feat: Allow :memory: for kvstore (llamastack#3696)

## Test Plan
added unit tests

Author: raghotham

llama_stack/providers/utils/kvstore/sqlite/sqlite.py

@@ -21,14 +21,27 @@ class SqliteKVStoreImpl(KVStore):
     def __init__(self, config: SqliteKVStoreConfig):
         self.db_path = config.db_path
         self.table_name = "kvstore"
+        self._conn: aiosqlite.Connection | None = None
 
     def __str__(self):
         return f"SqliteKVStoreImpl(db_path={self.db_path}, table_name={self.table_name})"
 
+    def _is_memory_db(self) -> bool:
+        """Check if this is an in-memory database."""
+        return self.db_path == ":memory:" or "mode=memory" in self.db_path
+
     async def initialize(self):
-        os.makedirs(os.path.dirname(self.db_path), exist_ok=True)
-        async with aiosqlite.connect(self.db_path) as db:
-            await db.execute(
+        # Skip directory creation for in-memory databases and file: URIs
+        if not self._is_memory_db() and not self.db_path.startswith("file:"):
+            db_dir = os.path.dirname(self.db_path)
+            if db_dir:  # Only create if there's a directory component
+                os.makedirs(db_dir, exist_ok=True)
+
+        # Only use persistent connection for in-memory databases
+        # File-based databases use connection-per-operation to avoid hangs
+        if self._is_memory_db():
+            self._conn = await aiosqlite.connect(self.db_path)
+            await self._conn.execute(
                 f"""
                 CREATE TABLE IF NOT EXISTS {self.table_name} (
                     key TEXT PRIMARY KEY,
@@ -37,19 +50,50 @@ async def initialize(self):
                 )
             """
             )
-            await db.commit()
+            await self._conn.commit()
+        else:
+            # For file-based databases, just create the table
+            async with aiosqlite.connect(self.db_path) as db:
+                await db.execute(
+                    f"""
+                    CREATE TABLE IF NOT EXISTS {self.table_name} (
+                        key TEXT PRIMARY KEY,
+                        value TEXT,
+                        expiration TIMESTAMP
+                    )
+                """
+                )
+                await db.commit()
+
+    async def shutdown(self):
+        """Close the persistent connection (only for in-memory databases)."""
+        if self._conn:
+            await self._conn.close()
+            self._conn = None
 
     async def set(self, key: str, value: str, expiration: datetime | None = None) -> None:
-        async with aiosqlite.connect(self.db_path) as db:
-            await db.execute(
+        if self._conn:
+            # In-memory database with persistent connection
+            await self._conn.execute(
                 f"INSERT OR REPLACE INTO {self.table_name} (key, value, expiration) VALUES (?, ?, ?)",
                 (key, value, expiration),
             )
-            await db.commit()
+            await self._conn.commit()
+        else:
+            # File-based database with connection per operation
+            async with aiosqlite.connect(self.db_path) as db:
+                await db.execute(
+                    f"INSERT OR REPLACE INTO {self.table_name} (key, value, expiration) VALUES (?, ?, ?)",
+                    (key, value, expiration),
+                )
+                await db.commit()
 
     async def get(self, key: str) -> str | None:
-        async with aiosqlite.connect(self.db_path) as db:
-            async with db.execute(f"SELECT value, expiration FROM {self.table_name} WHERE key = ?", (key,)) as cursor:
+        if self._conn:
+            # In-memory database with persistent connection
+            async with self._conn.execute(
+                f"SELECT value, expiration FROM {self.table_name} WHERE key = ?", (key,)
+            ) as cursor:
                 row = await cursor.fetchone()
                 if row is None:
                     return None
@@ -58,15 +102,36 @@ async def get(self, key: str) -> str | None:
                     logger.warning(f"Expected string value for key {key}, got {type(value)}, returning None")
                     return None
                 return value
+        else:
+            # File-based database with connection per operation
+            async with aiosqlite.connect(self.db_path) as db:
+                async with db.execute(
+                    f"SELECT value, expiration FROM {self.table_name} WHERE key = ?", (key,)
+                ) as cursor:
+                    row = await cursor.fetchone()
+                    if row is None:
+                        return None
+                    value, expiration = row
+                    if not isinstance(value, str):
+                        logger.warning(f"Expected string value for key {key}, got {type(value)}, returning None")
+                        return None
+                    return value
 
