创建 Docker Swarm 集群

Question

Docker Swarm 是由 Docker 提供的原生集群工具，通过它可以很方便的将多台主机组成一个集群。 其中，每个集群都可以有多台 manager 和多台 worker。

创建 Swarm 集群

创建 Swarm 集群的动作其实就是把一台主机 Node 初始化成 manager 的行为，方法超级简单，只需要在 manager node 主机上执行

docker swarm init --advertise-addr 172.27.0.8

Swarm initialized: current node (wrjpsf0ms32ioem9ozw5xu27r) is now a manager.
To add a worker to this swarm, run the following command:
    docker swarm join --token SWMTKN-1-0brpw02md8cpm97xld6go5tat7fuj7hggdvp7an5rm49ybhp8v-76mcm21ak8phkez4ktf8wa5b0 172.27.0.8:2377
To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.

docker swarm init 会随机生成两个 token，一个 worker token，一个 manager token。

比如上面输出中的 SWMTKN-1-0brpw02md8cpm97xld6go5tat7fuj7hggdvp7an5rm49ybhp8v-76mcm21ak8phkez4ktf8wa5b0 就是Worker Token

后面的 172.27.0.8:2377 就是当前 cluster 的 IP 和监听的端口

而根据提示，获取 manager token 通过执行下面命令来获取

docker swarm join-token manager

To add a manager to this swarm, run the following command:
    docker swarm join --token SWMTKN-1-0brpw02md8cpm97xld6go5tat7fuj7hggdvp7an5rm49ybhp8v-0zyncobrt5vfcms9r8f1exyok 172.27.0.8:2377

manager Token 为 SWMTKN-1-0brpw02md8cpm97xld6go5tat7fuj7hggdvp7an5rm49ybhp8v-0zyncobrt5vfcms9r8f1exyok

我们可以用 docker info 查一下 Swarm 状态

docker info |sed -n "/^Swarm/,+5 p"

WARNING: bridge-nf-call-ip6tables is disabled
Swarm: active
 NodeID: wrjpsf0ms32ioem9ozw5xu27r
 Is Manager: true
 ClusterID: 9pz2p3d57im2yo2v3vayb5w8n
 Managers: 1
 Nodes: 1

其中 Is Manager: true 说明本节点是作为 Manager， Managers: 1 说明集群中有一个Manager， Nodes: 1 说明集群中只有一个节点。

我们还可以通过 docker node ls 命令来查看集群中各节点的信息

docker node ls

ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS      ENGINE VERSION
wrjpsf0ms32ioem9ozw5xu27r *   VM_0_8_centos       Ready               Active              Leader              18.03.1-ce

ID后面的 * 号表示这个记录就是当前NODE的信息。

向集群中添加节点

现在我们往这个集群中添加一个 worker 节点，方法很简单，跟着 docker swarm init 输出中的命令来执行就行了

这次我们在 worker node 主机上执行

docker swarm join --token SWMTKN-1-0brpw02md8cpm97xld6go5tat7fuj7hggdvp7an5rm49ybhp8v-76mcm21ak8phkez4ktf8wa5b0 118.24.148.238:2377

This node joined a swarm as a worker.

注意到我这里 docker swarm join 的IP是 118.24.148.238, 而不是前面输出的 172.27.0.8, 这是因为 172.27.0.8 是我云主机的内网IP，而 118.24.148.238 才是映射出来的公网IP地址。

而我的 worker node 主机是通过公网IP来访问 manager node 主机的，因此这里对IP进行了修改。

另外，有时候可能会遇到需要把一个 work 节点提升到 manager 节点的可能，则可以在 join 命令中添加 --listen-addr ${WORKER_IP}:2377 作为监听准备

增加节点后，再来看一下集群中各节点的信息：

在 manager node 上执行

docker node ls

ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS      ENGINE VERSION
qpinc63kw5ta2t1b5ojhi8r1o     T520                Ready               Active                                  18.05.0-ce
wrjpsf0ms32ioem9ozw5xu27r *   VM_0_8_centos       Ready               Active              Leader              18.03.1-ce

可以看到多了一个NODE信息。

另外值得一说的是，类似 docker node ls 这些管理类的命令只能在 manager node 上执行，若在 worker node 上执行则会失败：

[lujun9972@T520 ~]$ docker node ls
Error response from daemon: This node is not a swarm manager. Worker nodes can't be used to view or modify cluster state. Please run this command on a manager node or promote the current node to a manager.

