[core] Fix crash when killing actor handle from previous session

python/ray/_private/worker.py

@@ -90,7 +90,13 @@
     raise_sys_exit_with_custom_error_message,
 )
 from ray.actor import ActorClass
-from ray.exceptions import ObjectStoreFullError, RayError, RaySystemError, RayTaskError
+from ray.exceptions import (
+    ActorHandleNotFoundError,
+    ObjectStoreFullError,
+    RayError,
+    RaySystemError,
+    RayTaskError,
+)
 from ray.experimental import tqdm_ray
 from ray.experimental.compiled_dag_ref import CompiledDAGRef
 from ray.experimental.internal_kv import (
@@ -3280,7 +3286,25 @@ def kill(actor: "ray.actor.ActorHandle", *, no_restart: bool = True):
             "ray.kill() only supported for actors. For tasks, try ray.cancel(). "
             "Got: {}.".format(type(actor))
         )
-    worker.core_worker.kill_actor(actor._ray_actor_id, no_restart)
+
+    # Attempt to kill the actor. If the actor handle is from a previous session,
+    # the C++ code will return NotFound status which will be converted to ActorHandleNotFoundError.
+    # We catch it here to provide a more helpful error message with job ID context.
+    try:
+        worker.core_worker.kill_actor(actor._ray_actor_id, no_restart)
+    except ActorHandleNotFoundError as e:
+        # Preserve the original exception type (it's already a ValueError subclass),
+        # but provide a more helpful error message with job ID context.
+        actor_job_id = actor._ray_actor_id.job_id
+        current_job_id = worker.current_job_id
+        raise ActorHandleNotFoundError(
+            f"ActorHandle objects are not valid across Ray sessions. "
+            f"The actor handle was created in job {actor_job_id.hex()}, "
+            f"but the current job is {current_job_id.hex()}. "
+            f"This typically happens when you try to use an actor handle "
+            f"from a previous session after calling ray.shutdown() and ray.init(). "
+            f"Please create a new actor handle in the current session."
+        ) from e
 
 
 @PublicAPI

python/ray/_raylet.pyx

@@ -196,8 +196,9 @@ include "includes/rpc_token_authentication.pxi"
 
 import ray
 from ray.exceptions import (
-    RayActorError,
+    ActorHandleNotFoundError,
     ActorDiedError,
+    RayActorError,
     RayError,
     RaySystemError,
     RayTaskError,
@@ -3736,10 +3737,16 @@ cdef class CoreWorker:
     def kill_actor(self, ActorID actor_id, c_bool no_restart):
         cdef:
             CActorID c_actor_id = actor_id.native()
+            CRayStatus status = CRayStatus.OK()
 
         with nogil:
-            check_status(CCoreWorkerProcess.GetCoreWorker().KillActor(
-                  c_actor_id, True, no_restart))
+            status = CCoreWorkerProcess.GetCoreWorker().KillActor(
+                c_actor_id, True, no_restart)
+
+        if status.IsNotFound():
+            raise ActorHandleNotFoundError(status.message().decode())
+
+        check_status(status)
 
     def cancel_task(self, ObjectRef object_ref, c_bool force_kill,
                     c_bool recursive):

python/ray/exceptions.py

@@ -998,6 +998,28 @@ def __str__(self):
         return self.error_message
 
 
+@DeveloperAPI
+class ActorHandleNotFoundError(ValueError, RayError):
+    """Raised when trying to kill an actor handle that doesn't exist.
+
+    This typically happens when using an actor handle from a previous Ray session
+    after calling ray.shutdown() and ray.init().
+
+    Note that this error is not only a subclass of RayError, but also a subclass of ValueError,
+    to maintain backward compatibility.
+
+    Args:
+        error_message: The error message that contains information about the actor handle.
+    """
+
+    def __init__(self, error_message: str):
+        super().__init__(error_message)
+        self.error_message = error_message
+
+    def __str__(self):
+        return self.error_message
+
+
 RAY_EXCEPTION_TYPES = [
     PlasmaObjectNotAvailable,
     RayError,
@@ -1029,5 +1051,6 @@ def __str__(self):
     RayCgraphCapacityExceeded,
     UnserializableException,
     ActorAlreadyExistsError,
+    ActorHandleNotFoundError,
     AuthenticationError,
 ]

python/ray/tests/test_ray_shutdown.py

@@ -475,5 +475,32 @@ def verify():
     wait_for_condition(verify)
 
 
+@pytest.mark.skipif(platform.system() == "Windows", reason="Hang on Windows.")
+def test_kill_actor_after_restart(shutdown_only):
+    """Test that killing an actor from a previous session raises a helpful error."""
+    # Set include_dashboard=False to have faster startup.
+    ray.init(num_cpus=1, include_dashboard=False)
+
+    @ray.remote
+    class A:
+        pass
+
+    a = A.remote()
+
+    # Restart ray
+    ray.shutdown()
+    ray.init(num_cpus=1, include_dashboard=False)
+
+    # Attempting to kill an actor from the previous session should raise
+    # a helpful error message instead of crashing the interpreter.
+    with pytest.raises(
+        ValueError, match="ActorHandle objects are not valid across Ray sessions"
+    ):
+        ray.kill(a)
+
+    ray.shutdown()
+    wait_for_condition(lambda: len(get_all_ray_worker_processes()) == 0)
+
+
 if __name__ == "__main__":
     sys.exit(pytest.main(["-sv", __file__]))

src/ray/core_worker/core_worker.cc

@@ -2557,12 +2557,16 @@ Status CoreWorker::KillActor(const ActorID &actor_id, bool force_kill, bool no_r
         } else {
           std::stringstream stream;
           stream << "Failed to find a corresponding actor handle for " << actor_id;
-          cb(Status::Invalid(stream.str()));
+          cb(Status::NotFound(stream.str()));
         }
       },
       "CoreWorker.KillActor");
   const auto &status = f.get();
-  actor_manager_->OnActorKilled(actor_id);
+  // Only call OnActorKilled if the kill was successful (status is OK).
+  // If the actor handle doesn't exist, OnActorKilled would crash.
+  if (status.ok()) {
+    actor_manager_->OnActorKilled(actor_id);
+  }
   return status;
 }