docker-compose 用--scale 参数快速实现一个负载均衡（单节点）

实验：

[root@ml cs]# ls
app.py docker-compose.yml Dockerfile

 

Dockerfile内容：

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

docker-compose.yml 内容：

version: "3"

services:

  redis:
    image: redis

  web:
    build:
      context: .
      dockerfile: Dockerfile
    ports: ["8080"]
    environment:
      REDIS_HOST: redis

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

app.py内容（每当浏览一次就会输入浏览次数和当然主机名字）：

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)

 

#启动

[root@ml cs]# docker-compose up -d

Creating cs_web_1   ... done
Creating cs_redis_1 ... done
Creating cs_lb_1    ... done

#查看一下，有一个redis、web、haproxy（lb）

[root@ml cs]# docker-compose  ps

   Name                 Command              State               Ports            
----------------------------------------------------------------------------------
cs_lb_1      /sbin/tini -- dockercloud-      Up      1936/tcp, 443/tcp,           
             ...                                     0.0.0.0:80->80/tcp           
cs_redis_1   docker-entrypoint.sh redis      Up      6379/tcp                     
             ...                                                                  
cs_web_1     python app.py                   Up      80/tcp,                      
                                                     0.0.0.0:32768->8080/tcp  

 

#使用--scale 参数启动3个web，注意的是这里的web=3是对应docker-compose.yml内容中的services: 下的名字，如果启动三个redis则redis=3，三个haproxy则lb=3

[root@ml cs]# docker-compose up --scale web=3 -d

Starting cs_web_1 ... 
Starting cs_web_1 ... done
Creating cs_web_2 ... done
Creating cs_web_3 ... done
cs_lb_1 is up-to-date

#在查一下，发现已经有三个web了

[root@ml cs]# docker-compose ps

   Name                 Command              State               Ports            
----------------------------------------------------------------------------------
cs_lb_1      /sbin/tini -- dockercloud-      Up      1936/tcp, 443/tcp,           
             ...                                     0.0.0.0:80->80/tcp           
cs_redis_1   docker-entrypoint.sh redis      Up      6379/tcp                     
             ...                                                                  
cs_web_1     python app.py                   Up      80/tcp,                      
                                                     0.0.0.0:32768->8080/tcp      
cs_web_2     python app.py                   Up      80/tcp,                      
                                                     0.0.0.0:32769->8080/tcp      
cs_web_3     python app.py                   Up      80/tcp,                      
                                                     0.0.0.0:32770->8080/tcp  

#访问（访问的是haproxy它做了端口映射的，web它们的端口是8080，因为web数量多做不了端口映射会有端口冲突）

[root@ml cs]# curl 127.0.0.1
Hello Container World! I have been seen 1 times and my hostname is 48e683350c0a.  #显示访问次数以及主机名
[root@ml cs]# curl 127.0.0.1
Hello Container World! I have been seen 2 times and my hostname is 9efbe3e7e4d0.
[root@ml cs]# curl 127.0.0.1
Hello Container World! I have been seen 3 times and my hostname is 8d0b962ae23a.
[root@ml cs]# curl 127.0.0.1
Hello Container World! I have been seen 4 times and my hostname is 48e683350c0a.
[root@ml cs]# curl 127.0.0.1
Hello Container World! I have been seen 5 times and my hostname is 9efbe3e7e4d0.