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Ansible: Up and Running by Lorin Hochstein

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Chapter 7. Complex Playbooks

In the last chapter, we went over a fully functional Ansible playbook for deploying the Mezzanine CMS. That example exercised a number of common Ansible features, but it didn’t cover all of them. This chapter touches on those additional features, which makes it a bit of a grab bag.

Running a Task on the Control Machine

Sometimes you want to run a particular task on the control machine instead of on the remote host. Ansible provides the local_action clause for tasks to support this.

Imagine that the server we wanted to install Mezzanine onto had just booted, so that if we ran our playbook too soon, it would error out because the server hadn’t fully started up yet.

We could start off our playbook by invoking the wait_for module to wait until the SSH server was ready to accept connections before we executed the rest of the playbook. In this case, we want this module to execute on our laptop, not on the remote host.

The first task of our playbook would have to start off like this:

- name: wait for ssh server to be running
  local_action: wait_for port=22 host="{{ inventory_hostname }}"
    search_regex=OpenSSH

Note how we’re referencing inventory_hostname in this task, which evaluates to the name of the remote host, not localhost. That’s because the scope of these variables is still the remote host, even though the task is executing locally.

Note

If your play involves multiple hosts, and you use local_action, the task will be executed multiple times, one for ...

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