【Docker】docker swarm集群搭建和相关命令分享

Docker swarm 集群通过 docker cli 来创建，并通过docker cli来实现应用的部署和集群的管理。

Docker swarm集群的搭建相对简单，这里使用三台虚拟机（一个管理节点，两个worker节点）来简单演示下集群的搭建过程。

|-----------------------------------------------------------------|
|            hostname           |                IP                  |
|-----------------------------------------------------------------|
|            master                 |     192.168.223.31       |
|-----------------------------------------------------------------|
|            node-01               |     192.168.223.32       |
|-----------------------------------------------------------------|
|            node-02               |     192.168.223.33       |
|-----------------------------------------------------------------|

虚拟机和docker-ce的安装这里就不做赘述了，安装后关闭系统默认的防火墙，关闭selinux，安装最新的docker-ce-20.10.17，并且修改docker.service，增加下面的参数配置。

# vi /lib/systemd/system/docker.service
 
在 ExecStart=/usr/bin/dockerd 后添加 -H tcp://0.0.0.0:2375 -H unix://var/run/docker.sock ,修改后的配置如下所示
 
[Service]
Type=notify
# the default is not to use systemd for cgroups because the delegate issues still
# exists and systemd currently does not support the cgroup feature set required
# for containers run by docker
ExecStart=/usr/bin/dockerd -H tcp://0.0.0.0:2375 -H unix://var/run/docker.sock -H fd:// --containerd=/run/containerd/containerd.sock
 
修改后，记得reload配置，并且重启docker服务
 
# systemctl daemon-reload
# systemctl restart docker.service

下面就给大家直接贴出我搭建和使用swarm集群过程的相关命令的记录。

---初始化集群的管理节点
# docker swarm init --advertise-addr 192.168.223.31
Swarm initialized: current node (betygbmft1wkh4kmrf5wx45mc) is now a manager.
 
To add a worker to this swarm, run the following command:
 
    docker swarm join --token SWMTKN-1-66syvw9yv8xr457lk4eviixyhd5fviw1gg3ktkwa1nkdp2rb44-14530poeryamdfwlssfynmxhk 192.168.223.31:2377
 
To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.
 
---从节点加入到管理节点
# docker swarm join --token SWMTKN-1-66syvw9yv8xr457lk4eviixyhd5fviw1gg3ktkwa1nkdp2rb44-14530poeryamdfwlssfynmxhk 192.168.223.31:2377
This node joined a swarm as a worker.
 
----查看集群的节点、状态
# docker node ls
ID                            HOSTNAME   STATUS    AVAILABILITY   MANAGER STATUS   ENGINE VERSION
betygbmft1wkh4kmrf5wx45mc *   master     Ready     Active         Leader           20.10.17
nq4urvgyfdjedabze9p5oll6q     node-01    Ready     Active                          20.10.17
t6wtou7b5jm07qltlrp35ha85     node-02    Ready     Active                          20.10.17
 
---创建网络
# docker network create --opt encrypted --driver overlay --attachable webnet
7e0huckau0g8olzsyvdts8ta2
 
---创建nginx服务（1）
# docker service create --replicas 2 --network webnet --name nginx --publish published=80,target=80 nginx:1.22.0
gf8n3ad4k1pkxqwej6xpdthhe
overall progress: 2 out of 2 tasks 
1/2: running   [==================================================>] 
2/2: running   [==================================================>] 
verify: Service converged 
 
or
---创建nginx服务（2）
# docker service create --replicas 3 --network webnet --name nginx -p 80:80 nginx:1.22.0
 
---查看服务信息
# docker service ls
ID             NAME      MODE         REPLICAS   IMAGE          PORTS
gf8n3ad4k1pk   nginx     replicated   2/2        nginx:1.22.0   *:80->80/tcp
 
---查看nginx进程
# docker service ps nginx
ID             NAME      IMAGE          NODE      DESIRED STATE   CURRENT STATE                ERROR     PORTS
4vxulka6ofd2   nginx.1   nginx:1.22.0   master    Running         Running about a minute ago             
res3qre7ywcx   nginx.2   nginx:1.22.0   node-01   Running         Running 3 minutes ago    
 
---查看服务明细
# docker service inspect nginx          
 
---服务扩展
# docker service scale nginx=3
nginx scaled to 3
overall progress: 3 out of 3 tasks 
1/3: running   [==================================================>] 
2/3: running   [==================================================>] 
3/3: running   [==================================================>] 
verify: Service converged 
 
# docker service ps nginx
ID             NAME      IMAGE          NODE      DESIRED STATE   CURRENT STATE            ERROR     PORTS
4vxulka6ofd2   nginx.1   nginx:1.22.0   master    Running         Running 10 minutes ago             
res3qre7ywcx   nginx.2   nginx:1.22.0   node-01   Running         Running 11 minutes ago             
xpwlus8bbo6z   nginx.3   nginx:1.22.0   node-02   Running         Running 25 seconds ago
 
---删除服务
# docker service rm nginx
nginx

Docker swarm集群的特性：

1）当swarm集群所有节点关机后重启，重启后，之前创建的服务都可以自动启动；

2）当swarm集群某个从节点宕机，从节点上运行的容器会在其他节点上启动，以确保replicas设置的副本数不变；

3）当swarm集群只有一个主节点，且该主节点宕机，那么主节点上运行的服务，不会在从节点上再启动，replicas指定的服务副本数将无法得到保障；

参考：

https://docs.docker.com/engine/reference/commandline/swarm_init/

https://docs.docker.com/engine/reference/commandline/swarm_join/