Pruning task could become orphaned on node shutdown

[qj0r9j0vc2]

Summary

The PruningTask spawned via tokio::spawn could become orphaned or fail silently if the parent node crashes or shuts down unexpectedly.

Problem Location

crates/storage/src/pruning.rs:141-231

Code Analysis

// crates/storage/src/pruning.rs:141-149
/// Start the background pruning task
pub fn start(self) -> tokio::task::JoinHandle<()> {
    let config = self.config.clone();
    let store = Arc::clone(&self.store);
    let handle = self.handle;

    tokio::spawn(async move {
        // pruning loop...
    })
}

While PruningHandle provides a shutdown() method, the pattern has issues:

1. No graceful shutdown guarantee: If the node panics, shutdown() is never called
2. No completion confirmation: Callers cannot await proper cleanup
3. Orphaned state possible: Mid-pruning crash could leave storage in inconsistent state

Impact

• Storage inconsistency if pruning is interrupted mid-transaction
• Potential data corruption if MDBX transaction is not properly committed/aborted
• Memory/resource leaks from long-running orphaned tasks

Recommended Fix

1. Integrate pruning task into structured shutdown via tokio_util::task::TaskTracker
2. Implement graceful drain before shutdown
3. Add transaction savepoints for crash recovery

// Better pattern with TaskTracker
pub struct NodeShutdownCoordinator {
    tracker: TaskTracker,
    token: CancellationToken,
}

impl NodeShutdownCoordinator {
    pub fn spawn_pruning(&self, task: PruningTask) {
        self.tracker.spawn(task.run(self.token.clone()));
    }
    
    pub async fn shutdown(&self) {
        self.token.cancel();
        self.tracker.close();
        self.tracker.wait().await;  // Wait for all tasks to complete
    }
}