将python程序做成image

做一个正常的image（958M）:

FROM python:3.7
COPY . /app
WORKDIR /app
RUN pip install -r requirements.txt
CMD ["gunicorn", "-w 4", "main:app"]

做一个小一点的image （139M）:

FROM python:3.7-alpine
COPY . /app
WORKDIR /app
RUN pip install -r requirements.txt
CMD ["gunicorn", "-w 4", "main:app"]

使用docker 17.05版本的新特性：multi-stage build (https://docs.docker.com/develop/develop-images/multistage-build/) 来再减小一点image(去掉pip cache)

FROM python:3.7-alpine as base
FROM base as builder
RUN mkdir /install
WORKDIR /install
COPY requirements.txt /requirements.txt
RUN pip install --install-option="--prefix=/install" -r /requirements.txt
FROM base
COPY --from=builder /install /usr/local
COPY src /app
WORKDIR /app
CMD ["gunicorn", "-w 4", "main:app"]