部署服务到集群中

我们在 manager node 上使用 docker service create 命令来创建一个服务.

但是在部署服务前，先需要保证集群中所有节点都预先有了要使用的镜像

docker service create 跟 docker start 的命令接口有点像：

docker service create --name web --publish 8080:80 nginx:alpine

rttpyxf8wbajmsr312j4r20ub

overall progress: 0 out of 1 tasks 
1/1:   overall progress: 0 out of 1 tasks 1/1: assigned  overall progress: 0 out of 1 tasks 1/1: starting  overall progress: 0 out of 1 tasks 1/1: starting  overall progress: 0 out of 1 tasks 1/1: starting  overall progress: 0 out of 1 tasks 1/1: running   overall progress: 1 out of 1 tasks 
verify: Waiting 5 seconds to verify that tasks are stable... verify: Waiting 5 seconds to verify that tasks are stable... verify: Waiting 5 seconds to verify that tasks are stable... verify: Waiting 5 seconds to verify that tasks are stable... verify: Waiting 5 seconds to verify that tasks are stable... verify: Waiting 4 seconds to verify that tasks are stable... verify: Waiting 4 seconds to verify that tasks are stable... verify: Waiting 4 seconds to verify that tasks are stable... verify: Waiting 4 seconds to verify that tasks are stable... verify: Waiting 4 seconds to verify that tasks are stable... verify: Waiting 3 seconds to verify that tasks are stable... verify: Waiting 3 seconds to verify that tasks are stable... verify: Waiting 3 seconds to verify that tasks are stable... verify: Waiting 3 seconds to verify that tasks are stable... verify: Waiting 3 seconds to verify that tasks are stable... verify: Waiting 2 seconds to verify that tasks are stable... verify: Waiting 2 seconds to verify that tasks are stable... verify: Waiting 2 seconds to verify that tasks are stable... verify: Waiting 2 seconds to verify that tasks are stable... verify: Waiting 2 seconds to verify that tasks are stable... verify: Waiting 1 seconds to verify that tasks are stable... verify: Waiting 1 seconds to verify that tasks are stable... verify: Waiting 1 seconds to verify that tasks are stable... verify: Waiting 1 seconds to verify that tasks are stable... verify: Waiting 1 seconds to verify that tasks are stable... verify: Service converged 

这里 --name web 表示创建的服务名称为 web, 这个服务是基于 nginx:alpine 这个镜像的，而且容器的HTTP端口发布在主机的8080端口上。

而上面命令中的输出 rttpyxf8wbajmsr312j4r20ub 则是这个服务的ID号

我们可以使用 docker service ls 来查看集群中的服务

docker service ls

ID                  NAME                MODE                REPLICAS            IMAGE               PORTS
rttpyxf8wbaj        web                 replicated          1/1                 nginx:alpine        *:8080->80/tcp

