Fix broken WebSocket heartbeat implementation

[geoffjay]

Summary

This PR fixes the broken WebSocket heartbeat implementation in nemo-data/src/sources/websocket.rs that was identified in task td-fbb644.

Problem

The original heartbeat implementation had a critical flaw:

• The heartbeat task would tick a timer and clone the message but never actually send it
• The WebSocket write handle was moved to the message reading loop, making it inaccessible to the heartbeat task
• This resulted in a CPU-burning no-op loop that provided no functionality

Here's the problematic code (lines 137-144):

Some(tokio::spawn(async move {
    let mut timer = tokio::time::interval(interval);
    loop {
        timer.tick().await;
        // Note: This won't work as write is moved, simplified for now
        let _ = msg.clone();
    }
}))

Solution

This PR implements a proper channel-based architecture:

1. Dedicated Write Task: A separate async task owns the WebSocket write handle and receives messages through a channel
2. Heartbeat Task: Sends heartbeat messages through the channel at configured intervals
3. Pong Responses: Also sent through the same channel for consistent message handling

Key Benefits:

• Eliminates the no-op CPU-burning loop
• Properly sends heartbeat messages as configured
• Clean separation of concerns (read, write, heartbeat)
• Maintains support for WebSocket ping/pong protocol
• Graceful cleanup on disconnection

Changes

File Modified: crates/nemo-data/src/sources/websocket.rs

• Added tokio::sync::mpsc::channel for coordinating outgoing messages
• Created dedicated write task that owns the write handle
• Updated heartbeat task to send messages through the channel
• Updated ping handler to send pong responses through the channel
• Added proper cleanup logic to drop channel and abort tasks

Testing

• ✅ Code compiles successfully
• ✅ All existing unit tests pass
• ✅ No new dependencies required

Resolves

Fixes: td-fbb644

Made with Cursor

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