[17/n] Pass monarch tensors to actor endpoints, part 2, actor messages sent in order

When you send a monarch.Tensor to an actor, what actually happens is that you instruct the stream managing the tensor to send the tensor to the actor.

In part 1, that stream directly told the actor what method to call, and where to send the result. The issue with that is ordering: from the perspective of the original caller it is as if we are sending a message to the actor directly. If the stream sends the message it is possible that it arrives out of order with respect to a message that goes directly to the actor (e.g. a message that contains no monarch.Tensors).

This resolves ordering issue: now the client sends a message to the actor 'CallMethodIndirect' that provides the pickled args/kwargs and method to invoke.

The local python values of the torch.Tensors still need to come from Stream actor, so CallMethodIndirect looks them up by messaging the (new) LocalStateBrokerActor which can transfer PyObjects between local actors without serialization.

Ordering is guarenteed for both tensors and actors because a message is sent to both the receiving actor _and_ the stream actor at the same time.

Differential Revision: [D78314012](https://our.internmc.facebook.com/intern/diff/D78314012/)

ghstack-source-id: 296356330
Pull Request resolved: #539

Author: zdevito

monarch_extension/src/convert.rs

@@ -176,35 +176,6 @@ impl<'a> MessageParser<'a> {
     fn parseWorkerMessageList(&self, name: &str) -> PyResult<Vec<WorkerMessage>> {
         self.attr(name)?.try_iter()?.map(|x| convert(x?)).collect()
     }
-    #[allow(non_snake_case)]
-    fn parseLocalStateList(&self, name: &str) -> PyResult<Vec<worker::LocalState>> {
-        let local_state_list = self.attr(name)?;
-        let mut result = Vec::new();
-
-        // Get the PyMailbox class for type checking
-        let mailbox_class = self
-            .current
-            .py()
-            .import("monarch._rust_bindings.monarch_hyperactor.mailbox")?
-            .getattr("Mailbox")?;
-
-        for item in local_state_list.try_iter()? {
-            let item = item?;
-            // Check if it's a Ref by trying to extract it
-            if let Ok(ref_val) = create_ref(item.clone()) {
-                result.push(worker::LocalState::Ref(ref_val));
-            } else if item.is_instance(&mailbox_class)? {
-                // It's a PyMailbox instance
-                result.push(worker::LocalState::Mailbox);
-            } else {
-                return Err(PyValueError::new_err(format!(
-                    "Expected Ref or Mailbox in local_state, got: {}",
-                    item.get_type().name()?
-                )));
-            }
-        }
-        Ok(result)
-    }
     fn parse_error_reason(&self, name: &str) -> PyResult<Option<(Option<ActorId>, String)>> {
         let err = self.attr(name)?;
         if err.is_none() {
@@ -465,11 +436,8 @@ fn create_map(py: Python) -> HashMap<u64, FnType> {
         Ok(WorkerMessage::SendResultOfActorCall(
             worker::ActorCallParams {
                 seq: p.parseSeq("seq")?,
-                actor: p.parse("actor")?,
-                index: p.parse("actor_index")?,
-                method: p.parse("method")?,
-                args_kwargs_tuple: p.parse("args_kwargs_tuple")?,
-                local_state: p.parseLocalStateList("local_state")?,
+                broker_id: p.parse("broker_id")?,
+                local_state: p.parseRefList("local_state")?,
                 mutates: p.parseRefList("mutates")?,
                 stream: p.parseStreamRef("stream")?,
             },

monarch_extension/src/mesh_controller.rs

@@ -38,6 +38,7 @@ use hyperactor_mesh::shared_cell::SharedCell;
 use hyperactor_mesh::shared_cell::SharedCellRef;
 use monarch_hyperactor::actor::PythonMessage;
 use monarch_hyperactor::actor::PythonMessageKind;
+use monarch_hyperactor::local_state_broker::LocalStateBrokerActor;
 use monarch_hyperactor::mailbox::PyPortId;
 use monarch_hyperactor::ndslice::PySlice;
 use monarch_hyperactor::proc_mesh::PyProcMesh;
@@ -78,6 +79,7 @@ pub(crate) fn register_python_bindings(module: &Bound<'_, PyModule>) -> PyResult
 struct _Controller {
     controller_handle: Arc<Mutex<ActorHandle<MeshControllerActor>>>,
     all_ranks: Slice,
+    broker_id: (String, usize),
 }
 
 static NEXT_ID: AtomicUsize = AtomicUsize::new(0);
@@ -123,9 +125,17 @@ impl _Controller {
         Ok(Self {
             controller_handle,
             all_ranks,
+            // note that 0 is the _pid_ of the broker, which will be 0 for
+            // top-level spawned actors.
+            broker_id: (format!("tensor_engine_brokers_{}", id), 0),
         })
     }
 
