優化 .net core 應用的 dockerfile

Intro

在給 .net core 應用的寫 dockerfile 的時候一直有個苦惱，就是如果有很多個項目，在 dockerfile 里寫起來就會很繁瑣，有很多項目文件要 copy，dockerfile 還不支持直接批量複製項目文件，今天要改的一個項目也是有好多個項目文件，不想再一個一個複製，於是 google 一下看有沒有比較好的解決方案，找到一個折中的解決方案，分享一下

Solution

1. 首先把所有的項目文件拷貝到 docker 鏡像內 COPY */*.csproj ./
2. 然後根據項目文件名稱創建項目文件夾，並移動項目文件到對應的項目目錄下

原來的 dockerfile

FROM mcr.microsoft.com/dotnet/core/sdk:3.0-alpine AS build-env
WORKDIR /src

# Copy csproj and restore as distinct layers
COPY ActivityReservation.Common/*.csproj ActivityReservation.Common/
COPY ActivityReservation.Models/*.csproj ActivityReservation.Models/
COPY ActivityReservation.DataAccess/*.csproj ActivityReservation.DataAccess/
COPY ActivityReservation.Business/*.csproj ActivityReservation.Business/
COPY ActivityReservation.Helper/*.csproj ActivityReservation.Helper/
COPY ActivityReservation.WechatAPI/*.csproj ActivityReservation.WechatAPI/
COPY ActivityReservation.AdminLogic/*.csproj ActivityReservation.AdminLogic/
COPY ActivityReservation.API/*.csproj ActivityReservation.API/
COPY ActivityReservation/ActivityReservation.csproj ActivityReservation/

# RUN dotnet restore ActivityReservation/ActivityReservation.csproj
## diff between netcore2.2 and netcore3.0
WORKDIR /src/ActivityReservation
RUN dotnet restore

# copy everything and build
COPY . .
RUN dotnet publish -c Release -o out ActivityReservation/ActivityReservation.csproj

# build runtime image
FROM mcr.microsoft.com/dotnet/core/aspnet:3.0-alpine

LABEL Maintainer="WeihanLi"
WORKDIR /app
COPY --from=build-env /src/ActivityReservation/out .
EXPOSE 80
ENTRYPOINT ["dotnet", "ActivityReservation.dll"]

修改之後的 dockerfile

FROM mcr.microsoft.com/dotnet/core/sdk:3.0-alpine AS build-env
WORKDIR /src

# Copy csproj and restore as distinct layers
# https://andrewlock.net/optimising-asp-net-core-apps-in-docker-avoiding-manually-copying-csproj-files-part-2/
COPY */*.csproj ./
RUN for file in $(ls *.csproj); do mkdir -p ${file%.*}/ && mv $file ${file%.*}/; done

## diff between netcore2.2 and netcore3.0
WORKDIR /src/ActivityReservation
RUN dotnet restore

# copy everything and build
COPY . .
RUN dotnet publish -c Release -o out ActivityReservation/ActivityReservation.csproj

# build runtime image
FROM mcr.microsoft.com/dotnet/core/aspnet:3.0-alpine

LABEL Maintainer="WeihanLi"
WORKDIR /app
COPY --from=build-env /src/ActivityReservation/out .
EXPOSE 80
ENTRYPOINT ["dotnet", "ActivityReservation.dll"]

是不是精簡了許多，來看一下修改前後的對比，更明顯的對比一下：

核心代碼：

 # 拷貝所有的二級目錄下的項目文件
COPY */*.csproj ./
# 根據項目文件名稱創建項目文件夾，並移動項目文件到對應的項目目錄下
RUN for file in $(ls *.csproj); do mkdir -p ${file%.*}/ && mv $file ${file%.*}/; done 

More

註：上面的方法適用於項目文件目錄名稱和項目文件名稱一致的情況，預設創建的項目應該都會符合這樣的要求，如果你的項目文件是三級目錄，如 src/*/*.csproj 的，需要自己根據項目情況調整 dockerfile

有沒有學到呢~~

Reference

• https://stackoverflow.com/questions/51372791/is-there-a-more-elegant-way-to-copy-specific-files-using-docker-copy-to-the-work
• https://andrewlock.net/optimising-asp-net-core-apps-in-docker-avoiding-manually-copying-csproj-files-part-2/
• https://github.com/WeihanLi/ActivityReservation/blob/dev/Dockerfile