tests: parametrize over --disable-frontend-multiprocessing

Author: dtrifiro

tests/conftest.py

@@ -63,13 +63,26 @@ def lora_adapter_path(request: pytest.FixtureRequest) -> str:
     return path
 
 
+@pytest.fixture(
+    scope="session",
+    params=[
+        pytest.param(True, id="disable-frontend-multiprocessing=True"),
+        pytest.param(False, id="disable-frontend-multiprocessing=False"),
+    ],
+)
+def disable_frontend_multiprocessing(request):
+    """Enable or disable the frontend-multiprocessing feature."""
+    return request.param
+
+
 @pytest.fixture(scope="session")
 def args(  # noqa: PLR0913
     request: pytest.FixtureRequest,
     monkeysession,
     grpc_server_port: ArgFixture[int],
     http_server_port: ArgFixture[int],
     lora_available: ArgFixture[bool],
+    disable_frontend_multiprocessing,
 ) -> argparse.Namespace:
     """Return parsed CLI arguments for the adapter/vLLM."""
     # avoid parsing pytest arguments as vllm/vllm_tgis_adapter arguments
@@ -81,6 +94,9 @@ def args(  # noqa: PLR0913
 
         extra_args.extend(("--enable-lora", f"--lora-modules={name}={path}"))
 
+    if disable_frontend_multiprocessing:
+        extra_args.append("--disable-frontend-multiprocessing")
+
     monkeysession.setattr(
         sys,
         "argv",
@@ -185,3 +201,13 @@ def target():
             task.cancel()
 
         t.join()
+
+    # Workaround: Instantiating the TGISStatLogger multiple times creates
+    # multiple Gauges etc which can only be instantiated once.
+    # By unregistering the Collectors from the REGISTRY we can
+    # work around this problem.
+
+    from prometheus_client.registry import REGISTRY
+
+    for name in list(REGISTRY._collector_to_names.keys()):  # noqa: SLF001
+        REGISTRY.unregister(name)