+    #[getter]
+    fn broker_id(&self) -> (String, usize) {
+        self.broker_id.clone()
+    }
+
     #[pyo3(signature = (seq, defs, uses, response_port, tracebacks))]
     fn node<'py>(
         &mut self,
@@ -626,6 +636,7 @@ enum ClientToControllerMessage {
 struct MeshControllerActor {
     proc_mesh: SharedCell<TrackedProcMesh>,
     workers: Option<SharedCell<RootActorMesh<'static, WorkerActor>>>,
+    brokers: Option<SharedCell<RootActorMesh<'static, LocalStateBrokerActor>>>,
     history: History,
     id: usize,
     debugger_active: Option<ActorRef<DebuggerActor>>,
@@ -730,6 +741,7 @@ impl Actor for MeshControllerActor {
         Ok(MeshControllerActor {
             proc_mesh: proc_mesh.clone(),
             workers: None,
+            brokers: None,
             history: History::new(world_size),
             id,
             debugger_active: None,
@@ -758,6 +770,10 @@ impl Actor for MeshControllerActor {
             .cast(selection::dsl::true_(), AssignRankMessage::AssignRank())?;
 
         self.workers = Some(workers);
+        let brokers = proc_mesh
+            .spawn(&format!("tensor_engine_brokers_{}", self.id), &())
+            .await?;
+        self.brokers = Some(brokers);
         Ok(())
     }
 }

monarch_hyperactor/src/actor.rs

@@ -21,6 +21,7 @@ use hyperactor::Context;
 use hyperactor::HandleClient;
 use hyperactor::Handler;
 use hyperactor::Named;
+use hyperactor::cap::CanSend;
 use hyperactor::forward;
 use hyperactor::message::Bind;
 use hyperactor::message::Bindings;
@@ -43,6 +44,8 @@ use tokio::sync::Mutex;
 use tokio::sync::oneshot;
 
 use crate::config::SHARED_ASYNCIO_RUNTIME;
+use crate::local_state_broker::BrokerId;
+use crate::local_state_broker::LocalStateBrokerMessage;
 use crate::mailbox::EitherPortRef;
 use crate::mailbox::PyMailbox;
 use crate::proc::InstanceWrapper;
@@ -171,6 +174,13 @@ impl PickledMessageClientActor {
     }
 }
 
+#[pyclass(module = "monarch._rust_bindings.monarch_hyperactor.actor")]
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
+pub enum UnflattenArg {
+    Mailbox,
+    PyObject,
+}
+
 #[pyclass(module = "monarch._rust_bindings.monarch_hyperactor.actor")]
 #[derive(Clone, Debug, Serialize, Deserialize, Named, PartialEq)]
 pub enum PythonMessageKind {
@@ -185,6 +195,14 @@ pub enum PythonMessageKind {
         rank: Option<usize>,
     },
     Uninit {},
+    CallMethodIndirect {
+        name: String,
+        local_state_broker: (String, usize),
+        id: usize,
+        // specify whether the argument to unflatten the local mailbox,
+        // or the next argument of the local state.
+        unflatten_args: Vec<UnflattenArg>,
+    },
 }
 
 impl Default for PythonMessageKind {
@@ -193,6 +211,11 @@ impl Default for PythonMessageKind {
     }
 }
 
+fn mailbox<'py, T: Actor>(py: Python<'py>, cx: &Context<'_, T>) -> Bound<'py, PyAny> {
+    let mailbox: PyMailbox = cx.mailbox_for_py().clone().into();
+    mailbox.into_bound_py_any(py).unwrap()
+}
+
 #[pyclass(frozen, module = "monarch._rust_bindings.monarch_hyperactor.actor")]
 #[derive(Clone, Serialize, Deserialize, Named, PartialEq, Default)]
 pub struct PythonMessage {
@@ -219,6 +242,56 @@ impl PythonMessage {
             _ => panic!("PythonMessage is not a response but {:?}", self),
         }
     }
+
+    pub async fn resolve_indirect_call<T: Actor>(
+        mut self,
+        cx: &Context<'_, T>,
+    ) -> anyhow::Result<(Self, PyObject)> {
+        let local_state: PyObject;
+        match self.kind {
+            PythonMessageKind::CallMethodIndirect {
+                name,
+                local_state_broker,
+                id,
+                unflatten_args,
+            } => {
+                let broker = BrokerId::new(local_state_broker).resolve(cx).unwrap();
+                let (send, recv) = cx.open_once_port();
+                broker.send(LocalStateBrokerMessage::Get(id, send))?;
+                let state = recv.recv().await?;
+                let mut state_it = state.state.into_iter();
+                local_state = Python::with_gil(|py| {
+                    let mailbox = mailbox(py, cx);
+                    PyList::new(
+                        py,
+                        unflatten_args.into_iter().map(|x| -> Bound<'_, PyAny> {
+                            match x {
+                                UnflattenArg::Mailbox => mailbox.clone(),
+                                UnflattenArg::PyObject => state_it.next().unwrap().into_bound(py),
+                            }
+                        }),
+                    )
+                    .unwrap()
+                    .into()
+                });
+                self.kind = PythonMessageKind::CallMethod {
+                    name,
+                    response_port: Some(state.response_port),
+                }
+            }
+            _ => {
+                local_state = Python::with_gil(|py| {
+                    let mailbox = mailbox(py, cx);
+                    py.import("itertools")
+                        .unwrap()
+                        .call_method1("repeat", (mailbox.clone(),))
+                        .unwrap()
+                        .unbind()
+                });
+            }
+        };
+        Ok((self, local_state))
+    }
 }
 
