Swarm
分布式系统中多容器管理的困难
生产环境中同一种类型的容器往往散落在各个主机节点上，因此无法回避下列问题：
- 怎么去管理这么多容器？
- 怎么能方便的横向扩展？
- 如果容器down了，怎么能自动恢复？
- 如何去更新容器而不影响业务？
- 如何去监控追踪这些容器？
- 怎么去调度容器的创建？
- 保护隐私数据？
Docker Swarm Mode Architecture
综上所述，容器编排应运而生，docker的容器编排工具的实现有很多，只不过swarm是内置于docker的容器编排工具，由docker公司内置到docker中。
Service & Replicas
- 在docker swarm模式下Service的概念和Docker Compose中的概念基本一致。
- 在Replicas横向扩展模式下，每个Replicas都是一个实际的容器，每个容器都会根据调度系统的计算，被分配在不同的node上运行。也就是说，通过Swarm Manager部署去部署一个Service时候，其实是不知道容器最终会运行在哪些swarm节点上的，这取决于Swarm的调度算法的计算结果(例如：根据节点负载)。
搭建3节点的swam cluster
# 初始化一个swarm集群，在Swarm Manager中: 192.168.31.220
[root@localhost ~]# docker swarm init --advertise-addr=192.168.31.220
Swarm initialized: current node (wx8spu6s1tszpo4hbvkc5v1qt) is now a manager.
To add a worker to this swarm, run the following command:
docker swarm join --token SWMTKN-1-5mxs3nwkgidt55i7erq1d663xvj94lanh2xdep76b4q7xxg15w-cdgbba27hiqeb0b6buzzv6whq 192.168.31.220:2377
To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.
# swarm node1 加入 cluster: 192.168.31.240
[root@centos7_two ~]# docker swarm join --token SWMTKN-1-5mxs3nwkgidt55i7erq1d663xvj94lanh2xdep76b4q7xxg15w-cdgbba27hiqeb0b6buzzv6whq 192.168.31.220:2377
This node joined a swarm as a worker.
# swarm node2 加入 cluster: 192.168.31.250
[root@centos7_three ~]# docker swarm join --token SWMTKN-1-5mxs3nwkgidt55i7erq1d663xvj94lanh2xdep76b4q7xxg15w-cdgbba27hiqeb0b6buzzv6whq 192.168.31.220:2377
This node joined a swarm as a worker.
# 在Swarm Manager中 查看Swam Cluster信息
[root@localhost ~]# docker node list
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
p4jexd5om3yofpgz3n4vyq2yt centos7_three Ready Active 18.09.7
ms9s0pquan1hvue2ubaxn2evl centos7_two Ready Active 18.09.7
wx8spu6s1tszpo4hbvkc5v1qt * localhost.localdomain Ready Active Leader 18.09.7
Service的创建维护和水平扩展
默认创建一个Service可能会运行在Cluster中的任意一个节点上。
# 创建一个service：create相当于run
[root@localhost ~]# docker service create --name demo busybox sh -c "while true;do sleep 3600;done"
jvomccrnms8cz14jbcthwg6ey
overall progress: 1 out of 1 tasks
1/1: running [==================================================>]
verify: Service converged
# 查看service：也就是container的位置 relicated 1/1 代表此容器水平扩展的数量
[root@localhost ~]# docker service ls
ID NAME MODE REPLICAS IMAGE PORTS
jvomccrnms8c demo replicated 1/1 busybox:latest
# 查看service(container)具体运行的位置：centos7_three
[root@localhost ~]# docker service ps demo
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
sfy5hefhksyw demo.1 busybox:latest centos7_three Running Running 2 minutes ago
# 在 centos7_three 节点中查看
[root@centos7_three ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
112843852d0c busybox:latest "sh -c 'while true;d…" 9 minutes ago Up 9 minutes demo.1.sfy5hefhksywi36rhst1zq06w
# 对指定service做水平扩展: 自带恢复能力，如果其中有一个replicated故障，会自动在Cluster中新增加一个replicated节点。 让分子和分母一直可以确保相等。 5ready/5num
[root@localhost lb-scale]# docker service scale demo=5
demo 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
# 查看service replicated 5/5 已经ready的数量/要扩展的数量
[root@localhost lb-scale]# docker service ls
ID NAME MODE REPLICAS IMAGE PORTS
jvomccrnms8c demo replicated 5/5 busybox:latest
# 查看指定的容器
[root@localhost lb-scale]# docker service ls
ID NAME MODE REPLICAS IMAGE PORTS
jvomccrnms8c demo replicated 5/5 busybox:latest
[root@localhost lb-scale]# docker service ps demo
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
sfy5hefhksyw demo.1 busybox:latest centos7_three Running Running 15 minutes ago
mh1ero6kazrw demo.2 busybox:latest centos7_three Running Running 2 minutes ago
jpynv8ne89xc demo.3 busybox:latest centos7_two Running Running 2 minutes ago
w705h9lauvrv demo.4 busybox:latest localhost.localdomain Running Running 2 minutes ago
mf9y8mg15we5 demo.5 busybox:latest localhost.localdomain Running Running 2 minutes ago
# 删除指定的Service(后台需要一系列复杂的操作，稍有延迟性)
[root@localhost lb-scale]# docker service rm demo
demo
# 离开ji'qu
docker swarm leave --force
Swarm部署wordpress
# 创建overlay网络：用于不同节点上的容器通信
[root@localhost ~]# docker network create -d overlay demo
2xaj5rg3s1ng1fj3xhju365tq
[root@localhost ~]# docker network ls | grep demo
2xaj5rg3s1ng demo overlay swarm
# 创建mysql 服务
[root@localhost ~]# docker service create --name mysql --env MYSQL_ROOT_PASSWORD=root --env MYSQL_DATABASE=wordpress --network demo --mount type=volume,source=mysql-data,destination=/var/lib/mysql mysql
[root@localhost ~]# docker service ls
ID NAME MODE REPLICAS IMAGE PORTS
w5bgs2khjfdc mysql replicated 1/1 mysql:latest
[root@localhost ~]# docker service ps mysql
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
ifhi4fb7g0wj mysql.1 mysql:latest localhost.localdomain Running Running 40 seconds ago
[root@localhost ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
32a3ea0323d4 mysql:latest "docker-entrypoint.s…" About a minute ago Up About a minute 3306/tcp, 33060/tcp mysql.1.ifhi4fb7g0wjgensmtfnj0u4l
# 创建wordpress 服务
[root@localhost ~]# docker service create --name wordpress -p 80:80 --env WORDPRESS_DB_PASSWORD=root --env WORDPRESS_DB_HOST=mysql --network demo wordpress
# 访问 centos7_three http://192.168.31.250 发现可以与mysql通信
[root@localhost ~]# docker service ps wordpress
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
bblw244vhc28 wordpress.1 wordpress:latest centos7_three Running Running 10 minutes ago