ansible之notify与handler

handler，用来执行某些条件下的任务，比如当配置文件发生变化的时候，通过notify触发handler去重启服务。

精髓所在：你可能会想这个功能有什么作用，我在下面多执行几个play不就完了？

其实他的特点是：
1.“notify”这个action可用于在每个play的最后被触发，这样可以避免多次有改变发生时每次都执行指定的操作，取而代之，仅在所
2.有的变化发生完成后一次性地执行指定操作。在notify中列出的操作称为handler，也即notify中调用handler中定义的操作。

- hosts: local
  remote_user: zing
  tasks:
    - name: copy properties
      copy: src=/home/zing/project.properties dest=/home/java/pro/project.properties
    - name: 
      file: path=/home/java/pro/project.properties mode=600
      notify:
        - restart server
  handlers:
    - name: restart server
      service: name=tomcat state=restarted

案例2：
heartbeat.yaml

         -hosts: hbhosts

           remote_user: root

           tasks:

             - name: ensure heartbeat latest version

               yum: name=heartbeat state=present

             - name: authkeys configure file

               copy: src=/root/hb_conf/authkeysdest=/etc/ha.d/authkeys

             - name: authkeys mode 600

               file: path=/etc/ha.d/authkeys mode=600

               notify:

                 - restart heartbeat

             - name: ha.cf configure file

               copy: src=/root/hb_conf/ha.cfdest=/etc/ha.d/ha.cf

               notify:

                  -restart heartbeat

           handlers:

                - name:restart heartbeat

                  service: name=heartbeat     state=restarted

个人项目中的一个案例:

#先判断centos6还是7  然后根据区别去做自启动服务，然后开启nginx服务
- name: config power on service in centos6
  shell: "cp -p {{ tengine_git_path }}/nginx /etc/init.d/;chkconfig nginx on "
  when: ansible_distribution == 'CentOS' and ansible_distribution_major_version == "6"
  notify:
   - start nginx

- name: config power on service in centos7
  shell: "cp -p {{ tengine_git_path }}/nginx.service /usr/lib/systemd/system/;systemctl enable nginx.service"
  when: ansible_distribution == 'CentOS' and ansible_distribution_major_version == "7"
  notify:
   - start nginx