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Deprecating Code

Our Ansible modules follow a strategy of deprecation which is intended to give the user of the modules ample time to upgrade to a new version of Ansible.

New releases of Ansible happen, at the time of this writing, about once a quarter.

With this in mind, the following process should allow a user 3 to 6 months to upgrade their Ansible installation to the new code. If the user misses this 3 to 6 month period, then they can upgrade incrementally (2.1 -> 2.2 -> 2.3) instead of upgrading directly to the latest version and, in the process, test that the incremental versions work with their playbooks.

Deprecation process

Let’s look at an example deprecation process

  • 2.0 - version to deprecate
  • 2.1 - deprecated version
  • 2.2 - version with deprecated feature removed

During the second release noted above, the module developer MUST insert adequate warnings for the user to see. Ansible will color warning messages so that they stick out from regular messages.

Raising deprecated warnings

To raise warnings about deprecated functionality, the module developer should add the following method to their ModuleManager class.

Additionally, the module developer should add the calling of that method when they collect the changes to report to the user. For example,

And finally, the module developer should populate the __warnings key of their changes attribute as needed. For example, in the bigip_gtm_wide_ip module, the following is used in the lb_method property when it sees you are using an option name that is deprecated. For example,

The changes attribute is typically updated during the call to _update_changed_options during update, or _set_changed_options during create.

If your module needs to detect changes outside of those two general methods, you should be doing so inside of the should_update method.

Note

To do your own ad-hoc detection inside of should_update, you will need to overload the base classes’ method. If you do this, you should decide whether or not it is still necessary to call the base classes’ method during the call to your overloaded method.

With that in place, you will find yourself with warning messages being raised by Ansible when you use the deprecated functionality.

Deprecating parameters

Below is an excerpt from how one might deprecate an option that we no longer want to use. You may do this for a number of reasons, but in most cases it is due to the original name not making sense in the context it is used.

For example, you might have named the original option rules when the more appropriate name for the option would have been irules.

Note

Ansible allows for aliasing of options so that specifying one is equivalent to specifying another. This is not the situation that we are referring to here. It is still perfectly acceptable to use option aliases if you want to. These guidelines are for when you specifically want to remove options that are presumably already in use.

Here is a sample ArgumentSpec from the version where we made the mistake. Let’s assume that this mistake was made in version 2.0.

Now, we wish to deprecate that option name. So, in version 2.1 of Ansible, we would do something like this.

Additionally, we would include the warnings necessary to make the user of the module aware that they are using deprecated functionality (the rules option).

Finally, during the release cycle of Ansible 2.2, we would want to change our spec to look like so.

Thus, removing the deprecated functionality.

Also, do not forget to remove any mention of the deprecation inside the actual module code. We don’t want the legacy code to stick around. This helps keep technical debt at bay.