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inqbus.ocf.agents 0.11

OCF resource agents based on inqbus.ocf.generic

Overview

OCF compatible resource agent classes programmed in python. Usually OCF-Agents are written as unix shell-script. We are running lots of high avaible python processes which are controlled by pacemaker. Using shell for controlling Python processes feels awkward, so we builded a python integration framework for OCF compatible agents.

What do you get

This package gives you some generic OCF agent classes for PID controlled daemons:

  • pidagent
  • openvpn

based on the inqbus.ocf.generic framework.

The inqbus.ocf.generic framework keeps away from you the gory details you have to go into writing an OCF compatible resource agent. Powerfull base classes bring to you:

  • A good test coverage of the agent code (How to test a shell script?)
  • Support of the complete set of OCF exitcodes and their respective business logik
  • OCF Paramter classes for integer, string, etc. values
  • Predefined generic OCF handlers (meta-data, validate)
  • The generation of the XML meta data is done for you automagically
  • Easy addition of handlers for e.g. start/stop/status
  • Inheritance of resource agents: encapsulate agent business logic and share it among similiar reasource agents

Inqbus.ocf.agents in addition brings the following functionality

  • the business logic for controlling the PID file
  • checking for the running state of the PID
  • starting and stopping the daemon (with checking for zombies and staggered kill signals to bring a process really down if it has to die)
  • checking for the PID status

in the base class PIDBaseAgent.

What is missing

We did not implement any business logic for the actions:

  • notify
  • demote
  • promote
  • master/slave
  • reload

but inqbus.ocf.generic framework can represent any OCF action that is specified yet or in the future - just implement a handler for the desired action:

class MyAgent(Agent):

    def config(self):
        """
        Register my actions
        """
        self.handlers['notify'] = Handler(MyAgent.do_notify, 10)
        self.handlers['future'] = Handler(MyAgent.do_future, 10)

Implementation

The PIDAgent and Openvpn classes are derived from PIDBaseAgent with minimal programming efford:

from pidbaseagent import PIDBaseAgent
from inqbus.ocf.generic.parameter import OCFString

class PIDAgent(PIDBaseAgent):

    def add_params(self):
        self.add_parameter(OCFString("executable",
                            longdesc="Path to the executable",
                            shortdesc="executable",
                            required= True) )
        self.add_parameter(OCFString( "pid_file",
                            longdesc="Path to the pid file",
                            shortdesc="executable",
                            required= True) )

    def get_pid_file(self):
        """tell the base class to find the PID file in the parameter 'pid_file'"""
        return self.params.pid_file.value

    def get_executable(self):
        """tell the base class how to find the executable path in the parameter 'executable'"""
        return self.params.executable.value

def main():
    """Entry point for the reasource agent shellscript"""
    import sys
    PIDAgent().run(sys.argv)

if __name__ == "__main__" : main()
    """Entry point for the command line"""

To use the inqbus.ocf.agents agent classes you need to set only one symlink per agent class into your Pacemaker (or other OCF HA) system.

Building arbitrary resource agent classes e.g. for IP addresses is easy utilizing the inqbus.ocf.generic <http://pypi.python.org/inqbus.ocf.generic>_ framework.

Documentation

Note

The dokumentation is not uploaded to packages.python.org yet. Please stay tuned.

This file and the source files for openvpn and the PIDAgent classes serve as a simple introduction to inqbus.ocf.agents. For more in depth documentation on writing your own reasource agents with the inqbus.ocf framework, have a look at

Requirements

Python >=2.7 or Python 3.x

Installation

We recomment a buildout based installation into a virtual environment but you may install inqbus.ocf.agents via pip or easy_install as well.

Installation via buildout

Note

This installation guide asumes /opt/ocf as installation directory. Please adjust the installation directory to your needs.

Build a virtual environment:

:/opt$ virtualenv --no-site-packages ocf
:/opt$ cd ocf
:/opt/ocf$ source bin/activate
(ocf):/opt/ocf$

Install the make environment buildout and initialize it:

(ocf):/opt/ocf$ easy_install zc.buildout
(ocf):/opt/ocf$ ./bin/buildout init

Create a buildout.cfg:

[buildout]
parts = app
        pidagent
        openvpn

# Buildout directories to use.
eggs-directory          = eggs

###############################################################################
# Download links for packages
# -----------------------------------------------------------------------------
# Add additional egg download sources here.
# Note that pypi.propertyshelf.com and mypypi.inqbus.de require authentication.
find-links = http://mypypi.inqbus.de/privateEggs

###############################################################################
# Extensions
# -----------------------------------------------------------------------------
# Load several extensions.
extensions = lovely.buildouthttp

[app]
recipe = z3c.recipe.scripts
eggs = inqbus.ocf.agents
interpreter = python_ocf

[openvpn]
recipe = collective.recipe.template
output = ${buildout:directory}/bin/openvpn.sh
inline =
    #!/bin/bash
    ${buildout:directory}/../bin/python ${buildout:directory}/bin/openvpn $*
mode = 755

[pidagent]
recipe = collective.recipe.template
output = ${buildout:directory}/bin/pidagent.sh
inline =
    #!/bin/bash
    ${buildout:directory}/../bin/python ${buildout:directory}/bin/pidagent $*
mode = 755

run buildout to install the package:

(ocf):/opt/ocf$ ./bin/buildout

Note

There will be to executable files installed for each agent. E.g. for the openvpn agent:

openvpn
    A python console script, referencing the python interpreter with an
    appropriate python path.

openvpn.sh
    A bash console wrapper around the openvpn python console script.
    This is a tribute to pacemaker which calls the agent via the bash interpreter.
    These kind of wrapper scripts you have to use as agents for pacemaker.

