How to dynamically end an include_tasks loop in Ansible

Due to the fact that we cannot run loop on block with Ansible, therefore I have to do include_tasks in the loop where the referenced file contains more than 1 task.

What if I need to dynamically end the loop earlier (lets say 5 iterations instead of 10 as defined by the loop: statements). trying to use when: condition but that only take in pre-defined/statically defined variables, if I have to update the variable that will be evaluated in when: for each iteration, I have to do register: or set_fact in a task before that, which is not possible when the loop task is running...

Also in the included_tasks I can set meta: end_play to end the loop and the play execution but that is not what I want, the play should continue after the loop.

Solution

You can't end it. You can only skip the rest. For example,

    - command: "echo {{ item }}"
      with_sequence: end=5
      register: out
      when: out.stdout|d(0)|int < 3

gives (on localhost)

  changed: [localhost] => (item=1)
  changed: [localhost] => (item=2)
  changed: [localhost] => (item=3)
  skipping: [localhost] => (item=4) 
  skipping: [localhost] => (item=5)

See:

include_tasks

The include_tasks situation is quite complex. The attribute ignore_conditional says:

The action is not subject to conditional execution so it will ignore the when: keyword

You can't use when with include_tasks, but you can apply keywords, including the keyword when, to the tasks within the include. For example, create the file

shell> cat tasks_1.yml
- name: Display item
  debug:
    var: item
- name: Execute command
  command: "echo {{ item }}"
  register: out
- name: Display stdout
  debug:
    var: out.stdout

When you include this file

    - include_tasks:
        file: tasks_1.yml
        apply:
          when: out.stdout|d(0)|int < 3
      with_sequence: end=5

you apply the condition "to the tasks within the include". Effectively, this will make the included tasks look like below

- name: Display item
  debug:
    var: item
  when: out.stdout|d(0)|int < 3
- name: Execute command
  command: "echo {{ item }}"
  register: out
  when: out.stdout|d(0)|int < 3
- name: Display stdout
  debug:
    var: out.stdout
  when: out.stdout|d(0)|int < 3

Run the play below

- hosts: localhost

  tasks:

    - include_tasks:
        file: tasks_1.yml
        apply:
          when: out.stdout|d(0)|int < 3
      with_sequence: end=5

gives (abridged)

TASK [include_tasks] **************************************************************************
included: /export/scratch/tmp7/test-389/tasks_1.yml for localhost => (item=1)
included: /export/scratch/tmp7/test-389/tasks_1.yml for localhost => (item=2)
included: /export/scratch/tmp7/test-389/tasks_1.yml for localhost => (item=3)
included: /export/scratch/tmp7/test-389/tasks_1.yml for localhost => (item=4)
included: /export/scratch/tmp7/test-389/tasks_1.yml for localhost => (item=5)

TASK [Display item] ***************************************************************************
ok: [localhost] => 
  item: '1'

TASK [Execute command] ************************************************************************
changed: [localhost]

TASK [Display stdout] *************************************************************************
ok: [localhost] => 
  out.stdout: '1'

TASK [Display item] ***************************************************************************
ok: [localhost] => 
  item: '2'

TASK [Execute command] ************************************************************************
changed: [localhost]

TASK [Display stdout] *************************************************************************
ok: [localhost] => 
  out.stdout: '2'

TASK [Display item] ***************************************************************************
ok: [localhost] => 
  item: '3'

TASK [Execute command] ************************************************************************
changed: [localhost]

TASK [Display stdout] *************************************************************************
skipping: [localhost]

TASK [Display item] ***************************************************************************
skipping: [localhost]

TASK [Execute command] ************************************************************************
skipping: [localhost]

TASK [Display stdout] *************************************************************************
ok: [localhost] => 
  out.stdout: VARIABLE IS NOT DEFINED!

TASK [Display item] ***************************************************************************
ok: [localhost] => 
  item: '5'

TASK [Execute command] ************************************************************************
changed: [localhost]

TASK [Display stdout] *************************************************************************
skipping: [localhost]

You can see that all iterations are included at once and then executed serially. The results look fine until item: '4'. The explanation always depends on the current value of the variable out.stdout before the execution of a task:

[ok] [Display item] item: '3'; out.stdout=2
[changed] [Execute command] out.stdout=2
[skipping] [Display stdout] out.stdout=3
[skipping] [Display item] out.stdout=3
[skipping] [Execute command] out.stdout=3
[ok] [Display stdout] out.stdout VARIABLE IS NOT DEFINED! (default(0) will apply because there is no attribute stdout in the registered variable out from the previous task)
[ok] [Display item] item: '5'; default(0)
[changed] [Execute command] default(0)
[skipping] [Display stdout] out.stdout=5

This is unusable.

You can improve the framework by creating a variable condition. For example, put the tasks into a block and always set the condition

shell> cat tasks_2.yml
- block:

    - name: Execute command {{ item }}
      command: "echo {{ item }}"
      register: out
    - debug:
        var: out.stdout

  always:

    - set_fact:
        condition: "{{ out.stdout|int < 3 }}"

Run the play below

- hosts: localhost

  tasks:

    - include_tasks:
        file: tasks_2.yml
        apply:
          when: condition|d(true)
      with_sequence: end=5

gives (abridged)

TASK [include_tasks] **************************************************************************
included: /export/scratch/tmp7/test-389/tasks_2.yml for localhost => (item=1)
included: /export/scratch/tmp7/test-389/tasks_2.yml for localhost => (item=2)
included: /export/scratch/tmp7/test-389/tasks_2.yml for localhost => (item=3)
included: /export/scratch/tmp7/test-389/tasks_2.yml for localhost => (item=4)
included: /export/scratch/tmp7/test-389/tasks_2.yml for localhost => (item=5)

TASK [Execute command 1] **********************************************************************
changed: [localhost]

TASK [debug] **********************************************************************************
ok: [localhost] => 
  out.stdout: '1'

TASK [set_fact] *******************************************************************************
ok: [localhost]

TASK [Execute command 2] **********************************************************************
changed: [localhost]

TASK [debug] **********************************************************************************
ok: [localhost] => 
  out.stdout: '2'

TASK [set_fact] *******************************************************************************
ok: [localhost]

TASK [Execute command 3] **********************************************************************
changed: [localhost]

TASK [debug] **********************************************************************************
ok: [localhost] => 
  out.stdout: '3'

TASK [set_fact] *******************************************************************************
ok: [localhost]

TASK [Execute command 4] **********************************************************************
skipping: [localhost]

TASK [debug] **********************************************************************************
skipping: [localhost]

TASK [set_fact] *******************************************************************************
skipping: [localhost]

TASK [Execute command 5] **********************************************************************
skipping: [localhost]

TASK [debug] **********************************************************************************
skipping: [localhost]

TASK [set_fact] *******************************************************************************
skipping: [localhost]

This seems reasonable.