[Bug]: Remote Docker Host not working

Module

Core

Testcontainers version

1.19.8

Using the latest Testcontainers version?

Yes

Host OS

Mac

Host Arch

x86

Docker version

Client:
 Cloud integration: v1.0.35
 Version:           24.0.2
 API version:       1.43
 Go version:        go1.20.4
 Git commit:        cb74dfc
 Built:             Thu May 25 21:51:16 2023
 OS/Arch:           darwin/amd64
 Context:           t1-local

Server:
 Engine:
  Version:          25.0.3
  API version:      1.44 (minimum version 1.24)
  Go version:       go1.21.8
  Git commit:       f417435e5f6216828dec57958c490c4f8bae4f98
  Built:            Wed Mar  6 12:07:44 2024
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          v1.7.10
  GitCommit:        4e1fe7492b9df85914c389d1f15a3ceedbb280ac
 runc:
  Version:          1.1.12
  GitCommit:        51d5e94601ceffbbd85688df1c928ecccbfa4685
 docker-init:
  Version:          0.19.0
  GitCommit:

What happened?

I use a Rancher setup on a windows machine running Rancher in my local network, with the Docker port 2375 exposed via:
docker run -d --restart=always -p 0.0.0.0:2375:2375 -v /var/run/docker.sock:/var/run/docker.sock alpine/socat tcp-listen:2375,fork,reuseaddr unix-connect:/var/run/docker.sock

It works fine on my Mac command-line using a t1-local context pointing to the remote machine tcp://michael-t1.local:2375: the command docker ps lists containers as expected.

In my .testcontainers.properties file, I added:

docker.host = tcp://michael-t1.local:2375
tc.host = tcp://michael-t1.local:2375

This does not seem to work, and I don't understand why.

Further context:

• Opening http://michael-t1.local:2375/info in my web browser returns the expected JSON.
• Setting different docker.client.strategy values makes no difference.
• Setting env DOCKER_HOST=tcp://michael-t1.local:2375 makes no difference.

In com.github.dockerjava.httpclient5.ApacheDockerHttpClientImpl, the socket timeout seems to be set to zero:

       // See https://github.com/docker-java/docker-java/pull/1590#issuecomment-870581289
        connectionManager.setDefaultSocketConfig(
            SocketConfig.copy(SocketConfig.DEFAULT)
                .setSoTimeout(Timeout.ZERO_MILLISECONDS)
                .build()
        );

It is hard to tell whats going on, since the ubershaded dependencies make debugging challenging.

Relevant log output

17:53:44.022 [main] INFO com.github.dockerjava.zerodep.shaded.org.apache.hc.client5.http.impl.classic.HttpRequestRetryExec -- Recoverable I/O exception (java.net.SocketException) caught when processing request to {}->http://michael-t1.local:2375
17:53:48.130 [main] INFO com.github.dockerjava.zerodep.shaded.org.apache.hc.client5.http.impl.classic.HttpRequestRetryExec -- Recoverable I/O exception (java.net.SocketException) caught when processing request to {}->http://michael-t1.local:2375
17:53:50.180 [main] INFO org.testcontainers.dockerclient.DockerMachineClientProviderStrategy -- docker-machine executable was not found on PATH ([/usr/local/opt/php@8.0/bin, /Users/michaelboeckling/Documents/Tools/zig, /Users/michaelboeckling/Documents/Projekte/zls/zig-out/bin, /Users/michaelboeckling/Documents/Tools/terraform/, /Users/michaelboeckling/.cargo/bin, /usr/local/bin, /usr/bin, /bin, /usr/sbin, /sbin, /opt/X11/bin, /Library/Apple/usr/bin, /Applications/Wireshark.app/Contents/MacOS])
17:53:50.181 [main] ERROR org.testcontainers.dockerclient.DockerClientProviderStrategy -- Could not find a valid Docker environment. Please check configuration. Attempted configurations were:
	TestcontainersHostPropertyClientProviderStrategy: failed with exception RuntimeException (java.net.SocketException: Connection reset). Root cause SocketException (Connection reset)
	EnvironmentAndSystemPropertyClientProviderStrategy: failed with exception RuntimeException (java.net.SocketException: Connection reset). Root cause SocketException (Connection reset)
	UnixSocketClientProviderStrategy: failed with exception InvalidConfigurationException (Could not find unix domain socket). Root cause NoSuchFileException (/var/run/docker.sock)
	DockerDesktopClientProviderStrategy: failed with exception NullPointerException (Cannot invoke "java.nio.file.Path.toString()" because the return value of "org.testcontainers.dockerclient.DockerDesktopClientProviderStrategy.getSocketPath()" is null)As no valid configuration was found, execution cannot continue.
See https://java.testcontainers.org/on_failure.html for more details.

java.lang.IllegalStateException: Could not find a valid Docker environment. Please see logs and check configuration

	at org.testcontainers.dockerclient.DockerClientProviderStrategy.lambda$getFirstValidStrategy$7(DockerClientProviderStrategy.java:277)
	at java.base/java.util.Optional.orElseThrow(Optional.java:403)
	at org.testcontainers.dockerclient.DockerClientProviderStrategy.getFirstValidStrategy(DockerClientProviderStrategy.java:268)
	at org.testcontainers.DockerClientFactory.getOrInitializeStrategy(DockerClientFactory.java:152)
	at org.testcontainers.DockerClientFactory.client(DockerClientFactory.java:194)
	at org.testcontainers.DockerClientFactory$1.getDockerClient(DockerClientFactory.java:106)
	at com.github.dockerjava.api.DockerClientDelegate.authConfig(DockerClientDelegate.java:109)
	at org.testcontainers.containers.GenericContainer.start(GenericContainer.java:329)

Additional Information

No response

Start with DockerClientProviderStrategy and the TestcontainersHostPropertyClientProviderStrategy failure, then inspect the ApacheDockerHttpClientImpl socket configuration mentioned in the report. Reproduce the remote tcp:// connection using the supplied .testcontainers.properties and Docker versions, and compare it with the working Docker CLI connection. Done means the remote Docker host is detected and usable, with a regression test covering the configuration.