1 启动
承接上文最后的 python 服务配置。
[root@icv-monitor-platform-dev flask-redis]# docker-compose up -d
Creating network "flaskredis_default" with the default driver
Creating flaskredis_redis_1 ... done
Creating flaskredis_web_1 ... done
[root@icv-monitor-platform-dev flask-redis]# docker-compose ps
Name Command State Ports
------------------------------------------------------------------------------------------------------
flaskredis_redis_1 docker-entrypoint.sh redis ... Up 6379/tcp
flaskredis_web_1 python app.py Up 0.0.0.0:8084->5000/tcp,:::8084->5000/tcp
[root@icv-monitor-platform-dev flask-redis]#2 水平扩展
[root@icv-monitor-platform-dev flask-redis]# docker-compose up --scale web=3 -d
WARNING: The "web" service specifies a port on the host. If multiple containers for this service are created on a single host, the port will clash.
Starting flaskredis_web_1 ...
Starting flaskredis_web_1 ... done
Creating flaskredis_web_2 ... error
Creating flaskredis_web_3 ... error
ERROR: for flaskredis_web_2 Cannot start service web: driver failed programming external connectivity on endpoint flaskredis_web_2 (b10d07ee0f306e673d569063bfa04194b8bc0d83c91d4822ebd6d9ce1554a73c): Bind for 0.0.0.0:8084 failed: port is already allocated
ERROR: for flaskredis_web_3 Cannot start service web: driver failed programming external connectivity on endpoint flaskredis_web_3 (655d397521c6cfd1f89faeb34de7b01eccc70db76dc126841126a15bbd9013b2): Bind for 0.0.0.0:8084 failed: port is already allocated
ERROR: for web Cannot start service web: driver failed programming external connectivity on endpoint flaskredis_web_2 (b10d07ee0f306e673d569063bfa04194b8bc0d83c91d4822ebd6d9ce1554a73c): Bind for 0.0.0.0:8084 failed: port is already allocated
ERROR: Encountered errors while bringing up the project.
[root@icv-monitor-platform-dev flask-redis]#显然是 docker-compose.yml中的如下语句导致的失败：
ports:
- 8084:5000将该段删除再重启。
[root@icv-monitor-platform-dev flask-redis]# vim docker-compose.yml
[root@icv-monitor-platform-dev flask-redis]# docker-compose up -d
Stopping and removing flaskredis_web_2 ...
Stopping and removing flaskredis_web_2 ... done
Stopping and removing flaskredis_web_3 ... done
Recreating flaskredis_web_1 ... done
[root@icv-monitor-platform-dev flask-redis]# docker-compose up --scale web=3 -d
flaskredis_redis_1 is up-to-date
Starting flaskredis_web_1 ... done
Creating flaskredis_web_2 ... done
Creating flaskredis_web_3 ... done
[root@icv-monitor-platform-dev flask-redis]# docker-compose ps
Name Command State Ports
----------------------------------------------------------------------
flaskredis_redis_1 docker-entrypoint.sh redis ... Up 6379/tcp
flaskredis_web_1 python app.py Up 5000/tcp
flaskredis_web_2 python app.py Up 5000/tcp
flaskredis_web_3 python app.py Up 5000/tcp
[root@icv-monitor-platform-dev flask-redis]#注意，这个 5000 端口是容器 namespace 的 5000 端口，而不是主机的 5000 端口。
所以，现在有 3 个 web 服务了，都在访问同一台 redis。假设现有 n 个 web 服务，同时访问一个 Redis
某次大促，访问量需求很大，如何快速操作呢？传统是需要加机器，而通过 docker-compose 就能快速水平扩展。
现在就能迅速扩展到 5 个：
[root@icv-monitor-platform-dev flask-redis]# docker-compose up --scale web=5 -d
flaskredis_redis_1 is up-to-date
Starting flaskredis_web_1 ... done
Starting flaskredis_web_2 ... done
Starting flaskredis_web_3 ... done
Creating flaskredis_web_4 ... done
Creating flaskredis_web_5 ... done
[root@icv-monitor-platform-dev flask-redis]# docker-compose ps
Name Command State Ports
----------------------------------------------------------------------
flaskredis_redis_1 docker-entrypoint.sh redis ... Up 6379/tcp
flaskredis_web_1 python app.py Up 5000/tcp
flaskredis_web_2 python app.py Up 5000/tcp
flaskredis_web_3 python app.py Up 5000/tcp
flaskredis_web_4 python app.py Up 5000/tcp
flaskredis_web_5 python app.py Up 5000/tcp
[root@icv-monitor-platform-dev flask-redis]#为真实演绎该架构，现加上 LB。
现删除所有服务：
[root@icv-monitor-platform-dev flask-redis]# docker-compose down
Stopping flaskredis_web_4 ... done
Stopping flaskredis_web_5 ... done
Stopping flaskredis_web_2 ... done
Stopping flaskredis_web_3 ... done
Stopping flaskredis_web_1 ... done
Stopping flaskredis_redis_1 ... done
Removing flaskredis_web_4 ... done
Removing flaskredis_web_5 ... done
Removing flaskredis_web_2 ... done
Removing flaskredis_web_3 ... done
Removing flaskredis_web_1 ... done
Removing flaskredis_redis_1 ... done
Removing network flaskredis_default
[root@icv-monitor-platform-dev flask-redis]#2.1 前置文件
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)
docker-compose.yml
version: "3"
services:
redis:
image: redis
web:
build:
context: .
