Merge pull request #1820 from yhheolab-oss/fix/project-server-active-project-race

fix(project_server): serialize access to the process-wide active project

CHANGELOG.md

@@ -3,7 +3,7 @@
 Status of the `main` branch. Changes prior to the next official version change will appear here.
 
 * General:
-  - Fix: the README, the Language Support docs page and the project template omitted several already-supported language servers
+  - Fix: Race conditions in ProjectServer when used by multiple clients in parallel   
   - Fix: a tool call exceeding the timeout blocked the task executor indefinitely; the executor now
     recovers without user-induced cancellation
   - Add Grok Build support (context `grok`, setup CLI, hooks)

src/serena/project_server.py

@@ -1,5 +1,6 @@
 import json
 import logging
+import threading
 from typing import TYPE_CHECKING
 
 import requests as requests_lib
@@ -61,6 +62,9 @@ class ProjectServer:
 
         self._agent = SerenaAgent(serena_config=serena_config)
         self._loaded_projects_by_root: dict[str, "Project"] = {}
+        self._project_load_locks_by_root: dict[str, threading.Lock] = {}
+        self._active_project_lock = threading.Lock()
+        self._loaded_projects_lock = threading.Lock()
         self._port = port
         self._host = host
 
@@ -91,19 +95,41 @@ class ProjectServer:
 
         key = str(registered_project.project_root)
 
-        if key in self._loaded_projects_by_root:
-            return self._loaded_projects_by_root[key]
+        # find or publish the per-project load lock while holding the shared dictionaries
+        with self._loaded_projects_lock:
+            project = self._loaded_projects_by_root.get(key)
+            if project is not None:
+                return project
+            project_load_lock = self._project_load_locks_by_root.get(key)
+            if project_load_lock is None:
+                project_load_lock = threading.Lock()
+                self._project_load_locks_by_root[key] = project_load_lock
 
-        with LogTime(f"Loading project '{project_root_or_name}'"):
-            project = registered_project.get_project_instance(serena_config)
-            project.create_language_server_manager()
-        self._loaded_projects_by_root[key] = project
-        return project
+        # initialize only this project; another project's cached lookup or cold load can proceed
+        with project_load_lock:
+            with self._loaded_projects_lock:
+                project = self._loaded_projects_by_root.get(key)
+                if project is not None:
+                    return project
+
+            with LogTime(f"Loading project '{project_root_or_name}'"):
+                project = registered_project.get_project_instance(serena_config)
+                project.create_language_server_manager()
+
+            with self._loaded_projects_lock:
+                self._loaded_projects_by_root[key] = project
+            return project
 
     def _query_project(self, req: QueryProjectRequest) -> str:
-        """Handle a /query_project request by invoking the agent on the specified project and tool."""
+        """Handle a /query_project request by invoking the agent on the specified project and tool.
+
+        The active project is process-wide state, whereas ``apply_ex`` runs the tool on the
+        agent's task executor thread. Without the lock, a second request entering
+        ``active_project_context`` while the first request's tool is still executing would
+        redirect that tool to the wrong project (and restore the wrong project afterwards).
+        """
         project = self._get_project(req.project_name)
-        with self._agent.active_project_context(project):
+        with self._active_project_lock, self._agent.active_project_context(project):
             tool = self._agent.get_tool_by_name(req.tool_name)
             if not tool.is_readonly():
                 raise ValueError(f"Tool '{req.tool_name}' is not read-only and cannot be executed via the query_project route")

