docker学习笔记（四）docker-swarm 容器集群服务 – 老陈是一个普通的文艺二逼青年

一、简介

Docker Swarm 是 Docker 官方三剑客项目之一，提供 Docker 容器集群服务，是 Docker 官方对容器云生态进行支持的核心方案。

Swarm 是使用 SwarmKit 构建的 Docker 引擎内置（原生）的集群管理和编排工具。

使用 Swarm 集群之前需要了解以下几个概念。

节点

节点分为管理 (manager) 节点和工作 (worker) 节点。

管理节点用于 Swarm 集群的管理，docker swarm 命令基本只能在管理节点执行（节点退出集群命令 docker swarm leave 可以在工作节点执行）。一个 Swarm 集群可以有多个管理节点，但只有一个管理节点可以成为 leader，leader 通过 raft 协议实现。

服务和任务

任务（Task）是 Swarm 中的最小的调度单位，目前来说就是一个单一的容器。

服务（Services）是指一组任务的集合，服务定义了任务的属性。服务有两种模式：

replicated services 按照一定规则在各个工作节点上运行指定个数的任务。
global services 每个工作节点上运行一个任务

两种模式通过 docker service create 的 --mode 参数指定。

二、创建 Swarm 集群

创建节点

首先创建3个或者更多docker-machine。分别命名为：

manager
vm2
vm3

$ docker-machine create --driver hyperv --hyperv-virtual-switch=DockerNAT manager
$ docker-machine create --driver hyperv --hyperv-virtual-switch=DockerNAT vm2
$ docker-machine create --driver hyperv --hyperv-virtual-switch=DockerNAT vm3

$ docker-machine create --driver hyperv --hyperv-virtual-switch=DockerNAT manager

$ docker-machine create --driver hyperv --hyperv-virtual-switch=DockerNAT vm2

$ docker-machine create --driver hyperv --hyperv-virtual-switch=DockerNAT vm3

我们进入manager主机，使用 docker swarm init 在管理节点初始化一个 Swarm 集群。

$ docker-machine ssh manager

$ ifconfig
docker0   Link encap:Ethernet  HWaddr 02:42:D8:74:28:E2
          inet addr:172.17.0.1  Bcast:172.17.255.255  Mask:255.255.0.0
          ...

eth0      Link encap:Ethernet  HWaddr 00:15:5D:5E:31:3F
          inet addr:192.168.31.147  Bcast:192.168.31.255  Mask:255.255.255.0
          ...

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          ...

$ docker swarm init --advertise-addr 192.168.31.147

Swarm initialized: current node (14ui5c2e2kd9z2bouj6if62fk) is now a manager.

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

    docker swarm join --token SWMTKN-1-1vy7232y4dbzumqbqohhtzu8ae7h9blfuiex6dgb62u8uywuex-7gdi98kpa2teq3pow94rwpsoy 192.168.31.147:2377

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

$ docker-machine ssh manager

$ ifconfig

docker0 Link encap:Ethernet HWaddr 02:42:D8:74:28:E2

inet addr:172.17.0.1 Bcast:172.17.255.255 Mask:255.255.0.0

...

eth0 Link encap:Ethernet HWaddr 00:15:5D:5E:31:3F

inet addr:192.168.31.147 Bcast:192.168.31.255 Mask:255.255.255.0

...

lo Link encap:Local Loopback

inet addr:127.0.0.1 Mask:255.0.0.0

...

$ docker swarm init --advertise-addr 192.168.31.147

Swarm initialized: current node (14ui5c2e2kd9z2bouj6if62fk) is now a manager.

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

docker swarm join --token SWMTKN-1-1vy7232y4dbzumqbqohhtzu8ae7h9blfuiex6dgb62u8uywuex-7gdi98kpa2teq3pow94rwpsoy 192.168.31.147:2377

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

加入节点

初始化完成后，将vm2、vm3节点假如管理节点。

在vm2、vm3节中分别执行命令

$ docker swarm join --token SWMTKN-1-1vy7232y4dbzumqbqohhtzu8ae7h9blfuiex6dgb62u8uywuex-7gdi98kpa2teq3pow94rwpsoy 192.168.31.147:2377
This node joined a swarm as a worker.

$ docker swarm join --token SWMTKN-1-1vy7232y4dbzumqbqohhtzu8ae7h9blfuiex6dgb62u8uywuex-7gdi98kpa2teq3pow94rwpsoy 192.168.31.147:2377

This node joined a swarm as a worker.

