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docker官网实例，用Dockerfile构建你的第一个python应用

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docker官网实例，用Dockerfile构建你的第一个python应用

By 李镇伟 2018年9月28日

#备注：默认读者已经安装好了docker环境

第一步：创建一个应用目录(后面使用该目录为工作目录，存放应用文件以及Dockerfile)：

mkdir /root/docker/lzwtestpython
cd /root/docker/lzwtestpython

第二步：为容器定义一个Dockerfile：

创建Dockerfile文件：

vi Dockerfile

输入Dockerfile文件内容：

# Use an official Python runtime as a parent image
FROM python:2.7-slim
# Set the working directory to /app
WORKDIR /app
# Copy the current directory contents into the container at /app
COPY . /app
# Install any needed packages specified in requirements.txt
RUN pip install --trusted-host pypi.python.org -r requirements.txt
# Make port 80 available to the world outside this container
EXPOSE 80
# Define environment variable
ENV NAME World
# Run app.py when the container launches
CMD ["python", "app.py"]

在文件内容中，我们可以看到，我们的python文件为app.py，下面我们需要去创建这个文件。一般来说,python项目中会包含一个 requirements.txt 文件,用于记录所有依赖包。

第三步：创建requirements.txt和app.py

创建requirements.txt文件：

vi requirements.txt

输入requirements.txt文件内容：

Flask
Redis
创建app.py文件：
vi app.py

输入app.py文件内容：

from flask import Flask
from redis import Redis, RedisError
import os
import socket
# Connect to Redis
redis = Redis(host="redis", db=0, socket_connect_timeout=2, socket_timeout=2)
app = Flask(__name__)
@app.route("/")
def hello():
    try:
        visits = redis.incr("counter")
    except RedisError:
        visits = "<i>cannot connect to Redis, counter disabled</i>"
    html = "<h3>Hello {name}!</h3>" 
           "<b>Hostname:</b> {hostname}<br/>" 
           "<b>Visits:</b> {visits}"
    return html.format(name=os.getenv("NAME", "world"), hostname=socket.gethostname(), visits=visits)
if __name__ == "__main__":
    app.run(host='0.0.0.0', port=80)

到这里，我们可以发现，我们没有真正的在电脑上安装python,和requirements.txt里提到的flask或者redis。看起来，你并没有搭建好python+flask+redis的环境。但是，通过接下来的步骤，你即将拥有。

第四步：创建应用

检查工作文件夹下的三个文件是否都创建完成，三个文件如下：

$ ls
Dockerfile		app.py			requirements.txt

现在开始运行创建Docker镜像命令，我们加上-t命令来命名，这里我们起一个很友好的名字friendlyhello（^_^）

docker build -t friendlyhello .