通过上面的 REPLICAS 可以知道，这个服务由单个容器提供，而且目前有一个容器在提供服务。

我们可以通过 docker service create 的 --replicas 参数来设置创建服务时启动的副本数，比如

docker service create --name ping --replicas 2 alpine ping www.baidu.com

k2cvjo3nb4o7d1cqr4thv4c51

overall progress: 0 out of 2 tasks 
1/2:   
2/2:   overall progress: 0 out of 2 tasks 1/2: assigned  2/2: assigned  overall progress: 0 out of 2 tasks 1/2: preparing 2/2: preparing overall progress: 0 out of 2 tasks 1/2: preparing 2/2: preparing overall progress: 0 out of 2 tasks 1/2: preparing 2/2: preparing overall progress: 0 out of 2 tasks 1/2: preparing 2/2: preparing overall progress: 0 out of 2 tasks 1/2: preparing 2/2: preparing overall progress: 0 out of 2 tasks 1/2: preparing 2/2: preparing overall progress: 0 out of 2 tasks 1/2: preparing 2/2: preparing overall progress: 0 out of 2 tasks 1/2: preparing 2/2: preparing overall progress: 0 out of 2 tasks 1/2: preparing 2/2: preparing overall progress: 0 out of 2 tasks 1/2: preparing 2/2: preparing overall progress: 0 out of 2 tasks 1/2: preparing 2/2: preparing overall progress: 0 out of 2 tasks 1/2: preparing 2/2: preparing overall progress: 0 out of 2 tasks 1/2: preparing 2/2: preparing overall progress: 0 out of 2 tasks 1/2: preparing 2/2: preparing overall progress: 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verify: Waiting 5 seconds to verify that tasks are stable... verify: Waiting 5 seconds to verify that tasks are stable... verify: Waiting 5 seconds to verify that tasks are stable... verify: Waiting 5 seconds to verify that tasks are stable... verify: Waiting 5 seconds to verify that tasks are stable... verify: Waiting 4 seconds to verify that tasks are stable... verify: Waiting 4 seconds to verify that tasks are stable... verify: Waiting 4 seconds to verify that tasks are stable... verify: Waiting 4 seconds to verify that tasks are stable... verify: Waiting 4 seconds to verify that tasks are stable... verify: Waiting 3 seconds to verify that tasks are stable... verify: Waiting 3 seconds to verify that tasks are stable... verify: Waiting 3 seconds to verify that tasks are stable... verify: Waiting 3 seconds to verify that tasks are stable... verify: Waiting 3 seconds to verify that tasks are stable... verify: Waiting 2 seconds to verify that tasks are stable... verify: Waiting 2 seconds to verify that tasks are stable... verify: Waiting 2 seconds to verify that tasks are stable... verify: Waiting 2 seconds to verify that tasks are stable... verify: Waiting 2 seconds to verify that tasks are stable... verify: Waiting 1 seconds to verify that tasks are stable... verify: Waiting 1 seconds to verify that tasks are stable... verify: Waiting 1 seconds to verify that tasks are stable... verify: Waiting 1 seconds to verify that tasks are stable... verify: Waiting 1 seconds to verify that tasks are stable... verify: Service converged 

这里创建了一个名为 ping 的服务，这个服务启动了两个alpine容器，执行 ping www.baidu.com 这个命令

我们再来看一下这个集群中的服务

docker service ls

ID                  NAME                MODE                REPLICAS            IMAGE               PORTS
k2cvjo3nb4o7        ping                replicated          2/2                 alpine:latest       
rttpyxf8wbaj        web                 replicated          1/1                 nginx:alpine        *:8080->80/tcp

