fix: flaky garbage collection resulting in testing errors (#423)

# change

Fixes #399. Applied a bit of defensive coding and attempted to create
some tests for it, however reproducing it with a local dev machine is
not easy. I did my best to reproduce the issue with garbage collection
in the new test.

---------

Co-authored-by: Balint Bartha <[email protected]>

Author: totallyzen

core/testcontainers/core/container.py

@@ -1,5 +1,5 @@
 import os
-from typing import Iterable, Optional, Tuple
+from typing import Optional, Tuple
 
 from docker.models.containers import Container
 
@@ -23,6 +23,7 @@ class DockerContainer:
         >>> with DockerContainer("hello-world") as container:
         ...    delay = wait_for_logs(container, "Hello from Docker!")
     """
+
     def __init__(self, image: str, docker_client_kw: Optional[dict] = None, **kwargs) -> None:
         self.env = {}
         self.ports = {}
@@ -42,7 +43,7 @@ def with_bind_ports(self, container: int, host: int = None) -> 'DockerContainer'
         self.ports[container] = host
         return self
 
-    def with_exposed_ports(self, *ports: Iterable[int]) -> 'DockerContainer':
+    def with_exposed_ports(self, *ports: int) -> 'DockerContainer':
         for port in ports:
             self.ports[port] = None
         return self
@@ -67,7 +68,7 @@ def start(self) -> 'DockerContainer':
         return self
 
     def stop(self, force=True, delete_volume=True) -> None:
-        self.get_wrapped_container().remove(force=force, v=delete_volume)
+        self._container.remove(force=force, v=delete_volume)
 
     def __enter__(self) -> 'DockerContainer':
         return self.start()
@@ -77,13 +78,14 @@ def __exit__(self, exc_type, exc_val, exc_tb) -> None:
 
     def __del__(self) -> None:
         """
-        Try to remove the container in all circumstances
+        __del__ runs when Python attempts to garbage collect the object.
+        In case of leaky test design, we still attempt to clean up the container.
         """
-        if self._container is not None:
-            try:
+        try:
+            if self._container is not None:
                 self.stop()
-            except:  # noqa: E722
-                pass
+        finally:
+            pass
 
     def get_container_host_ip(self) -> str:
         # infer from docker host
@@ -143,4 +145,4 @@ def get_logs(self) -> Tuple[str, str]:
     def exec(self, command) -> Tuple[int, str]:
         if not self._container:
             raise ContainerStartException("Container should be started before executing a command")
-        return self.get_wrapped_container().exec_run(command)
+        return self._container.exec_run(command)

core/testcontainers/core/docker_client.py

@@ -39,14 +39,22 @@ class DockerClient:
     """
     Thin wrapper around :class:`docker.DockerClient` for a more functional interface.
     """
+
     def __init__(self, **kwargs) -> None:
         self.client = docker.from_env(**kwargs)
 
     @ft.wraps(ContainerCollection.run)
-    def run(self, image: str, command: Union[str, List[str]] = None,
-            environment: Optional[dict] = None, ports: Optional[dict] = None,
-            detach: bool = False, stdout: bool = True, stderr: bool = False, remove: bool = False,
-            **kwargs) -> Container:
+    def run(
+            self, image: str,
+            command: Union[str, List[str]] = None,
+            environment: Optional[dict] = None,
+            ports: Optional[dict] = None,
+            detach: bool = False,
+            stdout: bool = True,
+            stderr: bool = False,
+            remove: bool = False,
+            **kwargs
+    ) -> Container:
         container = self.client.containers.run(
             image, command=command, stdout=stdout, stderr=stderr, remove=remove, detach=detach,
             environment=environment, ports=ports, **kwargs

core/tests/test_core.py

@@ -4,12 +4,22 @@
 from testcontainers.core.waiting_utils import wait_for_logs
 
 
-def test_raise_timeout():
+def test_timeout_is_raised_when_waiting_for_logs():
     with pytest.raises(TimeoutError):
         with DockerContainer("alpine").with_command("sleep 2") as container:
             wait_for_logs(container, "Hello from Docker!", timeout=1e-3)
 
 
+def test_garbage_collection_is_defensive():
+    # For more info, see https://github.com/testcontainers/testcontainers-python/issues/399
+    # we simulate garbage collection: start, stop, then call `del`
+    container = DockerContainer("postgres:latest")
+    container.start()
+    container.stop(force=True, delete_volume=True)
+    delattr(container, "_container")
+    del container
+
+
 def test_wait_for_hello():
     with DockerContainer("hello-world") as container:
         wait_for_logs(container, "Hello from Docker!")

pyproject.toml

@@ -123,7 +123,7 @@ priority = "primary"
 line-length = 120
 
 [tool.pytest.ini_options]
-addopts = "--cov-report=term --tb=short --strict-markers"
+addopts = "--cov-report=term --cov-report=html --tb=short --strict-markers"
 log_cli = true
 log_cli_level = "INFO"