Fix nagios module to recognize if file exists and is fifo pipe

[Klaas-]

SUMMARY

Ansible nagios module does not check if cmdfile is actually a fifo file. If the file does not exist (for example nagios is not started, it will create a normal file. If the file exists nagios won't start.

ISSUE TYPE

• Bugfix Pull Request

COMPONENT NAME

lib/ansible/modules/monitoring/nagios.py

ADDITIONAL INFORMATION

Before change:

[klaas@notebook ~]$ file /home/klaas/test.file
/home/klaas/test.file: cannot open `/home/klaas/test.file' (No such file or directory)
[klaas@notebook ~]$ ansible -i "localhost," --connection local -m nagios -a "action=downtime cmdfile=/home/klaas/test.file command=host comment=test host=test.tld services=host " all
[DEPRECATION WARNING]: Distribution fedora 30 on host localhost should use /usr/bin/python3, but is using /usr/bin/python for backward compatibility 
with prior Ansible releases. A future Ansible release will default to using the discovered platform python for this host. See 
https://docs.ansible.com/ansible/2.8/reference_appendices/interpreter_discovery.html for more information. This feature will be removed in version 
2.12. Deprecation warnings can be disabled by setting deprecation_warnings=False in ansible.cfg.
localhost | CHANGED => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python"
    },
    "changed": true,
    "nagios_commands": [
        "[1561907405] SCHEDULE_HOST_DOWNTIME;test.tld;1561907405;1561909205;1;0;1800;Ansible;test"
    ]
}
[klaas@notebook ~]$ file /home/klaas/test.file
/home/klaas/test.file: JSON data

After change (file doesn't exist):

[klaas@notebook ~]$ rm test.file 
[klaas@notebook ~]$ ansible -i "localhost," --connection local -m nagios -a "action=downtime cmdfile=/home/klaas/test.file command=host comment=test host=test.tld services=host" all
[DEPRECATION WARNING]: Distribution fedora 30 on host localhost should use /usr/bin/python3, but is using /usr/bin/python for backward compatibility 
with prior Ansible releases. A future Ansible release will default to using the discovered platform python for this host. See 
https://docs.ansible.com/ansible/2.8/reference_appendices/interpreter_discovery.html for more information. This feature will be removed in version 
2.12. Deprecation warnings can be disabled by setting deprecation_warnings=False in ansible.cfg.
localhost | FAILED! => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python"
    },
    "changed": false,
    "cmdfile": "/home/klaas/test.file",
    "msg": "nagios command file does not exist"
}

After change file not fifo:

[klaas@notebook ~]$ touch test.file
[klaas@notebook ~]$ ansible -i "localhost," --connection local -m nagios -a "action=downtime cmdfile=/home/klaas/test.file command=host comment=test host=test.tld services=host" all
[DEPRECATION WARNING]: Distribution fedora 30 on host localhost should use /usr/bin/python3, but is using /usr/bin/python for backward compatibility 
with prior Ansible releases. A future Ansible release will default to using the discovered platform python for this host. See 
https://docs.ansible.com/ansible/2.8/reference_appendices/interpreter_discovery.html for more information. This feature will be removed in version 
2.12. Deprecation warnings can be disabled by setting deprecation_warnings=False in ansible.cfg.
localhost | FAILED! => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python"
    },
    "changed": false,
    "cmdfile": "/home/klaas/test.file",
    "msg": "nagios command file is not a fifo file"
}

After change file is fifo: (you'll need to cat test.file from another shell)

[klaas@notebook ~]$ mkfifo test.file
[klaas@notebook ~]$ ansible -i "localhost," --connection local -m nagios -a "action=downtime cmdfile=/home/klaas/test.file command=host comment=test host=test.tld services=host" all
[DEPRECATION WARNING]: Distribution fedora 30 on host localhost should use /usr/bin/python3, but is using /usr/bin/python for backward compatibility 
with prior Ansible releases. A future Ansible release will default to using the discovered platform python for this host. See 
https://docs.ansible.com/ansible/2.8/reference_appendices/interpreter_discovery.html for more information. This feature will be removed in version 
2.12. Deprecation warnings can be disabled by setting deprecation_warnings=False in ansible.cfg.
localhost | CHANGED => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python"
    },
    "changed": true,
    "nagios_commands": [
        "[1561909146] SCHEDULE_HOST_DOWNTIME;test.tld;1561909146;1561910946;1;0;1800;Ansible;test"
    ]
}

[ansibot]

cc @tbielawa
click here for bot help

[felixfontein]

I think this looks ok. You need a changelog fragment, though.

[Klaas-]

@felixfontein thanks for looking over this -- added the changelog fragement

[ansibot]

@Klaas- This PR contains @ mentions in at least one commit message. Those mentions can cause cascading notifications through GitHub and need to be removed. Please squash or amend your commits to remove the mentions.

click here for bot help

[Klaas-]

fixed the issue with the @ in commit message and squashed the two commits

[felixfontein]

LGTM

[felixfontein]

@Klaas- thank you very much for fixing this! I'll create a backport PR so this will hopefully be included in the next 2.8.x release.