Docker swarm 是docker官方的三大项目之一，提供docker容器集群服务，是docker官方对容器云生态支持的核心方案，Docker Swarm项目开始于2014年，是Docker公司推出的第一个容器集群项目。使用docker swarm可以将多个docker主机封装为一个大型的虚拟docker主机，swarm集群提供给用户管理集群内所有容器的操作接口与使用一台docker主机几乎相同，从而可以快速打造一套容器云服务。
Docker Swarmkit项目开始于2016年，是Docker公司推出的第二个容器集群项目，于Docker1.12版本正式发布。虽然也叫Swarm，但是与第一个项目完全不同。该项目直接在Docker Engine上内嵌了集群管理功能，并新增了集群管理的用户接口。
两个容器集群项目可能实现了相同的功能，但其上层接口还是有很大的不同，Docker公司推荐用户使用更适合自己的项目，如果都没有使用过，推荐使用后者。另外，Docker Swarm项目并没有被Docker公司列为不推荐的项目，仍然会继续支持新的Docker Engine的功能。
swarm v1是典型的mater-slave结构，需要通过发现服务来选举出manager，而manager是中心管理节点，而各个节点通过运行agent接受manager的统一管理
swarm v2中，swarm集群会自动通过Raft协议分布式选举出manager节点，因此无需配置额外的发现服务，从而避免了单点瓶颈；且swarm v2内置了DNS负载均衡和对外部负载均衡机制的支持
本实验基于docker swarm v1版本，实验环境如下：
docker-1 192.168.1.193
docker-2 192.168.1.194
docker-3 192.168.1.195
在各个docker主机上安装swarm，启动docker daemon
root@docker-1:~# docker pull swarm
root@docker-1:~# docker run --rm swarm -v
swarm version 1.2.8 (48d86b1)
root@docker-1:~# service docker stop
docker stop/waiting
root@docker-1:~# dockerd -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock
root@docker-1:~# netstat -tunlp|grep docker
tcp6 0 0 :::2375 :::* LISTEN 1698/dockerd
root@docker-2:~# docker pull swarm
root@docker-2:~# service docker stop
docker stop/waiting
root@docker-2:~# dockerd -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock
root@docker-3:~# docker pull swarm
root@docker-3:~# service docker stop
docker stop/waiting
root@docker-3:~# dockerd -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock
在任意一个节点上使用docker swarm 命令来在docker hub上进行注册（采用docker hub的服务发现后端，但必须要求所有docker主机可以访问外网），且会产生一个token，用来标识和管理集群
root@docker-1:~# docker run --rm swarm create
1081dc3745b8dfd45ff863c13d74d96c
在所有要加入swarm集群的docker主机上执行swarm join命令，将各个节点加入swarm集群
root@docker-1:~# docker run -d swarm join --addr=192.168.1.193:2375 token://1081dc3745b8dfd45ff863c13d74d96c
fbc0c47268e1e631c4839b41107cac08bd33c9b27380283768efda84ab3ae373
root@docker-2:~# docker run -d swarm join --addr=192.168.1.194:2375 token://1081dc3745b8dfd45ff863c13d74d96c
b88ab2e5eb4e787ad56df06fd6f7e879aacbd35b36743d2943002b882cd8865f
root@docker-3:~# docker run -d swarm join --addr=192.168.1.195:2375 token://1081dc3745b8dfd45ff863c13d74d96c
1b62af7b1ecf7d428f7dd25df71a0523742cecdb1341eb76560225a77336b12f
因为没有配置manager节点，所以此命令无法使用
root@docker-1:~# docker node ls
Error response from daemon: This node is not a swarm manager. Use "docker swarm init" or "docker swarm join" to connect this node to swarm and try again.
