Starting with version 2.0, zenpacklib.py will ship as a separately installed ZenPack. This change offers several advantages over the earlier distribution method along with many new features and fixes. Existing ZenPacks based on earlier versions of zenpacklib.py should coexist peacefully with those based on the newer version, and eventual migration to version 2.0 should be relatively painless. Future versions of Zenoss-provided ZenPacks will use the newer ZenPackLib version as they are developed and released.
Migrating ZenPacks to 2.0¶
For the most part, migrating to ZenPackLib 2.0 should be straightforward and requires minimal changes to your ZenPack. These largely involve changing import statements where appropriate and removing the older zenpacklib.py files
ZenPacks based on ZenPackLib 2.0 will need to have a dependency set to prevent potential issues when installing or removing them. If ZenPackLib 2.0 is not installed, a dependent ZenPack should refuse to install until the dependency is met. Similarly, ZenPackLib 2.0 should refuse removal if dependent ZenPacks are still installed. To achieve this, make sure that the INSTALL_REQUIRES variable in the setup.py file contains the following:
INSTALL_REQUIRES = [‘ZenPacks.zenoss.ZenPackLib’]
Please note that “INSTALL_REQUIRES” may already contain entries, and these should be preserved if they exist.
This can also be configured in the GUI if the dependent ZenPack is installed in develop mode.
The __init__.py file will need its import statements changed.
from . import zenpacklib
from ZenPacks.zenoss.ZenPackLib import zenpacklib
CFG = zenpacklib.load_yaml()
remains unchanged unless some of the new logging capabilities are desired such as:
CFG = zenpacklib.load_yaml(verbose=True, level=10)
In addition, the statement (if it exists):
from . import schema
should be changed to:
schema = CFG.zenpack_module.schema
or added if it does not exist.
Care should also be taken to delete the zenpacklib.py and zenpacklib.pyc files in the ZenPack’s source directory, since leaving them in place may cause unforseen behavior.
Import statements should also be checked throughout any class overrides or other python files, since the statements will fail if they refer to the older zenpacklib.py.
The tag !ZenPackSpec is not necessary and should be removed from your yaml definitions.
Version 2.0 Logging¶
Logging has been substantially enhanced for ZenPackLib version 2.0 and provides numerous features to aid during development or troubleshooting. Logging can now be controlled on a per-ZenPack basis by supplying additional paramters to the “load_yaml()” method call in the ZenPack’s __init__.py.file:
The verbose parameter, if set to True, will enable logging for this particular ZenPack. We recommend setting verbose to True during ZenPack development so that various error messages can be seen. We also recommend returning this value to False prior to release of your ZenPack as some warning messages may not be useful to the end user.
The level paramter controls logging verbosity with the same numeric values used elsewhere in Zenoss. The default value is 30 (WARNING), but setting this to 20 (INFO) or 10 (DEBUG) may be useful during ZenPack development.
CFG = zenpacklib.load_yaml(verbose=True, level=10)
In this example, logging verbosity is enabled with at the DEBUG level.
Every class in ZenPackLib has a “LOG” attribute that can be called within any class override files you may have. For example, given the file BasicComponent.py class extension, logging features would be accessed as follows:
from . import schema class BasicComponent(schema.BasicComponent): """Class override for BasisComponent""" def hello_world(self): self.LOG.info("You called hello_world") return 'Hello World!'
Log messages generated within the new logging framework are written to the Zope logger (event.log) and can be viewed there. Logging used within class extension files will follow the verbosity and level parameters provided to the “load_yaml” method.
Please note that additional Zope configuration may be required to see log messages, since Zope configuration determines what is accepted for writing to its event log. For example, if Zope logging is set to “warn”, then any “info” or “debug” messages will not be logged regardless of the load_yaml parameters used. Zope logging in this case must be set to “info” for ZPL “info”, “warning”, and “critical” logging.
Older Versions of zenpacklib.py¶
The following applies to pre-2.0 versions of zenpacklib.py only. Starting with version 2.0, zenpacklib.py will ship as a separately installed ZenPack designed for use by dependent ZenPacks
Distributing zenpacklib.py with each ZenPack allows different ZenPacks in the same Zenoss system to use different versions of zenpacklib. This can make things simpler for the ZenPack author as they know which version of zenpacklib will be used. It will be the one that’s shipped with the ZenPack.
This approach does have the drawback of potentially forcing ZenPacks to be updated to include a new version of zenpacklib to support a new version of Zenoss. Care will be taken to make each zenpacklib version compatible with as many versions of Zenoss as possible. Furthermore, care will be taken to make future versions of Zenoss compatible with existing zenpacklib versions within reason.
The following table describes which versions of Zenoss are supported by different versions of zenpacklib.
|zenpacklib Version||Zenoss Versions|
|1.1||4.2 *, 5.0, 5.1, 5.2|
|1.0||4.2 *, 5.0, 5.1, 5.2|
Compatibility only considers <major>.<minor> versions of both zenpacklib and Zenoss. Maintenance or patch releases of each are always considered compatible.
Beginning with version 2.0, you can check the zenpacklib version with either:
from the command line, or by navigating to:
Advanced -> Settings -> ZenPacks
in the Zenoss GUI
You can check which version of zenpacklib you’re using in two ways. The first is by using the version command line option.
python zenpacklib.py version
If you have ZenPack code that needs the version it can also be accessed from Python code that has imported zenpacklib module through the module’s __version__ property.
from . import zenpacklib zenpacklib.__version__
Beginning with version 2.0, the ZenPacks.zenoss.ZenPackLib ZenPack will refuse to install unless PyYAML is already installed
zenpacklib requires that PyYAML be installed in the Zenoss system. PyYAML was not a standard part of a Zenoss system until Zenoss 5. To use zenpacklib, or to use a ZenPack built with zenpacklib on a Zenoss 4.2 system you must first make sure that PyYAML is installed.
PyYAML has been added to Zenoss 4.2.5 as of SP457, and Zenoss 4.2.4 as of SP776.
Checking for PyYAML¶
On your main Zenoss 4.2 server run the following command to check for PyYAML.
su - zenoss -c "python -c 'import yaml;print yaml.version'"
You will see the version of PyYAML if it installed.
You will see the following error if PyYAML is not installed.
Traceback (most recent call last): File "<string>", line 1, in <module> ImportError: No module named yaml
Run the following command to install PyYAML if it isn’t already installed.
su - zenoss -c "easy_install PyYAML"
It’s normal for the easy_install command to print many errors and warnings even when it successfully installs. Run the first command to verify it’s installed when complete.
If your Zenoss system is distributed to multiple servers for hubs, collectors, or any other reason you will need to update those hubs and collectors after installing PyYAML to make sure it also gets installed on them.