How to register a var in either one or another task

Question

This task collection doesn\'t work as I hoped it would:

- name: Find out whether syslog-ng is installed (yum)
  tags: syslog_forwarding
  command: yum -q list in         


        

Answer 1

Why not just slightly reorder your tasks to make your "configure" task immediately follow the test ("find out..") as a pair, i.e.:

- name: Find out whether syslog-ng is installed (yum)
- name: Configure syslog-ng to forward all logs to syslog servers (yum)
- name: Find out whether syslog-ng is installed (yum)
- name: Configure syslog-ng to forward all logs to syslog servers (apt)

That way even if the other test resets syslog_ng_check you don't care because the you've already used it.

Putting the find/configure pair for each of the two pkg managers in a block guarded by when: ansible_pkg_mgr == ... would be another way, and would make it more obvious that the ordering/grouping was important.

Answer 2

There are only workarounds. Skipped tasks will always overwrite registered variable.

One possible way:

- name: Find out whether syslog-ng is installed (yum)
  tags: syslog_forwarding
  command: yum -q list installed syslog-ng
  register: syslog_ng_check
  failed_when: False
  changed_when: False
  when: ansible_pkg_mgr == 'yum'

- set_fact:
    syslog_ng_flag: True
  when: syslog_ng_check.rc == 0

- name: Find out whether syslog-ng is installed (apt)
  tags: syslog_forwarding
  command: dpkg -s syslog-ng
  register: syslog_ng_check
  failed_when: False
  changed_when: False
  when: ansible_pkg_mgr == 'apt'

- set_fact:
    syslog_ng_flag: True
  when: syslog_ng_check.rc == 0

- name: Configure syslog-ng to forward all logs to syslog servers (apt)
  tags: syslog_forwarding
  template:
    src: syslog_ng_forward_all.conf.j2
    dest: /etc/syslog-ng/conf.d/syslog_forward.conf
  notify: restart syslog_ng
  when: syslog_ng_flag | default(false)