调整服务规模

使用命令 docker service scale ${SERVICE}=${NUMBER} 可以调整指定服务的规模，比如

docker service scale web=5

web scaled to 5

overall progress: 0 out of 5 tasks 
1/5:   
2/5:   
3/5:   
4/5:   
5/5:   1/5: running   overall progress: 1 out of 5 tasks 2/5: assigned  3/5: assigned  4/5: assigned  5/5: assigned  1/5: running   overall progress: 1 out of 5 tasks 2/5: preparing 3/5: ready     4/5: starting  5/5: preparing 1/5: running   overall progress: 1 out of 5 tasks 2/5: starting  3/5: starting  4/5: starting  5/5: starting  1/5: running   overall progress: 1 out of 5 tasks 1/5: running   2/5: starting  3/5: starting  4/5: starting  5/5: starting  overall progress: 1 out of 5 tasks 2/5: starting  3/5: starting  4/5: starting  5/5: starting  1/5: running   overall progress: 1 out of 5 tasks 2/5: starting  3/5: starting  4/5: starting  5/5: starting  1/5: running   overall progress: 1 out of 5 tasks 4/5: starting  5/5: starting  1/5: running   2/5: starting  3/5: starting  overall progress: 1 out of 5 tasks 2/5: starting  3/5: starting  4/5: starting  5/5: starting  1/5: running   overall progress: 1 out of 5 tasks 2/5: starting  3/5: starting  4/5: running   5/5: starting  1/5: running   overall progress: 2 out of 5 tasks 2/5: starting  3/5: starting  4/5: running   5/5: starting  1/5: running   overall progress: 2 out of 5 tasks 2/5: starting  3/5: starting  4/5: running   5/5: starting  1/5: running   overall progress: 2 out of 5 tasks 2/5: running   3/5: running   4/5: running   5/5: running   1/5: running   overall progress: 5 out of 5 tasks 
verify: Waiting 5 seconds to verify that tasks are stable... verify: Waiting 5 seconds to verify that tasks are stable... verify: Waiting 5 seconds to verify that tasks are stable... verify: Waiting 5 seconds to verify that tasks are stable... verify: Waiting 5 seconds to verify that tasks are stable... verify: Waiting 4 seconds to verify that tasks are stable... verify: Waiting 4 seconds to verify that tasks are stable... verify: Waiting 4 seconds to verify that tasks are stable... verify: Waiting 4 seconds to verify that tasks are stable... verify: Waiting 4 seconds to verify that tasks are stable... verify: Waiting 3 seconds to verify that tasks are stable... verify: Waiting 3 seconds to verify that tasks are stable... verify: Waiting 3 seconds to verify that tasks are stable... verify: Waiting 3 seconds to verify that tasks are stable... verify: Waiting 3 seconds to verify that tasks are stable... verify: Waiting 2 seconds to verify that tasks are stable... verify: Waiting 2 seconds to verify that tasks are stable... verify: Waiting 2 seconds to verify that tasks are stable... verify: Waiting 2 seconds to verify that tasks are stable... verify: Waiting 2 seconds to verify that tasks are stable... verify: Waiting 1 seconds to verify that tasks are stable... verify: Waiting 1 seconds to verify that tasks are stable... verify: Waiting 1 seconds to verify that tasks are stable... verify: Waiting 1 seconds to verify that tasks are stable... verify: Waiting 1 seconds to verify that tasks are stable... verify: Service converged 

这个命令将启动5个容器来提供web服务,我们再来看一下这个集群中的服务

docker service ls

ID                  NAME                MODE                REPLICAS            IMAGE               PORTS
k2cvjo3nb4o7        ping                replicated          2/2                 alpine:latest       
rttpyxf8wbaj        web                 replicated          5/5                 nginx:alpine        *:8080->80/tcp

我们可以看到 web 服务的 REPLICAS 变成了 5

查看服务详细信息

我们可以使用 docker service inspect 命令来查看某项服务的详细内容，比如

docker service inspect --pretty web

ID:             rttpyxf8wbajmsr312j4r20ub
Name:           web
Service Mode:   Replicated
 Replicas:      5
Placement:
UpdateConfig:
 Parallelism:   1
 On failure:    pause
 Monitoring Period: 5s
 Max failure ratio: 0
 Update order:      stop-first
RollbackConfig:
 Parallelism:   1
 On failure:    pause
 Monitoring Period: 5s
 Max failure ratio: 0
 Rollback order:    stop-first
ContainerSpec:
 Image:         nginx:alpine@sha256:56a9367b64eaef37894842a6f7a19a0ef8e7bd5de964aa844a70b3e2d758033c
Resources:
Endpoint Mode:  vip
Ports:
 PublishedPort = 8080
  Protocol = tcp
  TargetPort = 80
  PublishMode = ingress 