test/serena/test_project_server.py

@@ -0,0 +1,199 @@
+import threading
+from collections.abc import Iterator
+from concurrent.futures import ThreadPoolExecutor
+from concurrent.futures import TimeoutError as FutureTimeoutError
+from contextlib import contextmanager
+from pathlib import Path
+from typing import Any, cast
+from unittest.mock import MagicMock
+
+import pytest
+
+from serena.project_server import ProjectServer, QueryProjectRequest
+
+
+@pytest.fixture
+def project_server() -> ProjectServer:
+    server = ProjectServer.__new__(ProjectServer)
+    server._agent = MagicMock()
+    server._loaded_projects_by_root = {}
+    server._project_load_locks_by_root = {}
+    server._active_project_lock = threading.Lock()
+    server._loaded_projects_lock = threading.Lock()
+    return server
+
+
+def test_cached_project_lookup_is_not_blocked_by_unrelated_cold_load(project_server: ProjectServer) -> None:
+    cached_root = Path("/cached")
+    cold_root = Path("/cold")
+    cached_project = MagicMock()
+    cold_project = MagicMock()
+    cold_load_started = threading.Event()
+    allow_cold_load_to_finish = threading.Event()
+
+    cached_registration = MagicMock(project_root=cached_root)
+    cold_registration = MagicMock(project_root=cold_root)
+
+    def block_cold_load() -> None:
+        cold_load_started.set()
+        assert allow_cold_load_to_finish.wait(timeout=5)
+
+    cold_registration.get_project_instance.return_value = cold_project
+    cold_project.create_language_server_manager.side_effect = block_cold_load
+    project_server._loaded_projects_by_root[str(cached_root)] = cached_project
+    serena_config = cast(Any, project_server._agent.serena_config)
+    serena_config.get_registered_project.side_effect = {
+        "cached": cached_registration,
+        "cold": cold_registration,
+    }.get
+
+    with ThreadPoolExecutor(max_workers=2) as executor:
+        cold_future = executor.submit(project_server._get_project, "cold")
+        assert cold_load_started.wait(timeout=1)
+
+        cached_future = executor.submit(project_server._get_project, "cached")
+        try:
+            assert cached_future.result(timeout=1) is cached_project
+        finally:
+            allow_cold_load_to_finish.set()
+
+        assert cold_future.result(timeout=1) is cold_project
+
+
+def test_cold_loads_for_different_projects_can_run_concurrently(project_server: ProjectServer) -> None:
+    first_root = Path("/first")
+    second_root = Path("/second")
+    first_project = MagicMock()
+    second_project = MagicMock()
+    first_load_started = threading.Event()
+    allow_first_load_to_finish = threading.Event()
+
+    first_registration = MagicMock(project_root=first_root)
+    second_registration = MagicMock(project_root=second_root)
+
+    def block_first_load() -> None:
+        first_load_started.set()
+        assert allow_first_load_to_finish.wait(timeout=5)
+
+    first_registration.get_project_instance.return_value = first_project
+    first_project.create_language_server_manager.side_effect = block_first_load
+    second_registration.get_project_instance.return_value = second_project
+    serena_config = cast(Any, project_server._agent.serena_config)
+    serena_config.get_registered_project.side_effect = {
+        "first": first_registration,
+        "second": second_registration,
+    }.get
+
+    with ThreadPoolExecutor(max_workers=2) as executor:
+        first_future = executor.submit(project_server._get_project, "first")
+        assert first_load_started.wait(timeout=1)
+
+        second_future = executor.submit(project_server._get_project, "second")
+        try:
+            assert second_future.result(timeout=1) is second_project
+        finally:
+            allow_first_load_to_finish.set()
+
+        assert first_future.result(timeout=1) is first_project
+
+
+def test_concurrent_lookups_load_each_project_only_once(project_server: ProjectServer) -> None:
+    project_root = Path("/project")
+    project = MagicMock()
+    load_started = threading.Event()
+    second_lookup_started = threading.Event()
+    allow_load_to_finish = threading.Event()
+    registration = MagicMock(project_root=project_root)
+    lookup_count = 0
+    lookup_count_lock = threading.Lock()
+
+    def block_load() -> None:
+        load_started.set()
+        assert allow_load_to_finish.wait(timeout=5)
+
+    registration.get_project_instance.return_value = project
+    project.create_language_server_manager.side_effect = block_load
+    serena_config = cast(Any, project_server._agent.serena_config)
+
+    def get_registration(project_name: str) -> MagicMock:
+        nonlocal lookup_count
+        assert project_name == "project"
+        with lookup_count_lock:
+            lookup_count += 1
+            if lookup_count == 2:
+                second_lookup_started.set()
+        return registration
+
+    serena_config.get_registered_project.side_effect = get_registration
+
+    with ThreadPoolExecutor(max_workers=2) as executor:
+        first_future = executor.submit(project_server._get_project, "project")
+        assert load_started.wait(timeout=1)
+        second_future = executor.submit(project_server._get_project, "project")
+        assert second_lookup_started.wait(timeout=1)
+        allow_load_to_finish.set()
+
+        assert first_future.result(timeout=1) is project
+        assert second_future.result(timeout=1) is project
+
+    registration.get_project_instance.assert_called_once_with(serena_config)
+    project.create_language_server_manager.assert_called_once_with()
+
+
+def test_concurrent_queries_serialize_active_project_context(project_server: ProjectServer) -> None:
+    first_query_started = threading.Event()
+    second_lookup_finished = threading.Event()
+    allow_first_query_to_finish = threading.Event()
+    state_lock = threading.Lock()
+    state: dict[str, str | None] = {"active_project": None}
+
+    def get_project(project_name: str) -> str:
+        if project_name == "second":
+            second_lookup_finished.set()
+        return project_name
+
+    @contextmanager
+    def active_project_context(project: str) -> Iterator[None]:
+        with state_lock:
+            assert state["active_project"] is None
+            state["active_project"] = project
+        try:
+            yield
+        finally:
+            with state_lock:
+                state["active_project"] = None
+
+    def apply_tool(hold: bool = False) -> str:
+        if hold:
+            first_query_started.set()
+            assert allow_first_query_to_finish.wait(timeout=5)
+        with state_lock:
+            active_project = state["active_project"]
+        assert active_project is not None
+        return active_project
+
+    tool = MagicMock()
+    tool.is_readonly.return_value = True
+    tool.apply_ex.side_effect = apply_tool
+    server = cast(Any, project_server)
+    server._get_project = MagicMock(side_effect=get_project)
+    agent = cast(Any, project_server._agent)
+    agent.active_project_context.side_effect = active_project_context
+    agent.get_tool_by_name.return_value = tool
+    first_request = QueryProjectRequest(project_name="first", tool_name="read_file", tool_params_json='{"hold": true}')
+    second_request = QueryProjectRequest(project_name="second", tool_name="read_file", tool_params_json="{}")
+
+    with ThreadPoolExecutor(max_workers=2) as executor:
+        first_future = executor.submit(project_server._query_project, first_request)
+        assert first_query_started.wait(timeout=1)
+        second_future = executor.submit(project_server._query_project, second_request)
+        assert second_lookup_finished.wait(timeout=1)
+
+        try:
+            with pytest.raises(FutureTimeoutError):
+                second_future.result(timeout=0.1)
+        finally:
+            allow_first_query_to_finish.set()
+
+        assert first_future.result(timeout=1) == "first"
+        assert second_future.result(timeout=1) == "second"