Development Environment

The process of developing a ZenPack can be made much faster and less frustrating by starting with a good development environment. The following development environment setup is only a set of recommendations. If you already have tools or techniques that you’re more comfortable with or you consider superior, you should use them.

Installing Zenoss

To best develop and deploy ZenPacks into a production environment, I recommend having three Zenoss systems: development, staging and production.

Development Zenoss System

Your development Zenoss system should not be shared with others, and should be as minimal an installation as possible. This will allow for problems to be diagnosed, fixed and tested as quickly as possible.

I recommend installing Zenoss from the single zenoss-x.y.z RPM on Red Hat Enterprise Linux or CentOS. The Zenoss installation instructions will ordinarily have you install a zenoss-core-zenpacks RPM, and a zenoss- enterprise-zenpacks RPM for commercial Zenoss customers. To keep the system as small as possible, these should not be installed into your ZenPack development system.

Staging Zenoss System

The staging Zenoss system should be shared by all ZenPack developers. After a ZenPack has been successfully tested in the development system should it be installed into the staging environment.

This system should mimic the production system as closely as possible. It should be installed in the same way as the production system, and should have the same base set of ZenPacks installed. The purpose of the staging system is to do final integration testing before ZenPacks are installed into the production system.

Production Zenoss System

New ZenPacks and updates to existing ZenPacks should only be deployed into the production system after they’ve been successfully tested in the development and staging systems.

Running a Minimal Zenoss

Often times ZenPack development is done within virtual machines, or spare hardware that doesn’t have the same resources as a production Zenoss system. Additionally, during development you will need to restart Zenoss far more frequently than in a production setup. For these reasons you will want to run as little of Zenoss as necessary.

After installing your Zenoss development system, run the following commands to reduce your Zenoss deployment to the minimum typical processes.

su - zenoss
zenoss stop

cat > $ZENHOME/etc/daemons.txt << EOF
zeneventserver
zopectl
zeneventd
zenhub
zenjobs
EOF

touch $ZENHOME/etc/DAEMONS_TXT_ONLY

zenoss start

Note

For the commercial version of Zenoss you will need to add zencatalogservice to the top of daemons.txt.

See the following notes for more information on what these commands are doing.

  1. The su - zenoss command is an important one that you’ll be using very frequently. This command switches from the root user to the zenoss user. The hyphen (-) creates what’s called a login shell. This means that the zenoss user’s full environment will be loaded. This full environment is necessary to run any Zenoss commands.
  2. The zenoss stop command stops all Zenoss processes.
  3. The cat > ... that ends with EOF on a blank line writes those specific daemon names into the $ZENHOME/etc/daemons.txt file. This file contains the names of any daemons in addition to the default that should be started, stopped and otherwise managed by the zenoss master control script.
  4. The touch $ZENHOME/etc/DAEMONS_TXT_ONLY command will cause the zenoss master control script to only manage daemons listed in the aforementioned daemons.txt file.
  5. The zenoss start command will only start daemons listed in daemons.txt.

Running Zenoss in the Foreground

To take your development and debugging environment to the next level, I recommend running most Zenoss processes in the foreground with full debug logging enabled. This allows you to easily see exactly what is happening, and provides a very quick way, CTRL-C, to stop and start individual processes. Perhaps the most useful benefit is that you can use the Python debugger to set breakpoints without having them hang background daemons.

The zeneventserver process is the only process that I recommend running as a daemon while developing ZenPacks. This is because there are no changes you can make while developing a ZenPack that require restarting zeneventserver. There’s also no common reason you’d want to see its debugging output.

You can open multiple SSH sessions to your Zenoss server, or use the GNU screen or tmux terminal multiplexers to simultaneously run Zenoss processes in the foreground.

Open five (5) sessions as the zenoss user on your zenoss server using any of the aforementioned methods. The sessions should run the following commands respectively:

  1. zopectl fg
  2. zeneventd run -v10
  3. zenhub run -v10 --workers=0
  4. zenjobs run -v10 --cycle
  5. nothing: miscellaneous shell work is done here

The -v10 option enables DEBUG level logging for the process. The --workers=0 option to zenhub is important to prevent zenhub from spawning other worker process to do work. If work was performed in a worker process you may not have foreground visibility to it. The --cycle option to zenjobs is necessary to prevent it from executing all current pending jobs then exiting.

Installing ZenPacks

ZenPacks can be installed either from a packaged .egg file, or from a source directory. The only situations in which I recommend installing from a packaged egg is for the ZenPacks that ship with Zenoss and are automatically installed from their .egg file, and when the source is not available.

There are some important reasons why installing in development mode from a source directory is preferable. They include:

  • The running ZenPack code can be a checkout from version control. This makes it easier to audit ZenPack code for changes.
  • ZenPacks can be upgraded in-place. Depending on the changes, this can often allow for less Zenoss daemons needing to be restarted after upgrading a ZenPack.

When a new ZenPack is created in the user interface, it is created in development mode with the source directory located in $ZENHOME/ZenPacks/. To install or upgrade an existing ZenPack from it’s source directory, the --link option is used as follows.

zenpack --link --install $ZENHOME/ZenPacks/ZenPacks.namespace.ZenPackName