docker swarm 实现健康检测功能

swarm

Swarm是Docker公司在2014年12月初发布的一套较为简单的工具，用来管理Docker集群，它将一群Docker宿主机变成一个单一的，虚拟的主机。Swarm使用标准的Docker API接口作为其前端访问入口，换言之，各种形式的Docker Client(docker client in go, docker_py, docker等)均可以直接与Swarm通信。
Swarm deamon只是一个调度器（Scheduler）加路由器(router)，Swarm自己不运行容器，它只是接受docker客户端发送过来的请求，调度适合的节点来运行容器，这意味着，即使Swarm由于某些原因挂掉了，集群中的节点也会照常运行，当Swarm重新恢复运行之后，它会收集重建集群信息

swarm集群

使用的是docker自带的swarm mode，也就是docker集群的管理和编排。所谓的编排就是指多台集群的管理， 主机的配置，容器的调度等。
swarm mode是docker engine中自带的一种模式，很容易使用，并且无须安装其他的软件。 在使用swarm mode的时候，几台主机上都要先安装好docker。

搭建swarm集群

1.初始化

[root@server1 ~]# docker swarm init
Swarm initialized: current node (3w9leghq2cy8eu01wufxs12ft) is now a manager.

To add a worker to this swarm, run the following command:

    docker swarm join --token SWMTKN-1-1vfrxr6d0323fcoxpdb5keqywajangxu8i8lq0up2mo09boy36-ausloqbfrkfkbb5vlkad4ya18 172.25.68.1:2377                     ##token作为通讯的密钥

To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.

2.docker2和docker3加入swarm集群中

[root@server2 docker]# docker swarm join --token SWMTKN-1-1vfrxr6d0323fcoxpdb5keqywajangxu8i8lq0up2mo09boy36-ausloqbfrkfkbb5vlkad4ya18 172.25.68.1:2377
This node joined a swarm as a worker.

[root@server3 docker]# docker swarm join --token SWMTKN-1-1vfrxr6d0323fcoxpdb5keqywajangxu8i8lq0up2mo09boy36-ausloqbfrkfkbb5vlkad4ya18 172.25.68.1:2377
This node joined a swarm as a worker.

[root@server1 ~]# docker node ls						##查看节点状态
ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS      ENGINE VERSION
3w9leghq2cy8eu01wufxs12ft *   server1             Ready               Active              Leader              18.06.1-ce
7xtxjg5e9byvmke00fbfpswxa     server2             Ready               Active                                  18.06.1-ce
v3d9r7sksrvte5iifb2fs4qnn     server3             Ready               Active                                  18.06.1-ce

3.都导入nginx镜像

[root@server1 ~]# docker load -i nginx.tar 
[root@server2 ~]# docker load -i nginx.tar 
[root@server3 ~]# docker load -i nginx.tar

4.创建swarm的网络

[root@server1 ~]# docker network create -d overlay webnet
w7kdnfsbi1w2gqyc8ocufyhd6

[root@server1 ~]# docker network ls
NETWORK ID          NAME                DRIVER              SCOPE
cfcf10b23f5d        bridge              bridge              local
5a713ee1094b        docker_gwbridge     bridge              local
af113c71e06b        host                host                local
o0uztujanmpj        ingress             overlay             swarm
cf56e94132cb        none                null                local
w7kdnfsbi1w2        webnet              overlay             swarm

5.部署一个服务群集

#在manager节点部署nginx服务，服务数量为3个 ，使用nginx镜像
[root@server1 ~]# docker service create --name web --network webnet --publish 80:80 --replicas 3 nginx

[root@server1 ~]# docker service ls
ID                  NAME                MODE                REPLICAS            IMAGE               PORTS
nbziwdj808nd        web                 replicated          3/3                 nginx:latest        *:80->80/tcp

[root@server1 ~]# docker service ps web
ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE                ERROR               PORTS
g8rri3b9y6hk        web.1               nginx:latest        server2             Running             Running about a minute ago                       
rnmx4cyafvdv        web.2               nginx:latest        server3             Running             Running about a minute ago                       
y9pha70e4f4i        web.3               nginx:latest        server1             Running             Running about a minute ago

6.添加 6 个nginx 服务

[root@server1 ~]# docker service scale web=6

[root@server1 ~]# docker service ps web
ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE            ERROR               PORTS
g8rri3b9y6hk        web.1               nginx:latest        server2             Running             Running 2 minutes ago                        
rnmx4cyafvdv        web.2               nginx:latest        server3             Running             Running 2 minutes ago                        
y9pha70e4f4i        web.3               nginx:latest        server1             Running             Running 2 minutes ago                        
z0trqfutelz3        web.4               nginx:latest        server2             Running             Running 22 seconds ago                       
d2hky35dog9k        web.5               nginx:latest        server3             Running             Running 21 seconds ago                       
xhzch8cz6xn7        web.6               nginx:latest        server1             Running             Running 20 seconds ago         
              
[root@server1 ~]# docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS               NAMES
fccad5a3b596        nginx:latest        "nginx -g 'daemon of…"   45 seconds ago      Up 41 seconds       80/tcp              web.6.xhzch8cz6xn7636zy5o7qic8u
bb6f1cddfa90        nginx:latest        "nginx -g 'daemon of…"   3 minutes ago       Up 3 minutes        80/tcp              web.3.y9pha70e4f4if2r9ckwsn6lea

7.编写测试页面

[root@server1 ~]# vim index.html
server1
[root@server1 ~]# docker cp index.html bb6f1cddfa90:/usr/share/nginx/html

[root@server1 ~]# docker cp index.html fccad5a3b596:/usr/share/nginx/html

server2 server3同样操作，index.html内容分别为server2 server3

8.测试集群负载均衡

添加监控

1.导入镜像并创建监控

[root@server1 ~]# docker load -i visualizer.tar
[root@server1 ~]# docker service create \
> --name=viz \
> --publish=8080:8080/tcp \
> --constraint=node.role==manager \
> --mount=type=bind,src=/var/run/docker.sock,dst=/var/run/docker.sock \
> dockersamples/visualizer

2.查看监控和节点是否在线

[root@server1 ~]# docker service ls
ID                  NAME                MODE                REPLICAS            IMAGE                             PORTS
aejx2ocibogm        viz                 replicated          1/1                 dockersamples/visualizer:latest   *:8080->8080/tcp
nbziwdj808nd        web                 replicated          6/6                 nginx:latest                      *:80->80/tcp

3.浏览器：输入172.25.68.1:8080，可以看到6个nginx的进程被平均分在了三台机子上

滚动更新

#添加新的镜像
[root@server1 ~]# docker load -i httpd.tar
[root@server2 ~]# docker load -i httpd.tar
[root@server3 ~]# docker load -i httpd.tar
[root@server1 ~]# docker service update --image httpd --update-delay 5s --update-parallelism 5 web
##每隔五秒更新，每次更新五个机子

2.测试

浏览器的监控镜像由nginx变成了httpd

高可用

1.停掉一个node

[root@server2 ~]# systemctl stop docker

2.测试

浏览器的监控显示server2故障，并且6个httpd进程被平均分到docker1和docker3上