102、如何滚动更新 Service （Swarm09）

参考 https://www.cnblogs.com/CloudMan6/p/7988455.html

 

在前面的实验中，我们部署了多个副本的服务，本节将讨论如何滚动更新每一个副本。

 

滚动更新降低了应用更新的风险，如果某个副本更新失败，整个更新将暂停，其他副本则可以继续提供服务。

同时在更新的过程中，总是有副本在运行的，因此也保证了业务的连续性。

 

下面我们进行一个实验，将一个 3 副本的httpd Service，我们将 httpd镜像的版本进行升级

 

httpd:2.4.35  升级到 httpd:2.4.37

 

root@host03:~# docker service create --name httpd_2435 --replicas 3 httpd:2.4.35    #    创建Service 镜像 httpd:2.4.35，副本数3

8ppmoni91g7u22z4f4if61ro7

overall progress: 3 out of 3 tasks

1/3: running   

2/3: running   

3/3: running   

verify: Service converged 

root@host03:~# docker service update --image httpd:2.4.37 httpd_2435    #    更新Service 镜像到 httpd:2.4.37

httpd_2435

overall progress: 3 out of 3 tasks

1/3: running   

2/3: running   

3/3: running   

verify: Service converged

 

root@host03:~# docker service ps httpd_2435    #    更新前Service各副本状态

ID                  NAME                IMAGE               NODE                DESIRED ST          PORTS

hkb5vb4ocqu6        httpd_2435.1        httpd:2.4.35        host02              Running             

3v4vikx98pgm        httpd_2435.2        httpd:2.4.35        host01              Running             

d58skm47doqf        httpd_2435.3        httpd:2.4.35        host02              Running             

root@host03:~# docker service ps httpd_2435    #    更新副本2过程中

ID                  NAME                IMAGE               NODE                DESIRED ST          PORTS

hkb5vb4ocqu6        httpd_2435.1        httpd:2.4.35        host02              Running                  

ys34lst9obij        httpd_2435.2        httpd:2.4.37        host01              Ready                    

3v4vikx98pgm         \_ httpd_2435.2    httpd:2.4.35        host01              Shutdown                 

d58skm47doqf        httpd_2435.3        httpd:2.4.35        host02              Running                  

root@host03:~# docker service ps httpd_2435    #    更新副本2完毕

ID                  NAME                IMAGE               NODE                DESIRED ST          PORTS

hkb5vb4ocqu6        httpd_2435.1        httpd:2.4.35        host02              Running             

ys34lst9obij        httpd_2435.2        httpd:2.4.37        host01              Running             

3v4vikx98pgm         \_ httpd_2435.2    httpd:2.4.35        host01              Shutdown            

d58skm47doqf        httpd_2435.3        httpd:2.4.35        host02              Running             

root@host03:~# docker service ps httpd_2435    #    更新副本3完毕

ID                  NAME                IMAGE               NODE                DESIRED ST               PORTS

hkb5vb4ocqu6        httpd_2435.1        httpd:2.4.35        host02              Running                  

ys34lst9obij        httpd_2435.2        httpd:2.4.37        host01              Running                  

3v4vikx98pgm         \_ httpd_2435.2    httpd:2.4.35        host01              Shutdown                 

pujxt7yrum1d        httpd_2435.3        httpd:2.4.37        host01              Running                  

d58skm47doqf         \_ httpd_2435.3    httpd:2.4.35        host02              Shutdown                 

root@host03:~# docker service ps httpd_2435    #    更新副本1完毕

ID                  NAME                IMAGE               NODE                DESIRED ST               PORTS

hguoom4ihf8t        httpd_2435.1        httpd:2.4.37        host02              Running                  

hkb5vb4ocqu6         \_ httpd_2435.1    httpd:2.4.35        host02              Shutdown                 

ys34lst9obij        httpd_2435.2        httpd:2.4.37        host01              Running                  

3v4vikx98pgm         \_ httpd_2435.2    httpd:2.4.35        host01              Shutdown                 

pujxt7yrum1d        httpd_2435.3        httpd:2.4.37        host01              Running                  

d58skm47doqf         \_ httpd_2435.3    httpd:2.4.35        host02              Shutdown                 

 

root@host03:~# docker service update --rollback httpd_2435    #    回滚到之前的版本

httpd_2435

rollback: manually requested rollback

overall progress: rolling back update: 3 out of 3 tasks

1/3: running   

2/3: running   

3/3: running   

verify: Service converged

 

root@host03:~# docker service ps httpd_2435    #    回滚到之前的版本后，新开了一个 httpd:2.4.25，而不是使用之前的 httpd:2.4.35

ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE                ERROR               PORTS

py7dm0500o2z        httpd_2435.1        httpd:2.4.35        host02              Running             Running 19 seconds ago                           

hguoom4ihf8t         \_ httpd_2435.1    httpd:2.4.37        host02              Shutdown            Shutdown 20 seconds ago                          

hkb5vb4ocqu6         \_ httpd_2435.1    httpd:2.4.35        host02              Shutdown            Shutdown about an hour ago                       

rdvhf3z4zh7r        httpd_2435.2        httpd:2.4.35        host01              Running             Running 17 seconds ago                           

ys34lst9obij         \_ httpd_2435.2    httpd:2.4.37        host01              Shutdown            Shutdown 18 seconds ago                          

3v4vikx98pgm         \_ httpd_2435.2    httpd:2.4.35        host01              Shutdown            Shutdown about an hour ago                       

xed1n7sy7td8        httpd_2435.3        httpd:2.4.35        host01              Running             Running 22 seconds ago                           

pujxt7yrum1d         \_ httpd_2435.3    httpd:2.4.37        host01              Shutdown            Shutdown 23 seconds ago                          

d58skm47doqf         \_ httpd_2435.3    httpd:2.4.35        host02              Shutdown            Shutdown about an hour ago     

 

 

默认配置下，Swarm一次只能更新一个副本，并且两个副本之间没有等待时间，我们可以通过 -- update-parallelism 设置并行更新的副本数目，通过--update-delay 指定滚动更新的时间间隔。

 

下面的例子中，我们有20个副本，更新并发数 4 ，更新延时 10s

 

root@host03:~# docker service update --image httpd:2.2 --update-parallelism 4 --update-delay 10s httpd_2435

 

ps：弹性伸缩时，即增减副本数并不受此限制，会以最快的速度完成伸缩