[PATCH] trackInitialHost evicts only the first stale entry found instead of all expired entries

[ormidales]

Category: performance
Severity: patch
File(s): background.js (l.~170)

Description

When initialHostByRequest reaches MAX_TRACKED_REQUESTS, trackInitialHost iterates the map to find a stale (TTL-expired) entry and breaks after finding the first one. This means only one slot is freed per insertion under pressure, so bursts of requests can cause repeated single-entry evictions instead of a bulk cleanup. The dedicated cleanupStaleTrackedRequests interval handles background cleanup, but under sustained load the per-insertion eviction loop is inefficient. Evicting all expired entries at once when the cap is reached would be more robust.

Problematic code example

if (initialHostByRequest.size >= MAX_TRACKED_REQUESTS) {
  const now = Date.now();
  let evictKey = null;
  for (const [key, entry] of initialHostByRequest) {
    if (now - entry.trackedAt > REQUEST_TRACK_TTL_MS) {
      evictKey = key;
      break; // ← stops after the first stale entry
    }
  }
  if (evictKey === null) {
    evictKey = initialHostByRequest.keys().next().value;
  }
  initialHostByRequest.delete(evictKey);
  redirectedRequestIds.delete(evictKey);
}

Suggested fix

Collect and delete all stale entries in one pass before falling back to the oldest-inserted eviction:

if (initialHostByRequest.size >= MAX_TRACKED_REQUESTS) {
  const now = Date.now();
  const staleKeys = [];
  for (const [key, entry] of initialHostByRequest) {
    if (now - entry.trackedAt > REQUEST_TRACK_TTL_MS) {
      staleKeys.push(key);
    }
  }
  if (staleKeys.length > 0) {
    for (const key of staleKeys) {
      initialHostByRequest.delete(key);
      redirectedRequestIds.delete(key);
    }
  } else {
    const evictKey = initialHostByRequest.keys().next().value;
    initialHostByRequest.delete(evictKey);
    redirectedRequestIds.delete(evictKey);
  }
}

Acceptance criteria

• All TTL-expired entries are removed in a single pass when the cap is reached
• Fallback to oldest-inserted eviction is used only when no stale entry exists
• Both initialHostByRequest and redirectedRequestIds are kept in sync
• Unit tests cover the bulk-eviction path