fix: AsyncRedisSaver cannot be constructed outside an async context (#179)

Author: bsbodden

langgraph/checkpoint/redis/aio.py

@@ -101,7 +101,9 @@ def __init__(
             checkpoint_prefix=checkpoint_prefix,
             checkpoint_write_prefix=checkpoint_write_prefix,
         )
-        self.loop = asyncio.get_running_loop()
+        # Deferred: the event loop is captured in asetup() so that the saver can
+        # be constructed outside an async context (Issue #179).
+        self.loop: Optional[asyncio.AbstractEventLoop] = None
 
         # Instance-level cache for frequently used keys (limited size to prevent memory issues)
         self._key_cache: Dict[str, str] = {}
@@ -243,6 +245,13 @@ async def __aexit__(
 
     async def asetup(self) -> None:
         """Set up the checkpoint saver."""
+        # Capture the running event loop here so that sync wrapper methods
+        # (get_tuple, put, put_writes, …) can dispatch coroutines to it via
+        # asyncio.run_coroutine_threadsafe.  Deferring this to asetup() instead
+        # of __init__ lets callers construct the saver outside an async context
+        # (Issue #179).
+        self.loop = asyncio.get_running_loop()
+
         self.create_indexes()
         await self.checkpoints_index.create(overwrite=False)
         await self.checkpoint_writes_index.create(overwrite=False)
@@ -1307,6 +1316,11 @@ def put_writes(
             task_id (str): Identifier for the task creating the writes.
             task_path (str): Path of the task creating the writes.
         """
+        if self.loop is None:
+            raise RuntimeError(
+                "AsyncRedisSaver must be set up before calling synchronous methods. "
+                "Call `await saver.asetup()` or use `async with saver:` first."
+            )
         return asyncio.run_coroutine_threadsafe(
             self.aput_writes(config, writes, task_id), self.loop
         ).result()
@@ -1315,6 +1329,11 @@ def get_channel_values(
         self, thread_id: str, checkpoint_ns: str = "", checkpoint_id: str = ""
     ) -> Dict[str, Any]:
         """Retrieve channel_values using efficient FT.SEARCH with checkpoint_id (sync wrapper)."""
+        if self.loop is None:
+            raise RuntimeError(
+                "AsyncRedisSaver must be set up before calling synchronous methods. "
+                "Call `await saver.asetup()` or use `async with saver:` first."
+            )
         try:
             if asyncio.get_running_loop() is self.loop:
                 raise asyncio.InvalidStateError(
@@ -1345,6 +1364,11 @@ def get_tuple(self, config: RunnableConfig) -> Optional[CheckpointTuple]:
         Raises:
             asyncio.InvalidStateError: If called from the wrong thread/event loop
         """
+        if self.loop is None:
+            raise RuntimeError(
+                "AsyncRedisSaver must be set up before calling synchronous methods. "
+                "Call `await saver.asetup()` or use `async with saver:` first."
+            )
         try:
             # check if we are in the main thread, only bg threads can block
             if asyncio.get_running_loop() is self.loop:
@@ -1381,6 +1405,11 @@ def put(
         Raises:
             asyncio.InvalidStateError: If called from the wrong thread/event loop
         """
+        if self.loop is None:
+            raise RuntimeError(
+                "AsyncRedisSaver must be set up before calling synchronous methods. "
+                "Call `await saver.asetup()` or use `async with saver:` first."
+            )
         try:
             # check if we are in the main thread, only bg threads can block
             if asyncio.get_running_loop() is self.loop:

langgraph/checkpoint/redis/ashallow.py

@@ -77,7 +77,9 @@ def __init__(
             checkpoint_prefix=checkpoint_prefix,
             checkpoint_write_prefix=checkpoint_write_prefix,
         )
-        self.loop = asyncio.get_running_loop()
+        # Deferred: the event loop is captured in asetup() so that the saver can
+        # be constructed outside an async context (Issue #179).
+        self.loop: Optional[asyncio.AbstractEventLoop] = None
 