查看各个节点的容器情况，可以与后续实验做对比
root@docker-1:~# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
fbc0c47268e1 swarm "/swarm join --add..." 6 minutes ago Up 6 minutes 2375/tcp competent_benz
root@docker-1:~# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
fbc0c47268e1 swarm "/swarm join --add..." 6 minutes ago Up 6 minutes 2375/tcp competent_benz
root@docker-2:~# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
b88ab2e5eb4e swarm "/swarm join --add..." 4 minutes ago Up 4 minutes 2375/tcp romantic_poincare
root@docker-2:~# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
b88ab2e5eb4e swarm "/swarm join --add..." 4 minutes ago Up 4 minutes 2375/tcp romantic_poincare
root@docker-3:~# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
b88ab2e5eb4e swarm "/swarm join --add..." 4 minutes ago Up 4 minutes 2375/tcp romantic_poincare
root@docker-3:~# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
b88ab2e5eb4e swarm "/swarm join --add..." 4 minutes ago Up 4 minutes 2375/tcp romantic_poincare
用swarm manage命令将docker-1节点配置成为管理节点该命令将启用manager服务,且默认监听到2375端口，所有集群的管理都可以通过该服务的接口进行操作，但是manager服务和docker服务
的监听端口相同，而这样做是为了兼容其他基于docker的服务，可以无缝的切换到swarm平台；但有与本次实验采用的是docker容器的方式启用manager服务，本地的2375端口已被docker daemon占用，
所以将manager服务的端口映射到一个空闲的端口12375
root@docker-1:~# docker run -d -p 12375:2375 swarm manage token://1081dc3745b8dfd45ff863c13d74d96c
ad81e842302de642ba7bf5514b12ce6ea46070abc68c6e15a4eefc0b8e5dfc57
root@docker-1:~# netstat -tunlp |grep docker
tcp6 0 0 :::12375 :::* LISTEN 2191/docker-proxy
tcp6 0 0 :::2375 :::* LISTEN 1698/dockerd
产看docker-1节点运行的容器和所有容器
root@docker-1:~# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
ad81e842302d swarm "/swarm manage tok..." 4 seconds ago Up 3 seconds 0.0.0.0:12375->2375/tcp hungry_benz
fbc0c47268e1 swarm "/swarm join --add..." 19 minutes ago Up 19 minutes 2375/tcp competent_benz
root@docker-1:~# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
ad81e842302d swarm "/swarm manage tok..." 13 seconds ago Up 12 seconds 0.0.0.0:12375->2375/tcp hungry_benz
fbc0c47268e1 swarm "/swarm join --add..." 19 minutes ago Up 19 minutes 2375/tcp competent_benz
可以再任意节点执行swarm list 命令查看集群的节点列表
root@docker-1:~# docker run --rm swarm list token://1081dc3745b8dfd45ff863c13d74d96c
192.168.1.193:2375
192.168.1.195:2375
192.168.1.194:2375
root@docker-2:~# docker run --rm swarm list token://1081dc3745b8dfd45ff863c13d74d96c
192.168.1.193:2375
192.168.1.195:2375
192.168.1.194:2375
在docker-1主机上分别执行节点和集群的docker info看看，可以对比一下
WARNING: No swap limit support
root@docker-1:~# docker -H 192.168.1.193:12375 info
Containers: 5
Running: 5
Paused: 0
Stopped: 0
Images: 5
Server Version: swarm/1.2.8
Role: primary
Strategy: spread
Filters: health, port, containerslots, dependency, affinity, constraint, whitelist
Nodes: 3
docker-1: 192.168.1.193:2375
└ ID: A3OC:Z223:S7IY:6KF6:U2TE:N26E:CEMT:2VEH:5AR6:LVY5:U2KI:52P5|192.168.1.193:2375
└ Status: Healthy
└ Containers: 2 (2 Running, 0 Paused, 0 Stopped)
└ Reserved CPUs: 0 / 1
└ Reserved Memory: 0 B / 763 MiB
└ Labels: kernelversion=4.4.0-31-generic, operatingsystem=Ubuntu 14.04.5 LTS, ostype=linux, storagedriver=aufs
