Connecting to a SQL Server database running in a Docker container from another docker container

Question

I am creating a database in a Docker container via the following

docker run -e "ACCEPT_EULA=Y" -e "SA_PASSWORD=YourStrong@Passw0rd" -p 1433:1433 --network MyAppNetwork --name MyAppDb -d mcr.microsoft.com/mssql/server:2017-latest-ubuntu

I am then running my ASP.NET Core 3.0 application

docker run -p 5000:80 -e "ASPNETCORE_ENVIRONMENT=Development" --network MyAppNetwork --name MyApp myimage

Inside the app there is a connection string

Data Source=MyAppDb;Initial Catalog=MyAppDb;User ID=sa;Password=YourStrong@Passw0rd

and I perpetually get the error

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)

I have tried MyAppDb,1433 localhost localhost,1433... nothing works

Docker documentation says you should be able to refer to other docker containers via their name as long as they are on the same network, but its not behaving as expected for me. I did try not specifying a network so the containers are just defaulting to the bridge, but nothing changed.

Note: I can connect to the database perfectly fine from my host machine, but from within the other docker container, nothing works.

Any ideas?

-- update --

docker network inspect MyAppNetwork

[
    {
        "Name": "MyAppNetwork",
        "Id": "2f334b2df38c199ef423fdbe65c15e33b43d983e91a3398d75f0d988d5588c13",
        "Created": "2019-10-03T10:40:40.3165785Z",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": {},
            "Config": [
                {
                    "Subnet": "172.19.0.0/16",
                    "Gateway": "172.19.0.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Containers": {
"f3106bc710fe760e257dd05aace7e76827d953600e5520556b040706f10246fb": {
                "Name": "MyAppDb",
                "EndpointID": "c4c58df89b4117674a0db57dfe276086eb48dda36fcc6a0989425b65fc130c41",
                "MacAddress": "02:42:ac:13:00:02",
                "IPv4Address": "172.19.0.2/16",
                "IPv6Address": ""
            }
        },
        "Options": {},
        "Labels": {}
]

"IP packet forwarding is governed by the ip_forward system parameter. Packets can only pass between containers if this parameter is 1", ref: Understand container communication — AlwaysLearning
– AlwaysLearning, Commented Oct 3, 2019 at 11:02
You're also using a custom network. What does docker network inspect MyAppNetwork tell you? — AlwaysLearning
– AlwaysLearning, Commented Oct 3, 2019 at 11:09
ill edit it into the original question - done - nothing anything wrong? — Gary MacPherson
– Gary MacPherson, Commented Oct 3, 2019 at 11:11
Whilst running the MyAppDb and MyApp containers should appear inside MyAppNetwork's "Containers": {} collection. MyApp should be able to connect to 172.19.some.address,1433 using the IPv4Address indicated against MyAppDb in the containers collection. User-defined networks has more information about this. If DNS is properly configured and running inside the network, MyApp should also be able to resolve and connect to MyAppDb,1433. — AlwaysLearning
– AlwaysLearning, Commented Oct 3, 2019 at 11:20

Gary MacPherson · Accepted Answer · 2019-10-14 14:46:10Z

I spent many hours on this trying to do it "properly" but eventually I just gave up and went back to using the deprecated Links feature based solution within a docker-compose file

https://docs.docker.com/network/links/

Worked immediately without any issues what so ever. I will revisit this when the next major update to Docker comes out and removes the Link feature.

docker-compose.yml

version: "3.5"

networks:
  myappnetwork:
    name: myappnetwork

services:
  myapp:
    build: .
    restart: always
    container_name: myapp
    depends_on: [myappdb]
    environment:
      ASPNETCORE_ENVIRONMENT: Development
    networks:
      - myappnetwork
    ports:
      - 5000:80
    links:
      - myappdb
  myappdb:
    image: mcr.microsoft.com/mssql/server:2017-latest-ubuntu
    restart: always
    container_name: myappdb
    environment:
      ACCEPT_EULA: Y
      SA_PASSWORD: YourStrong@Passw0rd
    networks:
      - myappnetwork
    ports:
      - 1433:1433

dockerfile

FROM mcr.microsoft.com/dotnet/core/sdk:3.0 AS build
WORKDIR /app

# copy csproj and restore as distinct layers
COPY *.sln .
COPY MyApp/*.csproj ./MyApp/
RUN dotnet restore

# copy everything else and build app
COPY MyApp/. ./MyApp/
WORKDIR /app/MyApp
RUN dotnet publish -c Release -o out

FROM mcr.microsoft.com/dotnet/core/aspnet:3.0 AS runtime
WORKDIR /app
COPY --from=build /app/MyApp/out ./
ENTRYPOINT ["dotnet", "MyApp.dll"]

appsettings.json

{
  "ConnectionStrings": {
    "DefaultConnection": "Data Source=myappdb,1433;Initial Catalog=myappdb;User ID=sa;Password=YourStrong@Passw0rd"
  }
}

nPcomp · Accepted Answer · 2019-10-03 16:34:51Z

0

You can try following:

After you start running the SQL container, get the IP of the container by

docker inspect MyAppDb | grep IPAddress

If this is a Linux server you should be able to connect another container by the IP address. Or you can use the IP of the host server that docker containers run.

Additionally, you may need to add:

Trusted_Connection=false; attribute to your connection string.

edited Oct 3, 2019 at 16:34

answered Oct 3, 2019 at 13:07

nPcomp

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1 Comment

Gary MacPherson Over a year ago

I have tried to go down this path, and it lead me to a dead end as the IP address that returns is unresolvable from within the other container. I may have been able to fix it eventually, but its still a dead end as there is no point in a 1 command start process that then needs a manual step to make it work.

Sunil Jatolia · Accepted Answer · 2025-02-13 05:19:37Z

0

On Windows, use

host.docker.internal

docker creates a custom domain in the host file to reach containers.

Check this link:

answered Feb 13 at 5:19

Sunil Jatolia

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1 Comment

Thom A Feb 13 at 12:38

Please don't post the same answer one 2 (or more) questions. If you feel a question is answered by a different question, then use the flag/vote to close as duplicate feature.

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