Debug and Extend a Priority-Aware Python Thread Pool

Problem Statement

You are tasked with implementing a PriorityThreadPool class. Unlike a standard pool, this implementation must prioritize tasks based on an integer priority (where a lower integer denotes a higher priority).

Requirements

1. submit(func, args, priority): Add a task to the internal queue. Threads should pick up the highest priority task available. Use heapq for the underlying data structure.
2. shutdown(wait=True): Prevent new tasks from being submitted and ensure worker threads exit gracefully. If wait is True, block until all active tasks complete.
3. Exception Handling: If a worker thread encounters an exception during task execution, the pool should log the error and ensure the thread remains alive to process subsequent tasks.

Interface

import threading
import heapq
import queue

class PriorityThreadPool:
    def __init__(self, num_threads):
        # Initialize threads and queue
        pass

    def submit(self, func, args=(), priority=0):
        # Add task to queue with priority
        pass

    def shutdown(self, wait=True):
        # Stop accepting tasks and shut down threads
        pass

Constraints

• Use threading and queue primitives.
• Ensure submit is thread-safe.
• Avoid busy-waiting loops.

Example

pool = PriorityThreadPool(num_threads=2)
pool.submit(lambda x: print(f"Task {x}"), args=(1,), priority=10)
pool.submit(lambda x: print(f"Task {x}"), args=(2,), priority=1)
# Output should ensure Task 2 executes before Task 1 due to priority.