[RFC] Allow synchronous delegation of restart to alternative init system

[lucafavatella]

Depends on #75

Closes #70

[lucafavatella]

Travis CI failure:

TASK [ansible-riak : install riak_shell.config with templated configuration] ***

fatal: [riak-test]: FAILED! => {"failed": true, "msg": "The conditional check 'riak_package == \"riak-ts\" and riak_shell_nodes is defined' failed. The error was: error while evaluating conditional (riak_package == \"riak-ts\" and riak_shell_nodes is defined): {{ riak_shell_nodes_list.split() }}: {% for host in groups[riak_shell_group] %}riak@{{ hostvars[host][riak_shell_interface]['ipv4']['address'] }} {% endfor %}: 'dict object' has no attribute u'riak'\n\nThe error appears to have been in '/home/travis/build/basho-labs/ansible-riak/tasks/main.yml': line 40, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n- name: install riak_shell.config with templated configuration\n  ^ here\n"}

(looks similar to failure in #75 (comment) )

[lucafavatella]

Travis CI failure:

Issue is not caused by this PR - see #77

[lucafavatella]

I became concerned with variable scope at execution time of the handler. Do you know if this riak_init_system is safe here? I am considering templating the trigger with the variable, and in turn specifying trigger name with system.

[lucafavatella]

Better not to change this to variable in notify, because of ansible/ansible#17922

[lucafavatella]

Relevant note is that tasks/main.yml flushes handlers, so variable scope is more predictable in principle in this case

[lucafavatella]

Semantics of handlers in Ansible - at least as of 2.2.1.0 - appears to me to be under active development yet e.g. wrt notification of extra-role handlers. So delegating task to handler seems not a wise change at this stage. Closing this then.

For using runit I ended up forking and applying minimal addition:

- name: Reboot Riak to accept the new config and ensure it is enabled to start at bootup
  command: sv restart riak
  when: riak_init_system == 'runit'