fix(core): Determine docker socket for rootless docker (testcontainers#779)

fixes testcontainers#537

Use docker_api to determine the `socket_path` (defined in
[`UnixHTTPAdapter`](https://github.com/docker/docker-py/blob/db7f8b8bb67e485a7192846906f600a52e0aa623/docker/transport/unixconn.py#L55)).

Replaces:
testcontainers#710

Author: CarliJoy

core/testcontainers/core/config.py

@@ -6,6 +6,8 @@
 from pathlib import Path
 from typing import Optional, Union
 
+import docker
+
 
 class ConnectionMode(Enum):
     bridge_ip = "bridge_ip"
@@ -24,14 +26,32 @@ def use_mapped_port(self) -> bool:
         return True
 
 
+def get_docker_socket() -> str:
+    """
+    Determine the docker socket, prefer value given by env variable
+
+    Using the docker api ensure we handle rootless docker properly
+    """
+    if socket_path := environ.get("TESTCONTAINERS_DOCKER_SOCKET_OVERRIDE"):
+        return socket_path
+
+    client = docker.from_env()
+    try:
+        socket_path = client.api.get_adapter(client.api.base_url).socket_path
+        # return the normalized path as string
+        return str(Path(socket_path).absolute())
+    except AttributeError:
+        return "/var/run/docker.sock"
+
+
 MAX_TRIES = int(environ.get("TC_MAX_TRIES", 120))
 SLEEP_TIME = int(environ.get("TC_POOLING_INTERVAL", 1))
 TIMEOUT = MAX_TRIES * SLEEP_TIME
 
 RYUK_IMAGE: str = environ.get("RYUK_CONTAINER_IMAGE", "testcontainers/ryuk:0.8.1")
 RYUK_PRIVILEGED: bool = environ.get("TESTCONTAINERS_RYUK_PRIVILEGED", "false") == "true"
 RYUK_DISABLED: bool = environ.get("TESTCONTAINERS_RYUK_DISABLED", "false") == "true"
-RYUK_DOCKER_SOCKET: str = environ.get("TESTCONTAINERS_DOCKER_SOCKET_OVERRIDE", "/var/run/docker.sock")
+RYUK_DOCKER_SOCKET: str = get_docker_socket()
 RYUK_RECONNECTION_TIMEOUT: str = environ.get("RYUK_RECONNECTION_TIMEOUT", "10s")
 TC_HOST_OVERRIDE: Optional[str] = environ.get("TC_HOST", environ.get("TESTCONTAINERS_HOST_OVERRIDE"))
 

core/tests/test_config.py

@@ -5,12 +5,14 @@
     TC_FILE,
     get_user_overwritten_connection_mode,
     ConnectionMode,
+    get_docker_socket,
 )
 
 from pytest import MonkeyPatch, mark, LogCaptureFixture
 
 import logging
 import tempfile
+from unittest.mock import Mock
 
 
 def test_read_tc_properties(monkeypatch: MonkeyPatch) -> None:
@@ -84,3 +86,61 @@ def test_valid_connection_mode(monkeypatch: pytest.MonkeyPatch, mode: str, use_m
 def test_no_connection_mode_given(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.delenv("TESTCONTAINERS_CONNECTION_MODE", raising=False)
     assert get_user_overwritten_connection_mode() is None
+
+
+def test_get_docker_socket_uses_env(monkeypatch: pytest.MonkeyPatch) -> None:
+    """
+    If TESTCONTAINERS_DOCKER_SOCKET_OVERRIDE env var is given prefer it
+    """
+    monkeypatch.setenv("TESTCONTAINERS_DOCKER_SOCKET_OVERRIDE", "/var/test.socket")
+    assert get_docker_socket() == "/var/test.socket"
+
+
+@pytest.fixture
+def mock_docker_client_connections(monkeypatch: pytest.MonkeyPatch) -> None:
+    """
+    Ensure the docker client does not make any actual network calls
+    """
+    from docker.transport.sshconn import SSHHTTPAdapter
+    from docker.api.client import APIClient
+
+    # ensure that no actual connection is tried
+    monkeypatch.setattr(SSHHTTPAdapter, "_connect", Mock())
+    monkeypatch.setattr(SSHHTTPAdapter, "_create_paramiko_client", Mock())
+    monkeypatch.setattr(APIClient, "_retrieve_server_version", Mock(return_value="1.47"))
+
+
+@pytest.mark.usefixtures("mock_docker_client_connections")
+def test_get_docker_host_default(monkeypatch: pytest.MonkeyPatch) -> None:
+    """
+    If non socket docker-host is given return default
+
+    Still ryuk will properly still not work but this is the historical default
+
+    """
+    monkeypatch.delenv("TESTCONTAINERS_DOCKER_SOCKET_OVERRIDE", raising=False)
+    # Define Fake SSH Docker client
+    monkeypatch.setenv("DOCKER_HOST", "ssh://remote_host")
+    assert get_docker_socket() == "/var/run/docker.sock"
+
+
+@pytest.mark.usefixtures("mock_docker_client_connections")
+def test_get_docker_host_non_root(monkeypatch: pytest.MonkeyPatch) -> None:
+    """
+    Use the socket determined by the Docker API Adapter
+    """
+    monkeypatch.delenv("TESTCONTAINERS_DOCKER_SOCKET_OVERRIDE", raising=False)
+    # Define a Non-Root like Docker Client
+    monkeypatch.setenv("DOCKER_HOST", "unix://var/run/user/1000/docker.sock")
+    assert get_docker_socket() == "/var/run/user/1000/docker.sock"
+
+
+@pytest.mark.usefixtures("mock_docker_client_connections")
+def test_get_docker_host_root(monkeypatch: pytest.MonkeyPatch) -> None:
+    """
+    Use the socket determined by the Docker API Adapter
+    """
+    monkeypatch.delenv("TESTCONTAINERS_DOCKER_SOCKET_OVERRIDE", raising=False)
+    # Define a Root like Docker Client
+    monkeypatch.setenv("DOCKER_HOST", "unix://")
+    assert get_docker_socket() == "/var/run/docker.sock"