         # Instance-level cache for frequently used keys (limited size to prevent memory issues)
         self._key_cache: Dict[str, str] = {}
@@ -139,6 +141,13 @@ async def from_conn_string(
 
     async def asetup(self) -> None:
         """Initialize Redis indexes asynchronously."""
+        # Capture the running event loop here so that sync wrapper methods
+        # (get_tuple, put, put_writes, …) can dispatch coroutines to it via
+        # asyncio.run_coroutine_threadsafe.  Deferring this to asetup() instead
+        # of __init__ lets callers construct the saver outside an async context
+        # (Issue #179).
+        self.loop = asyncio.get_running_loop()
+
         await self.checkpoints_index.create(overwrite=False)
         await self.checkpoint_writes_index.create(overwrite=False)
 
@@ -725,6 +734,11 @@ def create_indexes(self) -> None:
 
     def get_tuple(self, config: RunnableConfig) -> Optional[CheckpointTuple]:
         """Retrieve a checkpoint tuple from Redis synchronously."""
+        if self.loop is None:
+            raise RuntimeError(
+                "AsyncShallowRedisSaver must be set up before calling synchronous methods. "
+                "Call `await saver.asetup()` or use `async with saver:` first."
+            )
         try:
             if asyncio.get_running_loop() is self.loop:
                 raise asyncio.InvalidStateError(
@@ -747,6 +761,11 @@ def put(
         new_versions: ChannelVersions,
     ) -> RunnableConfig:
         """Store only the latest checkpoint synchronously."""
+        if self.loop is None:
+            raise RuntimeError(
+                "AsyncShallowRedisSaver must be set up before calling synchronous methods. "
+                "Call `await saver.asetup()` or use `async with saver:` first."
+            )
         return asyncio.run_coroutine_threadsafe(
             self.aput(config, checkpoint, metadata, new_versions), self.loop
         ).result()
@@ -759,6 +778,11 @@ def put_writes(
         task_path: str = "",
     ) -> None:
         """Store intermediate writes synchronously."""
+        if self.loop is None:
+            raise RuntimeError(
+                "AsyncShallowRedisSaver must be set up before calling synchronous methods. "
+                "Call `await saver.asetup()` or use `async with saver:` first."
+            )
         return asyncio.run_coroutine_threadsafe(
             self.aput_writes(config, writes, task_id), self.loop
         ).result()
@@ -771,6 +795,11 @@ def get_channel_values(
         channel_versions: Optional[Dict[str, Any]] = None,
     ) -> dict[str, Any]:
         """Retrieve channel_values dictionary with properly constructed message objects (sync wrapper)."""
+        if self.loop is None:
+            raise RuntimeError(
+                "AsyncShallowRedisSaver must be set up before calling synchronous methods. "
+                "Call `await saver.asetup()` or use `async with saver:` first."
+            )
         try:
             if asyncio.get_running_loop() is self.loop:
                 raise asyncio.InvalidStateError(

tests/test_async.py

@@ -848,3 +848,77 @@ async def test_root_graph_checkpoint(
         checkpoints = [c async for c in checkpointer.alist(config)]
         assert len(checkpoints) > 0
         assert checkpoints[-1].checkpoint["id"] == latest["id"]
+
+
+# --- Issue #179: AsyncRedisSaver construction outside async context ---
+
+
+def test_async_redis_saver_construction_outside_event_loop(redis_url: str) -> None:
+    """AsyncRedisSaver should be constructable outside an async context (Issue #179).
+
+    Previously, AsyncRedisSaver.__init__ called asyncio.get_running_loop() which
+    raised RuntimeError when no event loop was running.
+    """
+    # This must not raise RuntimeError even when there is no running event loop
+    saver = AsyncRedisSaver(redis_url)
+    assert saver is not None
+    # Loop should be None until asetup() is called
+    assert saver.loop is None
+
+
+def test_async_redis_saver_construction_with_client_outside_event_loop(
+    redis_url: str,
+) -> None:
+    """AsyncRedisSaver should accept a pre-built client without a running loop (Issue #179).
+
+    The typical use-case from the issue: constructing the saver synchronously,
+    then setting up (and using it) later inside an async lifespan handler.
+    """
+    from redis.asyncio import Redis as AsyncRedis
+
+    client = AsyncRedis.from_url(redis_url)
+    try:
+        saver = AsyncRedisSaver(redis_client=client)
+        assert saver is not None
+        assert saver.loop is None
+    finally:
+        asyncio.run(client.aclose())
+
+
+@pytest.mark.asyncio
+async def test_async_redis_saver_loop_captured_in_asetup(redis_url: str) -> None:
+    """asetup() must capture the running event loop so sync wrappers work (Issue #179)."""
+    saver = AsyncRedisSaver(redis_url)
+    assert saver.loop is None  # not yet set
+
+    await saver.asetup()
+
+    # After asetup the loop attribute must point to the current running loop
+    assert saver.loop is not None
+    assert saver.loop is asyncio.get_running_loop()
+
+    await saver._redis.aclose()
+
+
+@pytest.mark.asyncio
+async def test_async_redis_saver_context_manager_after_sync_construction(
+    redis_url: str,
+) -> None:
+    """Saver built outside an event loop must still work as an async context manager."""
+    # Simulate sync-land construction (no running event loop at this point in an
+    # async test, but we at least verify the object is usable end-to-end).
+    saver = AsyncRedisSaver(redis_url)
+
+    async with saver:
+        # After entering the context the loop must be set
+        assert saver.loop is asyncio.get_running_loop()
+
+        # Basic functional smoke test
+        config: RunnableConfig = {
+            "configurable": {"thread_id": "issue-179-test", "checkpoint_ns": ""}
+        }
+        chk: Checkpoint = empty_checkpoint()
+        meta: CheckpointMetadata = {"source": "input", "step": 0, "writes": {}}
+        await saver.aput(config, chk, meta, {})
+        result = await saver.aget_tuple(config)
+        assert result is not None

