Asynchronous Actions and Polling — Ansible Documentation

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# Asynchronous Actions and Polling

By default tasks in playbooks block, meaning the connections stay open until the task is done on each node. This may not always be desirable, or you may be running operations that take longer than the SSH timeout.

The easiest way to do this is to kick them off all at once and then poll until they are done.

You will also want to use asynchronous mode on very long running operations that might be subject to timeout.

To launch a task asynchronously, specify its maximum runtime and how frequently you would like to poll for status. The default poll value is 10 seconds if you do not specify a value for poll:

    ---

    - hosts: all
      remote_user: root

      tasks:

      - name: simulate long running op (15 sec), wait for up to 45 sec, poll every 5 sec
        command: /bin/sleep 15
        async: 45
        poll: 5

Note

There is no default for the async time limit. If you leave off the ‘async’ keyword, the task runs synchronously, which is Ansible’s default.

Alternatively, if you do not need to wait on the task to complete, you may “fire and forget” by specifying a poll value of 0:

    ---

    - hosts: all
      remote_user: root

      tasks:

      - name: simulate long running op, allow to run for 45 sec, fire and forget
        command: /bin/sleep 15
        async: 45
        poll: 0

Note

You shouldn’t “fire and forget” with operations that require exclusive locks, such as yum transactions, if you expect to run other commands later in the playbook against those same resources.

Note

Using a higher value for `--forks` will result in kicking off asynchronous tasks even faster. This also increases the efficiency of polling.

If you would like to perform a variation of the “fire and forget” where you “fire and forget, check on it later” you can perform a task similar to the following:

    ---
    # Requires ansible 1.8+
    - name: 'YUM - fire and forget task'
      yum: name=docker-io state=installed
      async: 1000
      poll: 0
      register: yum_sleeper

    - name: 'YUM - check on fire and forget task'
      async_status: jid={{ yum_sleeper.ansible_job_id }}
      register: job_result
      until: job_result.finished
      retries: 30

Note

If the value of `async:` is not high enough, this will cause the “check on it later” task to fail because the temporary status file that the `async_status:` is looking for will not have been written or no longer exist

If you would like to run multiple asynchronous tasks while limiting the amount of tasks running concurrently, you can do it this way:

    #####################
    # main.yml
    #####################
    - name: Run items asynchronously in batch of two items
      vars:
        sleep_durations:
          - 1
          - 2
          - 3
          - 4
          - 5
        durations: "{{ item }}"
      include_tasks: execute_batch.yml
      with_items:
        - "{{ sleep_durations | batch(2) | list }}"

    #####################
    # execute_batch.yml
    #####################
    - name: Async sleeping for batched_items
      command: sleep {{ async_item }}
      async: 45
      poll: 0
      with_items: "{{ durations }}"
      loop_control:
        loop_var: "async_item"
      register: async_results

    - name: Check sync status
      async_status:
        jid: "{{ async_result_item.ansible_job_id }}"
      with_items: "{{ async_results.results }}"
      loop_control:
        loop_var: "async_result_item"
      register: async_poll_results
      until: async_poll_results.finished
      retries: 30

See also

Playbooks
  An introduction to playbooks
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