     async def delete(self, key: str) -> None:
-        async with aiosqlite.connect(self.db_path) as db:
-            await db.execute(f"DELETE FROM {self.table_name} WHERE key = ?", (key,))
-            await db.commit()
+        if self._conn:
+            # In-memory database with persistent connection
+            await self._conn.execute(f"DELETE FROM {self.table_name} WHERE key = ?", (key,))
+            await self._conn.commit()
+        else:
+            # File-based database with connection per operation
+            async with aiosqlite.connect(self.db_path) as db:
+                await db.execute(f"DELETE FROM {self.table_name} WHERE key = ?", (key,))
+                await db.commit()
 
     async def values_in_range(self, start_key: str, end_key: str) -> list[str]:
-        async with aiosqlite.connect(self.db_path) as db:
-            async with db.execute(
+        if self._conn:
+            # In-memory database with persistent connection
+            async with self._conn.execute(
                 f"SELECT key, value, expiration FROM {self.table_name} WHERE key >= ? AND key <= ?",
                 (start_key, end_key),
             ) as cursor:
@@ -75,13 +140,35 @@ async def values_in_range(self, start_key: str, end_key: str) -> list[str]:
                     _, value, _ = row
                     result.append(value)
                 return result
+        else:
+            # File-based database with connection per operation
+            async with aiosqlite.connect(self.db_path) as db:
+                async with db.execute(
+                    f"SELECT key, value, expiration FROM {self.table_name} WHERE key >= ? AND key <= ?",
+                    (start_key, end_key),
+                ) as cursor:
+                    result = []
+                    async for row in cursor:
+                        _, value, _ = row
+                        result.append(value)
+                    return result
 
     async def keys_in_range(self, start_key: str, end_key: str) -> list[str]:
         """Get all keys in the given range."""
-        async with aiosqlite.connect(self.db_path) as db:
-            cursor = await db.execute(
+        if self._conn:
+            # In-memory database with persistent connection
+            cursor = await self._conn.execute(
                 f"SELECT key FROM {self.table_name} WHERE key >= ? AND key <= ?",
                 (start_key, end_key),
             )
             rows = await cursor.fetchall()
             return [row[0] for row in rows]
+        else:
+            # File-based database with connection per operation
+            async with aiosqlite.connect(self.db_path) as db:
+                cursor = await db.execute(
+                    f"SELECT key FROM {self.table_name} WHERE key >= ? AND key <= ?",
+                    (start_key, end_key),
+                )
+                rows = await cursor.fetchall()
+                return [row[0] for row in rows]

tests/unit/utils/kvstore/test_sqlite_memory.py

@@ -0,0 +1,30 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+
+from llama_stack.providers.utils.kvstore.config import SqliteKVStoreConfig
+from llama_stack.providers.utils.kvstore.sqlite.sqlite import SqliteKVStoreImpl
+
+
+async def test_memory_kvstore_persistence_behavior():
+    """Test that :memory: database doesn't persist across instances."""
+    config = SqliteKVStoreConfig(db_path=":memory:")
+
+    # First instance
+    store1 = SqliteKVStoreImpl(config)
+    await store1.initialize()
+    await store1.set("persist_test", "should_not_persist")
+    await store1.shutdown()
+
+    # Second instance with same config
+    store2 = SqliteKVStoreImpl(config)
+    await store2.initialize()
+
+    # Data should not be present
+    result = await store2.get("persist_test")
+    assert result is None
+
+    await store2.shutdown()