## 逐台主机执行 升级负载均衡时，需要逐台进行，以实现恢复升级。 ### serial语句 一般来说，当task失败时，ansible会停止执行失败的那台主机上的任务。 ~~~ - name: upgrade packages on servers behind load balance hosts: localhost serial: 1 max_fail_percentage: 25 tasks: ...... ~~~ > 这里超过25%失败 ## 只执行一次 比如数据库备份，在多台主机只只需要选出一台进行备份。 ### run_once语句 ~~~ - name：run database migrations command: /opt/run_migrations run_once: true ~~~ # 过滤 ## default 过滤器 指定变量的默认值 ~~~ “HOST”: "{{ database_host | default('localhost') }}" ~~~ ## 文件路径过滤器 处理包含控制主机文件系统的文件路径。 ~~~ basename # 文件路径中的文件名 dirname # 文件路径中的目录 expanduser # 将文件路径中 ~ 替换为文件路径 realpath # 处理符号链接后的文件实际路径 ~~~ ## order 主机执行顺序 ``` - hosts: all order: sorted gather_facts: False tasks: - debug: var: inventory_hostname Possible values for order are: inventory: The default. The order is ‘as provided’ by the inventory reverse_inventory: As the name implies, this reverses the order ‘as provided’ by the inventory sorted: Hosts are alphabetically sorted by name reverse_sorted: Hosts are sorted by name in reverse alphabetical order shuffle: Hosts are randomly ordered each run ``` ## 改变输出结果 ``` tasks: - name: run this command and ignore the result shell: /usr/bin/somecommand || /bin/true ``` ## notify listener ``` As of Ansible 2.2, handlers can also “listen” to generic topics, and tasks can notify those topics as follows: handlers: - name: restart memcached service: name: memcached state: restarted listen: "restart web services" - name: restart apache service: name: apache state:restarted listen: "restart web services" tasks: - name: restart everything command: echo "this task will restart the web services" notify: "restart web services" ``` ## handlers ``` handlers notified 在 pre_tasks, tasks, and post_tasks 每个部分执行完自动刷新 handlers handlers notified 在 roles 每个执行完自动刷新, 在每个 task执行之前. 下面的 meta：flush_handlers 可以立即刷新 handlers tasks: - shell: some tasks go here - meta: flush_handlers - shell: some other tasks ``` ## 在模板中忽略未定义的变量报错 ``` {{ variable | mandatory }} ``` ## 判断变量类型 ``` {{ myvar | type_debug }} ``` ## to_uuid ``` {{ hostname | to_uuid }} ``` ## 路径处理和编码 ``` {{ path | realpath }} To get the relative path of a link, from a start point (new in version 1.7): {{ path | relpath('/etc') }} To get the root and extension of a path or filename (new in version 2.0): # with path == 'nginx.conf' the return would be ('nginx', '.conf') {{ path | splitext }} To work with Base64 encoded strings: {{ encoded | b64decode }} {{ decoded | b64encode }} ``` ## [自定义过滤插件][1] [1]:https://coding.net/u/echohiyang/p/ansible_plugins/git