Docker Swarm 是 Docker 的集群管理工具。它将Docker 主机池转变为单个虚拟 Docker 主机。swarm 集群由管理节点（manager）和工作节点（work node）构成。
swarm mananger：负责整个集群的管理工作包括集群配置、服务管理等所有跟集群有关的工作。
work node：即图中的 available node，主要负责运行相应的服务来执行任务（task）。
开启Docker API
修改配置文件
vim /lib/systemd/system/docker.service 将 ExecStart=/usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock 修改为 ExecStart=/usr/bin/dockerd -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock
重启服务
[root@master ~]# systemctl daemon-reload
[root@master ~]# systemctl restart docker
swarm集群创建
主节点开启
[root@master ~]# docker swarm init --advertise-addr 192.168.1.10#创建好主节点时会提示—token配置参数，在配置子节点时需要使用该参数（如图）
子节点开启
使用命令docker swarm join --token
[root@node ~]# docker swarm join --token SWMTKN-1-55cvdjet5qrnkayuaa70aozysu3ztjh1ic21y0x8gw9sb5fgcb-b2om9dp4scs452l4gkqmd0814 192.168.1.10:2377 This node joined a swarm as a worker.
可使用命令查询join使用的token值
docker swarm join-token worker
使用docker node ls查询节点状态
[root@master ~]# docker node ls ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION y8xp0iwjwkmfbxq4rc6qfekpc * master Ready Active Leader 18.09.6 cscxignpj1qb60c4y8dsgf7s7 node Ready Active 18.09.6
swarm集群使用
部署服务
部署一个httpd的service，创建名称为web-server
[root@master ~]# docker service create --name web-server httpd iwjwdip5t893m58tetpegh6wu overall progress: 1 out of 1 tasks 1/1: running [==================================================>] verify: Service converged
查看服务状态
查看当前集群中的service
[root@master ~]# docker service ls ID NAME MODE REPLICAS IMAGE PORTS iwjwdip5t893 web-server replicated 1/1 httpd:latest
查看部署的web-server状态
[root@master ~]# docker service ps web-server ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS ggrt8ldrjts3 web-server.1 httpd:latest node Running Running 45 seconds ago #此时web-server的NODE为node节点，状态为running
服务伸缩/拓展副本
将服务数增加副本，同时运行多个实例
service scale可调整副本数，增加或减少
[root@master ~]# 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
#此时查看服务状态就有5个web-server部署在node节点或master节点
[root@master ~]# docker service ps web-server ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ggrt8ldrjts3 web-server.1 httpd:latest node Running Running 6 minutes ago ue2rls32fdyi web-server.2 httpd:latest master Running Running 41 seconds ago n5e626vifmv8 web-server.3 httpd:latest node Running Running about a minute ago iq7y8ru24oy5 web-server.4 httpd:latest master Running Running 41 seconds ago tp56mrrszkel web-server.5 httpd:latest node Running Running about a minute ago
服务访问
将web-server的80端口映射到外部
[root@master ~]# docker service update --publish-add 80:80 web-server web-server 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
测试
Portainer安装
Portainer 是 Docker 的图形化管理工具，提供状态显示面板、应用模板快速部署、容器镜像网络数据卷的基本操作（包括上传和下载镜像、创建容器等操作）、事件日志显示、容器控制台操作、Swarm 集群和服务等集中管理和操作、登录用户管理和控制等功能。功能 十分全面，基本能满足中小型企业对容器管理的全部需求。
Master 节点，安装 Portainer。
[root@master ~]# docker service create --name portainer --publish 9000:9000 --replicas=1 --constraint 'node.role == manager' --mount type=bind,src=//var/run/docker.sock,dst=/var/run/docker.sock --mount type=volume,src=portainer_data,dst=/data portainer/portainer -H unix:///var/run/docker.sock wbpvqhg13fzrqrwl7epcbhqgo overall progress: 1 out of 1 tasks 1/1: running [==================================================>] verify: Service converged
portainer以一个容器服务开启，可在容器进程中查询
[root@master ~]# docker ps
网页访问http://ip:9000
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