使用 docker-compose 将带有 MySQL 持久化数据库的 ASP.NET Core Web 应用 Docker 化为两个单独的容器

Question

I have some issues trying to dockerize the web app I have written(ResumePostingService). I have a Dockerfile for my application and one for my database as well as an Init sql file to create the database some tables and insert some data. I also have a docker-compose file. I have watched quite a few tutorials on the subject but every time I see something different and I get a different kind of error.

The latest error I am getting after the docker-compose up command when I go to localhost:8080 on my browser is the following:

InvalidOperationException: Unable to resolve service for type 'ResumePostingService.Models.ResumePostingServiceDatabaseContext' while attempting to activate 'ResumePostingService.Pages.LoginModel'.

Can anyone help me on what I am doing wrong?

Dockerfile(app)

FROM mcr.microsoft.com/dotnet/core/sdk:3.1 AS build-env
WORKDIR /app
# Copy csproj and restore as distinct layers
COPY *.csproj ./
RUN dotnet restore

# Copy everything else and build
COPY . ./
RUN dotnet publish -c Release -o out

# Build runtime image
FROM mcr.microsoft.com/dotnet/core/aspnet:3.1
WORKDIR /app
COPY --from=build-env /app/out .
ENTRYPOINT ["dotnet", "ResumePostingService.dll"]

docker-compose.yml

version: '3.8'
services:
 db:
  build: ./Db
  volumes:
   - data-volume:/var/lib/db
 app:
  build:
   context: .
   dockerfile: Dockerfile
  ports:
   - '8080:80'
  depends_on:
   - db
volumes:
  data-volume:

Dockerfile(db)

FROM mysql:8.0.21
COPY *.sql /docker-entrypoint-initdb.d

ENV MYSQL_ROOT_PASSWORD myEpicPass

EXPOSE 3306

My connection string on the appsettings.json file

"Default": "server=127.0. 0.1;user=root;password=myEpicPass;port=3306;database=ResumePostingServiceDB"

The command I use to connect to the db inside Startup.cs

services.AddTransient(_ => new MySqlConnection(Configuration["ConnectionStrings:Default"]));

Answer 1

You need to change 127.0.0.1 to the service name (like in compose file), in your case it's db , so the connection string should look like this:

"Default": "server=db;user=root;password=myEpicPass;port=3306;database=ResumePostingServiceDB"

More information about networking in docker-compose: https://docs.docker.com/compose/networking/