+# 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 I<Python 2> is supported and at least I<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>
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
+
+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
=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
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, 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, i.e. words following the
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
=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
-This plugin is not compatible with python3. Trying to compile it with python3
-will fail because of the ways string, unicode and bytearray bahavior was
-changed.
-
-=item
-
Not all aspects of the collectd API are accessible from python. This includes
-but is not limited to meta-data, filters and data sets.
+but is not limited to filters and data sets.
=back
projects / collectd.git / blobdiff