tests/test_shallow_async.py

@@ -1,3 +1,4 @@
+import asyncio
 from typing import Any, AsyncGenerator, Dict
 
 import pytest
@@ -494,3 +495,72 @@ async def test_shallow_redis_saver_inline_storage(redis_url: str) -> None:
             # Clean up test data
             await redis_client.flushdb()
             await redis_client.aclose()
+
+
+# --- Issue #179: AsyncShallowRedisSaver construction outside async context ---
+
+
+def test_async_shallow_redis_saver_construction_outside_event_loop(
+    redis_url: str,
+) -> None:
+    """AsyncShallowRedisSaver should be constructable outside an async context (Issue #179).
+
+    Previously, AsyncShallowRedisSaver.__init__ called asyncio.get_running_loop() which
+    raised RuntimeError when no event loop was running.
+    """
+    # This must not raise RuntimeError even when there is no running event loop
+    saver = AsyncShallowRedisSaver(redis_url)
+    assert saver is not None
+    # Loop should be None until asetup() is called
+    assert saver.loop is None
+
+
+def test_async_shallow_redis_saver_construction_with_client_outside_event_loop(
+    redis_url: str,
+) -> None:
+    """AsyncShallowRedisSaver accepts a pre-built client without a running loop (Issue #179)."""
+    from redis.asyncio import Redis as AsyncRedis
+
+    client = AsyncRedis.from_url(redis_url)
+    try:
+        saver = AsyncShallowRedisSaver(redis_client=client)
+        assert saver is not None
+        assert saver.loop is None
+    finally:
+        asyncio.run(client.aclose())
+
+
+@pytest.mark.asyncio
+async def test_async_shallow_redis_saver_loop_captured_in_asetup(
+    redis_url: str,
+) -> None:
+    """asetup() must capture the running event loop so sync wrappers work (Issue #179)."""
+    saver = AsyncShallowRedisSaver(redis_url)
+    assert saver.loop is None  # not yet set
+
+    await saver.asetup()
+
+    assert saver.loop is not None
+    assert saver.loop is asyncio.get_running_loop()
+
+    await saver._redis.aclose()
+
+
+@pytest.mark.asyncio
+async def test_async_shallow_redis_saver_context_manager_after_sync_construction(
+    redis_url: str,
+) -> None:
+    """Saver built outside an event loop must still work as an async context manager."""
+    saver = AsyncShallowRedisSaver(redis_url)
+
+    async with saver:
+        assert saver.loop is asyncio.get_running_loop()
+
+        config: RunnableConfig = {
+            "configurable": {"thread_id": "issue-179-shallow-test", "checkpoint_ns": ""}
+        }
+        chk: Checkpoint = empty_checkpoint()
+        meta: CheckpointMetadata = {"source": "input", "step": 0, "writes": {}}
+        await saver.aput(config, chk, meta, {})
+        result = await saver.aget_tuple(config)
+        assert result is not None