+# 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
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 information provided in the
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
=item
-This plugin is not compatible with python3. Trying to compile it with python3
-will fail because of the ways string, unicode and bytearray behavior 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