Fix error when there are no docker volumes present yet

[underwaynyc]

SUMMARY

The existing code will attempt to iterate over None. A quick if statement protects the for loop and returns None. Return of None because there are no volumes.

ISSUE TYPE

• Bugfix Pull Request

COMPONENT NAME

In the cloud module, in the docker module, the docker_volume command

ANSIBLE VERSION

ansible 2.4.0 (devel cd32ed1929) last updated 2017/08/14 04:01:47 (GMT +000)
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/home/underway/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /home/underway/underway-server/ansible-fork/lib/ansible
  executable location = /home/underway/underway-server/ansible-fork/bin/ansible
  python version = 2.7.13 (default, Jan 19 2017, 14:48:08) [GCC 6.3.0 20170118]

ADDITIONAL INFORMATION

Attempt to create a volume, where there isn't one on the server yet. Manually do docker volume ls -q | xargs docker volume rm if needed

- name: Install pip
   easy_install:
    name: pip
    ��state: present

- name: Install docker-py via pip
   pip:
    name: docker-py
    state: present

- name: Create docker volume
  docker_volume:
     name: volume_name
     state: present

Before:

TASK [Create docker volume] *******************************************************************************************fatal: [HOST_NAME]: FAILED! => {"changed": false, "failed": true, "module_stderr": "Shared connection to HOST_NAME closed.\r\n", "module_stdout": "Traceback (most recent call last):\r\n  File \"/tmp/ansible_wJEYrH/ansible_module_docker_volume.py\", line 254, in <module>\r\n    main()\r\n  File \"/tmp/ansible_wJEYrH/ansible_module_docker_volume.py\", line 249, in main\r\n    cm = DockerVolumeManager(client)\r\n  File \"/tmp/ansible_wJEYrH/ansible_module_docker_volume.py\", line 138, in __init__\r\n    self.existing_volume = self.get_existing_volume()\r\n  File \"/tmp/ansible_wJEYrH/ansible_module_docker_volume.py\", line 152, in get_existing_volume\r\n    for volume in volumes[u'Volumes']:\r\nTypeError: 'NoneType' object is not iterable\r\n", "msg": "MODULE FAILURE", "rc": 0}
        to retry, use: --limit @RETRY_FILE.retry

After:

TASK [Create docker volume ] ****************************************************************************************************changed: [HOSTNAME]

[ansibot]

cc @agronholm
click here for bot help

[ansibot]

The test ansible-test sanity --test pep8 failed with the following errors:

lib/ansible/modules/cloud/docker/docker_volume.py:152:32: E711 comparison to None should be 'if cond is None:'
lib/ansible/modules/cloud/docker/docker_volume.py:154:1: W293 blank line contains whitespace

click here for bot help

[danramteke]

@chouseknecht @alikins Any word on this? Would love to get this fix in (or someone else's fix for the same error) so I can go back to using Ansible's master branch.

[agronholm]

@chouseknecht it's too bad this didn't make it into 2.4.0.0, but it should be merged ASAP. I could not imagine that the Docker API would give a None instead of an empty list when there are no volumes.

[s-hertel]

rebuild_merge