3 Mar
2021
3 Mar
'21
11:42 a.m.
Branch: refs/heads/master
Home: https://github.com/tribe29/checkmk
Commit: 45b981b1ff3b59f9dace1449a796874a7a6025cc
https://github.com/tribe29/checkmk/commit/45b981b1ff3b59f9dace1449a796874a7…
Author: Andreas Umbreit <andreas.umbreit(a)tribe29.com>
Date: 2021-03-03 (Wed, 03 Mar 2021)
Changed paths:
A .werks/12149
Log Message:
-----------
12149 Support for Python 2 Agent Plugins
With Werk #11080, we made the huge step to port the entire Checkmk
codebase from Python 2 to Python 3. This also affects all Python based
agent plugins, that can be found under
<tt>~/share/check_mk/agents/plugins</tt>
and that can be deployed via the agent bakery or manually.
However, there are still many UNIX systems out there that don't support Python 3
yet. In order to still ensure a functional monitoring on these hosts, all
builtin Python based agent plugins now also support Python 2.
<h3>Automatic Python 3/Python 2 agent plugin mechanism</h3>
This is realized by the following mechanism:
<ul>
<li>All python based agent plugins are written in Python 3 and end with
<tt>.py</tt></li>
<li>For all builtin Python 3 agent plugins, an additional Python 2 plugin is
available,
that ends with <tt>_2.py</tt>. E.g., you will find a Python 2 agent plugin
named
<tt>apache_status_2.py</tt> right next to it's Python 3 counterpart
<tt>apache_status.py</tt></li>.
<li>When deploying the agent plugin via agent bakery, both files will be deployed
via the agent package. The UNIX agent will then automatically decide which file
will be executed. If there is a Python installation >= 3.4 available on the system,
the Python 3 variant will be executed. If there is instead a Python installation >=
2.6
available, the Python 2 variant will be executed. If none of the two variants are
available, the plugin won't be executed.</li>
<li>When deploying manually, the same mechanism holds true. You just have to
include
both files, if you want to make use of this feature. Please note that a python based
plugin must end with <tt>_2.py</tt> to be executed via Python 2.</li>
</ul>
<h3>New agent rule "Python agent plugin execution (UNIX)"</h3>
The agent will detect a Python 3 installation by the command <tt>python3</tt>
and a
Python 2 installation by the commands <tt>python2</tt> or
<tt>python</tt>. If this
mechanism is not suitable for you, or if you want to use Python 2, even if there
is a Python 3 installation available, there exists a new agent ruleset called
"Python agent plugin execution (UNIX)" for that purpose. Here, you can enforce
either
Python 2 or Python 3. Additionally, you can provide a custom Python command, if your
host's Python installation differs from one of the above mentioned commands.
<h3>New error communication</h3>
If the Python based plugins can't be executed on a host system, either because there
is no
suitable Python installation available, or the manually configured command doesn't
exist, you will be noticed via the Check_MK service of the host, that will show
a suitable error message and yield a <tt>WARN</tt> state.
This also means that the Checkmk agent package installation will no longer fail
if there is no suitable Python installation available.
<h3>Incompatibilities</h3>
This Werk is marked as incompatible due to some circumstances:
<ul>
<li>Due to the fact that Python based plugins now require a <tt>.py</tt>
ending, some builtin
plugins had to be renamed. You'll have to consider this when deploying via
a custom script that references the plugin's path on the Checkmk site. However, the
agent bakery will still choose the right files.</li>
<li>As Python 3 is the new default, and Python 2 was the old default, many Python
based plugins
will silently be executed with a different interpreter as before. If you still want Python
2,
(and there is a Python 3 installation that would get chosen automatically,) you'll
have to
configure the above mentioned rule (if deploying via agent bakery), or explicitly deploy
the
<tt>_2.py</tt> version.</li>
<li>When deploying your own Python based agent plugins, you have to keep in mind
that a Python 3
plugin has to end with <tt>.py</tt> and a Python 2 plugin has to end with
<tt>_.py</tt>.
In particular, the shebang (if any) will be ignored. If you explicitly wish to disable
this
mechanism, you can still write your Python based plugins as an executable script without
a
<tt>.py</tt> suffix (Of course, the shebang will be used, then).</li>
</ul>
CMK-7318
Change-Id: I3803743a983a0eedce6f439c08978a4b727a415d