Blocking ray.get/wait inside async context will warn instead of error (…

…#7262)

python/ray/worker.py

@@ -1447,6 +1447,10 @@ def show_in_webui(message, key="", dtype="text"):
     worker.core_worker.set_webui_display(key.encode(), message_encoded)
 
 
+# Global varaible to make sure we only send out the warning once
+blocking_get_inside_async_warned = False
+
+
 def get(object_ids, timeout=None):
     """Get a remote object or a list of remote objects from the object store.
 
@@ -1456,7 +1460,7 @@ def get(object_ids, timeout=None):
     object has been created). If object_ids is a list, then the objects
     corresponding to each object in the list will be returned.
 
-    This method will error will error if it's running inside async context,
+    This method will issue a warning if it's running inside async context,
     you can use ``await object_id`` instead of ``ray.get(object_id)``. For
     a list of object ids, you can use ``await asyncio.gather(*object_ids)``.
 
@@ -1481,9 +1485,13 @@ def get(object_ids, timeout=None):
     if hasattr(
             worker,
             "core_worker") and worker.core_worker.current_actor_is_asyncio():
-        raise RayError("Using blocking ray.get inside async actor. "
-                       "This blocks the event loop. Please "
-                       "use `await` on object id with asyncio.gather.")
+        global blocking_get_inside_async_warned
+        if not blocking_get_inside_async_warned:
+            logger.warning("Using blocking ray.get inside async actor. "
+                           "This blocks the event loop. Please use `await` "
+                           "on object id with asyncio.gather if you want to "
+                           "yield execution to the event loop instead.")
+            blocking_get_inside_async_warned = True
 
     with profiling.profile("ray.get"):
         is_individual_id = isinstance(object_ids, ray.ObjectID)
@@ -1549,6 +1557,10 @@ def put(value, weakref=False):
         return object_id
 
 
+# Global variable to make sure we only send out the warning once.
+blocking_wait_inside_async_warned = False
+
+
 def wait(object_ids, num_returns=1, timeout=None):
     """Return a list of IDs that are ready and a list of IDs that are not.
 
@@ -1567,8 +1579,9 @@ def wait(object_ids, num_returns=1, timeout=None):
     precede B in the ready list. This also holds true if A and B are both in
     the remaining list.
 
-    This method will error if it's running inside an async context. Instead of
-    ``ray.wait(object_ids)``, you can use ``await asyncio.wait(object_ids)``.
+    This method will issue a warning if it's running inside an async context.
+    Instead of ``ray.wait(object_ids)``, you can use
+    ``await asyncio.wait(object_ids)``.
 
     Args:
         object_ids (List[ObjectID]): List of object IDs for objects that may or
@@ -1586,9 +1599,12 @@ def wait(object_ids, num_returns=1, timeout=None):
     if hasattr(worker,
                "core_worker") and worker.core_worker.current_actor_is_asyncio(
                ) and timeout != 0:
-        raise RayError("Using blocking ray.wait inside async method. "
-                       "This blocks the event loop. Please use `await` "
-                       "on object id with asyncio.wait. ")
+        global blocking_wait_inside_async_warned
+        if not blocking_wait_inside_async_warned:
+            logger.warning("Using blocking ray.wait inside async method. "
+                           "This blocks the event loop. Please use `await` "
+                           "on object id with asyncio.wait. ")
+            blocking_wait_inside_async_warned = True
 
     if isinstance(object_ids, ObjectID):
         raise TypeError(