管理节点

在manager主机

$ docker node ls              
ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS      ENGINE VERSION
14ui5c2e2kd9z2bouj6if62fk *   manager             Ready               Active              Leader              18.09.9
28pzxdp7xd1h5e87668yd0qun     vm2                 Ready               Active                                  18.09.9
4j31uznmbtgfcmjp5on11p65e     vm3                 Ready               Active                                  18.09.9

$ docker node ls

ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION

14ui5c2e2kd9z2bouj6if62fk * manager Ready Active Leader 18.09.9

28pzxdp7xd1h5e87668yd0qun vm2 Ready Active 18.09.9

4j31uznmbtgfcmjp5on11p65e vm3 Ready Active 18.09.9

三、服务管理

创建服务

在manager主机中创建3个nginx副本的集群

$ docker service create --replicas 3 -p 80:80 --name nginx nginx:1.13.7-alpine
6ka5qr4o0tgffdtdh2q4u4ghi
overall progress: 3 out of 3 tasks
1/3: running   [==================================================>]
2/3: running   [==================================================>]
3/3: running   [==================================================>]

$ docker service create --replicas 3 -p 80:80 --name nginx nginx:1.13.7-alpine

6ka5qr4o0tgffdtdh2q4u4ghi

overall progress: 3 out of 3 tasks

1/3: running [==================================================>]

2/3: running [==================================================>]

3/3: running [==================================================>]

创建成功后，访问任意节点ip即可。

查看服务

使用 docker service ls 来查看当前 Swarm 集群运行的服务。

$ docker service ls
ID                  NAME                MODE                REPLICAS            IMAGE                 PORTS
6ka5qr4o0tgf        nginx               replicated          3/3                 nginx:1.13.7-alpine   *:80->80/tcp

$ docker service ls

ID NAME MODE REPLICAS IMAGE PORTS

6ka5qr4o0tgf nginx replicated 3/3 nginx:1.13.7-alpine *:80->80/tcp

使用 docker service ps 来查看某个服务的详情。

$ docker service ps nginx
ID                  NAME                IMAGE                 NODE                DESIRED STATE       CURRENT STATE           ERROR               PORTS
egb5yz60yyf0        nginx.1             nginx:1.13.7-alpine   manager             Running             Running 3 minutes ago
4vj7vmmgnp0l        nginx.2             nginx:1.13.7-alpine   vm2                 Running             Running 3 minutes ago
0irw2uln3uv9        nginx.3             nginx:1.13.7-alpine   vm3                 Running             Running 3 minutes ago

$ docker service ps nginx

ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS

egb5yz60yyf0 nginx.1 nginx:1.13.7-alpine manager Running Running 3 minutes ago

4vj7vmmgnp0l nginx.2 nginx:1.13.7-alpine vm2 Running Running 3 minutes ago

0irw2uln3uv9 nginx.3 nginx:1.13.7-alpine vm3 Running Running 3 minutes ago

使用 docker service logs 来查看某个服务的日志。

$ docker service logs nginx
nginx.2.4vj7vmmgnp0l@vm2    | 10.255.0.2 - - [23/Sep/2019:10:48:29 +0000] "GET / HTTP/1.1" 200 612 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.132 Safari/537.36" "-"
nginx.2.4vj7vmmgnp0l@vm2    | 2019/09/23 10:48:29 [error] 6#6: *1 open() "/usr/share/nginx/html/favicon.ico" failed (2: No such file or directory), client: 10.255.0.2, server: localhost, request: "GET /favicon.ico HTTP/1.1", host: "192.168.31.147", referrer: "http://192.168.31.147/"
nginx.2.4vj7vmmgnp0l@vm2    | 10.255.0.2 - - [23/Sep/2019:10:48:29 +0000] "GET /favicon.ico HTTP/1.1" 404 571 "http://192.168.31.147/" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.132 Safari/537.36" "-"

