Docker:在 Git 中构建上下文并使用 .NET 项目和子模块会导致一个大问题 [英] Docker: Build context and working with .NET projects and submodules in Git causes a big problem

问题描述

Docker 的构建上下文很重要，因为没有将上下文设置为路径high up"中的某个位置.通常会给你带来可怕的构建上下文之外的禁止路径问题.

然后，在输出文件夹中，我放置以下简单的 Dockerfile:

 FROM mcr.microsoft.com/dotnet/core/runtime:3.1-buster-slim AS base工作目录/应用程序复制 ..运行 chmod +x/appCMD [dotnet"，/app/AlfaPortal.dll"]

然后命令 docker build --tag yourtag:whatever . 将创建图像

这个图像在 Linux 机器上效果很好.

The build context for Docker is important, since not having the context set to a location in the path "high up" will normally give you the dreaded Forbidden path outside the build context problem.

This discussion, regarding .NET project with Project References, led me to the conclusion that the Docker tools in Visual Studio places the Dockerfile incorrectly in the project folder, when it seems it needs to be in the folder where the solution file exists. This is so that the build context is the same folder as the solution file, and thus, the dependencies of the underlying projects are found (the .net core project file DockerfileContext tag doesn't seem to have any effect).

However, I think it normal that not all references needed are below the sln-folder, but instead are referenced even higher up. This is the case for me, when I use GIT submodules, and those submodules are placed higher up than the folder of the solution. Something like this:

+ MyGitRepo
|
+-- MySolution
|   |
|   +-- MyProject (ref: MyCoolLibrary)
|   |
|   +-- MyOtherProject (ref: MyCoolLibrary)
|
+-- Submodules
   |
   +-- MyCoolLibrary

The MyProject is something I want as a stand-alone container. Visual Studio fixed with the the built-in tools, but then placed the Dockerfile inside the project folder, and I got the "Forbidden path..." error.

I then placed the Dockerfile in the "MySolution" folder, but of course, that didn't help, since the submodules are a level up.

So I thought, in the docker-compose.yml I specify context: ../. and that should work, right? I ended up with a docker-compose file like this, placed in the MySolution folder:

version: '3.4'

services:
  alfacom:
    image: ${DOCKER_REGISTRY-}MyProject
    build:
      context: ../.
      dockerfile: MySolution/Dockerfile-MyProject

But, the problem I think I have is that I have a lot of projects in the repo folder, and then I read this:

A context is processed recursively. So, a PATH includes any subdirectories... The build is run by the Docker daemon, not by the CLI. The first thing a build process does is send the entire context (recursively) to the daemon.

This would be madness; sending all that to the daemon is not only huge, but unnecessary, as the "MySolution" does not depend on everything in the MyGitRepo, but only some of the submodules.

What can be done here? I really want to keep the MySolution in that repo, because the repo contains all solutions and projects for this system, sort of. How should I approach this?

解决方案

I actually have a better workaround for this problem, and that is to use the Publish function in Visual Studio, and then create a super-simple Dockerfile inside the publish folder, and create the image from there.

Using NuGet packages, as I write in my first answer above, resolves the immediate problem with Docker build, but, it introduces some serious problems, like code browsing and debugging. Debugging code inside NuGet packages isn't possible, which makes this approach more or less useless.

Instead, I do the following:

• Publish the app, using the built-in Visual Studio functionality, this is what I use:

• Then, in the output folder, I place the following simple Dockerfile:

   FROM mcr.microsoft.com/dotnet/core/runtime:3.1-buster-slim AS base
   WORKDIR /app
   COPY . .
   RUN chmod +x /app
   CMD ["dotnet", "/app/AlfaPortal.dll"]
  

• And then the command docker build --tag yourtag:whatever . will create the image

This image works great on a Linux machine.

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