[Bug]: docker.host parameter doesn't work anymore

[also1366]

Testcontainers version

0.21.0

Using the latest Testcontainers version?

Yes

Host OS

Linux

Host arch

x86

Go version

1.20

Docker version

Server: Docker Engine - Community
 Engine:
  Version:          24.0.2
  API version:      1.43 (minimum version 1.12)
  Go version:       go1.20.4
  Git commit:       659604f
  Built:            Thu May 25 21:52:17 2023
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.6.21
  GitCommit:        3dce8eb055cbb6872793272b4f20ed16117344f8
 runc:
  Version:          1.1.7
  GitCommit:        v1.1.7-0-g860f061
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0
 rootlesskit:
  Version:          1.1.0
  ApiVersion:       1.1.1
  NetworkDriver:    slirp4netns
  PortDriver:       builtin
  StateDir:         /tmp/rootlesskit1968203600
 slirp4netns:
  Version:          1.0.1
  GitCommit:        6a7b16babc95b6a3056b33fb45b74a6f62262dd4

Docker info

Client: Docker Engine - Community
 Version:    24.0.2
 Context:    rootless
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.10.5
    Path:     /usr/libexec/docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
    Version:  v2.18.1
    Path:     /usr/libexec/docker/cli-plugins/docker-compose
  scan: Docker Scan (Docker Inc.)
    Version:  v0.23.0
    Path:     /usr/libexec/docker/cli-plugins/docker-scan

Server:
 Containers: 12
  Running: 9
  Paused: 0
  Stopped: 3
 Images: 444
 Server Version: 24.0.2
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: false
  userxattr: true
 Logging Driver: json-file
 Cgroup Driver: systemd
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 3dce8eb055cbb6872793272b4f20ed16117344f8
 runc version: v1.1.7-0-g860f061
 init version: de40ad0
 Security Options:
  seccomp
   Profile: builtin
  rootless
  cgroupns
 Kernel Version: 6.1.0-0.deb11.7-amd64
 Operating System: Debian GNU/Linux 11 (bullseye)
 OSType: linux
 Architecture: x86_64
 CPUs: 12
 Total Memory: 30.96GiB
 Name: hamlet
 ID: OHFM:AHIA:VZBD:46XM:4WBY:HAF5:7A4F:LWAD:YKMU:FZ3O:XZXO:YHCX
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Username: whoisxmlapi
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

What happened?

I have a .testcontainers.properties file in my home directory:
docker.host=unix:///var/run/user/1000/docker.sock

The library reads the docker host and strips "unix://" part.
Then it provides the host "/var/run/user/1000/docker.sock" to the docker library.
Though the docker library expects the host to start with "unix://" and throws an error.

It works fine for me in version 0.20.1

When I run the test with the env variable DOCKER_HOST=unix:///var/run/user/1000/docker.sock it works.
It doesn't strip "unix://".

I read this PR that behaviour somewhat changed, but I don't understand what's happening.
#1161

Am I doing something wrong?

Relevant log output

=== RUN   TestContainers/TestElasticsearch
Testcontainers properties file has been found: /home/user/.testcontainers.properties
    main_test.go:37: failed to start container: unable to parse docker host `/var/run/user/1000/docker.sock`, failed to create Docker provider

Additional information

No response

[mdelapenya]

Hi @also1366 thanks for opening this bug report.

I'm adding this unit test to the docker_host_test.go and it fails:

	t.Run("Unix Docker Host is passed as docker.host", func(t *testing.T) {
		content := "docker.host=" + DockerSocketSchema + "/this/is/a/sample.sock"

		setupTestcontainersProperties(t, content)

		host := extractDockerHost(context.Background())

		assert.Equal(t, DockerSocketSchema + "/this/is/a/sample.sock", host)
	})

I'm taking a look at how Java does this: https://java.testcontainers.org/features/configuration/#customizing-docker-host-detection, and I think we have to fix the dockerHostFromProperties function to not parse the URL, and to behave as the DOCKER_HOST env var, as you suggests.

// dockerHostFromProperties returns the docker host from the ~/.testcontainers.properties file, if it's not empty
func dockerHostFromProperties(ctx context.Context) (string, error) {
	cfg := config.Read()
	socketPath := cfg.Host
	if socketPath != "" {
-		parsed, err := parseURL(socketPath)
-		if err != nil {
-			return "", err
-		}
-
-		return parsed, nil
+		return socketPath, nil
	}

	return "", ErrDockerSocketNotSetInProperties
}

I'm checking with the other maintainers internally, but it feels that we should change this as shown above. Will ping you back

[mdelapenya]

@also1366 we merged the PR so if you are able to check the latest commit from main, it should be fixed

Thanks!