## 逐臺主機執行 升級負載均衡時，需要逐臺進行，以實現恢復升級。 ### serial語句 一般來說，當task失敗時，ansible會停止執行失敗的那臺主機上的任務。 ~~~ - name: upgrade packages on servers behind load balance hosts: localhost serial: 1 max_fail_percentage: 25 tasks: ...... ~~~ > 這里超過25%失敗 ## 只執行一次 比如數據庫備份，在多臺主機只只需要選出一臺進行備份。 ### run_once語句 ~~~ - name：run database migrations command: /opt/run_migrations run_once: true ~~~ # 過濾 ## default 過濾器 指定變量的默認值 ~~~ “HOST”: "{{ database_host | default('localhost') }}" ~~~ ## 文件路徑過濾器 處理包含控制主機文件系統的文件路徑。 ~~~ basename # 文件路徑中的文件名 dirname # 文件路徑中的目錄 expanduser # 將文件路徑中 ~ 替換為文件路徑 realpath # 處理符號鏈接后的文件實際路徑 ~~~ ## order 主機執行順序 ``` - 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 ``` ## 改變輸出結果 ``` 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 每個部分執行完自動刷新 handlers handlers notified 在 roles 每個執行完自動刷新, 在每個 task執行之前. 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 ``` ## 在模板中忽略未定義的變量報錯 ``` {{ variable | mandatory }} ``` ## 判斷變量類型 ``` {{ myvar | type_debug }} ``` ## to_uuid ``` {{ hostname | to_uuid }} ``` ## 路徑處理和編碼 ``` {{ 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 }} ``` ## [自定義過濾插件][1] [1]:https://coding.net/u/echohiyang/p/ansible_plugins/git