上一篇：Docker的那些事儿—如何安装docker-compose？
安装了Compose，下面就来通过一个例子认识Docker Compose是如何使用的？
目标：通过Docker Compose构建一个简单的Python Web应用程序，并且借助redis实现简单的计数功能。
Step 1：定义应用的依赖关系
1、创建项目目录：mycompose
2、在项目目录下创建app.py文件，内容如下：
import time
import redis
from flask import Flask
app= Flask(__name__)
cache= redis.Redis(host='redis', port=6379)
def get_hit_count():
retries = 5
while True:
try:
return cache.incr('hits')
except redis.exceptions.ConnectionErroras exc:
if retries == 0:
raise exc
retries -= 1
time.sleep(0.5)
@app.route('/')
def hello():
count = get_hit_count()
return 'Hello World! I have been seen {}times.\n'.format(count)
if__name__ == "__main__":
app.run(host="0.0.0.0",debug=True)
3、在项目目录下创建requirements.txt文件，内容如下：
flask
redis
Step 2：创建Dockerfile文件
在项目目录下创建名字为Dockerfile文件，内容如下：
FROM python:3.4-alpine
ADD . /code
WORKDIR /code
RUN pip install -r requirements.txt
CMD ["python", "app.py"]
Step 3：定义Compose文件
在项目目录下创建名字为docker-compose.yml文件，内容如下：
version: '3'
services:
web:
build: .
ports:
-"5000:5000"
redis:
image:"redis:alpine"
上述Compose文件定义了两个服务：web服务和redis服务。其中redis服务使用的是Docker Hub上的镜像；web服务使用的是上述Dockerfile构建的镜像，并且做了端口的映射。
Step 4：使用Compose构建并运行应用
在项目目录下，执行docker-compose up启动应用
root@Ubuntu-001:~/mycompose#docker-compose up
Creating network"mycompose_default" with the default driver
Building web
Step 1/5 : FROM python:3.4-alpine
3.4-alpine: Pulling fromlibrary/python
81033e7c1d6a: Pull complete
9b61101706a6: Pull complete
415e2a07c89b: Pull complete
f22df7a3f000: Pull complete
8c16bf19c1f9: Pull complete
Digest:sha256:fe436cb066394d81cf49448a04dec7c765082445a500bc44f1ae5e8a455793bd
Status: Downloaded newerimage for python:3.4-alpine
---> 5c72717ec319
Step 2/5 : ADD . /code
---> 7b20a034f7a4
Step 3/5 : WORKDIR /code
Removing intermediatecontainer c837500a2226
---> d77fc02cacc1
Step 4/5 : RUN pip install -rrequirements.txt
---> Running in 59d8d8c0ecf6
Collecting flask (from -rrequirements.txt (line 1))
Downloading Flask-0.12.2-py2.py3-none-any.whl(83kB)
Collecting redis (from -rrequirements.txt (line 2))
Downloading redis-2.10.6-py2.py3-none-any.whl(64kB)
Collecting Werkzeug>=0.7(from flask->-r requirements.txt (line 1))
DownloadingWerkzeug-0.14.1-py2.py3-none-any.whl (322kB)
Collecting click>=2.0(from flask->-r requirements.txt (line 1))
Downloading click-6.7-py2.py3-none-any.whl(71kB)
Collecting Jinja2>=2.4(from flask->-r requirements.txt (line 1))
Downloading Jinja2-2.10-py2.py3-none-any.whl(126kB)
Collectingitsdangerous>=0.21 (from flask->-r requirements.txt (line 1))
Downloading itsdangerous-0.24.tar.gz (46kB)
CollectingMarkupSafe>=0.23 (from Jinja2>=2.4->flask->-r requirements.txt(line 1))
Downloading MarkupSafe-1.0.tar.gz
Building wheels for collectedpackages: itsdangerous, MarkupSafe
Running setup.py bdist_wheel for itsdangerous:started
Running setup.py bdist_wheel foritsdangerous: finished with status 'done'
Stored in directory:/root/.cache/pip/wheels/fc/a8/66/24d655233c757e178d45dea2de22a04c6d92766abfb741129a
Running setup.py bdist_wheel for MarkupSafe:started
Running setup.py bdist_wheel for MarkupSafe:finished with status 'done'
Stored in directory:/root/.cache/pip/wheels/88/a7/30/e39a54a87bcbe25308fa3ca64e8ddc75d9b3e5afa21ee32d57
Successfully builtitsdangerous MarkupSafe
Installing collectedpackages: Werkzeug, click, MarkupSafe, Jinja2, itsdangerous, flask, redis
Successfully installedJinja2-2.10 MarkupSafe-1.0 Werkzeug-0.14.1 click-6.7 flask-0.12.2itsdangerous-0.24 redis-2.10.6
Removing intermediatecontainer 59d8d8c0ecf6
---> 51143f11c451
Step 5/5 : CMD["python", "app.py"]
---> Running in 422960a19b01
Removing intermediatecontainer 422960a19b01
---> de5cc3ead62d
Successfully builtde5cc3ead62d
Successfully taggedmycompose_web:latest
WARNING: Image for serviceweb was built because it did not already exist. To rebuild this image you mustuse `docker-compose build` or `docker-compose up --build`.
