System.Data.SqlClient.SqlException: A network-related or instance- docker compose with ASP.NET Core 2.1 and SQL Server

Question

Docker compose

version: '3.4'

services:
  legalregtech.web.host:
    image: ${DOCKER_REGISTRY-}legalregtechwebhost
    build:
      context: .
      dockerfile: src/LegalRegTech.Web.Host/Dockerfile
    networks:
      - dev-net
    ports:
      - "22742:80"
    depends_on:
      - sqlServer
  
  sqlServer:
    image: "mcr.microsoft.com/mssql/server:2019-latest"
    environment:
        ACCEPT_EULA: 'Y'
        SA_PASSWORD: 'XXXXX'
    ports:
      - "1433:1433"
    networks:
      - dev-net
    volumes:
      - /C/Databases/SqlServer/Data:/var/opt/mssql/data 
networks:
  dev-net:
    driver: bridge
    ipam:
      driver: default
      config:
        - subnet: 172.172.0.0/16
          gateway: 172.172.0.1

Docker file:

FROM mcr.microsoft.com/dotnet/aspnet:2.1 AS base
WORKDIR /app
EXPOSE 80

FROM mcr.microsoft.com/dotnet/sdk:2.1 AS build
WORKDIR /src
COPY ["src/LegalRegTech.Web.Host/LegalRegTech.Web.Host.csproj", "src/LegalRegTech.Web.Host/"]
COPY ["src/LegalRegTech.Web.Core/LegalRegTech.Web.Core.csproj", "src/LegalRegTech.Web.Core/"]
COPY ["src/LegalRegTech.Application/LegalRegTech.Application.csproj", "src/LegalRegTech.Application/"]
COPY ["src/LegalRegTech.AzureCosmosDB/LegalRegTech.AzureCosmosDB/LegalRegTech.GraphDBConnector.csproj", "src/LegalRegTech.AzureCosmosDB/LegalRegTech.AzureCosmosDB/"]
COPY ["src/LegalRegTech.Core.Shared/LegalRegTech.Core.Shared.csproj", "src/LegalRegTech.Core.Shared/"]
COPY ["src/LegalRegTech.Core/LegalRegTech.Core.csproj", "src/LegalRegTech.Core/"]
COPY ["src/LegalRegTech.Application.Shared/LegalRegTech.Application.Shared.csproj", "src/LegalRegTech.Application.Shared/"]
COPY ["src/LegalRegTech.EntityFrameworkCore/LegalRegTech.EntityFrameworkCore.csproj", "src/LegalRegTech.EntityFrameworkCore/"]
RUN dotnet restore "src/LegalRegTech.Web.Host/LegalRegTech.Web.Host.csproj"
COPY . .

RUN dotnet publish "LegalRegTech.Web.Host.csproj" -c Release -o /app/publish

FROM base AS final
WORKDIR /app
COPY --from=build /app/publish .
ENTRYPOINT ["dotnet", "LegalRegTech.Web.Host.dll"]

I get this exception:

Unhandled Exception: System.Data.SqlClient.SqlException: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: TCP Provider, error: 40 - Could not open a connection to SQL Server)

at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, Boolean applyTransientFaultHandling, String accessToken)
at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)
at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)
at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection) at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource1 retry, DbConnectionOptions userOptions) at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource1 retry)
at System.Data.SqlClient.SqlConnection.Open()
at Hangfire.SqlServer.SqlServerStorage.CreateAndOpenConnection()
at Hangfire.SqlServer.SqlServerStorage.UseConnection[T](DbConnection dedicatedConnection, Func2 func) at Hangfire.SqlServer.SqlServerStorage.UseConnection(DbConnection dedicatedConnection, Action1 action)
at Hangfire.SqlServer.SqlServerStorage.Initialize()
at LegalRegTech.Web.Startup.Startup.ConfigureServices(IServiceCollection services) in /src/src/LegalRegTech.Web.Host/Startup/Startup.cs:line 149

SQL Server is running fine, I am able to connect through SSMS in local computer. I think in the container the app is not able to connect to the SQL Server.

When running docker-compose up a network get created as below

It gets created with the suffix 6clicks_ which is the root folder of my application and when I do the inspect on that network the container is {}

[
    {
        "Name": "6clicks_dev-net",
        "Id": "b6f693ce2402e7c52d0c8af3048eaebd86ed19b41a43dca381f30712c00f4193",
        "Created": "2021-12-10T02:34:23.8790393Z",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": [
                {
                    "Subnet": "172.172.0.0/16"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Containers": {},
        "Options": {},
        "Labels": {
            "com.docker.compose.network": "dev-net",
            "com.docker.compose.project": "6clicks",
            "com.docker.compose.version": "2.0.0"
        }
    }
]

Connection string:

"ConnectionStrings": {
    "Default": "Data Source=127.0.0.1; Initial Catalog=xxxxx;User ID=sa; Password=xxxxx; Persist Security Info=True; MultipleActiveResultSets=True"
}

The reason I can see on the docker logs is Login failed for user 'sa'. Reason: Password did not match that for the login provided. [CLIENT: 172.172.0.2]. However I am able to login in with SSMS with same password

Answer 1

Since legalregtech.web.host is not configured to connect to sqlServer explicitly, it tries to connect 127.0.0.1 as configured in your appsettings.json file.

For use within docker-compose, it's easiest to simply override this connection string to reach the sqlServer service by adding an environment variable:

  legalregtech.web.host:
    # ...
    environment: 
      - ConnectionStrings__Default=Data Source=sqlServer; Initial Catalog=xxxxx;User ID=sa; Password=xxxxx; Persist Security Info=True; MultipleActiveResultSets=True

(A more compact connection string would be: Server=sqlServer;Database=xxxxx;User ID=sa;Password=xxxxx;MultipleActiveResultSets=True;)

---

Here's a fully working docker-compose file:

version: '3.4'

services:

  mssql:
    image: mcr.microsoft.com/mssql/server
    environment:
      - MSSQL_SA_PASSWORD=zHDgRw7qw4QJyrrhgXK2mG45
      - ACCEPT_EULA=Y
      - MSSQL_PID=Developer
    
  dotnetapp:
    image: dotnetapp
    depends_on: 
      - mssql
    build:
      context: .
      dockerfile: Dockerfile
    restart: always
    environment: 
      - ConnectionStrings__Default=Server=mssql;Database=amplily;User ID=sa;Password=zHDgRw7qw4QJyrrhgXK2mG45;MultipleActiveResultSets=True;