# Playbook Modules Ansible consist of many pre-built modules that helps us to create playbooks. For example, * set\_fact * pause * prompt * wait\_for * assemble * add\_host * group\_by * fetch ### set\_fact This module allows us to add or change facts during the execution. For example if we consider the below playbook, ``` --- # YAML documents begin with the document separator --- # The minus in YAML this indicates a list item. The playbook contains a list # of plays, with each play being a dictionary - # Hosts: where our play will run and options it will run with hosts: ubuntu3,centos3 # Tasks: the list of tasks that will be executed within the play, this section # can also be used for pre and post tasks tasks: - name: Set a fact set_fact: our_fact: Ansible Rocks! - name: Show custom fact debug: msg: "{{ our_fact }}" # Three dots indicate the end of a YAML document ... ``` In the first task we are setting a fact with the name `out_fact` and in the second task we print it's value using the `debug` module. In addition to that, we can set multiple facts in the same iteration of the `set_fact` module. For example, let's modify our playbook in such a way, ``` --- # YAML documents begin with the document separator --- # The minus in YAML this indicates a list item. The playbook contains a list # of plays, with each play being a dictionary - # Hosts: where our play will run and options it will run with hosts: ubuntu3,centos3 # Tasks: the list of tasks that will be executed within the play, this section # can also be used for pre and post tasks tasks: - name: Set a fact set_fact: our_fact: Ansible Rocks! ansible_distribution: "{{ ansible_distribution | upper }}" - name: Show our_fact debug: msg: "{{ our_fact }}" - name: Show ansible_distribution debug: msg: "{{ ansible_distribution }}" # Three dots indicate the end of a YAML document ... ``` Then, let's assume that we have to set facts conditionally, for example, based on the environment. In such cases, we can do this by using the `when` key word along with the `set_fact` module, ``` --- # YAML documents begin with the document separator --- # The minus in YAML this indicates a list item. The playbook contains a list # of plays, with each play being a dictionary - # Hosts: where our play will run and options it will run with hosts: ubuntu3,centos3 # Tasks: the list of tasks that will be executed within the play, this section # can also be used for pre and post tasks tasks: - name: Set our installation variables for CentOS set_fact: webserver_application_port: 80 webserver_application_path: /usr/share/nginx/html webserver_application_user: root when: ansible_distribution == 'CentOS' - name: Set our installation variables for Ubuntu set_fact: webserver_application_port: 8080 webserver_application_path: /var/www/html webserver_application_user: nginx when: ansible_distribution == 'Ubuntu' - name: Show pre-set distribution based facts debug: msg: "webserver_application_port:{{ webserver_application_port }} webserver_application_path:{{ webserver_application_path }} webserver_application_user:{{ webserver_application_user }}" # Three dots indicate the end of a YAML document ... ``` `pause` module allows us to temporarily stop the playbook execution for a specified time period. It is also possible to interrput the pause by clieck control+C keys. For example, ``` --- # YAML documents begin with the document separator --- # The minus in YAML this indicates a list item. The playbook contains a list # of plays, with each play being a dictionary - # Hosts: where our play will run and options it will run with hosts: ubuntu3,centos3 # Tasks: the list of tasks that will be executed within the play, this section # can also be used for pre and post tasks tasks: - name: Pause our playbook for 10 seconds pause: seconds: 10 # Three dots indicate the end of a YAML document ... ``` Running this playbook will output the following: ``` $ ansible-playbook pause_playbook.yaml PLAY [ubuntu3,centos3] **************************************************************** TASK [Gathering Facts] **************************************************************** ok: [ubuntu3] ok: [centos3] TASK [Pause our playbook for 10 seconds] ********************************************** Pausing for 10 seconds (ctrl+C then 'C' = continue early, ctrl+C then 'A' = abort) ok: [ubuntu3] PLAY RECAP **************************************************************************** centos3 : ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0 ubuntu3 : ok=2 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0 ``` In a situation where we have to take a manual action, we can use the `pause` module with `prompt` option. This will allow us to show a message to the user and ask to perform an action. For example, ``` --- # YAML documents begin with the document separator --- # The minus in YAML this indicates a list item. The playbook contains a list # of plays, with each play being a dictionary - # Hosts: where our play will run and options it will run with hosts: ubuntu3,centos3 # Tasks: the list of tasks that will be executed within the play, this section # can also be used for pre and post tasks tasks: - name: Prompt user to verify before continue pause: prompt: Please check that the webserver is running, press enter to continue # Three dots indicate the end of a YAML document ... ``` Running this playbook will result in the following output, ``` ansible-playbook pause_playbook.yaml PLAY [ubuntu3,centos3] ********************************************************** TASK [Gathering Facts] ********************************************************** ok: [centos3] ok: [ubuntu3] TASK [Prompt user to verify before continue] ************************************ [Prompt user to verify before continue] Please check that the webserver is running, press enter to continue: ok: [ubuntu3] PLAY RECAP ********************************************************************** centos3 : ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0 ubuntu3 : ok=2 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0 ``` In some cases when we want to wait for certian operations to be completed, we could use the `wait_for` module rather than using `pause`. For example, in a situation where we have to wait until a port becomes available. ``` --- # YAML documents begin with the document separator --- # The minus in YAML this indicates a list item. The playbook contains a list # of plays, with each play being a dictionary - # Hosts: where our play will run and options it will run with hosts: ubuntu3,centos3 # Tasks: the list of tasks that will be executed within the play, this section # can also be used for pre and post tasks tasks: - name: Wait for the webserver to be running on port 80 wait_for: port: 80 # Three dots indicate the end of a YAML document ... ``` `assemble` module allows us to concatenate multiple files into one. For example, imagin a situation where we keep a comman ssh config file along with additional host specific configurations in separate files. Now that when we want to connect with those, we can use the `assemble` module to create a single ssh config file. For example, let's start by creating a couple of ssh config files in `conf.d` directory like below, `conf.d/defaults`: ``` ## Defaults Port 22 Protocol 2 ForwardX11 yes GSSAPIAuthentication no ``` `conf.d/centos1`: ``` ## Custom for centos1 Host centos1 User root Port 2222 ``` `assemble_playbook.yaml` : ``` --- # YAML documents begin with the document separator --- # The minus in YAML this indicates a list item. The playbook contains a list # of plays, with each play being a dictionary - # Hosts: where our play will run and options it will run with hosts: ubuntu-c # Tasks: the list of tasks that will be executed within the play, this section # can also be used for pre and post tasks tasks: - name: Assemble conf.d to sshd_config assemble: src: conf.d dest: sshd_config # Three dots indicate the end of a YAML document ... ``` In above playbook, it takes all content inside `config.d` directory and create a single config file with the name `sshd_config`. Which would contain a merged set of entries like below, ``` ## Custom for centos1 Host centos1 User root Port 2222 ## Defaults Port 22 Protocol 2 ForwardX11 yes GSSAPIAuthentication no ``` `add_host` is another module where we can add hosts to our inventory dynamically. This useful when we create hosts in our playbook. Playbook example for this looks like below, ``` --- # YAML documents begin with the document separator --- # The minus in YAML this indicates a list item. The playbook contains a list # of plays, with each play being a dictionary - # Hosts: where our play will run and options it will run with hosts: ubuntu-c # Tasks: the list of tasks that will be executed within the play, this section # can also be used for pre and post tasks tasks: - name: Add centos1 to adhoc_group add_host: name: centos1 groups: adhoc_group1, adhoc_group2 # The minus in YAML this indicates a list item. The playbook contains a list # of plays, with each play being a dictionary - # Hosts: where our play will run and options it will run with hosts: adhoc_group1 # Tasks: the list of tasks that will be executed within the play, this section # can also be used for pre and post tasks tasks: - name: Ping all in adhoc_group1 ping: # Three dots indicate the end of a YAML document ... ``` Above playbook will add `centos1` to `adhoc_group1` and `adhoc_group2` and then ping all instances in `adhoc_group1`. Similarly `group_by` module associates / group items based on what's been advised. For example, below playbook group each host by OS distribution and then ping all centos instances in the custom group. ``` --- # YAML documents begin with the document separator --- # The minus in YAML this indicates a list item. The playbook contains a list # of plays, with each play being a dictionary - # Hosts: where our play will run and options it will run with hosts: all # Tasks: the list of tasks that will be executed within the play, this section # can also be used for pre and post tasks tasks: - name: Create group based on ansible_distribution group_by: key: "custom_{{ ansible_distribution | lower }}" # The minus in YAML this indicates a list item. The playbook contains a list # of plays, with each play being a dictionary - # Hosts: where our play will run and options it will run with hosts: custom_centos # Tasks: the list of tasks that will be executed within the play, this section # can also be used for pre and post tasks tasks: - name: Ping all in custom_centos ping: # Three dots indicate the end of a YAML document ... ``` Finally, `fetch` module allows us to get files from the remote machine. For example, ``` --- # YAML documents begin with the document separator --- # The minus in YAML this indicates a list item. The playbook contains a list # of plays, with each play being a dictionary - # Hosts: where our play will run and options it will run with hosts: centos # Tasks: the list of tasks that will be executed within the play, this section # can also be used for pre and post tasks tasks: - name: Fetch /etc/redhat-release fetch: src: /etc/redhat-release dest: /tmp/redhat-release # Three dots indicate the end of a YAML document ... ```