Ansible detailed explanation (thirteen) - Tag and Handler in Ansible

Today, I will continue to introduce Linux operation and maintenance related knowledge. The main content of this article is the Tag and Handler in Ansible.

1. Definition and invocation of Tag in Ansible

In Ansible, when writing a Playbook, it is supported to define one or more Tag tags for tasks. When executing a Playbook, we can use the -t parameter to determine what task to execute according to the Tag. A playbook with tags looks like this:

---
- hosts: exp
  remote_user: root
  tasks:
  - name: Install Apache
    yum: name=httpd state=installed
    tags: httpd
  - name: Install Nginx
    yum: name=nginx state=installed
    tags: nginx
  - name: Stop firewalld & iptables & selinux
    shell: systemctl stop firewalld ; iptables -F ; setenforce 0
    tags:
    - httpd
    - nginx

In the above configuration, we define httpd and nginx labels for the three tasks respectively, so that when we call the Playbook, we can specify the tasks to be executed according to the labels. Join us to execute the installation of Apache, you can execute the command:

ansible-playbook tag.yml -t httpd

In this way, all tasks with httpd tags in the Playbook will be executed, and tasks without httpd tags will not be executed. The execution results of the above commands are as follows:
insert image description here

Second, the definition and call of Handler in Ansible

Ansible's Playbook also supports the use of Handler. The so-called Handler is a special task, which is always executed after all tasks are executed. An example of a Playbook with Handler in Ansible is as follows:

---
- hosts: exp
  remote_user: root
  tasks:
  - name: Install Apache
    yum: name=httpd state=installed
  - name: Config Apache
    copy: src=httpd.conf dest=/etc/httpd/httpd.cong
    notify: Restart Apache
  - name: Stop firewalld
    shell: systemctl stop firewalld;iptables -F;setenforce 0;
  handlers:
  - name: Restart Apache
    service: name=httpd state=restarted

In the Playbook, after the Config Apache instruction, there is a notify, which indicates the function of calling Ansible Handler, and there is a handler module behind the Playbook'. In this module, the Handler of Restart Apache is defined and configured later. The Handler should perform a hit operation. In this way, after all tasks are executed, the Handler will be executed.
The execution result of the Playbook is as follows: It can be
insert image description here
seen that the role of Ansible's Handler.
Originality is not easy, please indicate the source for reprinting: https://blog.csdn.net/weixin_40228200