服务编排的rolling_updates

更新某个服务时，如果该服务包括超过一个以上容器（使用 scale 标签定义），在第 n 个容器更新成功后，再去做第 n+1 个容器的更新，以此来最小化停止服务时间。
[backcolor=transparent]示例：
部署 WordPress 服务，通过scale标签指定部署 2 个容器，使用rolling_updates标签可以使 WordPress 对外停止服务的时间最小化。

1. [backcolor=transparent]web[backcolor=transparent]:
2. [backcolor=transparent]  image[backcolor=transparent]:[backcolor=transparent] wordpress
3. [backcolor=transparent]  ports[backcolor=transparent]:
4. [backcolor=transparent]    [backcolor=transparent]-[backcolor=transparent] [backcolor=transparent]80
5. [backcolor=transparent]  restart[backcolor=transparent]:[backcolor=transparent] always
6. [backcolor=transparent]  links[backcolor=transparent]:
7. [backcolor=transparent]    [backcolor=transparent]-[backcolor=transparent] [backcolor=transparent]'db:mysql'
8. [backcolor=transparent]  labels[backcolor=transparent]:
9. [backcolor=transparent]    aliyun[backcolor=transparent].[backcolor=transparent]logs[backcolor=transparent]:[backcolor=transparent] [backcolor=transparent]/var/[backcolor=transparent]log
10. [backcolor=transparent]    aliyun[backcolor=transparent].[backcolor=transparent]routing[backcolor=transparent].[backcolor=transparent]port_80[backcolor=transparent]:[backcolor=transparent] http[backcolor=transparent]:[backcolor=transparent]//wordpress
11. [backcolor=transparent]    aliyun[backcolor=transparent].[backcolor=transparent]rolling_updates[backcolor=transparent]:[backcolor=transparent] [backcolor=transparent]'true'
12. [backcolor=transparent]    aliyun[backcolor=transparent].[backcolor=transparent]scale[backcolor=transparent]:[backcolor=transparent] [backcolor=transparent]'2'
13. [backcolor=transparent]db[backcolor=transparent]:
14. [backcolor=transparent]  image[backcolor=transparent]:[backcolor=transparent] mariadb
15. [backcolor=transparent]  environment[backcolor=transparent]:
16. [backcolor=transparent]    MYSQL_ROOT_PASSWORD[backcolor=transparent]:[backcolor=transparent] example
17. [backcolor=transparent]  restart[backcolor=transparent]:[backcolor=transparent] always
18. [backcolor=transparent]  labels[backcolor=transparent]:
19. [backcolor=transparent]    aliyun[backcolor=transparent].[backcolor=transparent]logs[backcolor=transparent]:[backcolor=transparent] [backcolor=transparent]/var/[backcolor=transparent]log[backcolor=transparent]/[backcolor=transparent]mysql

• 默认值为 1，即每次只更新一个容器。
• 当其值大于 1 的时候，rolling_updates 过程中，每次会以 parallelism 定义的值来并行更新相应个数的容器，实现批量更新。
• 当定义值无效时，默认为 1。[backcolor=transparent]注意：为了确保始终有容器在提供服务，建议 parallelism 定义的值小于服务包含的容器数。

1. [backcolor=transparent]web[backcolor=transparent]:
2. [backcolor=transparent]  image[backcolor=transparent]:[backcolor=transparent] nginx[backcolor=transparent]:[backcolor=transparent]latest
3. [backcolor=transparent]  restart[backcolor=transparent]:[backcolor=transparent] always
4. [backcolor=transparent]  environment[backcolor=transparent]:
5. [backcolor=transparent]      [backcolor=transparent]-[backcolor=transparent] [backcolor=transparent]"reschedule:on-node-failure"
6. [backcolor=transparent]  ports[backcolor=transparent]:
7. [backcolor=transparent]      [backcolor=transparent]-[backcolor=transparent] [backcolor=transparent]80
8. [backcolor=transparent]  labels[backcolor=transparent]:
9. [backcolor=transparent]    aliyun[backcolor=transparent].[backcolor=transparent]scale[backcolor=transparent]:[backcolor=transparent] [backcolor=transparent]"3"
10. [backcolor=transparent]    aliyun[backcolor=transparent].[backcolor=transparent]rolling_updates[backcolor=transparent]:[backcolor=transparent] [backcolor=transparent]'true'
11. [backcolor=transparent]    aliyun[backcolor=transparent].[backcolor=transparent]rolling_updates[backcolor=transparent].[backcolor=transparent]parallelism[backcolor=transparent]:[backcolor=transparent] [backcolor=transparent]"2"