Conditional task using when_changed

[Jon Chappell]

Greetings,

I'm running into unexpected behavior when trying to use a when_changed statement to trigger an immediate service reload if a change is made.  We wanted to do this instead of doing a flush_handlers to avoid impacting the timing handlers that were triggered by other plays.  

The following set of tasks in a role:

---

- name: Add the PostgreSQL user.

  postgresql_user:

    login_user: postgres

    name: stuff

    password: password_here

    role_attr_flags: CREATEDB

    state: present

  sudo_user: postgres

- name: Make the PostgreSQL stuff user allow password auth.

  lineinfile:

    create: yes

    dest: /etc/postgresql/9.3/main/pg_hba.conf

    line: "local   all             stuff                                  md5"

    regexp: "local\\s+all\\s+(stuff|all)\\s+(peer|md5)"

    state: present

  register: result

- name: Reload PostgreSQL if permissions have changed.

  service:

    name: postgresql

    status: reloaded

  when_changed: $result

-----------------------

When the middle play runs, it generates this output:

TASK: [Make the PostgreSQL stuff user allow password auth.] ******************

changed: [33.33.33.100] => {"changed": true, "item": "", "msg": "line replaced"}

After that, we get the following error:

TASK: [Reload PostgreSQL if permissions have changed.] ************************

fatal: [33.33.33.100] => Conditional expression must evaluate to True or False: is_changed($result)

FATAL: all hosts have already failed -- aborting

As best I can tell, we're calling when_changed appropriately.  Does anyone have insight into what we're doing wrong, or a reason why doing this action this way instead of through a handler would be incorrect?

[James Cammarata]

Does this happen if you use the new syntax of "when: result.changed"?

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James Cammarata <jcamm...@ansibleworks.com>
Sr. Software Engineer, AnsibleWorks, Inc.
http://www.ansibleworks.com/

[Jon Chappell]

Looks like it works with the new syntax.  I didn't even see a mention to that in the docs.  Must have slipped by me.

[Michael DeHaan]

So BTW, this is wrong:

  when_changed: $result

Do this:

   when_changed: result

You only need to say "{{ foo }}" when you are forcing getting a string somewhere, and should never be using old style variables.

Michael DeHaan <mic...@ansibleworks.com>
CTO, AnsibleWorks, Inc.
http://www.ansibleworks.com/

[Michael DeHaan]

Also, a bit confused here by the topic.

"changed_when" is a thing that controls when something reports changed or not.

"when" is something that decides if something executes or not

"when: foo.changed" is a thing

you can also say

"when: foo|changed" and this better works with tasks that might be skipped, etc, and doesn't require them to have a ".changed" attribute.

[Michael DeHaan]

There is no "when_changed" :)