fix(sessions): open a sqlite connection per operation, not per thread (#1022)

strix/core/sessions.py

@@ -4,6 +4,8 @@ from __future__ import annotations
 
 import asyncio
 import logging
+import sqlite3
+from contextlib import contextmanager
 from typing import TYPE_CHECKING, Any, cast
 from weakref import WeakKeyDictionary
 
@@ -12,7 +14,7 @@ from agents.memory import SQLiteSession
 
 
 if TYPE_CHECKING:
-    from collections.abc import Callable
+    from collections.abc import Callable, Iterator
     from pathlib import Path
 
     from agents.items import TResponseInputItem
@@ -22,9 +24,25 @@ if TYPE_CHECKING:
 logger = logging.getLogger(__name__)
 
 
+class _PooledConnectionSession(SQLiteSession):
+    @contextmanager
+    def _locked_connection(self) -> Iterator[sqlite3.Connection]:
+        with self._lock:
+            if self._closed:
+                raise RuntimeError("SQLiteSession is closed")
+            if self._is_memory_db:
+                yield self._shared_connection
+                return
+            connection = sqlite3.connect(str(self.db_path), check_same_thread=False)
+            try:
+                yield connection
+            finally:
+                connection.close()
+
+
 def open_agent_session(agent_id: str, path: Path) -> SQLiteSession:
     path.parent.mkdir(parents=True, exist_ok=True)
-    return SQLiteSession(session_id=agent_id, db_path=path)
+    return _PooledConnectionSession(session_id=agent_id, db_path=path)
 
 
 async def seed_initial_input(session: Session, initial_input: Any) -> bool:

tests/test_session_fd.py

@@ -0,0 +1,117 @@
+from __future__ import annotations
+
+import asyncio
+from pathlib import Path
+from typing import Any, cast
+
+import pytest
+
+from strix.core.sessions import open_agent_session
+
+
+def _count_open_fds() -> int | None:
+    for path in (Path("/proc/self/fd"), Path("/dev/fd")):
+        if path.is_dir():
+            return len(list(path.iterdir()))
+    return None
+
+
+@pytest.mark.asyncio
+async def test_sessions_hold_no_descriptors_while_parked(tmp_path: Path) -> None:
+    """Descriptor use must track live operations, not the number of sessions.
+
+    The SDK keeps a connection per (session, pool thread) open for the session's
+    whole life. An agent parks rather than exits, so its session lives for the
+    scan, and fan-out multiplies those handles until the process runs out of file
+    descriptors (#1018). A session that is not mid-operation should hold none.
+    """
+    baseline = _count_open_fds()
+    if baseline is None:
+        pytest.skip("no /proc/self/fd or /dev/fd on this platform")
+
+    sessions = [open_agent_session(f"a{i}", tmp_path / f"s{i}.db") for i in range(60)]
+    try:
+        for _ in range(4):
+            await asyncio.gather(
+                *(s.add_items([{"role": "user", "content": "x"}]) for s in sessions)
+            )
+            await asyncio.gather(*(s.get_items() for s in sessions))
+        parked = _count_open_fds()
+        assert parked is not None
+        # 60 parked sessions, yet descriptors are back at the baseline.
+        assert parked - baseline <= 5, f"parked fds grew by {parked - baseline}"
+    finally:
+        for s in sessions:
+            s.close()
+
+
+@pytest.mark.asyncio
+async def test_in_flight_descriptors_track_concurrency_not_session_count(
+    tmp_path: Path,
+) -> None:
+    baseline = _count_open_fds()
+    if baseline is None:
+        pytest.skip("no /proc/self/fd or /dev/fd on this platform")
+
+    sessions = [open_agent_session(f"a{i}", tmp_path / f"s{i}.db") for i in range(200)]
+    peak = baseline
+    try:
+
+        async def sample() -> None:
+            nonlocal peak
+            for _ in range(500):
+                current = _count_open_fds()
+                if current is not None:
+                    peak = max(peak, current)
+                await asyncio.sleep(0)
+
+        async def load() -> None:
+            for _ in range(4):
+                await asyncio.gather(
+                    *(s.add_items([{"role": "user", "content": "x"}]) for s in sessions)
+                )
+
+        await asyncio.gather(load(), sample())
+        # 200 sessions, but peak is bounded by the thread pool, well under 200.
+        assert peak - baseline < 100, f"in-flight fds peaked at +{peak - baseline}"
+    finally:
+        for s in sessions:
+            s.close()
+
+
+@pytest.mark.asyncio
+async def test_history_survives_the_per_operation_connection(tmp_path: Path) -> None:
+    session = open_agent_session("agent-1", tmp_path / "agents.db")
+    try:
+        for i in range(30):
+            await session.add_items([{"role": "user", "content": f"m{i}"}])
+        items = [cast("dict[str, Any]", i) for i in await session.get_items()]
+        assert [i["content"] for i in items] == [f"m{i}" for i in range(30)]
+    finally:
+        session.close()
+
+
+@pytest.mark.asyncio
+async def test_concurrent_sessions_sharing_one_file_stay_consistent(tmp_path: Path) -> None:
+    db = tmp_path / "shared.db"
+    sessions = [open_agent_session(f"a{i}", db) for i in range(10)]
+    try:
+        await asyncio.gather(
+            *(s.add_items([{"role": "user", "content": s.session_id}]) for s in sessions)
+        )
+        # Each session sees only its own row despite sharing the file.
+        for s in sessions:
+            items = [cast("dict[str, Any]", i) for i in await s.get_items()]
+            assert [i["content"] for i in items] == [s.session_id]
+    finally:
+        for s in sessions:
+            s.close()
+
+
+@pytest.mark.asyncio
+async def test_a_closed_session_refuses_operations(tmp_path: Path) -> None:
+    session = open_agent_session("agent-1", tmp_path / "agents.db")
+    await session.add_items([{"role": "user", "content": "x"}])
+    session.close()
+    with pytest.raises(RuntimeError, match="closed"):
+        await session.add_items([{"role": "user", "content": "y"}])