A new PrioritizedTask dataclass is added that disable comparison on the task: dict element.

* Added new test to confirm that tasks with identical priorities do not raise TypeErrors.

Author: yadudoc

parsl/executors/high_throughput/mpi_resource_management.py

@@ -4,6 +4,7 @@
 import pickle
 import queue
 import subprocess
+from dataclasses import dataclass, field
 from enum import Enum
 from typing import Dict, List, Optional
 
@@ -69,6 +70,14 @@ def __str__(self):
         return f"MPINodesUnavailable(requested={self.requested} available={self.available})"
 
 
+@dataclass(order=True)
+class PrioritizedTask:
+    # Comparing dict will fail since they are unhashable
+    # This dataclass limits comparison to the priority field
+    priority: int
+    task: Dict = field(compare=False)
+
+
 class TaskScheduler:
     """Default TaskScheduler that does no taskscheduling
 
@@ -111,7 +120,7 @@ def __init__(
         super().__init__(pending_task_q, pending_result_q)
         self.scheduler = identify_scheduler()
         # PriorityQueue is threadsafe
-        self._backlog_queue: queue.PriorityQueue = queue.PriorityQueue()
+        self._backlog_queue: queue.PriorityQueue[PrioritizedTask] = queue.PriorityQueue()
         self._map_tasks_to_nodes: Dict[str, List[str]] = {}
         self.available_nodes = get_nodes_in_batchjob(self.scheduler)
         self._free_node_counter = SpawnContext.Value("i", len(self.available_nodes))
@@ -169,7 +178,7 @@ def put_task(self, task_package: dict):
                 allocated_nodes = self._get_nodes(nodes_needed)
             except MPINodesUnavailable:
                 logger.info(f"Not enough resources, placing task {tid} into backlog")
-                self._backlog_queue.put((nodes_needed, task_package))
+                self._backlog_queue.put(PrioritizedTask(nodes_needed, task_package))
                 return
             else:
                 resource_spec["MPI_NODELIST"] = ",".join(allocated_nodes)
@@ -183,8 +192,8 @@ def put_task(self, task_package: dict):
     def _schedule_backlog_tasks(self):
         """Attempt to schedule backlogged tasks"""
         try:
-            _nodes_requested, task_package = self._backlog_queue.get(block=False)
-            self.put_task(task_package)
+            prioritized_task = self._backlog_queue.get(block=False)
+            self.put_task(prioritized_task.task)
         except queue.Empty:
             return
         else:

parsl/tests/test_mpi_apps/test_mpi_scheduler.py

@@ -161,3 +161,28 @@ def test_MPISched_contention():
     assert task_on_worker_side['task_id'] == 2
     _, _, _, resource_spec = unpack_res_spec_apply_message(task_on_worker_side['buffer'])
     assert len(resource_spec['MPI_NODELIST'].split(',')) == 8
+
+
+@pytest.mark.local
+def test_hashable_backlog_queue():
+    """Run multiple large tasks that to force entry into backlog_queue
+    where queue.PriorityQueue expects hashability/comparability
+    """
+
+    task_q, result_q = SpawnContext.Queue(), SpawnContext.Queue()
+    scheduler = MPITaskScheduler(task_q, result_q)
+
+    assert scheduler.available_nodes
+    assert len(scheduler.available_nodes) == 8
+
+    assert scheduler._free_node_counter.value == 8
+
+    for i in range(3):
+        mock_task_buffer = pack_res_spec_apply_message("func", "args", "kwargs",
+                                                       resource_specification={
+                                                           "num_nodes": 8,
+                                                           "ranks_per_node": 2
+                                                       })
+        task_package = {"task_id": i, "buffer": mock_task_buffer}
+        scheduler.put_task(task_package)
+    assert scheduler._backlog_queue.qsize() == 2, "Expected 2 backlogged tasks"