Allow filtering of instances by tags in GCE dynamic inventory

[pschiffe]

SUMMARY

This enables to exclude instances in the project not relevant to the play, what benefits performance and can help to avoid mistakes.

ISSUE TYPE

• Feature Pull Request

COMPONENT NAME

GCE dynamic inventory

ANSIBLE VERSION

ansible 2.4.2.0
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/home/pschiffe/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/site-packages/ansible
  executable location = /usr/bin/ansible
  python version = 2.7.14 (default, Jan 17 2018, 14:28:32) [GCC 7.2.1 20170915 (Red Hat 7.2.1-2)]

/cc @smarterclayton

[smarterclayton]

We’ve found value in this in automation where many inventories are in the same GCP project. The filter prevents accidental typos from blowing out every host within the project. Effectively a safety barrier for automation.

[pschiffe]

/cc @maciej-lasyk @Asher256 @dohoangkhiem @calfonso @abadger @sivel

[samdoran]

Rather than using conditionals for each option, which can be a bit expensive, set a default value when the config object is created. Then you can just call config.get() and it will use the default if the key isn't in the file, or it will pull the value from the key in the file.

[ansibot]

The test ansible-test sanity --test pep8 [explain] failed with 1 error:

contrib/inventory/gce.py:257:21: E128 continuation line under-indented for visual indent

click here for bot help

[samdoran]

rebuild_merge

[samdoran]

@pschiffe There is a new inventory plugin system in Ansible. In the near future, we will stop accepting new features to scripts in favor of using inventory plugins. While we don't have docs yet, I can point you at some good examples of existing inventory plugins if you're interested in porting this to a plugin.

openstack.py
virtualbox.py

Thanks for your contribution!