Ansible

Ansible is a configuration management software.

Connects via ssh or docker to a list of inventory machines and executes a series of tasks eventually grouped in playbooks.

At first, create an inventory file with all your hosts.



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cd /notebooks/exercise-00



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cat inventory

Now check if you can ping the local host.



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# Check connections versus the local host in the "course" group

!ansible -i inventory -m ping course



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# Pinging all hosts gives some errors too, due to missing hosts or no ssh-key exchange
!ansible -i inventory -m ping all

Further on inventories

You can split your servers in many inventory files, like

staging

# staging inventory file
# run with
# ansible -i staging ...
 [ws]
 staging-ws-[0:3]

 [jboss]
 staging-boss-[0:6]

production

# production inventory file
# run with
# ansible -i production ...
 [ws]
 ws-[0:3]

 [jboss]
 boss-[0:6]

Playbooks

To run a group of tasks with ansible, just:

create a playbook.yml
run ansible-playbook -i inventory playbook.yml

A playbook is a list of tasks in yml format, something like

#
# playbook.yml
#
- name: >-
    All public traffic is redirected via https.
    Beware: in real world, if your site accept credentials,
            you should close port 80 instead!
  uri:
    url: http://{{server_host}}/
    follow_redirects: none
    status_code: 301

- name: This webapp  is served
  uri:
    url: https://{{server_host}}/webapp-1
    validate_certs: false
    status_code: 200
    HEADER_testflag: test

- name: The WS is serverd and requires authentication
  uri:
    url: https://{{server_host}}/rest/v1/method
    validate_certs: false
    status_code: 401

In this case, instead of making actual installation|setup tasks, we just created a testsuite validating our deployment. Now we must write another playbook which takes care of deployng the actual machine.

Testing our course environment

We can write a playbook to test our course environment.



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!cat python-course-test.yml



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!ansible-playbook -i inventory python-course-test.yml

As you can see something is missing: this playbook is not going to modify our machine but only test that everything is in place.

See ansible-playbook --check and --diff for further infos.

We can run a setup playbook, conventionally named site.yml (click to edit).



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!cat site.yml



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!ansible-playbook -i inventory site.yml --limit=course  # in this case the --limit does not change anything ;)



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