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Thread-safe message dispatching

Aider-AI/aider
Based on 2 comments
Python

When implementing communication between multiple threads, ensure that messages are correctly routed to their intended recipients. Avoid designs where all worker threads consume from a single shared queue when messages are intended for specific threads, as this creates race conditions where messages can be processed by the wrong thread.

Concurrency Python

Reviewer Prompt

When implementing communication between multiple threads, ensure that messages are correctly routed to their intended recipients. Avoid designs where all worker threads consume from a single shared queue when messages are intended for specific threads, as this creates race conditions where messages can be processed by the wrong thread.

Instead, consider one of these approaches:

  1. Use separate queues for each recipient thread
  2. Implement a central dispatcher that routes messages to the correct recipient
  3. Use an event-based pattern with callbacks or futures

Example of problematic code:

def _server_loop(self, server: McpServer, loop: asyncio.AbstractEventLoop) -> None:
    while True:
        # All threads compete for the same messages
        msg: CallArguments = self.message_queue.get()
        
        # If message not for this server, discard it
        if msg.server_name != server.name:
            self.message_queue.task_done()
            continue
            
        # Process the message...

Better implementation:

class McpManager:
    def __init__(self):
        # One queue per server for proper message routing
        self.server_queues = {}  # server_name -> queue
        self.result_queue = queue.Queue()
        
    def add_server(self, server_name):
        self.server_queues[server_name] = queue.Queue()
        
    def _call(self, io, server_name, function, args={}):
        # Route message to specific server queue
        if server_name in self.server_queues:
            self.server_queues[server_name].put(CallArguments(server_name, function, args))
            result = self.result_queue.get()
            return result.response
        return None
        
    def _server_loop(self, server: McpServer, loop: asyncio.AbstractEventLoop) -> None:
        # Each server only processes its own messages
        server_queue = self.server_queues[server.name]
        while True:
            msg = server_queue.get()
            # Process message...

This pattern prevents race conditions and ensures messages are always processed by their intended recipients.

2
Comments Analyzed
Python
Primary Language
Concurrency
Category

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