process_group: add PG timeouts + automatically assign manager port (#60)

Author: d4l3k

torchft/manager.py

@@ -46,7 +46,7 @@
     from torchft.process_group import ProcessGroup
 
 MANAGER_ADDR_KEY: str = "manager_addr"
-MANAGER_DEFAULT_PORT: int = int(os.environ.get("TORCHFT_MANAGER_PORT", 29511))
+MANAGER_PORT_ENV: str = "TORCHFT_MANAGER_PORT"
 REPLICA_ID_KEY: str = "replica_id"
 
 T = TypeVar("T")
@@ -74,6 +74,12 @@ class Manager:
     """
     Manager manages the full fault tolerant training loop.
 
+    This requires the that the TCPStore specified by the store_addr and
+    store_port or MASTER_ADDR and MASTER_PORT environment variables to be
+    started prior to creating this manager. If using a modern version of
+    torchelastic this will already be the case. Otherwise, it should be started
+    via torch.distributed.init_process_group prior to creating this manager.
+
     NOTE: when saving periodic checkpoints you must save and restore the
     Manager's state_dict as well to avoid synchronization issues.
     """
@@ -84,7 +90,6 @@ def __init__(
         load_state_dict: Callable[[T], None],
         state_dict: Callable[[], T],
         min_replica_size: int,
-        port: int = MANAGER_DEFAULT_PORT,
         use_async_quorum: bool = True,
         timeout: timedelta = timedelta(seconds=60),
         rank: Optional[int] = None,
@@ -94,13 +99,18 @@ def __init__(
         store_port: Optional[int] = None,
         lighthouse_addr: Optional[str] = None,
         replica_id: Optional[str] = None,
+        port: Optional[int] = None,
     ) -> None:
         """
         Args:
             load_state_dict: function to load the state dict when recovering
             state_dict: function to save the state dict with recovering
             min_replica_size: minimum number of replicas on each step
-            port: if rank==0, the port to run the manager server on
+            port: if rank==0, the port to run the manager server on.
+                Port assignment priority:
+                1. this argument
+                2. TORCHFT_MANAGER_PORT env var
+                3. arbitrary port assigned via 0
             use_async_quorum: whether to run the quorum asynchronously during the forward pass
             timeout:
                 the default timeout for all operation, if you're using per
@@ -150,6 +160,10 @@ def _manager_state_dict() -> Dict[str, T]:
 
         if rank == 0:
             hostname = socket.gethostname()
+
+            if port is None:
+                port = int(os.environ.get(MANAGER_PORT_ENV, 0))
+
             addr = f"http://{hostname}:{port}"
             bind = f"[::]:{port}"
             lighthouse_addr = lighthouse_addr or os.environ["TORCHFT_LIGHTHOUSE"]
@@ -166,7 +180,7 @@ def _manager_state_dict() -> Dict[str, T]:
                 world_size=world_size,
             )
 
-            self._store.set(MANAGER_ADDR_KEY, addr)
+            self._store.set(MANAGER_ADDR_KEY, self._manager.address())
             self._store.set(REPLICA_ID_KEY, replica_id)
 
         addr = self._store.get(MANAGER_ADDR_KEY).decode("utf-8")

torchft/process_group.py

@@ -17,10 +17,11 @@
 """
 
 import logging
+import queue
 import threading
 from abc import ABC
 from datetime import timedelta
-from typing import TYPE_CHECKING, Dict, List, Optional, Type
+from typing import TYPE_CHECKING, Dict, List, Optional, Type, Union
 
 import torch
 import torch.distributed as dist
@@ -53,8 +54,23 @@
 _FUTURE_EXCEPTION = "fut_exception"
 
 
-def _get(queue: mp.Queue, timeout: float) -> object:
-    v = queue.get(timeout=timeout)
+def _get(q: mp.Queue, timeout: Union[float, timedelta]) -> object:
+    """
+    Gets an item from a queue with a timeout. If the timeout is exceeded then
+    a TimeoutError is raised.
+
+    If an exception is returned from the queue then it is raised.
+
+    Args:
+        q: queue to get from
+        timeout: timeout in seconds
+    """
+    if isinstance(timeout, timedelta):
+        timeout = timeout.total_seconds()
+    try:
+        v = q.get(timeout=timeout)
+    except queue.Empty as e:
+        raise TimeoutError(f"queue.get() timed out after {timeout} seconds") from e
     if isinstance(v, Exception):
         raise v
     return v
@@ -95,6 +111,9 @@ def configure(self, store_addr: str, rank: int, world_size: int) -> None:
         Every time this is called it must be provided with a unique prefixed
         store address. I.e. localhost:1234/my/prefix/1
 