$ docker service logs nginx

nginx.2.4vj7vmmgnp0l@vm2 | 10.255.0.2 - - [23/Sep/2019:10:48:29 +0000] "GET / HTTP/1.1" 200 612 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.132 Safari/537.36" "-"

nginx.2.4vj7vmmgnp0l@vm2 | 2019/09/23 10:48:29 [error] 6#6: *1 open() "/usr/share/nginx/html/favicon.ico" failed (2: No such file or directory), client: 10.255.0.2, server: localhost, request: "GET /favicon.ico HTTP/1.1", host: "192.168.31.147", referrer: "http://192.168.31.147/"

nginx.2.4vj7vmmgnp0l@vm2 | 10.255.0.2 - - [23/Sep/2019:10:48:29 +0000] "GET /favicon.ico HTTP/1.1" 404 571 "http://192.168.31.147/" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.132 Safari/537.36" "-"

服务伸缩

我们可以使用 docker service scale 对一个服务运行的容器数量进行伸缩。

当业务处于高峰期时，我们需要扩展服务运行的容器数量。

$ docker service scale nginx=5
nginx 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

$ docker service scale nginx=5

nginx 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

当业务平稳时，我们需要减少服务运行的容器数量。

$ docker service scale nginx=2
...

$ docker service scale nginx=2

...

删除服务

使用 docker service rm 来从 Swarm 集群移除某个服务。

$ docker service rm nginx

1 2	$ docker service rm nginx

四、composer 文件部署服务

部署服务使用 docker stack deploy，其中 -c 参数指定 compose 文件名。

$ docker stack deploy -c docker-compose.yml wordpress
Creating network wordpress_overlay
Creating network wordpress_default
Creating service wordpress_wordpress
Creating service wordpress_db
Creating service wordpress_visualizer

$ docker stack deploy -c docker-compose.yml wordpress

Creating network wordpress_overlay

Creating network wordpress_default

Creating service wordpress_wordpress

Creating service wordpress_db

Creating service wordpress_visualizer

docker-compose.yml参考如下：

version: "3"

services:
  wordpress:
    image: wordpress
    ports:
      - 80:80
    networks:
      - overlay
    environment:
      WORDPRESS_DB_HOST: db:3306
      WORDPRESS_DB_USER: wordpress
      WORDPRESS_DB_PASSWORD: wordpress
    deploy:
      mode: replicated
      replicas: 3

  db:
    image: mysql
    networks:
       - overlay
    volumes:
      - db-data:/var/lib/mysql
    environment:
      MYSQL_ROOT_PASSWORD: somewordpress
      MYSQL_DATABASE: wordpress
      MYSQL_USER: wordpress
      MYSQL_PASSWORD: wordpress
    deploy:
      placement:
        constraints: [node.role == manager]

  visualizer:
    image: dockersamples/visualizer:stable
    ports:
      - "8080:8080"
    stop_grace_period: 1m30s
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock"
    deploy:
      placement:
        constraints: [node.role == manager]

volumes:
  db-data:
networks:
  overlay:

version: "3"

services:

wordpress:

image: wordpress

ports:

- 80:80

networks:

- overlay

environment:

WORDPRESS_DB_HOST: db:3306

WORDPRESS_DB_USER: wordpress

WORDPRESS_DB_PASSWORD: wordpress

deploy:

mode: replicated

replicas: 3

db:

image: mysql

networks:

- overlay

volumes:

- db-data:/var/lib/mysql

environment:

MYSQL_ROOT_PASSWORD: somewordpress

MYSQL_DATABASE: wordpress

MYSQL_USER: wordpress

MYSQL_PASSWORD: wordpress

deploy:

placement:

constraints: [node.role == manager]

visualizer:

image: dockersamples/visualizer:stable

ports:

- "8080:8080"

stop_grace_period: 1m30s

volumes:

- "/var/run/docker.sock:/var/run/docker.sock"

deploy:

placement:

constraints: [node.role == manager]

volumes:

db-data:

networks:

overlay:

查看服务

$ docker stack ls
NAME                SERVICES            ORCHESTRATOR
wordpress           3                   Swarm

$ docker stack ls

NAME SERVICES ORCHESTRATOR

wordpress 3 Swarm

移除服务

要移除服务，使用 docker stack down

$ docker stack down wordpress
Removing service wordpress_db
Removing service wordpress_visualizer
Removing service wordpress_wordpress
Removing network wordpress_overlay
Removing network wordpress_default

$ docker stack down wordpress

Removing service wordpress_db

Removing service wordpress_visualizer

Removing service wordpress_wordpress

Removing network wordpress_overlay

Removing network wordpress_default

本文参考：

https://yeasy.gitbooks.io/docker_practice/swarm/