Pulling redis(redis:alpine)...
alpine: Pulling fromlibrary/redis
ff3a5c916c92: Pull complete
aae70a2e6027: Pull complete
87c655da471c: Pull complete
a0bd51ac7350: Pull complete
755565c3ea2b: Pull complete
8bf100ea488d: Pull complete
Digest:sha256:4f54ade2260d5c80283d044ab9657f390cb8effd9a7a847765693a3670f6874a
Status: Downloaded newerimage for redis:alpine
Creating mycompose_web_1 ... done
Creating mycompose_redis_1... done
Attaching tomycompose_redis_1, mycompose_web_1
redis_1 | 1:C 08 Mar 14:41:49.790 # oO0OoO0OoO0OoRedis is starting oO0OoO0OoO0Oo
redis_1 | 1:C 08 Mar 14:41:49.790 # Redisversion=4.0.8, bits=64, commit=00000000, modified=0, pid=1, just started
redis_1 | 1:C 08 Mar 14:41:49.790 # Warning: noconfig file specified, using the default config. In order to specify a configfile use redis-server /path/to/redis.conf
redis_1 | 1:M 08 Mar 14:41:49.798 * Runningmode=standalone, port=6379.
redis_1 | 1:M 08 Mar 14:41:49.798 # WARNING: The TCPbacklog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconnis set to the lower value of 128.
redis_1 | 1:M 08 Mar 14:41:49.798 # Serverinitialized
redis_1 | 1:M 08 Mar 14:41:49.798 # WARNINGovercommit_memory is set to 0! Background save may fail under low memorycondition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.confand then reboot or run the command 'sysctl vm.overcommit_memory=1' for this totake effect.
redis_1 | 1:M 08 Mar 14:41:49.798 # WARNING you haveTransparent Huge Pages (THP) support enabled in your kernel. This will create latencyand memory usage issues with Redis. To fix this issue run the command 'echonever > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it toyour /etc/rc.local in order to retain the setting after a reboot. Redis must berestarted after THP is disabled.
redis_1 | 1:M 08 Mar 14:41:49.799 * DB loaded fromdisk: 0.000 seconds
redis_1 | 1:M 08 Mar 14:41:49.799 * Ready to acceptconnections
web_1 | *Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
web_1 | *Restarting with stat
web_1 | *Debugger is active!
web_1 | *Debugger PIN: 246-553-608
从docker-compose up的过程可以总结如下：
1、构建mycompose_default网络，该网络供下面容器启动使用
2、基于Dockerfile构建mycompose_web:latest镜像
3、从Docker Hub pull redis:alpine镜像
4、分别启动mycompose_web_1和mycompose_redis_1容器
5、Attach到mycompose_web_1和mycompose_redis_1容器
注意：这里无论创建的网络、镜像还是容器，其前缀名都是基于项目名的
打开新的终端窗口，查询运行的容器
打开浏览器键入http://192.168.1.106:5000，其中192.168.1.106是Ubuntu-001主机的IP
刷新页面后
可以看到收到两条get请求，浏览器每刷新一次，发送一条get请求
其中192.168.1.101是我的本地电脑的IP
打开新的终端，查询镜像
在原来的终端窗口按CTRL+C或者在新的终端窗口使用docker-compose down停止应用
下一篇：Docker的那些事儿—一个例子教你docker compose是如何使用的（二）？
