097、如何实现Service伸缩？（Swarm04）

参考https://www.cnblogs.com/CloudMan6/p/7885667.html

 

上一节部署了只有一个副本的Service，不过对于web服务，我们通常会运行多个实例，这样可以做负载均衡，同时也能提高可用性。

 

swarm 要实现这个目标非常简单，增加Service 的副本数就可以了。在 swarm-manager 上执行如下命令

 

root@host03:~# docker service scale web_server=5

web_server scaled to 5

overall progress: 5 out of 5 tasks

1/5: running   [==================================================>]

2/5: running   [==================================================>]

3/5: running   [==================================================>]

4/5: running   [==================================================>]

5/5: running   [==================================================>]

verify: Service converged

 

root@host03:~# docker service ps web_server    #    副本数增加过程中

ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE              ERROR               PORTS

jykct1jmfrte        web_server.1        httpd:latest        host03              Running             Running 20 minutes ago                         

n4afxlx16tny        web_server.2        httpd:latest        host03              Running             Running 13 seconds ago                         

kmtovvs8i1rk        web_server.3        httpd:latest        host01              Running             Preparing 14 seconds ago                       

mlsb1ey4n65r        web_server.4        httpd:latest        host02              Running             Preparing 14 seconds ago                       

a08aabmfiprh        web_server.5        httpd:latest        host02              Running             Preparing 14 seconds ago                       

root@host03:~# docker service ps web_server    #    副本数增加完毕

ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE            ERROR               PORTS

jykct1jmfrte        web_server.1        httpd:latest        host03              Running             Running 21 minutes ago                       

n4afxlx16tny        web_server.2        httpd:latest        host03              Running             Running 52 seconds ago                       

kmtovvs8i1rk        web_server.3        httpd:latest        host01              Running             Running 29 seconds ago                       

mlsb1ey4n65r        web_server.4        httpd:latest        host02              Running             Running 31 seconds ago                       

a08aabmfiprh        web_server.5        httpd:latest        host02              Running             Running 31 seconds ago       

root@host03:~# docker service ls    #    要求副本数和实际副本数均已达到 5 

ID                  NAME                MODE                REPLICAS            IMAGE               PORTS

9aa10i3l6xjw        web_server          replicated          5/5                 httpd:latest     

 

设置 swarm-manager 为仅manager模式

 

root@host03:~# docker node update --availability drain host03    #    将 swarm-manager（host03）设置为仅 manager

host03

root@host03:~# docker node ls    #    host03 AVAILABILITY 已经变成 Drain

ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS      ENGINE VERSION

hvt2ez9e7zvqm2hz8nix1eke7     host01              Ready               Active                                  18.09.6

asn5ufnogzkyqigk4mizatoer     host02              Ready               Active                                  18.09.6

h6rzavsz2vjxstwj3pytiebjb *   host03              Ready               Drain               Leader              18.09.6

root@host03:~# docker service ps web_server    #    可以看到 host03 上的容器都已 shutdown，另外在host01 上新起了两个容器

ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE               ERROR               PORTS

tznw0lrn8wh8        web_server.1        httpd:latest        host01              Running             Running 14 seconds ago                          

jykct1jmfrte         \_ web_server.1    httpd:latest        host03              Shutdown            Shutdown 15 seconds ago                         

4x32c9x1hizg        web_server.2        httpd:latest        host01              Running             Running 14 seconds ago                          

n4afxlx16tny         \_ web_server.2    httpd:latest        host03              Shutdown            Shutdown 15 seconds ago                         

kmtovvs8i1rk        web_server.3        httpd:latest        host01              Running             Running about an hour ago                       

mlsb1ey4n65r        web_server.4        httpd:latest        host02              Running             Running about an hour ago                       

a08aabmfiprh        web_server.5        httpd:latest        host02              Running             Running about an hour ago                       

 

弹性收缩，将副本数由 5 降到 3

 

root@host03:~# docker service scale web_server=3    #    副本数设置为 3

web_server scaled to 3

overall progress: 3 out of 3 tasks

1/3: running   [==================================================>]

2/3: running   [==================================================>]

3/3: running   [==================================================>]

verify: Service converged

root@host03:~# docker service ps web_server    #    可以查看编号为 3 和 5 的容器被删除了

ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE               ERROR               PORTS

tznw0lrn8wh8        web_server.1        httpd:latest        host01              Running             Running 2 minutes ago                           

jykct1jmfrte         \_ web_server.1    httpd:latest        host03              Shutdown            Shutdown 2 minutes ago                          

4x32c9x1hizg        web_server.2        httpd:latest        host01              Running             Running 2 minutes ago                           

n4afxlx16tny         \_ web_server.2    httpd:latest        host03              Shutdown            Shutdown 2 minutes ago                          

mlsb1ey4n65r        web_server.4        httpd:latest        host02              Running             Running about an hour ago