Enable preemption checkpointing

Summary:
Pull Request resolved: https://github.com/facebookresearch/d2go/pull/639

Expose ability to add a preemption checkpointing hook running in a separate process group.

Reviewed By: wat3rBro, ynonaolga

Differential Revision: D51115437

fbshipit-source-id: c843802bc59da9f57c09c8d9a20f3d72d5b98edf

d2go/runner/default_runner.py

@@ -6,11 +6,13 @@ import contextlib
 import logging
 import os
 from collections import OrderedDict
+from datetime import timedelta
 from functools import lru_cache
 from typing import Any, List, Optional, Type, Union
 
 import detectron2.utils.comm as comm
 import torch
+import torch.distributed as dist
 from d2go.checkpoint.api import is_distributed_checkpoint
 from d2go.checkpoint.fsdp_checkpoint import FSDPCheckpointer
 from d2go.config import CfgNode, CONFIG_SCALING_METHOD_REGISTRY, temp_defrost
@@ -78,6 +80,7 @@ logger = logging.getLogger(__name__)
 
 
 ALL_TB_WRITERS = []
+CONTROL_PG_TIMEOUT = timedelta(minutes=30)
 
 
 @lru_cache()
@@ -156,10 +159,28 @@ def get_monitoring_service() -> Any:
     return contextlib.nullcontext()
 
 
+@fb_overwritable()
+def create_preemption_hook(
+    cfg: CfgNode,
+    periodic_checkpointer: PeriodicCheckpointer,
+    process_group: Optional[dist.ProcessGroup],
+) -> Any:
+    return None
+
+
 class BaseRunner(object):
     def __init__(self):
         identifier = f"D2Go.Runner.{self.__class__.__name__}"
         torch._C._log_api_usage_once(identifier)
+        # initialize the control pg for stuff like checkpoint and preemption handling
+        logger.info("Initializing control pg")
+        self._control_pg: Optional[dist.ProcessGroup] = None
+        if dist.is_initialized():
+            logger.info("Create gloo CPU control pg")
+            self._control_pg = dist.new_group(
+                backend=dist.Backend.GLOO,
+                timeout=CONTROL_PG_TIMEOUT,
+            )
 
     def _initialize(self, cfg):
         """Runner should be initialized in the sub-process in ddp setting"""
@@ -520,6 +541,7 @@ class Detectron2GoRunner(D2GoDataAPIMixIn, BaseRunner):
             self._create_after_step_hook(
                 cfg, model, optimizer, scheduler, periodic_checkpointer
             ),
+            create_preemption_hook(cfg, periodic_checkpointer, self._control_pg),
             hooks.EvalHook(
                 cfg.TEST.EVAL_PERIOD,
                 lambda: self.do_test(cfg, model, train_iter=trainer.iter),