我们可以看一看执行的命令的回显：

Sending build context to Docker daemon  4.608kB
Step 1/7 : FROM python:2.7-slim
2.7-slim: Pulling from library/python
802b00ed6f79: Pull complete
10b2d5f7ed73: Pull complete
1073a127cf89: Pull complete
90283f3dc1cd: Pull complete
Digest: sha256:0a43a6d7858af4a42427c792b682936d2cd34e183fb026627f53ddb556d4bf62
Status: Downloaded newer image for python:2.7-slim
 ---> c9cde4658340
Step 2/7 : WORKDIR /app
 ---> Running in 5b6e0800c538
Removing intermediate container 5b6e0800c538
 ---> 3ac183b809ce
Step 3/7 : COPY . /app
 ---> b05ac52c77de
Step 4/7 : RUN pip install --trusted-host pypi.python.org -r requirements.txt
 ---> Running in 58bd2a10311e
Collecting Flask (from -r requirements.txt (line 1))
  Downloading https://files.pythonhosted.org/packages/7f/e7/08578774ed4536d3242b14dacb4696386634607af824ea997202cd0edb4b/Flask-1.0.2-py2.py3-none-any.whl (91kB)
Collecting Redis (from -r requirements.txt (line 2))
  Downloading https://files.pythonhosted.org/packages/3b/f6/7a76333cf0b9251ecf49efff635015171843d9b977e4ffcf59f9c4428052/redis-2.10.6-py2.py3-none-any.whl (64kB)
Collecting itsdangerous>=0.24 (from Flask->-r requirements.txt (line 1))
  Downloading https://files.pythonhosted.org/packages/dc/b4/a60bcdba945c00f6d608d8975131ab3f25b22f2bcfe1dab221165194b2d4/itsdangerous-0.24.tar.gz (46kB)
Collecting Jinja2>=2.10 (from Flask->-r requirements.txt (line 1))
  Downloading https://files.pythonhosted.org/packages/7f/ff/ae64bacdfc95f27a016a7bed8e8686763ba4d277a78ca76f32659220a731/Jinja2-2.10-py2.py3-none-any.whl (126kB)
Collecting Werkzeug>=0.14 (from Flask->-r requirements.txt (line 1))
  Downloading https://files.pythonhosted.org/packages/20/c4/12e3e56473e52375aa29c4764e70d1b8f3efa6682bef8d0aae04fe335243/Werkzeug-0.14.1-py2.py3-none-any.whl (322kB)
Collecting click>=5.1 (from Flask->-r requirements.txt (line 1))
  Downloading https://files.pythonhosted.org/packages/fa/37/45185cb5abbc30d7257104c434fe0b07e5a195a6847506c074527aa599ec/Click-7.0-py2.py3-none-any.whl (81kB)
Collecting MarkupSafe>=0.23 (from Jinja2>=2.10->Flask->-r requirements.txt (line 1))
  Downloading https://files.pythonhosted.org/packages/4d/de/32d741db316d8fdb7680822dd37001ef7a448255de9699ab4bfcbdf4172b/MarkupSafe-1.0.tar.gz
Building wheels for collected packages: itsdangerous, MarkupSafe
  Running setup.py bdist_wheel for itsdangerous: started
  Running setup.py bdist_wheel for itsdangerous: finished with status 'done'
  Stored in directory: /root/.cache/pip/wheels/2c/4a/61/5599631c1554768c6290b08c02c72d7317910374ca602ff1e5
  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/33/56/20/ebe49a5c612fffe1c5a632146b16596f9e64676768661e4e46
Successfully built itsdangerous MarkupSafe
Installing collected packages: itsdangerous, MarkupSafe, Jinja2, Werkzeug, click, Flask, Redis
Successfully installed Flask-1.0.2 Jinja2-2.10 MarkupSafe-1.0 Redis-2.10.6 Werkzeug-0.14.1 click-7.0 itsdangerous-0.24
Removing intermediate container 58bd2a10311e
 ---> 20b7d92b6075
Step 5/7 : EXPOSE 80
 ---> Running in 45f7bfcee8c8
Removing intermediate container 45f7bfcee8c8
 ---> 0c99f24bb0ca
Step 6/7 : ENV NAME World
 ---> Running in 4d192a73ee76
Removing intermediate container 4d192a73ee76
 ---> da526dcf3514
Step 7/7 : CMD ["python", "app.py"]
 ---> Running in 50226d88c2d5
Removing intermediate container 50226d88c2d5
 ---> bb0d475e1b3c
Successfully built bb0d475e1b3c
Successfully tagged friendlyhello:latest

分析回显，我们可以看到执行的过程有7步：

Step 1/7 : FROM python:2.7-slim
Step 2/7 : WORKDIR /app
Step 3/7 : COPY . /app
Step 4/7 : RUN pip install --trusted-host pypi.python.org -r requirements.txt
Step 5/7 : EXPOSE 80
Step 6/7 : ENV NAME World
Step 7/7 : CMD ["python", "app.py"]

这7步，是在Dockerfile里指定的(所以Dockerfile最关键啊#_#)。
命令执行完后，我们可以输入如下命令来查看本机安装的docker 镜像

$ docker image ls
REPOSITORY            TAG                 IMAGE ID
friendlyhello         latest              326387cea398第五步

第五步：运行应用

运行应用，并且把你物理机（或者云服务器）的4000端口映射到我们容器的80端口，使用-p命令：

docker run -p 4000:80 friendlyhello

哈？你问为什么要这样做？因为你的app.py文件里指的是80端口，如果我们没有使用docker,直接是在自己电脑上运行该python程序，确实可以通过http://0.0.0.0:80进行访问。目前在我们的容器中，确实也是80端口启用了，但是要让我们的其他用户访问这台物理机地址的容器内的python应用，需要把物理机的端口4000与容器的80端口进行映射。现在，请用http://localhost:4000 来检查一下吧

如果你是布置在别的机器上而非本机的话，也可以用地址加端口号的方式来访问。例如http://192.168.99.100:4000/ 或者http://www.yinyubo.cn:4000/
没有浏览器的话，也可以通过curl命令工具来访问

$ curl http://localhost:4000
<h3>Hello World!</h3><b>Hostname:</b> 8fc990912a14<br/><b>Visits:</b> <i>cannot connect to Redis, counter disabled</i>

如果你需要关闭docker应用的话，可以用如下方法：

$ docker container ls
CONTAINER ID        IMAGE               COMMAND             CREATED
1fa4ab2cf395        friendlyhello       "python app.py"     28 seconds ago

先获得docker 容器的ID，然后用docker container stop 命令来关闭它，例如：

docker container stop 1fa4ab2cf395
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