 impl std::fmt::Debug for PythonMessage {
@@ -408,30 +481,16 @@ impl PanicFlag {
 }
 
 #[async_trait]
-impl Handler<LocalPythonMessage> for PythonActor {
-    async fn handle(
-        &mut self,
-        cx: &Context<Self>,
-        message: LocalPythonMessage,
-    ) -> anyhow::Result<()> {
-        let mailbox: PyMailbox = PyMailbox {
-            inner: cx.mailbox_for_py().clone(),
-        };
+impl Handler<PythonMessage> for PythonActor {
+    async fn handle(&mut self, cx: &Context<Self>, message: PythonMessage) -> anyhow::Result<()> {
+        let (message, local_state) = message.resolve_indirect_call(cx).await?;
+
         // Create a channel for signaling panics in async endpoints.
         // See [Panics in async endpoints].
         let (sender, receiver) = oneshot::channel();
 
         let future = Python::with_gil(|py| -> Result<_, SerializablePyErr> {
-            let mailbox = mailbox.into_bound_py_any(py).unwrap();
-            let local_state: Option<Vec<Bound<'_, PyAny>>> = message.local_state.map(|state| {
-                state
-                    .into_iter()
-                    .map(|e| match e {
-                        LocalState::Mailbox => mailbox.clone(),
-                        LocalState::PyObject(obj) => obj.into_bound_py_any(py).unwrap(),
-                    })
-                    .collect()
-            });
+            let mailbox = mailbox(py, cx);
             let (rank, shape) = cx.cast_info();
             let awaitable = self.actor.call_method(
                 py,
@@ -440,7 +499,7 @@ impl Handler<LocalPythonMessage> for PythonActor {
                     mailbox,
                     rank,
                     PyShape::from(shape),
-                    message.message,
+                    message,
                     PanicFlag {
                         sender: Some(sender),
                     },
@@ -463,20 +522,6 @@ impl Handler<LocalPythonMessage> for PythonActor {
     }
 }
 
-#[async_trait]
-impl Handler<PythonMessage> for PythonActor {
-    async fn handle(&mut self, cx: &Context<Self>, message: PythonMessage) -> anyhow::Result<()> {
-        self.handle(
-            cx,
-            LocalPythonMessage {
-                message,
-                local_state: None,
-            },
-        )
-        .await
-    }
-}
-
 /// Helper struct to make a Python future passable in an actor message.
 ///
 /// Also so that we don't have to write this massive type signature everywhere
@@ -576,24 +621,14 @@ impl AsyncEndpointInvocationHandler for AsyncEndpointTask {
         Ok(())
     }
 }
-#[derive(Debug)]
-pub enum LocalState {
-    Mailbox,
-    PyObject(PyObject),
-}
-
-#[derive(Debug)]
-pub struct LocalPythonMessage {
-    pub message: PythonMessage,
-    pub local_state: Option<Vec<LocalState>>,
-}
 
 pub fn register_python_bindings(hyperactor_mod: &Bound<'_, PyModule>) -> PyResult<()> {
     hyperactor_mod.add_class::<PickledMessage>()?;
     hyperactor_mod.add_class::<PickledMessageClientActor>()?;
     hyperactor_mod.add_class::<PythonActorHandle>()?;
     hyperactor_mod.add_class::<PythonMessage>()?;
     hyperactor_mod.add_class::<PythonMessageKind>()?;
+    hyperactor_mod.add_class::<UnflattenArg>()?;
     hyperactor_mod.add_class::<PanicFlag>()?;
     Ok(())
 }

monarch_hyperactor/src/lib.rs

@@ -14,6 +14,7 @@ pub mod alloc;
 pub mod bootstrap;
 pub mod channel;
 pub mod config;
+pub mod local_state_broker;
 pub mod mailbox;
 pub mod ndslice;
 pub mod proc;