fix(webapp): guard the OTLP worker pool against double-reap and late messages

A crashing worker fires both error and exit, so reap() ran twice (double respawn
and double backoff increment). reap() now returns early once the worker has been
removed. The message handler also ignores late messages from an already-reaped
worker, which otherwise pushed a dead worker back into the idle set.

Author: ericallam

apps/webapp/app/v3/otlpWorkerPool.server.ts

@@ -54,6 +54,7 @@ export class OtlpWorkerPool {
     });
 
     worker.on("message", (msg: { id: number; ok: boolean; result?: any; error?: string }) => {
+      if (this.workers.indexOf(worker) === -1) return; // late message from an already-reaped worker
       this.consecutiveFailures = 0;
       this.busyByWorker.delete(worker);
       const task = this.tasks.get(msg.id);
@@ -84,6 +85,13 @@ export class OtlpWorkerPool {
   // On crash/timeout: fail the worker's in-flight task (if still pending), drop the worker, and
   // respawn with exponential backoff so a persistently failing worker can't tight-loop.
   private reap(worker: Worker, error: Error) {
+    const wi = this.workers.indexOf(worker);
+    if (wi === -1) return; // already reaped (error + exit can both fire for one crash)
+    this.workers.splice(wi, 1);
+
+    const ii = this.idle.indexOf(worker);
+    if (ii !== -1) this.idle.splice(ii, 1);
+
     const inFlightId = this.busyByWorker.get(worker);
     this.busyByWorker.delete(worker);
     if (inFlightId !== undefined) {
@@ -94,10 +102,7 @@ export class OtlpWorkerPool {
         task.reject(error);
       }
     }
-    const wi = this.workers.indexOf(worker);
-    if (wi !== -1) this.workers.splice(wi, 1);
-    const ii = this.idle.indexOf(worker);
-    if (ii !== -1) this.idle.splice(ii, 1);
+
     void worker.terminate().catch(() => {});
     this.scheduleRespawn();
   }