docker-compose的scale的用法

用到的三個文件

docker-compose

version: "3"

services:

  redis:
    image: redis

  web:
    build:
      context: .
      dockerfile: Dockerfile
    environment:
      REDIS_HOST: redis

  lb:
    image: dockercloud/haproxy
    links:
      - web
    ports:
      - 8080:80
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock 

Dockerfile

FROM python:2.7
LABEL maintaner="Peng Xiao [e-mail]"
COPY . /app
WORKDIR /app
RUN pip install flask redis
EXPOSE 80
CMD [ "python", "app.py" ]

app.py

from flask import Flask
from redis import Redis
import os
import socket

app = Flask(__name__)
redis = Redis(host=os.environ.get('REDIS_HOST', '127.0.0.1'), port=6379)


@app.route('/')
def hello():
    redis.incr('hits')
    return 'Hello Container World! I have been seen %s times and my hostname is %s.\n' % (redis.get('hits'),socket.gethostname())


if __name__ == "__main__":
    app.run(host="0.0.0.0", port=80, debug=True)

創建docker-compose的文件夾

mkdir scale

將三個文件上傳進來

rz

執行docker-compose

docker-compose up --scale web=3 -d

瀏覽器輸入宿主ip:8080，報錯如下：Could not find a version that satisfies the requirement Werkzeug>=0.15

顯然pip沒有找到依賴庫的合適版本，升級一下pip，在Dockerfile中修改

RUN pip install flask redis

修改為 

RUN python -m pip install --upgrade pip && pip install flask redis

再次執行執行docker-compose

docker-compose up --scale web=3 -d

瀏覽器輸入宿主ip:8080

 

Hello Container World! I have been seen 5 times and my hostname is 8e5e7d7e796f.

Hello Container World! I have been seen 6 times and my hostname is 5b521b5758a0.

Hello Container World! I have been seen 8 times and my hostname is 03b02d13f35d.

 

刷新三次，每次的web都不一樣，很方便實現負載均衡

 

（只是單機實驗，生產環境中肯定不是在單機上做負載均衡）