Docker集群之swarm

avatar 2020年2月25日18:31:52 评论 1,278 次浏览

我们使用物理机或者云主机,通过应用把所有服务器连接到一起供多个服务使用,这样既达到了资源的合理利用又能保证系统的稳定性,这就是集群。集群的好处是能够根据流量的增加与减少进行机器灵活伸缩,灵活简单实用。但是这里说的是Docker的集群,在Docker 1.12以及以上版本中,Docker官方推出了Swarm容器集群服务,简单的理解为把多个主机上的Docker组成一个Docker集群,使容器跨网组成跨主机的子网网络。

swarm简介

swarm是管理集群工具,主要作用就是把若干台Docker主机抽象的组成一个整体,可以通过一个统一入口管理这些主机上的docker资源。swarm和kubernetes类似,但是更轻,具有的功能比kubernetes更少一些。

安装docker

我使用的是yum安装,可以参考https://www.wulaoer.org/?p=260 只执行到[6]就可以了。

swarm集群环境配置

docker安装之后不能直接pull swarm的。swarm需要每台安装docker的服务器上开启基于HTTP的DockerAPI,在集群中有一台是swarmManager的管理者,用来管理整个集群中的容器资源。管理者不是针对服务,而是针对集群的管理,例如:在一台服务器上的docker关闭了,swarm会把这台服务器上运行的服务迁移到另外一台正常的服务器上。默认环境下docker是没有开启API,所以需要手动开启。

[root@wulaoer.org ~]# vim /lib/systemd/system/docker.service 
[Unit]
Description=Docker Application Container Engine
Documentation=https://docs.docker.com
After=network-online.target firewalld.service
Wants=network-online.target

[Service]
Type=notify
# the default is not to use systemd for cgroups because the delegate issues still
# exists and systemd currently does not support the cgroup feature set required
# for containers run by docker
ExecStart=/usr/bin/dockerd -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock  #追加启动参数
ExecReload=/bin/kill -s HUP $MAINPID

也可以直接使用sed替换

sed -i 's/ExecStart.*/& -H tcp:\/\/0.0.0.0:2375 -H unix:\/\/\/var\/run\/docker.sock/g'  /lib/systemd/system/docker.service

docker配置了API之后才可以启动docker,这个端口是随意的,也可以换成另外一个不使用的端口。下面重启docker服务,查看一下是否开启了API。

[root@wulaoer.org ~]# systemctl daemon-reload
[root@wulaoer.org ~]# systemctl restart docker
[root@wulaoer.org ~]# netstat -tlnp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 127.0.0.1:25            0.0.0.0:*               LISTEN      1463/master         
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      981/sshd            
tcp6       0      0 ::1:25                  :::*                    LISTEN      1463/master         
tcp6       0      0 :::8090                 :::*                    LISTEN      4544/java           
tcp6       0      0 :::8091                 :::*                    LISTEN      17883/java          
tcp6       0      0 127.0.0.1:8000          :::*                    LISTEN      4544/java           
tcp6       0      0 :::2375                 :::*                    LISTEN      18413/dockerd       
tcp6       0      0 :::3306                 :::*                    LISTEN      1405/mysqld         
tcp6       0      0 :::22                   :::*                    LISTEN      981/sshd 

swarm开启了API,我们就可以pull一下swam了,

[root@wulaoer.org ~]# docker pull swarm
Using default tag: latest
latest: Pulling from library/swarm
d85c18077b82: Pull complete 
1e6bb16f8cb1: Pull complete 
85bac13497d7: Pull complete 
Digest: sha256:b866583a3b8791bcd705b7bc0fd94c66b695a1a2dbaeb5f59ed29940e5015dc8
Status: Downloaded newer image for swarm:latest

注意,如果pull swarm下载不下来,可以尝试修改一下hosts文件,利用dig工具查看,先安装dig

[root@wulaoer.org ~]#  yum install bind-utils       
[root@wulaoer.org ~]#  dig @114.114.114.114 registry-1.docker.io

; <<>> DiG 9.11.4-P2-RedHat-9.11.4-9.P2.el7 <<>> @114.114.114.114 registry-1.docker.io
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 19575
;; flags: qr rd ra; QUERY: 1, ANSWER: 8, AUTHORITY: 4, ADDITIONAL: 8