dockerfile: Dockerfile
environment:
REDIS_HOST: redis
lb:
image: dockercloud/haproxy
links:
- web
ports:
- 8084:80
volumes:
- /var/run/docker.sock:/var/run/docker.sockDockerfile
FROM python:2.7
LABEL maintaner="JavaEdge@"
COPY . /app
WORKDIR /app
RUN pip install flask redis
EXPOSE 80
CMD [ "python", "app.py" ]2.2 操作
2.2.1 扩容
[root@icv-monitor-platform-dev flask-redis]# docker-compose up -d
Creating network "flaskredis_default" with the default driver
Pulling lb (dockercloud/haproxy:latest)...
latest: Pulling from dockercloud/haproxy
1160f4abea84: Pull complete
b0df9c632afc: Pull complete
a49b18c7cd3a: Pull complete
Digest: sha256:040d1b321437afd9f8c9ba40e8340200d2b0ae6cf280a929a1e8549698c87d30
Creating flaskredis_redis_1 ... done
Creating flaskredis_web_1 ... done
Creating flaskredis_redis_1 ...
Creating flaskredis_lb_1 ... done
[root@icv-monitor-platform-dev flask-redis]# docker-compose ps
Name Command State Ports
---------------------------------------------------------------------------------------------------------------------
flaskredis_lb_1 /sbin/tini -- dockercloud- ... Up 1936/tcp, 443/tcp, 0.0.0.0:8084->80/tcp,:::8084->80/tcp
flaskredis_redis_1 docker-entrypoint.sh redis ... Up 6379/tcp
flaskredis_web_1 python app.py Up 5000/tcp
[root@icv-monitor-platform-dev flask-redis]# curl 127.0.0.1:8084
Hello Container World! I have been seen 1 times and my hostname is 8f3e8e1cb9a7.
[root@icv-monitor-platform-dev flask-redis]#hostname输出即是_web_1的 host name。
扩展到 3 个，再访问 8084 端口：
[root@icv-monitor-platform-dev flask-redis]# docker-compose up --scale web=3 -d
flaskredis_redis_1 is up-to-date
Starting flaskredis_web_1 ... done
Creating flaskredis_web_2 ... done
Creating flaskredis_web_3 ... done
flaskredis_lb_1 is up-to-date
[root@icv-monitor-platform-dev flask-redis]# docker-compose ps
Name Command State Ports
---------------------------------------------------------------------------------------------------------------------
flaskredis_lb_1 /sbin/tini -- dockercloud- ... Up 1936/tcp, 443/tcp, 0.0.0.0:8084->80/tcp,:::8084->80/tcp
flaskredis_redis_1 docker-entrypoint.sh redis ... Up 6379/tcp
flaskredis_web_1 python app.py Up 5000/tcp
flaskredis_web_2 python app.py Up 5000/tcp
flaskredis_web_3 python app.py Up 5000/tcp
[root@icv-monitor-platform-dev flask-redis]# curl 127.0.0.1:8084
Hello Container World! I have been seen 2 times and my hostname is 8f3e8e1cb9a7.
[root@icv-monitor-platform-dev flask-redis]#注意每次请求对应的 host name：
[root@icv-monitor-platform-dev flask-redis]# curl 127.0.0.1:8084
Hello Container World! I have been seen 2 times and my hostname is 8f3e8e1cb9a7.
[root@icv-monitor-platform-dev flask-redis]# curl 127.0.0.1:8084
Hello Container World! I have been seen 3 times and my hostname is 22b1d642d8a6.
[root@icv-monitor-platform-dev flask-redis]# curl 127.0.0.1:8084
Hello Container World! I have been seen 4 times and my hostname is 57169f8a658f.
[root@icv-monitor-platform-dev flask-redis]# curl 127.0.0.1:8084
Hello Container World! I have been seen 5 times and my hostname is 8f3e8e1cb9a7.
[root@icv-monitor-platform-dev flask-redis]# curl 127.0.0.1:8084
Hello Container World! I have been seen 6 times and my hostname is 22b1d642d8a6.
[root@icv-monitor-platform-dev flask-redis]# curl 127.0.0.1:8084
Hello Container World! I have been seen 7 times and my hostname is 57169f8a658f.
[root@icv-monitor-platform-dev flask-redis]#显然触发了默认的轮询LB！
2.2.2 缩容
大促过了，我们又要缩容了：
[root@icv-monitor-platform-dev flask-redis]# docker-compose up --scale web=1 -dStopping and removing flaskredis_web_2 ...
Stopping and removing flaskredis_web_2 ... done
Stopping and removing flaskredis_web_3 ... done
Starting flaskredis_web_1 ... done
flaskredis_lb_1 is up-to-date
[root@icv-monitor-platform-dev flask-redis]#
