# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
+=encoding UTF-8
+
=head1 NAME
collectd-python - Documentation of collectd's C<python plugin>
=head1 SYNOPSIS
- <LoadPlugin python>
- Globals true
- </LoadPlugin>
+ LoadPlugin python
# ...
<Plugin python>
ModulePath "/path/to/your/python/modules"
=item B<LoadPlugin> I<Plugin>
-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 embedded
-interpreter will start anyway but you won't be able to load certain Python
-modules, e.g. "time".
+Loads the Python plugin I<Plugin>.
=item B<Encoding> I<Name>
=over 4
-=item
+=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
+=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,
To quit collectd send I<EOF> (press I<Ctrl+D> at the beginning of a new line).
-=item
+=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
=item configuration functions
-This type of functions is called during configuration if an appropriate
+These are called during configuration if an appropriate
B<Module> block has been encountered. It is called once for each B<Module>
block which matches the name of the callback as provided with the
B<register_config> method - see below.
=item init functions
-This type of functions is called once after loading the module and before any
+These are called once after loading the module and before any
calls to the read and write functions. It should be used to initialize the
internal state of the plugin (e.E<nbsp>g. open sockets, ...). This is the
earliest point where you may use threads.
=item read functions
-This type of function is used to collect the actual data. It is called once
+These are used to collect the actual data. It is called once
per interval (see the B<Interval> configuration option of collectd). Usually
it will call B<plugin_dispatch_values> to dispatch the values to collectd
which will pass them on to all registered B<write functions>. If this function
=item write functions
-This type of function is used to write the dispatched values. It is called
+These are used to write the dispatched values. It is called
once for every value that was dispatched by any plugin.
=item flush functions
-This type of function is used to flush internal caches of plugins. It is
+These are used to flush internal caches of plugins. It is
usually triggered by the user only. Any plugin which caches data before
writing it to disk should provide this kind of callback function.
=item log functions
-This type of function is used to pass messages of plugins or the daemon itself
+These are used to pass messages of plugins or the daemon itself
to the user.
=item notification function
-This type of function is used to act upon notifications. In general, a
+These are used to act upon notifications. In general, a
notification is a status message that may be associated with a data instance.
Usually, a notification is generated by the daemon if a configured threshold
has been exceeded (see the section "THRESHOLD CONFIGURATION" in
=over 4
-=item
+=item *
I<callback> is a callable object that will be called every time the event is
triggered.
-=item
+=item *
I<data> is an optional object that will be passed back to the callback function
every time it is called. If you omit this parameter no object is passed back to
your callback, not even None.
-=item
+=item *
I<name> is an optional identifier for this callback. The default name is
B<python>.I<module>. I<module> is taken from the B<__module__> attribute of
your callback function. Every callback needs a unique identifier, so if you
-want to register the same callback multiple time in the same module you need to
-specify a name here. Otherwise it's save to ignore this parameter I<identifier>
-is the full identifier assigned to this callback.
+want to register the same callback multiple times in the same module you need to
+specify a name here. Otherwise it's safe to ignore this parameter.
+
+=item *
+
+I<identifier> is the full identifier assigned to this callback.
=back
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 B<flush>(I<plugin[, timeout][, identifier]) -> None
Flush one or all plugins. I<timeout> and the specified I<identifiers> are
passed on to the registered flush-callbacks. If omitted, the timeout defaults
=over 4
-=item
+=item *
Please feel free to send in new plugins to collectd's mailing list at
E<lt>collectdE<nbsp>atE<nbsp>verplant.orgE<gt> for review and, possibly,
=over 4
-=item
+=item *
collectd is heavily multi-threaded. Each collectd thread accessing the Python
plugin will be mapped to a Python interpreter thread. Any such thread will be
from collectd (i.E<nbsp>e. if it registers more than one callback or if a
registered callback may be called more than once in parallel).
-=item
+=item *
The Python thread module is initialized just before calling the init callbacks.
This means you must not use Python's threading module prior to this point. This
includes all config and possibly other callback as well.
-=item
+=item *
The python plugin exports the internal API of collectd which is considered
unstable and subject to change at any time. We try hard to not break backwards
=over 4
-=item
+=item *
Not all aspects of the collectd API are accessible from Python. This includes
but is not limited to filters and data sets.
projects / collectd.git / blobdiff