└ UpdatedAt: 2017-10-15T13:18:50Z
└ ServerVersion: 17.05.0-ce
docker-2: 192.168.1.194:2375
└ ID: LTSZ:NUCW:U7PJ:E2MB:UD4K:QNS4:EOYG:YC5B:XEYU:BNM5:MZGE:X4R4|192.168.1.194:2375
└ Status: Healthy
└ Containers: 2 (2 Running, 0 Paused, 0 Stopped)
└ Reserved CPUs: 0 / 1
└ Reserved Memory: 0 B / 776.6 MiB
└ Labels: kernelversion=4.4.0-31-generic, operatingsystem=Ubuntu 14.04.5 LTS, ostype=linux, storagedriver=aufs
└ UpdatedAt: 2017-10-15T13:19:04Z
└ ServerVersion: 17.05.0-ce
docker-3: 192.168.1.195:2375
└ ID: A42N:WYIC:KJRG:SPED:IJIS:IYQP:23T4:EWDP:6CT7:IFMB:ZIDF:37WN|192.168.1.195:2375
└ Status: Healthy
└ Containers: 1 (1 Running, 0 Paused, 0 Stopped)
└ Reserved CPUs: 0 / 1
└ Reserved Memory: 0 B / 513.1 MiB
└ Labels: kernelversion=4.4.0-31-generic, operatingsystem=Ubuntu 14.04.5 LTS, ostype=linux, storagedriver=aufs
└ UpdatedAt: 2017-10-15T13:19:03Z
└ ServerVersion: 17.05.0-ce
Plugins:
Volume:
Network:
Swarm:
NodeID:
Is Manager: false
Node Address:
Kernel Version: 4.4.0-31-generic
Operating System: linux
Architecture: amd64
CPUs: 3
Total Memory: 2.005GiB
Name: ad81e842302d
Docker Root Dir:
Debug Mode (client): false
Debug Mode (server): false
Experimental: false
Live Restore Enabled: false
可以发现docker-1上运行有创建manager服务和swarm join时的两个容器，docker-2上运行有swarm join和 ping www.baidu.com
(这个容器是在docker-3上通过manager服务创建的，但却运行在docker-2上，可见是swarm集群调度策略分配的）的两个容器，docker-3上只有swarm join
创建一个nginx服务
root@docker-1:~# docker -H 192.168.1.193:12375 run -d --name my-web --publish 8080:80 nginx
2a888979b129767ff73562587e5cf6672aac13c47d69ea4673887d87f6be552a
通过下面命令可以看到nginx运行在docker-3上（swarm调度策略分配的）
root@docker-1:~# docker -H 192.168.1.193:12375 ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
2a888979b129 nginx "nginx -g 'daemon ..." 15 seconds ago Up 14 seconds 192.168.1.195:8080->80/tcp docker-3/my-web
41ca94b3da41 centos "ping www.baidu.com" 2 hours ago Up 2 hours docker-2/vigilant_bose
root@docker-3:~# netstat -tunlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 910/sshd
tcp6 0 0 :::22 :::* LISTEN 910/sshd
tcp6 0 0 :::2375 :::* LISTEN 1549/dockerd
tcp6 0 0 :::8080 :::* LISTEN 3761/docker-proxy
root@docker-1:~# curl http://192.168.1.195:8080
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
进入nginx容器进行服务修改
root@docker-1:~# docker -H 192.168.1.193:12375 exec -it 2a888979b129 /bin/bash
root@2a888979b129:/# apt-get update &&apt-get install -y vim net-tools
root@2a888979b129:/# netstat -tunlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 1/nginx: master pro
修改nginx服务的配置文件
root@2a888979b129:/# vim /etc/nginx/conf.d/default.conf
location / {
root /var/www/html/;
index index.html index.htm;
}
root@2a888979b129:/# mkdir /var/www/html/ -p
root@2a888979b129:/# vim /var/www/html/index.html
<h1> Hello,Docker ^_^</h1>
root@2a888979b129:/# service nginx restart
[....] Restarting nginx: nginx
重启nginx后，nginx容器会终止，需要重新启动
root@docker-1:~# docker -H 192.168.1.193:12375 start 2a888979b129
2a888979b129
修改后，访问成功
root@docker-2:~# curl http://192.168.1.195:8080
<h1> Hello,Docker ^_^</h1>
更多Docker相关教程见以下内容：