+        This function will block until the underlying ProcessGroup is created.
+        If an error occurs this will throw.
+
         Args:
             store_addr: address of the store to use
             rank: rank of this process
@@ -187,7 +206,6 @@ def __repr__(self) -> str:
 
 
 class ProcessGroupWrapper(ProcessGroup):
-    PG_CLASS: Type[BaseProcessGroup]  # pyre-fixme[13]: never initialized
     """
     This is a wrapper around any ProcessGroup with a reconfiguration method.
     """
@@ -209,9 +227,10 @@ def configure(self, store_addr: str, rank: int, world_size: int) -> None:
 
         store = create_store_client(store_addr)
 
-        # TODO: set global timeout
-        # pyre-fixme[20]: expects argument options
-        self._pg = self.PG_CLASS(store, rank, world_size)
+        self._pg = self._create_pg(store, rank, world_size)
+
+    def _create_pg(self, store: Store, rank: int, world_size: int) -> BaseProcessGroup:
+        raise NotImplementedError("not implemented")
 
     def allreduce(self, tensors: List[torch.Tensor], opts: object) -> Work:
         return self.parent.allreduce(tensors, opts)
@@ -244,9 +263,13 @@ class ProcessGroupGloo(ProcessGroupWrapper):
     This is a reconfigurable version of ProcessGroupGloo.
     """
 
-    PG_CLASS: Type[BaseProcessGroup] = (
-        BaseProcessGroupGloo  # pyre-fixme[16]: no attribute ProcessGroupGloo
-    )
+    def __init__(self, timeout: timedelta = timedelta(seconds=60.0)) -> None:
+        super().__init__()
+        self._timeout = timeout
+
+    def _create_pg(self, store: Store, rank: int, world_size: int) -> BaseProcessGroup:
+        # pyre-fixme[16]: no attribute ProcessGroupGloo
+        return BaseProcessGroupGloo(store, rank, world_size, self._timeout)
 
     def getBackendName(self) -> str:
         return "torchft-gloo"
@@ -263,9 +286,9 @@ class ProcessGroupNCCL(ProcessGroupWrapper):
     abort when reconfiguring, we need to ensure this is safe.
     """
 
-    PG_CLASS: Type[BaseProcessGroup] = (
-        BaseProcessGroupNCCL  # pyre-fixme[16]: no attribute ProcessGroupNCCL
-    )
+    def _create_pg(self, store: Store, rank: int, world_size: int) -> BaseProcessGroup:
+        # pyre-fixme[16]: no attribute ProcessGroupNCCL
+        return BaseProcessGroupNCCL(store, rank, world_size)
 
     def getBackendName(self) -> str:
         return "torchft-nccl"
@@ -546,10 +569,9 @@ class ProcessGroupBaby(ProcessGroup):
 
     """
 
-    PG_CLASS: Type[BaseProcessGroup]  # pyre-fixme[13]: never initialized
     WORK_CLASS: Type[_BabyWork] = _BabyWork
 
-    def __init__(self, timeout: float = 60.0) -> None:
+    def __init__(self, timeout: Union[float, timedelta] = 60.0) -> None:
         super().__init__(0, 1)
 
         self._world_size = -1
@@ -562,7 +584,10 @@ def __init__(self, timeout: float = 60.0) -> None:
         self._futures: Dict[int, Future[object]] = {}
         self._futures_lock = threading.Lock()
 
-        self._timeout = timeout
+        if isinstance(timeout, timedelta):
+            timeout = timeout.total_seconds()
+
+        self._timeout: float = timeout
 
     def configure(self, store_addr: str, rank: int, world_size: int) -> None:
         if self._p is not None:
@@ -581,7 +606,7 @@ def configure(self, store_addr: str, rank: int, world_size: int) -> None:
 
         ctx = mp.get_context("spawn")
         self._tx = ctx.Queue()
-        self._rx = ctx.Queue()
+        self._rx = rx = ctx.Queue()
 
         # futures need thread to fire callbacks
         self._future_queue = ctx.Queue()
@@ -602,6 +627,17 @@ def configure(self, store_addr: str, rank: int, world_size: int) -> None:
         )
         self._p.start()
 
+        # fetch the status of the PG init
+        # if an exception was returned _get will throw
+        assert _get(rx, self._timeout) is None
+
+    @classmethod
+    def _create_pg(cls, store: Store, rank: int, world_size: int) -> BaseProcessGroup:
+        """
+        This is a class method to avoid pickling the class.
+        """
+        raise NotImplementedError("not implemented")
+
     @classmethod
     def _worker(
         cls,
@@ -615,8 +651,13 @@ def _worker(
         try:
             store = create_store_client(store_addr)
 
-            # pyre-fixme[20]: expects argument options
-            pg = cls.PG_CLASS(store, rank, world_size)
+            try:
+                pg = cls._create_pg(store, rank, world_size)
+            except Exception as e:
+                logger.exception(f"got exception in worker: {e}")
+                tx.put(e)
+                return
+            tx.put(None)
 
             work = {}
             next_op_id: int = 0
@@ -737,9 +778,10 @@ class ProcessGroupBabyGloo(ProcessGroupBaby):
     ProcessGroupBabyNCCL.
     """
 
