Can Testcontainers itself be used from inside a container?

[jernejg]

Hey, one question. I'm trying to run dotnet test from inside the container using:

docker run -it -v /var/run/docker.sock:/var/run/docker.sock my:tag

Found this suggestion here Sibling docker containers

But I get this exception

Error Message:
   DotNet.Testcontainers.Containers.ResourceReaperException : Initialization has been cancelled.

Is it even possible to run .net Testcontainers from inside docker?

[jernejg]

Hm looks like it works if I disable Ryuk

.WithCleanUp(false)

[HofmeisterAn]

It works with WithCleanUp(true) too. See my answer below. I do not recommend WithCleanUp(false) as a "fix".

[HofmeisterAn]

Yes, sibling containers are working. The ResourceReaper use it as well. Following example incl. running the default ResourceReaper in the background works fine:

var testcontainers = new TestcontainersBuilder<TestcontainersContainer>()
  .WithImage("docker")
  .WithCommand(KeepTestcontainersUpAndRunning.Command)
  .WithBindMount("/var/run/docker.sock", "/var/run/docker.sock", AccessMode.ReadOnly)
  .Build();

await testcontainers.StartAsync()
  .ConfigureAwait(false);

var execResult = await testcontainers.ExecAsync(new[] { "docker", "ps" })
  .ConfigureAwait(false);

execResult contains the sibling containers:

CONTAINER ID   IMAGE                              COMMAND                  CREATED          STATUS                  PORTS                     NAMES
0d63ae7b2bb4   docker:latest                      "docker-entrypoint.s…"   1 second ago     Up Less than a second                             priceless_wu
e900901ee327   ghcr.io/psanetra/ryuk:2021.12.20   "/app"                   13 seconds ago   Up 12 seconds           0.0.0.0:59230->8080/tcp   testcontainers-ryuk-a815fb8c-f78f-4da9-a670-9ec706d96c07

---

Error Message:
   DotNet.Testcontainers.Containers.ResourceReaperException : Initialization has been cancelled.

This might happen if the default ResourceReaper does not start within 10 seconds. It's unusual, but maybe 10 seconds are not enough for your machine. Can you try to increase the default initTimeout?

https://github.com/HofmeisterAn/dotnet-testcontainers/blob/ffa5a812bde1b8e8de40e1849fe180b7e9b148fd/src/DotNet.Testcontainers/Containers/ResourceReaper.cs#L141

Unfortunately, you need to check out the repository. There is no option yet to change initTimeout for the default ResourceReaper.

[HofmeisterAn]

Yes, you're right. It's not necessary, I think the current code works. My suggestion will just prevent the Initialization has been cancelled. (flaky test) exception if each ping has a timeout of 5 seconds (10 seconds in total).

[PSanetra]

Ah yes, a shorter timeout probably makes sense in that case. Maybe a dns lookup via Dns.GetHostEntry would also be faster. I am not sure if there are any tradeoffs using that api.

[HofmeisterAn]

I did some tests yesterday. It looks like both methods (Dns.GetHostEntry, Ping.Send) do not fail immediately or after the specific timeout. Both methods fail after approximately 2 seconds on my system if the host name does not exist. This may be different on other operating systems. It looks like the Ping.Send timeout refers to the ping response, not the command itself. I'll try different implementations in the next days.

[PSanetra]

Another idea might be to get the default gateway address in a similar way like in testcontainers-java. Although I guess it should be possible to just use the dotnet api to get the default network interface and gateway ip as the tests are running anyway in a container, right? Maybe via NetworkInterface.GetAllNetworkInterfaces. (Edit: I forgot that the target container might run in a different network.)

[HofmeisterAn]

This should work:
https://github.com/HofmeisterAn/dotnet-testcontainers/blob/f25ed8705fa72c9d03eb185c41bd783db0fbb908/src/DotNet.Testcontainers/Containers/TestcontainersContainer.cs#L355