python - 错误 : pg_config executable not found when installing psycopg2 on Alpine in Docker

Question

我正在尝试使用带有 Docker 的 Postgres 构建一个 Flask 应用程序。我想连接到 Postgres 的 AWS RDS 实例，但将 Docker 用于我的 Flask 应用程序。但是，在尝试设置 psycopg2 时会遇到错误，因为它找不到 pg_config。这是错误:

Building api
Step 1/5 : FROM python:3.6.3-alpine3.6
 ---> 84c98ca3b5c5
Step 2/5 : WORKDIR /usr/src/app
 ---> Using cache
 ---> 407c158f5ee4
Step 3/5 : COPY . .
 ---> 966df18d329e
Step 4/5 : RUN pip install -r requirements.txt
 ---> Running in 284cc97aeb63
Collecting aniso8601==1.3.0 (from -r requirements.txt (line 1))
  Downloading aniso8601-1.3.0.tar.gz (57kB)
Collecting click==6.7 (from -r requirements.txt (line 2))
  Downloading click-6.7-py2.py3-none-any.whl (71kB)
Collecting Flask==0.12.2 (from -r requirements.txt (line 3))
  Downloading Flask-0.12.2-py2.py3-none-any.whl (83kB)
Collecting Flask-RESTful==0.3.6 (from -r requirements.txt (line 4))
  Downloading Flask_RESTful-0.3.6-py2.py3-none-any.whl
Collecting Flask-SQLAlchemy==2.3.2 (from -r requirements.txt (line 5))
  Downloading Flask_SQLAlchemy-2.3.2-py2.py3-none-any.whl
Collecting itsdangerous==0.24 (from -r requirements.txt (line 6))
  Downloading itsdangerous-0.24.tar.gz (46kB)
Collecting Jinja2==2.9.6 (from -r requirements.txt (line 7))
  Downloading Jinja2-2.9.6-py2.py3-none-any.whl (340kB)
Collecting MarkupSafe==1.0 (from -r requirements.txt (line 8))
  Downloading MarkupSafe-1.0.tar.gz
Collecting psycopg2==2.7.3.1 (from -r requirements.txt (line 9))
  Downloading psycopg2-2.7.3.1.tar.gz (425kB)
    Complete output from command python setup.py egg_info:
    running egg_info
    creating pip-egg-info/psycopg2.egg-info
    writing pip-egg-info/psycopg2.egg-info/PKG-INFO
    writing dependency_links to pip-egg-info/psycopg2.egg-info/dependency_links.txt
    writing top-level names to pip-egg-info/psycopg2.egg-info/top_level.txt
    writing manifest file 'pip-egg-info/psycopg2.egg-info/SOURCES.txt'
    Error: pg_config executable not found.

    Please add the directory containing pg_config to the PATH
    or specify the full executable path with the option:

        python setup.py build_ext --pg-config /path/to/pg_config build ...

    or with the pg_config option in 'setup.cfg'.

    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-build-01lf5grh/psycopg2/
ERROR: Service 'api' failed to build: The command '/bin/sh -c pip install -r requirements.txt' returned a non-zero code: 1

这是我的 Dockerfile:

FROM python:3.6.3-alpine3.6

WORKDIR /usr/src/app

COPY . .

RUN pip install -r requirements.txt

CMD ["python", "app.py"]

许多其他人似乎在本地也有类似的问题，但没有一个涉及使用 Docker。这似乎是一个 Docker 问题，因为我可以设置本地虚拟环境并且设置工作正常，因为我在本地安装了 Postgres，它能够找到我的本地 pg_config。

似乎在容器构建/设置期间，Docker 试图在容器中查找 pg_config。有没有办法在容器中安装 pg_config，即使我不会使用 Postgres 的容器化实例，而是使用 RDS 上的实例？

欢迎任何有关如何解决此问题的建议。

Answer 1

使用 Python 3.4.8、3.5.5、3.6.5 和 2.7.14 测试(只需将 3 替换为 2):

# You can use a specific version too, like python:3.6.5-alpine3.7
FROM python:3-alpine

WORKDIR /usr/src/app

COPY requirements.txt .

RUN \
 apk add --no-cache postgresql-libs && \
 apk add --no-cache --virtual .build-deps gcc musl-dev postgresql-dev && \
 python3 -m pip install -r requirements.txt --no-cache-dir && \
 apk --purge del .build-deps

COPY . .

CMD ["python3", "app.py"]

说明:要构建 Psycopg，您需要包 gcc musl-dev postgresql-dev。然后你还需要 pg_config 可执行文件:虽然简单地安装 postgresql-dev 可以工作，但 postgresql-libs 也可以，并且占用的空间少了 12 MB。

---

这是答案的原始版本(基于 this Dockerfile)，我在其中手动将 Python 安装到纯 Alpine 镜像上，因为当时 Python 没有为 Python 3.6 和 Alpine 3.7 提供 Docker 镜像。如果你想像这样安装 Python 2.7，也可以执行 apk add py2-pip(在旧的 Alpine 存储库中称为 py-pip)。

FROM alpine:3.7

WORKDIR /usr/src/app

COPY requirements.txt .

RUN \
 apk add --no-cache python3 postgresql-libs && \
 apk add --no-cache --virtual .build-deps gcc python3-dev musl-dev postgresql-dev && \
 python3 -m pip install -r requirements.txt --no-cache-dir && \
 apk --purge del .build-deps

COPY . .

CMD ["python3", "app.py"]