Configuration

First check the installation:

(ocf):/opt/ocf$ ./bin/openvpn.sh
Usage: openvpn.py <start|validate-all|stop|monitor|meta-data>

Note

You have to identify the OCF agent location of your OS to proceed. On Debian the OCF agents live under:

/usr/lib/ocf/resource.d/

Also you are free to set a provider directory for the agents. Here we asume as provider name

inqbus

Integrating the openvpn agent class into Pacemaker:

:/opt/ocf$ cd /usr/lib/ocf/resource.d/
:/usr/lib/ocf/resource.d/$ mkdir inqbus
:/usr/lib/ocf/resource.d/$ cd inqbus
:/usr/lib/ocf/resource.d/inqbus$ ln -s /opt/ocf/bin/openvpn.sh .

Note

You may repeat this last line with other resource agent classes (also available yet: pidagent):

:/usr/lib/ocf/resource.d/inqbus$ ln -s /opt/ocf/bin/pidagent.sh .

Now the configuration is complete an you can use the OCF python resource agents as the others that came with heartbeat or pacemaker.

Running the tests

The test are formulated using the nose testing framework.

Note

Please be carefull running the tests! The tests will use the TEMP-Directory and create some files in there. More agressivly the tests will bring up unix-processes since the agents are intended to do exactly that thing. PIDagent will use the harmless dummy_daemon implementation of a NOOP unix daemon that comes with this package. The OpenVPN-Agent will try to start a true openvpn-instance at localhost:1194.

To run the tests you need the source code. There are two ways to obtain it.

  1. Clone the Mercurial repository from BitBucket:

    $ hg clone https://bitbucket.org/inqbus/inqbus.ocf.agents
    
  1. Download the package from PyPI and unpack it:

    $ wget http://pypi.python.org/packages/source/i/inqbus.ocf.agents/inqbus.ocf.agents-0.1.tar.gz
    $ tar xzvf inqbus.ocf.agents-0.1.tar.gz
    

Testing with buildout

The easiest way to test is with buildout:

$ ./bin/buildout
...
$ ./bin/nose --with-coverage
...
inqbus.ocf.agents.openvpn            91%
inqbus.ocf.agents.pidagent           83%
inqbus.ocf.agents.pidbaseagent       74%
inqbus.ocf.generic.agent             88%
inqbus.ocf.generic.container         100%
inqbus.ocf.generic.exits             84%
inqbus.ocf.generic.handlers          96%
inqbus.ocf.generic.parameter         83%

The test coverage is high. We includet the ocf-tester testcases in our test suite. Maximum testcoverage is only possible if running the tests as root since most of the tests are integration tests, which steer real unix daemons. In case of the openvpn agent a real openvpn instance is brought up.

Dispite the high level of testing there is still a portion of 10 to 26% of untested code. This code mainly attributes to the many plausability exits that are not easily tested. How should we test for a broken filesystem or a process that has become a zombie? If you think you have the answer to that questions, you are warmest welcome in the development team.

Testing with ocf-tester

Independently of the python tests pacemaker comes with the ocf-tester script. You may use the dummy_daemon that comes with inqbus.ocf.agents to test the pidagent:

:/opt/ocf/buildout$ ocf-tester -n test \
-o pid_file=/tmp/dummy_daemon.pid \
-o executable=./bin/dummy_daemon \
`pwd`/bin/pidagent.sh

Bugs and Issues

This software is work in progress. Please help us to improve it: https://bitbucket.org/inqbus/inqbus.ocf.agents

Please contact volker.jaenisch@inqbus.de if you have any question.

License

This software is licensed under the New BSD License. See the LICENSE.txt file in the top distribution directory for the full license text. Changelog =========

0.1 (unreleased)

  • Initial release

0.11 (bugfix-release)

  • added "cd to config dir" paramter for openvpn agent.
  • introduced ovpn_pid_dir paramter for openvpn agent.
  • fixed some flaws in README.txt
  • fixed that temporary files are deletetd from /tmp after tests
 
File Type Py Version Uploaded on Size
inqbus.ocf.agents-0.11-py2.6.egg (md5) Python Egg 2.6 2011-12-04 39KB
inqbus.ocf.agents-0.11.tar.gz (md5) Source 2011-12-04 15KB
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