6.docker-compose
Docker compose
本节课我们学习一个多docker的案例:使用redis对多实例服务器进行访问量计数。
我们需要设计一种统计方式，一个比较符合直觉的思路是将redis和网络应用打包在一起部署。
这种模式比较接近于边车模式，但是当我们需要部署多实例时，统计很可能失去意义
因此，我们需要用一个单独的redis服务器。
准备NodeJS Web应用
mkdir visit
cd visit
touch package.json
touch index.js
touch Dockerfile
vim package.json
{
"dependencies": {
"express": "*",
"redis": "2.8.0"
},
"scripts": {
"start": "node index.js"
}
}
vim index.js
const express = require('express');
const redis = require('redis');
const app = express();
const client = redis.createClient();
client.set('visits', 0);
app.get('/', (req, res) => {
client.get('visits', (err, visits) => {
res.send('Number of visits: ' + visits);
client.set('visits', parseInt(visits) + 1);
});
});
app.listen(8081, () => {
console.log('Listening on port 8081');
});
创建Dockerfile 构建镜像
FROM node:14-alpine
WORKDIR '/app'
COPY package.json .
RUN npm install
COPY . .
CMD ["npm","start"]
docker build -t s09g/visit:latest .
启动docker
尝试启动
docker run -p 8081:8081 s09g/visit
# (node:18) UnhandledPromiseRejectionWarning: Error: The client is closed
# at Commander._RedisClient_sendCommand (/app/node_modules/@redis/client/dist/lib/client/index.js:440:31)
启动失败，因为redis client没有办法连上redis服务器
在新的窗口中启动redis
docker run redis
回到原有窗口
docker run -p 8081:8081 s09g/visit
依然失败
定义Docker Compose文件
我们需要将两个隔离的docker环境进行连接，最简单的工具就是docker compose
vim docker-compose.yml
version: '3'
services:
redis-server:
image: 'redis'
node-app:
build: .
ports:
- '8081:8081'
vim index.js
const express = require('express');
const redis = require('redis');
const app = express();
const client = redis.createClient({
host: 'redis-server',
port: 6379
});
client.set('visits', 0);
app.get('/', (req, res) => {
client.get('visits', (err, visits) => {
res.send('Number of visits: ' + visits);
client.set('visits', parseInt(visits) + 1);
});
});
app.listen(8081, () => {
console.log('Listening on port 8081');
});
启动docker compose
# 启动容器
docker compose up
# 构建+启动容器
docker compose up --build
访问 localhost:8081，并且刷新
docker compose 管理
# detach 不向终端打印log
docker compose up -d
# 终止容器
docker compose down
# 查看容器状态
docker compose ps
docker compose 重启设置
修改 index.js，人为退出程序 exit(0)
vim index.js
const express = require('express');
const redis = require('redis');
const process = require('process');
const app = express();
const client = redis.createClient({
host: 'redis-server',
port: 6379
});
client.set('visits', 0);
app.get('/', (req, res) => {
process.exit(0);
client.get('visits', (err, visits) => {
res.send('Number of visits: ' + visits);
client.set('visits', parseInt(visits) + 1);
});
});
app.listen(8081, () => {
console.log('Listening on port 8081');
});
Note:exit(0)为正常退出，别的数字为异常退出
重新构建启动
docker compose up --build
# ...
# visit-node-app-1 exited with code 0
在新窗口中查看容器进程，只有redis
docker ps
# CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
# 8ff9924662e5 redis "docker-entrypoint.s…" 43 seconds ago Up 42 seconds 6379/tcp visit-redis-server-1
我们的目标是web应用可以自动重启，我们可以修改docker-compose.yml文件
Restart 有四种可选值:
"no": 不重启 (需要引号，没有引号的no被yaml当做false)always: 无论原因，一律重启on-failure: 仅在异常退出时重启unless-stopped: 仅在手动stop时停止，否则一律重启
vim docker-compose.yml
version: '3'
services:
redis-server:
image: 'redis'
node-app:
restart: always
build: .
ports:
- '8081:8081'
访问 localhost:8081
docker compose up --build
# ...
# visit-node-app-1 |
# visit-node-app-1 | > @ start /app
# visit-node-app-1 | > node index.js
# visit-node-app-1 |
# visit-node-app-1 | Listening on port 8081
# visit-node-app-1 exited with code 0
# visit-node-app-1 |
# visit-node-app-1 | > @ start /app
# visit-node-app-1 | > node index.js
# visit-node-app-1 |
# visit-node-app-1 | Listening on port 8081
web 应用重启成功
修改restart为on-failure
version: '3'
services:
redis-server:
image: 'redis'
node-app:
restart: on-failure
build: .
ports:
- '8081:8081'
访问 localhost:8081
docker compose up --build
web 应用没有重启