How to stop Ansible from starting then restarting a service? - ansible

Question

In many of my Ansible roles I have a handler to restart a service and a task to make sure the service is enabled and started. When this is a first run Ansible will start my service (Ensure mongodb is started and enabled) and then at the end run the restart handler. How do I tell Ansible to only start it once.
Sample play:
---
- name: Install MongoDB package
yum: name="mongodb-org-{{ mongodb_version }}" state=present
- name: Configure mongodb
template: src=mongod.conf.j2 dest=/etc/{{ mongodb_config_file }} owner=root group=root mode=0644
notify: mongodb restart
- name: Ensure mongodb is started and enabled
service: name={{ mongodb_daemon_name }} state=started enabled=yes

Answer 1

Insert a flush_handlers task just in the front of the server started task to run the restart handler. Like:
- name: flush handlers
meta: flush_handlers
## your service start task
- name: Ensure mongodb is started and enabled
service:
service: name={{ mongodb_daemon_name }} state=started enabled=yes
If handlers are notified, the handler will restart the services (I assume you have handlers that restart the services).
If handlers are not notified, the Ensure service started task will start the service if it is not already started.

Answer 2

It's been a while since I asked this but anywho, if it helps, the solution I ended up with is below...
The trick is to...
Have the service task in the tasks/main.yml file with the parameters state: started and enabled: yes split out into their own tasks
For the Ensure mongodb is started task register a mongodb_service_started variable
Use the newly registered variable mongodb_service_started in the when clause of the Restart mongodb handler to only run when the Ensure mongodb is started task did NOT change
This ensures that your application does not get started then subsequently restarted in the same play and prevents your application from being stopped when it is running some critical function on startup. For example database migrations. Restarting a service right after it's been started can cause an inconsistent state.
tasks/main.yml
---
- name: Install MongoDB package
yum:
name: "mongodb-org-{{ mongodb_version }}"
state: present
notify: Restart mongodb
- name: Configure mongodb
template:
src: mongod.conf.j2
dest: "/etc/{{ mongodb_config_file }}"
owner: root
group: root
mode: 0644
notify: Restart mongodb
- name: Ensure mongodb is started
service:
name: "{{ mongodb_daemon_name }}"
state: started
register: mongodb_service_started
- name: Ensure mongodb is enabled
service:
name: "{{ mongodb_daemon_name }}"
enabled: yes
handlers/main.yml
---
- name: Restart mongodb
service:
name: "{{ mongodb_daemon_name }}"
state: started
when: mongodb_service_started.changed == False

Answer 3

May be you are looking something like this:
---
- name: Install MongoDB package
yum: name="mongodb-org-{{ mongodb_version }}" state=present
register: mongodb_install
- name: Configure mongodb
template: src=mongod.conf.j2 dest=/etc/{{ mongodb_config_file }} owner=root group=root mode=0644
notify: mongodb restart
- name: Ensure mongodb is started and enabled
service: name={{ mongodb_daemon_name }} state=started enabled=yes
when: mongodb_install.changed

Answer 4

I can think of two three ways.
Option #1. Remove the state from the task that enables the service and move it to a handler.
According to the Ansible documentation, "notify handlers are always run in the same order they are defined." Since started is idempotent and restarted always starts the service, the second handler (start) won't run if the first one does (restart).
# roles/mongodb/tasks/main.yml
- name: Install MongoDB package
yum: name="mongodb-org-{{ mongodb_version }}" state=present
- name: Configure mongodb
template: src=mongod.conf.j2 dest=/etc/{{ mongodb_config_file }} owner=root group=root mode=0644
notify: mongodb restart
- name: Ensure mongodb is started and enabled
service: name={{ mongodb_daemon_name }} enabled=yes
notify: mongodb start
# roles/mongodb/handlers/main.yml
- name: mongodb restart
service: name={{ mongodb_daemon_name }} state=restarted
- name: mongodb start
service: name={{ mongodb_daemon_name }} state=started
However, handlers are only triggered if the task is changed, so this doesn't ensure that the service is running if neither of those tasks are considered changed. For instance, if the service was already installed, enabled, and configured earlier, but someone has logged on to the host and shut it down manually, then it won't be started when this playbook is run.
Option #2. Add a post_task that always runs and ensures the service has been started.
Handlers are flushed before post tasks, so if the configuration has been changed, either during first installation or because it changed, the service will either be started or restarted. However, if nothing has changed and the service isn't running for some reason, it will explicitly be started during the post_task.
# roles/mongodb/tasks/main.yml
- name: Install MongoDB package
yum: name="mongodb-org-{{ mongodb_version }}" state=present
- name: Configure mongodb
template: src=mongod.conf.j2 dest=/etc/{{ mongodb_config_file }} owner=root group=root mode=0644
notify: mongodb restart
- name: Ensure mongodb is started and enabled
service: name={{ mongodb_daemon_name }} enabled=yes
# In your playbook, e.g., site.yml
- hosts: all
roles:
- mongodb
post_tasks:
- name: Ensure mongodb is running
service: name={{ mongodb_daemon_name }} state=started
Option #3. Like Option #1, except always trigger the "start" handler
# roles/mongodb/tasks/main.yml
# ...same as Option #1 above...
- name: Ensure mongodb is started and enabled
service: name={{ mongodb_daemon_name }} enabled=yes
notify: mongodb start
changed_when: yes
As long as seeing a "change" in your output doesn't bother you, this will work the way you want.

Answer 5

If you have a handler (in the handlers directory of your role) then you do not need an additional task to start/enable mongo. In your handler you should not start but restart (state=restarted). When notified for the first time it will start and enable your service, and in future when the service is running, it will re-start.
- name: mongodb restart
service: name={{ mongodb_daemon_name }} state=restarted enabled=yes
No additional task required.