为 Python 项目构建 Docker 镜像时如何避免重新安装包? [英] How to avoid reinstalling packages when building Docker image for Python projects?
问题描述
我的 Dockerfile 类似于
My Dockerfile is something like
FROM my/base
ADD . /srv
RUN pip install -r requirements.txt
RUN python setup.py install
ENTRYPOINT ["run_server"]
每次构建新映像时，都必须重新安装依赖项，这在我所在的地区可能会非常慢.
Every time I build a new image, dependencies have to be reinstalled, which could be very slow in my region.
我想到的一种缓存已安装包的方法是用更新的图像覆盖my/base图像，如下所示:
One way I think of to cache packages that have been installed is to override the my/base image with newer images like this:
docker build -t new_image_1 .
docker tag new_image_1 my/base
所以下次我用这个 Dockerfile 构建时，my/base 已经安装了一些包.
So next time I build with this Dockerfile, my/base already has some packages installed.
但是这个解决方案有两个问题:
But this solution has two problems:
- 并非总是可以覆盖基本图像
- 随着新图像的分层，基础图像变得越来越大
那么我可以使用什么更好的解决方案来解决这个问题?
So what better solution could I use to solve this problem?
关于我机器上的docker的一些信息:
Some information about the docker on my machine:
☁ test docker version
Client version: 1.1.2
Client API version: 1.13
Go version (client): go1.2.1
Git commit (client): d84a070
Server version: 1.1.2
Server API version: 1.13
Go version (server): go1.2.1
Git commit (server): d84a070
☁ test docker info
Containers: 0
Images: 56
Storage Driver: aufs
Root Dir: /var/lib/docker/aufs
Dirs: 56
Execution Driver: native-0.2
Kernel Version: 3.13.0-29-generic
WARNING: No swap limit support
推荐答案
尝试构建一个看起来像这样的 Dockerfile:
Try to build a Dockerfile which looks something like this:
FROM my/base
WORKDIR /srv
ADD ./requirements.txt /srv/requirements.txt
RUN pip install -r requirements.txt
ADD . /srv
RUN python setup.py install
ENTRYPOINT ["run_server"]
Docker 将在 pip 安装期间使用缓存，只要您不对 requirements.txt 进行任何更改，而不管 . 处的其他代码文件是否存在改变与否.这是一个例子.
Docker will use cache during pip install as long as you do not make any changes to the requirements.txt, irrespective of the fact whether other code files at . were changed or not. Here's an example.
这是一个简单的 Hello, World! 程序:
Here's a simple Hello, World! program:
$ tree
.
├── Dockerfile
├── requirements.txt
└── run.py
0 directories, 3 file
# Dockerfile
FROM dockerfile/python
WORKDIR /srv
ADD ./requirements.txt /srv/requirements.txt
RUN pip install -r requirements.txt
ADD . /srv
CMD python /srv/run.py
# requirements.txt
pytest==2.3.4
# run.py
print("Hello, World")
docker build 的输出:
The output of docker build:
Step 1 : WORKDIR /srv
---> Running in 22d725d22e10
---> 55768a00fd94
Removing intermediate container 22d725d22e10
Step 2 : ADD ./requirements.txt /srv/requirements.txt
---> 968a7c3a4483
Removing intermediate container 5f4e01f290fd
Step 3 : RUN pip install -r requirements.txt
---> Running in 08188205e92b
Downloading/unpacking pytest==2.3.4 (from -r requirements.txt (line 1))
Running setup.py (path:/tmp/pip_build_root/pytest/setup.py) egg_info for package pytest
....
Cleaning up...
---> bf5c154b87c9
Removing intermediate container 08188205e92b
Step 4 : ADD . /srv
---> 3002a3a67e72
Removing intermediate container 83defd1851d0
Step 5 : CMD python /srv/run.py
---> Running in 11e69b887341
---> 5c0e7e3726d6
Removing intermediate container 11e69b887341
Successfully built 5c0e7e3726d6
我们修改run.py:
# run.py
print("Hello, Python")
再次尝试构建，输出如下:
Try to build again, below is the output:
Sending build context to Docker daemon 5.12 kB
Sending build context to Docker daemon
Step 0 : FROM dockerfile/python
---> f86d6993fc7b
Step 1 : WORKDIR /srv
---> Using cache
---> 55768a00fd94
Step 2 : ADD ./requirements.txt /srv/requirements.txt
---> Using cache
---> 968a7c3a4483
Step 3 : RUN pip install -r requirements.txt
---> Using cache
---> bf5c154b87c9
Step 4 : ADD . /srv
---> 9cc7508034d6
Removing intermediate container 0d7cf71eb05e
Step 5 : CMD python /srv/run.py
---> Running in f25c21135010
---> 4ffab7bc66c7
Removing intermediate container f25c21135010
Successfully built 4ffab7bc66c7
如上所示，这次docker在构建过程中使用了缓存.现在，让我们更新 requirements.txt:
As you can see above, this time docker uses cache during the build. Now, let's update requirements.txt:
# requirements.txt
pytest==2.3.4
ipython
以下是docker build的输出:
Below is the output of docker build:
Sending build context to Docker daemon 5.12 kB
Sending build context to Docker daemon
Step 0 : FROM dockerfile/python
---> f86d6993fc7b
Step 1 : WORKDIR /srv
---> Using cache
---> 55768a00fd94
Step 2 : ADD ./requirements.txt /srv/requirements.txt
---> b6c19f0643b5
Removing intermediate container a4d9cb37dff0
Step 3 : RUN pip install -r requirements.txt
---> Running in 4b7a85a64c33
Downloading/unpacking pytest==2.3.4 (from -r requirements.txt (line 1))
Running setup.py (path:/tmp/pip_build_root/pytest/setup.py) egg_info for package pytest
Downloading/unpacking ipython (from -r requirements.txt (line 2))
Downloading/unpacking py>=1.4.12 (from pytest==2.3.4->-r requirements.txt (line 1))
Running setup.py (path:/tmp/pip_build_root/py/setup.py) egg_info for package py
Installing collected packages: pytest, ipython, py
Running setup.py install for pytest
Installing py.test script to /usr/local/bin
Installing py.test-2.7 script to /usr/local/bin
Running setup.py install for py
Successfully installed pytest ipython py
Cleaning up...
---> 23a1af3df8ed
Removing intermediate container 4b7a85a64c33
Step 4 : ADD . /srv
---> d8ae270eca35
Removing intermediate container 7f003ebc3179
Step 5 : CMD python /srv/run.py
---> Running in 510359cf9e12
---> e42fc9121a77
Removing intermediate container 510359cf9e12
Successfully built e42fc9121a77
请注意 docker 在 pip 安装期间如何不使用缓存.如果它不起作用，请检查您的 docker 版本.
Notice how docker didn't use cache during pip install. If it doesn't work, check your docker version.
Client version: 1.1.2
Client API version: 1.13
Go version (client): go1.2.1
Git commit (client): d84a070
Server version: 1.1.2
Server API version: 1.13
Go version (server): go1.2.1
Git commit (server): d84a070
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