Docker compose with C# and MySql

Question

I have a problem when trying to connect to dockerized mysql database from my dockerized microservice (on the same user defined bridge network).

This is my c# image:

FROM mcr.microsoft.com/dotnet/sdk:6.0 as build
COPY ./User /microservices/User
COPY ./Associated /microservices/Associated
WORKDIR /microservices/User/User.API
RUN dotnet restore
RUN dotnet build -o /app
RUN dotnet publish -o /publish -c Debug
 
FROM mcr.microsoft.com/dotnet/aspnet:6.0 as base
COPY --from=build  /publish /app
WORKDIR /app
ENV ASPNETCORE_URLS=http://+:5114
EXPOSE 5114
ENTRYPOINT ["dotnet", "User.dll"]
# CMD ["./User"]

This is my compose file:

services:
  user_api:
    image: df_user_api:latest
    container_name: user_api
    build:
      context: .
      dockerfile: df_user_api
    ports: [5114:5114]
    depends_on: [mysql]
    networks: [associated]
  mysql:
    image: mysql:latest
    container_name: mysql
    restart: unless-stopped
    environment:
      MYSQL_ROOT_PASSWORD: roottooR1!
      MYSQL_DATABASE: webshop2023
      MYSQL_USER: test
      MYSQL_PASSWORD: test123
      MYSQL_LOG_CONSOLE: "1"
      MYSQL_LOG_ERROR: "/var/log/mysql/error.log"
    ports: [3306:3306]
    networks: [associated]
    volumes:
      - "mysql-data:/var/lib/mysql"
      - "mysql-log:/var/log/mysql"
      - "mysql-conf:/etc/mysql/conf.d"
networks:
  associated:
    name: associated
volumes:
  mysql-data:
    driver: local
  mysql-log:
    driver: local
  mysql-conf:
    driver: local

error:

fail: Microsoft.AspNetCore.Server.Kestrel[13]
user_api  |       Connection id "0HN006R0TSPN5", Request id "0HN006R0TSPN5:00000004": An unhandled exception was thrown by the application.
user_api  |       MySqlConnector.MySqlException (0x80004005): Unable to connect to any of the specified MySQL hosts.

Confusing part is that I can connect to dockerized mysql via mysql workbench from the host machine as: localhost:3036 (because mysql is exposed towards 0.0.0.0 by default)

Same is true for locally running c# microservice, I can connect to dockerized mysql also via localhost:3036.

These are my connection strings:

From localhost:

"server=localhost;port=3306;user=test;password=test123;database=webshop2023"

From within docker network:

"server=mysql;port=3306;user=test;password=test123;database=webshop2023"

I would be delighted if someone tells me what I am doing wrong. Sorry if the question is duplicate but I have read many articles aleready and I can't seem to figure out why it is not working.

Answer 1

It seems that everything was right, except that MySql framework that I was using was case sensitive on linux regarding the connection string parameters. Everyone that is developing on windows machine and then migrating your code to linux containers be exact with upper and lower case characters to not waste so much time like me.