4.5 - Task control

In this lab we learn about task control.

Task 1

Write an ad-hoc command that sleeps for 1000 seconds and runs on node1
Ensure that the command times out after 10 seconds if not completed by then. Run the task.
Use the time command to see how long your ad-hoc command had to run. Use man time to see how time works.
Now add a polling interval of 30 seconds. Run the task, and ensure with the time command, that it had a longer runtime.
See what happens if you only specify the polling interval but no async timeout. Tip: set a sleep duration of only 10 seconds.

Task 2

Write a playbook async.yml that does the same as in the task above:
Run a command that sleeps for 1000 second and runs on node1.
Let the task wait at most for 10 seconds before timing out.
Run the task.

Task 3 (Advanced)

In the playbook async.yml do the following:

Put the task above in the background and change the values of the sleepduration, polling intervall ans async time to reasonable values.
Check back with an async_status task if the sleep-task has finished.
Run the playbook.

If unsure, check the documentation about async_status for an example.

Solutions

$ ansible node1 -i hosts -B 10 -a "/usr/bin/sleep 1000"
node1 | FAILED | rc=-1 >>
async task did not complete within the requested time - 10s
$
$ time ansible node1 -i hosts -B 10 -a "/usr/bin/sleep 1000"
node1 | FAILED | rc=-1 >>
async task did not complete within the requested time - 10s

real	0m17.626s #<- a bit more than 10 seconds
user	0m3.603s
sys	0m0.510s
$ time ansible node1 -i hosts -B 10 -P 30 -a "/usr/bin/sleep 1000"
node1 | FAILED | rc=-1 >>
async task did not complete within the requested time - 10s

real	0m32.625s #<- more than the polling intervall
user	0m5.541s
sys	0m0.684s
$

Setting the poll parameter without the async parameter results in the job not beeing put in background.

$ ansible node1 -i hosts -P 30 -a "/usr/bin/sleep 10"
node1 | CHANGED | rc=0 >>
$

$ cat async.yml 
---
- hosts: node1
  tasks:
    - name: sleeping beauty
      command: "/usr/bin/sleep 1000"
      async: 10

$ ansible-playbook -i hosts async.yml 

PLAY [node1] **************************************************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************************************************
ok: [node1]

TASK [sleeping beauty] ****************************************************************************************************************************************************************************************
fatal: [node1]: FAILED! => {"changed": false, "msg": "async task did not complete within the requested time - 10s"}

PLAY RECAP ****************************************************************************************************************************************************************************************************
node1                      : ok=1    changed=0    unreachable=0    failed=1    skipped=0    rescued=0    ignored=0   

$

$ cat async.yml 
---
- hosts: node1
  tasks:
    - name: sleeping beauty
      command: "/usr/bin/sleep 30"
      async: 60
      poll: 0
      register: sleepingbeauty

    - name: check back if task in background has finished
      async_status:
        jid: '{{ sleepingbeauty.ansible_job_id }}'
      register: beauty_status
      until: beauty_status.finished
      retries: 50

$ ansible-playbook -i hosts async.yml 

PLAY [node1] **************************************************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************************************************
ok: [node1]

TASK [sleeping beauty] ****************************************************************************************************************************************************************************************
changed: [node1]

TASK [check back if task in background has finished] **********************************************************************************************************************************************************
FAILED - RETRYING: check back if task in background has finished (50 retries left).
FAILED - RETRYING: check back if task in background has finished (49 retries left).
FAILED - RETRYING: check back if task in background has finished (48 retries left).
FAILED - RETRYING: check back if task in background has finished (47 retries left).
FAILED - RETRYING: check back if task in background has finished (46 retries left).
FAILED - RETRYING: check back if task in background has finished (45 retries left).
changed: [node1]

PLAY RECAP ****************************************************************************************************************************************************************************************************
node1                      : ok=3    changed=2    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   

$