我们还可以使用 docker service ps ${SERVICE} 来查看服务运行在那几个node主机上

docker service ps web

ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE            ERROR               PORTS
xsldf1trr9ea        web.1               nginx:alpine        VM_0_8_centos       Running             Running 35 minutes ago                       
rf7s8r2e44xy        web.2               nginx:alpine        VM_0_8_centos       Running             Running 5 minutes ago                        
g0fc0edmriig        web.3               nginx:alpine        VM_0_8_centos       Running             Running 5 minutes ago                        
2y39megirflj        web.4               nginx:alpine        VM_0_8_centos       Running             Running 5 minutes ago                        
on0k4qnv7d5v        web.5               nginx:alpine        VM_0_8_centos       Running             Running 5 minutes ago                        

可以看到所有的容器都是运行在 VM_0_8_centos 这个节点上的，我们在这个节点上直接运行 docker ps 命令来看看是不是有5个nginx容器在运行

docker ps  |grep nginx:alpine

e93f8e412c4d        nginx:alpine        "nginx -g 'daemon of…"   11 minutes ago      Up 11 minutes       80/tcp              web.2.rf7s8r2e44xyvmqdno7442oez
abecc4812055        nginx:alpine        "nginx -g 'daemon of…"   11 minutes ago      Up 11 minutes       80/tcp              web.3.g0fc0edmriigwx4crz64zv3id
cc7d82708eec        nginx:alpine        "nginx -g 'daemon of…"   11 minutes ago      Up 11 minutes       80/tcp              web.4.2y39megirflj5nwko3kvhl8yu
4d695daec1ef        nginx:alpine        "nginx -g 'daemon of…"   11 minutes ago      Up 11 minutes       80/tcp              web.5.on0k4qnv7d5v6b0g6z8s361s2
fa08b0567c13        nginx:alpine        "nginx -g 'daemon of…"   42 minutes ago      Up 42 minutes       80/tcp              web.1.xsldf1trr9eavsdsh9efpne55

可以看到确实是5个容器在跑，与结果温和

删除服务

删除服务就特别简单了，直接在manager node上运行 docker service rm ${SERVICE} 就行了，比如

docker service rm ping  

ping

然后我们再用查看一下集群中的服务

docker service ls

ID                  NAME                MODE                REPLICAS            IMAGE               PORTS
rttpyxf8wbaj        web                 replicated          5/5                 nginx:alpine        *:8080->80/tcp

现在只剩下 web 这一个服务了

服务升级

当提供服务容器的镜像发生更改后，可以使用 docker service update --image ${NEW_IMAGE} ${SERVICE} 来进行服务升级。

docker service update --image nginx:1.15.1-alpine-perl web

我们再来看一下集群中的服务

docker service ls

ID                  NAME                MODE                REPLICAS            IMAGE                      PORTS
rttpyxf8wbaj        web                 replicated          5/5                 nginx:1.15.1-alpine-perl   *:8080->80/tcp

可以看到，服务镜像已经发生了改变。

NODE退出集群

要将某个NODE退出集群十分简单，只需要在那个node上执行 docker swarm leave 即可。

比如我在 worker node 上执行

docker swarm leave

Node left the swarm.

再在 manager node 上查看一下 node 信息

docker node ls

ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS      ENGINE VERSION
qpinc63kw5ta2t1b5ojhi8r1o     T520                Down                Active                                  18.05.0-ce
wrjpsf0ms32ioem9ozw5xu27r *   VM_0_8_centos       Ready               Active              Leader              18.03.1-ce

可以看到集群中 T520 的状态已经变成 Down 了，要想把这个节点完全从集群中移除，则可以在 manager node 上执行 docker node rm 命令

docker node rm T520

T520

再查看一下 node 信息

docker node ls

ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS      ENGINE VERSION
wrjpsf0ms32ioem9ozw5xu27r *   VM_0_8_centos       Ready               Active              Leader              18.03.1-ce

好了， T520 这个 node 已经被彻底移除了。