Azure Pipeline - Communication TCP between tests and containers with TCP Server

[ghost]

Hi,

Context:
I implemented one test project which created three containers connected with a custom network.
One of the containers has one TCP server listening. The test creates a TCP client that communicates with the container and validates the communication
Locally it works on my computer. In the azure pipeline, it fails.

In the Azure pipeline, three containers and test-containers-ryuk have IP's addresses assigned
Testcontainers-ryuk - 172.19.0.1
Container 1 - 172.19.0.2
Container 2 - 172.19.0.3
Container 3 (TCP server) - 172.19.0.4

Also, when the test checks for TCP server listening (in the test I log the values) , the container doesn't expose TCP port.
In azure, when I check for hostname + GetMappedPublicPort, I get localhost and public port. This is't available in azure.

The Azure setup is:

pool:  vmImage: ubuntu-latest
container: mcr.microsoft.com/dotnet/sdk:6.0

In the container, I execute the task for the test.

  - task: DotNetCoreCLI@2
    timeoutInMinutes: 5
    continueOnError: true
    inputs:
      command: 'test'
      projects: $(TEST_FOLDER)/tests/**/*.Tests.Integration.csproj
      arguments: '$(Test_Integration_Args)'
      testRunTitle: 'Run Integration tests'
    displayName: 'Run Integration Tests' 

The container configuration with TCP server is the following

From the forums discussions, it seems I'm trying to Run a docker inside docker.
What do I need to configure to expose the TCP Server to the test?

[HofmeisterAn]

From the forums discussions, it seems I'm trying to Run a docker inside docker.

That does not look like DinD. Sorry, I missed the YML (pipeline) configuration. Yep, that is probably DinD, but should not have an impact.

Take a look into our docs, they cover a very similar use case. Notice following:

The communication between those containers won't require exposing ports through the host anymore.

If I got it right, you try to set up a communication between the containers. Does that help? BTW, I would not recommend to assign a fix container name. This will prevent running multiple tests parallel, etc.

[ghost]

The communication between the containers works.
The problem is the communication between the Integration test and the container with the TCP server. The tests are in the container (container: mcr.microsoft.com/dotnet/sdk:6.0) and the three containers are created inside of the test container

Data of IP's

[HofmeisterAn]

Ok, we checked the Azure DevOps Pipeline YML configuration and container: mcr.microsoft.com/dotnet/sdk:6.0 mounts the Docker socket (not DinD). Can you create an empty /.dockerenv file (in the OS root directory) in the container that runs your build (aka mcr.microsoft.com/dotnet/sdk:6.0) and test if it works (pipeline task that create the file before running the test is fine)?

[ghost]

Doesn't work. It has already a .dockerenv.

[HofmeisterAn]

Which hostname or IP address returns _tcpServerContainer? Based on the exception above I assume localhost? Which sounds wrong, you should get the Docker gateway address:

testcontainers-dotnet/src/Testcontainers/Containers/TestcontainersContainer.cs

Lines 386 to 403 in 446f002

	if (!this.client.IsRunningInsideDocker)
	{
	return localhost;
	}
	var endpointSettings = this.container.NetworkSettings.Networks.TryGetValue("bridge", out var network) ? network : new EndpointSettings();
	if (!string.IsNullOrWhiteSpace(endpointSettings.Gateway))
	{
	return endpointSettings.Gateway;
	}
	var networkSettings = this.container.NetworkSettings;
	if (!string.IsNullOrWhiteSpace(networkSettings.Gateway))
	{
	return networkSettings.Gateway;
	}
	return localhost;

[HofmeisterAn]

I've set up a small example project that returns the gateway IP. Is that the case for your configuration?

[ghost]

Yes, I used you alpine container with mosquitto container in same test and the results was

[HofmeisterAn]

That looks right. As I asked above, can you check the result of _tcpServerContainer? Do you use localhost as a fixed value? In your screenshot above it looks like you are accessing localhost instead of the gateway.

[ghost]

Hi Andre,

It worked

Now, the error is other, but isn't related with this.

It seems when I connected the containers to the network bridge, all returned the hostname as localhost.

Is there a way to have the bridge between containers and also access to _tcpServerContainer?

Thank you for the help

[HofmeisterAn]

Indeed, this looks like an unsupported case. I extended my example and noticed the same behavior. It does not find a gateway address, because Testcontainers looks for a network named bridge (which does not exist / is assigned to the container).

testcontainers-dotnet/src/Testcontainers/Containers/TestcontainersContainer.cs

Line 391 in 446f002

var endpointSettings = this.container.NetworkSettings.Networks.TryGetValue("bridge", out var network) ? network : new EndpointSettings();

If Testcontainers reads the right gateway address it will work, see my example.

[ghost]

It works, thank you. You're the best =). You can close the Q.A.

[HofmeisterAn]

Great 🙌. I created and new issue to add the missing functionality.