How do I exit Ansible playbook without error on a

问题:

I want to exit without an error (I know about assert and fail modules) when I meet a certain condition. The following code exits but with a failure:

  tasks:

    - name: Check if there is something to upgrade
      shell: if apt-get --dry-run upgrade | grep -q "0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded"; then echo "no"; else echo "yes"; fi
      register: upgrading

    - name: Exit if nothing to upgrade
      fail: msg="Nothing to upgrade"
      when: upgrading.stdout == "no"

回答1:

In Ansible 2.2, you can use end_play with the meta module:

- meta: end_play

You can also specify when for conditionally ending the play:

- meta: end_play
  when: upgrading.stdout == "no"

Note, though, that the task is not listed in the output of ansible-playbook, regardless of whether or not the play actually ends. Also, the task is not counted in the recap. So, you could do something like:

- block:
    - name: "end play if nothing to upgrade"
      debug:
        msg: "nothing to upgrade, ending play"

    - meta: end_play
  when: upgrading.stdout == "no"

which will announce the end of the play right before ending it, only when the condition is met. If the condition is not met, you'll see the task named end play if nothing to upgrade appropriately skipped, which would provide more info to the user as to why the play is, or is not, ending.

Of course, this will only end the current play and not all remaining plays in the playbook.

回答2:

Lets use what Tymoteusz suggested for roles:

Split your play into two roles where first role will execute the check (and sets some variable holding check's result) and second one will act based on result of the check.

I have created aaa.yaml with this content:

---
- hosts: all
  remote_user: root
  roles:
    - check
    - { role: doit, when: "check.stdout == '0'" }
...

then role check in roles/check/tasks/main.yaml:

---
- name: "Check if we should continue"
  shell:
    echo $(( $RANDOM % 2 ))
  register: check
- debug:
    var: check.stdout
...

and then role doit in roles/doit/tasks/main.yaml:

---
- name: "Do it only on systems where check returned 0"
  command:
    date
...

And this was the output:

TASK [check : Check if we should continue] *************************************
Thursday 06 October 2016  21:49:49 +0200 (0:00:09.800)       0:00:09.832 ****** 
changed: [capsule.example.com]
changed: [monitoring.example.com]
changed: [satellite.example.com]
changed: [docker.example.com]

TASK [check : debug] ***********************************************************
Thursday 06 October 2016  21:49:55 +0200 (0:00:05.171)       0:00:15.004 ****** 
ok: [monitoring.example.com] => {
    "check.stdout": "0"
}
ok: [satellite.example.com] => {
    "check.stdout": "1"
}
ok: [capsule.example.com] => {
    "check.stdout": "0"
}
ok: [docker.example.com] => {
    "check.stdout": "0"
}

TASK [doit : Do it only on systems where check returned 0] *********************
Thursday 06 October 2016  21:49:55 +0200 (0:00:00.072)       0:00:15.076 ****** 
skipping: [satellite.example.com]
changed: [capsule.example.com]
changed: [docker.example.com]
changed: [monitoring.example.com]

It is not perfect: looks like you will keep seeing skipping status for all tasks for skipped systems, but might do the trick.

回答3:

A better and more logical way to solve it may be to do the reverse and rather than fail if there is nothing to upgrade (which is a separate step that does only that) you could append all your upgrading tasks with a conditional depending on the upgrade variable. In essence just add

when: upgrading.changed

to tasks that should be only executed during an upgrade.

It is a bit more work, but it also brings clarity and self contains the logic that affects given task within itself, rather than depending on something way above which may or may not terminate it early.

回答4:

The following was helpful in my case, as meta: end_play seems to stop the execution for all hosts, not just the one that matches.

First establish a fact:

- name: Determine current version
  become: yes
  slurp:
    src: /opt/app/CHECKSUM
  register: version_check
  ignore_errors: yes

- set_fact:
  is_update_needed: "{{ ( version_check['checksum'] | b64decode != installer_file.stat.checksum)  }}"

Now include that part that should only executed on this condition:

# update-app.yml can be placed in the same role folder
- import_tasks: update-app.yml
  when: is_update_needed