;; QUESTION SECTION:
;registry-1.docker.io.          IN      A

;; ANSWER SECTION:
registry-1.docker.io.   600     IN      A       34.199.77.19
registry-1.docker.io.   600     IN      A       52.201.142.14
registry-1.docker.io.   600     IN      A       34.197.189.129
registry-1.docker.io.   600     IN      A       34.205.88.205
registry-1.docker.io.   600     IN      A       34.201.196.144
registry-1.docker.io.   600     IN      A       34.228.211.243
registry-1.docker.io.   600     IN      A       34.232.31.24
registry-1.docker.io.   600     IN      A       34.199.40.84

;; AUTHORITY SECTION:
docker.io.              55871   IN      NS      ns-421.awsdns-52.com.
docker.io.              55871   IN      NS      ns-1168.awsdns-18.org.
docker.io.              55871   IN      NS      ns-513.awsdns-00.net.
docker.io.              55871   IN      NS      ns-1827.awsdns-36.co.uk.

;; ADDITIONAL SECTION:
ns-421.awsdns-52.com.   55442   IN      A       205.251.193.165
ns-421.awsdns-52.com.   55442   IN      AAAA    2600:9000:5301:a500::1
ns-513.awsdns-00.net.   86382   IN      A       205.251.194.1
ns-513.awsdns-00.net.   86382   IN      AAAA    2600:9000:5302:100::1
ns-1168.awsdns-18.org.  86382   IN      A       205.251.196.144
ns-1168.awsdns-18.org.  86382   IN      AAAA    2600:9000:5304:9000::1
ns-1827.awsdns-36.co.uk. 86382  IN      A       205.251.199.35
ns-1827.awsdns-36.co.uk. 86382  IN      AAAA    2600:9000:5307:2300::1

;; Query time: 2 msec
;; SERVER: 114.114.114.114#53(114.114.114.114)
;; WHEN: Fri Feb 14 14:56:02 CST 2020
;; MSG SIZE  rcvd: 482

[root@wulaoer.org ~]# vim /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
34.199.77.19    registry-1.docker.io

创建swarm集群

swarm镜像已经下载完成,先创建swarm集群便于区分。我们可以在三个节点上都部署swarm集群交叉一下,相当于三个集群中都有三个节点。

[root@wulaoer.org ~]# docker swarm init --advertise-addr 10.211.55.145 #这个IP是本机的IP
Swarm initialized: current node (nenu012qektax3uptdrzxbiab) is now a manager.

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

	docker swarm join --token SWMTKN-1-1eazlzz2qooqy4fggrte1mdllq0e9qpx87veydi4r99uy008t5-50l1mwq2osibjjdq55xql1lqc 10.211.55.145:2377

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

创建集群后会生成一个集群token,方便客户端加入集群,下面根据集群的token加入到集群中。

[root@server09 ~]# docker swarm join --token SWMTKN-1-1eazlzz2qooqy4fggrte1mdllq0e9qpx87veydi4r99uy008t5-50l1mwq2osibjjdq55xql1lqc 10.211.55.145:2377
This node joined a swarm as a worker.

[root@server08 ~]# docker swarm join --token SWMTKN-1-1eazlzz2qooqy4fggrte1mdllq0e9qpx87veydi4r99uy008t5-50l1mwq2osibjjdq55xql1lqc 10.211.55.145:2377
This node joined a swarm as a worker.

[root@wulaoer.org ~]# docker node ls
ID                            HOSTNAME                STATUS              AVAILABILITY        MANAGER STATUS
nenu012qektax3uptdrzxbiab *   wulaoer.org             Ready               Active              Leader
k5zby5vidu5jnkjptz4h7sxbu     server08                Ready               Active              
fn8v8ztfi3rq0b4h51g02dpzj     server09                Ready               Active              

swarm集群创建完成,节点也加入到了集群中,这里看到在一个集群中只有一个leader,leader是负载另外两个节点的状态,可以根据需要进行扩容或缩减应用。下个章节说swarm的基本使用

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