fix(sqlite): enable WAL for concurrent plugin callback commits

Dockerfile.acceptance

@@ -0,0 +1,2 @@
+FROM local/langbot-oss-411:688e7761
+COPY src/langbot/pkg/persistence/databases/sqlite.py /app/src/langbot/pkg/persistence/databases/sqlite.py

src/langbot/pkg/persistence/databases/sqlite.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import sqlalchemy
 import sqlalchemy.ext.asyncio as sqlalchemy_asyncio
 
 from .. import database
@@ -13,3 +14,8 @@ class SQLiteDatabaseManager(database.BaseDatabaseManager):
         db_file_path = self.ap.instance_config.data.get('database', {}).get('sqlite', {}).get('path', 'data/langbot.db')
         engine_url = f'sqlite+aiosqlite:///{db_file_path}'
         self.engine = sqlalchemy_asyncio.create_async_engine(engine_url)
+        # Reader transactions must not block independent plugin callback commits.
+        # Configure the persistent journal before serving requests, not per write.
+        async with self.engine.connect() as connection:
+            await connection.execute(sqlalchemy.text('PRAGMA journal_mode=WAL'))
+            await connection.commit()

tests/integration/persistence/test_sqlite_concurrency.py

@@ -0,0 +1,34 @@
+from types import SimpleNamespace
+
+import pytest
+import sqlalchemy as sa
+
+from langbot.pkg.core import app  # noqa: F401 - initialize manager registration before database imports
+from langbot.pkg.persistence.databases.sqlite import SQLiteDatabaseManager
+
+pytestmark = [pytest.mark.integration, pytest.mark.asyncio]
+
+
+async def test_writer_commits_while_independent_reader_is_open(tmp_path):
+    application = SimpleNamespace(
+        instance_config=SimpleNamespace(data={'database': {'sqlite': {'path': str(tmp_path / 'concurrency.db')}}})
+    )
+    manager = SQLiteDatabaseManager(application)
+    await manager.initialize()
+    engine = manager.get_engine()
+    try:
+        async with engine.begin() as connection:
+            await connection.execute(sa.text('CREATE TABLE probe (id INTEGER PRIMARY KEY, value TEXT)'))
+            await connection.execute(sa.text("INSERT INTO probe VALUES (1, 'old')"))
+        async with engine.connect() as reader:
+            await reader.execute(sa.text('BEGIN'))
+            assert (await reader.execute(sa.text('SELECT value FROM probe'))).scalar_one() == 'old'
+            async with engine.connect() as writer:
+                await writer.execute(sa.text('PRAGMA busy_timeout=250'))
+                await writer.execute(sa.text("UPDATE probe SET value='new' WHERE id=1"))
+                await writer.commit()
+            await reader.rollback()
+        async with engine.connect() as connection:
+            assert (await connection.execute(sa.text('SELECT value FROM probe'))).scalar_one() == 'new'
+    finally:
+        await engine.dispose()