Shutting down Catalog sync with

Error message

Shutting down Catalog sync with %d unsent notifications

What it means

CacheNotifier.stop() logs a warning when the Catalog sync executor is shut down while its in-memory 'updates' queue still holds notifications that were never delivered. The queued table/property change notifications are discarded by shutdownNow(), so subscribers may miss updates. This is a lifecycle diagnostics warning, not an exception.

Solutions

No action needed for the warning itself; it only indicates potentially lost notifications — dependent caches will resync on their next periodic resync().
If frequent, increase the notification queue drain rate (check executor configuration) or reduce catalog update frequency.
Ensure a clean shutdown path: call stop() only after consumers have caught up (graceful lifecycle ordering).
Verify affected caches via resync after restart to repair any missed notifications.

Example fix

// before
notifier.stop(); // warning: unsent notifications
// after
catalogReceiver.resync(); // after stop/restart, force full resync to recover dropped notifications

Defensive patterns

Strategy: fallback

Prevention

Treat notifications as best-effort and always resync() after restart.
Keep the updates queue drained; monitor its size in metrics.
Shut down sync receivers before producers during lifecycle teardown.

When it happens

Trigger: Calling stop() (directly or via stopGracefully/Lifecycle.stop) while notification tasks are still pending in the updates queue; broker or coordinator shutdown while catalogs are being updated faster than notifications are drained.

Common situations: Druid process shutdown under heavy catalog churn; misconfigured short sync intervals combined with slow consumers; failing fast during startup teardown after a failed lifecycle init.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/fa7003cf64e44381. Report an issue: GitHub.

Appendix: source

Thrown at extensions-core/druid-catalog/src/main/java/org/apache/druid/catalog/sync/CacheNotifier.java:118

  @VisibleForTesting
  public void stopGracefully()
  {
    try {
      while (!updates.isEmpty()) {
        Threads.sleepFor(100, TimeUnit.MILLISECONDS);
      }
    }
    catch (InterruptedException e) {
      // Ignore
    }
    stop();
  }

  public void stop()
  {
    if (!updates.isEmpty()) {
      LOG.warn("Shutting down Catalog sync with %d unsent notifications", updates.size());
    }
    exec.shutdownNow();
    LOG.info("Catalog sync stopped");
  }
}

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