-    PG_CLASS: Type[BaseProcessGroup] = (
-        BaseProcessGroupGloo  # pyre-fixme[16]: no attribute ProcessGroupGloo
-    )
+    @classmethod
+    def _create_pg(cls, store: Store, rank: int, world_size: int) -> BaseProcessGroup:
+        # pyre-fixme[16]: no attribute ProcessGroupGloo
+        return BaseProcessGroupGloo(store, rank, world_size)
 
     def getBackendName(self) -> str:
         return "torchft-baby-gloo"
@@ -761,11 +803,13 @@ class ProcessGroupBabyNCCL(ProcessGroupBaby):
     tensors may leak in the current PyTorch implementation. TODO fix
     """
 
-    PG_CLASS: Type[BaseProcessGroup] = (
-        BaseProcessGroupNCCL  # pyre-fixme[16]: no attribute ProcessGroupNCCL
-    )
     WORK_CLASS = _BabyWorkNCCL
 
+    @classmethod
+    def _create_pg(cls, store: Store, rank: int, world_size: int) -> BaseProcessGroup:
+        # pyre-fixme[16]: no attribute ProcessGroupNCCL
+        return BaseProcessGroupNCCL(store, rank, world_size)
+
     def getBackendName(self) -> str:
         return "torchft-baby-nccl"
 

torchft/process_group_test.py

@@ -6,6 +6,7 @@
 
 import os
 from concurrent.futures import ThreadPoolExecutor
+from datetime import timedelta
 from typing import Any, Dict, Tuple
 from unittest import TestCase, skipUnless
 from unittest.mock import Mock
@@ -122,6 +123,16 @@ def test_gloo(self) -> None:
         m = torch.nn.parallel.DistributedDataParallel(m, process_group=pg)
         m(torch.rand(2, 3))
 
+    def test_gloo_timeout(self) -> None:
+        store = TCPStore(
+            host_name="localhost", port=0, is_master=True, wait_for_workers=False
+        )
+
+        store_addr = f"localhost:{store.port}/prefix"
+        pg = ProcessGroupGloo(timeout=timedelta(seconds=0.01))
+        with self.assertRaisesRegex(RuntimeError, "timeout after 10ms"):
+            pg.configure(store_addr, 0, 2)
+
     # pyre-fixme[56]: Pyre was not able to infer the type of argument
     @skipUnless(torch.cuda.is_available(), "needs CUDA")
     def test_nccl(self) -> None:
@@ -155,28 +166,44 @@ def test_baby_gloo(self) -> None:
             host_name="localhost", port=0, is_master=True, wait_for_workers=False
         )
 
-        store_addr = f"localhost:{store.port}/prefix"
+        store_addr: str = f"localhost:{store.port}/prefix"
+
+        def run(rank: int) -> Tuple[torch.Tensor, Work]:
+            a = ProcessGroupBabyGloo()
+            a.configure(store_addr, rank, 2)
 
-        a = ProcessGroupBabyGloo()
-        b = ProcessGroupBabyGloo()
+            self.assertEqual(a.size(), 2)
 
-        a.configure(store_addr, 0, 2)
-        b.configure(store_addr, 1, 2)
+            at = torch.tensor([rank + 1])
 
-        self.assertEqual(a.size(), 2)
+            a_work = a.allreduce([at], ReduceOp.SUM)
+            return at, a_work
 
-        at = torch.tensor([1])
-        bt = torch.tensor([2])
+        with ThreadPoolExecutor(max_workers=2) as executor:
+            a_fut = executor.submit(run, 0)
+            b_fut = executor.submit(run, 1)
 
-        a_work = a.allreduce([at], ReduceOp.SUM)
-        b_work = b.allreduce([bt], ReduceOp.SUM)
+        at, a_work = a_fut.result()
+        bt, b_work = b_fut.result()
 
         a_work.wait()
         fut = b_work.get_future()
 
         fut.wait()
 
-        torch.testing.assert_close(at, bt)
+        torch.testing.assert_close(at, torch.tensor([3]))
+        torch.testing.assert_close(bt, torch.tensor([3]))
+
+    def test_baby_gloo_timeout(self) -> None:
+        store = TCPStore(
+            host_name="localhost", port=0, is_master=True, wait_for_workers=False
+        )
+
+        store_addr = f"localhost:{store.port}/prefix"
+
+        a = ProcessGroupBabyGloo(timeout=timedelta(seconds=0.01))
+        with self.assertRaisesRegex(TimeoutError, "timed out after 0.01 seconds"):
+            a.configure(store_addr, 0, 2)
 
     def test_dummy(self) -> None:
         pg = ProcessGroupDummy(0, 1)