE<gt>> block: B<Data> and B<Host>:
 
 There are two types of blocks that can be contained in the
 C<E<lt>PluginE<nbsp>snmpE<gt>> block: B<Data> and B<Host>:
 


@@ -81,15 +88,35 @@ defined.
 =item B<Table> I<true|false>
 
 Define if this is a single list of values or a table of values. The difference
 =item B<Table> I<true|false>
 
 Define if this is a single list of values or a table of values. The difference

-is that when querying a list of values from SNMP that data is going to be
-dispatched as one value-list to the daemon (i.E<nbsp>e.  one RRD file will be
-created). If the correcponding data-set needs more than one value (has more
-than one data-source) you will still need to configure more than one B<Values>
-(see below).
-
-If B<Table> is set to I<true> then the plugin will search the entire subtree
-and dispatch all values it can find. This is handy for the typical SNMP
-tables, such as the interface table (C<IF-MIB::ifTable>).
+is the following:
+
+When B<Table> is set to B<false>, the OIDs given to B<Values> (see below) are
+queried using the C<GET> SNMP command (see L<snmpget(1)>) and transmitted to
+collectd. B<One> value list is dispatched and, eventually, one file will be
+written.
+
+When B<Table> is set to B<true>, the OIDs given to B<Values> (see below) are
+queried using the C<GETNEXT> SNMP command until the subtree is left. After all
+the lists (think: all columns of the table) have been read B<several> values
+sets will be dispatches and, eventually, several files will be written. If you
+configure a B<Type> (see above) which needs more than one data source (for
+example C<if_octets> which needs C<rx> and C<tx>) you will need to specify more
+than one (two, in the example case) OIDs with the B<Values> option. This has
+nothing to do with the B<Table> setting.
+
+For example, if you want to query the number of users on a system, you can use
+C<HOST-RESOURCES-MIB::hrSystemNumUsers.0>. This is one value and belongs to one
+value list, therefore B<Table> must be set to B<false>. Please note that, in
+this case, you have to include the sequence number (zero in this case) in the
+OID.
+
+Counter example: If you want to query the interface table provided by the
+C<IF-MIB>, e.E<nbsp>g. the bytes transmitted. There are potentially many
+interfaces, so you will want to set B<Table> to B<true>. Because the
+C<if_octets> type needs two values, received and transmitted bytes, you need to
+specify two OIDs in the B<Values> setting, in this case likely
+C<IF-MIB::ifHCInOctets> and C<IF-MIB::ifHCOutOctets>. But, this is because of
+the B<Type> setting, not the B<Table> setting.

 
 Since the semantic of B<Instance> and B<Values> depends on this setting you
 need to set it before setting them. Doing vice verse will result in undefined
 
 Since the semantic of B<Instance> and B<Values> depends on this setting you
 need to set it before setting them. Doing vice verse will result in undefined


@@ -98,7 +125,7 @@ behavior.
 =item B<Instance> I<Instance>
 
 Sets the type-instance of the values that are dispatched. The meaning of this
 =item B<Instance> I<Instance>
 
 Sets the type-instance of the values that are dispatched. The meaning of this

-setting depends on wether B<Table> is set to I<true> or I<false>:
+setting depends on whether B<Table> is set to I<true> or I<false>:

 
 If B<Table> is set to I<true>, I<Instance> is interpreted as an SNMP-prefix
 that will return a list of strings. Those strings are then used as the actual
 
 If B<Table> is set to I<true>, I<Instance> is interpreted as an SNMP-prefix
 that will return a list of strings. Those strings are then used as the actual


@@ -142,7 +169,7 @@ Set the address to connect to.
 
 =item B<Version> B<1>|B<2>
 
 
 =item B<Version> B<1>|B<2>
 

-Set the SNMP version to use. When giving B<2> version 2c is actually used.
+Set the SNMP version to use. When giving B<2> version C<2c> is actually used.

 Version 3 is not supported by this plugin.
 
 =item B<Community> I<Community>
 Version 3 is not supported by this plugin.
 
 =item B<Community> I<Community>


@@ -170,11 +197,6 @@ wise to select a reasonable value once and never change it.
 
 =back
 
 
 =back
 

-=head1 BUGS
-
-All configured hosts are queried sequencially, so timeouts may cause gaps in
-graphs.
-

 =head1 SEE ALSO
 
 L<collectd(1)>,
 =head1 SEE ALSO
 
 L<collectd(1)>,