What causes "Failed to notify listeners" in apache/iceberg?

Read the logged exception to identify the failing listener.

Failed to notify listeners

Error message

Failed to notify listeners

What it means

Inside SnapshotProducer.notifyListeners(), any RuntimeException thrown while building or dispatching commit events (including CommitMetricsResult creation) is caught and logged as this warning. It signals that one of the registered listeners failed; the table commit is unaffected. This is a second, inner guard distinct from the outer catch around notifyListeners().

Solutions

Read the logged exception to identify the failing listener.
Fix the listener so its callbacks never throw RuntimeException.
Add defensive error handling inside the listener around external calls.
Verify listener code matches the current Iceberg event/report API version.

Example fix

// before
public void notify(Event event) { report(buildReport(event)); } // unchecked failure surfaces as warning
// after
public void notify(Event event) {
  try { report(buildReport(event)); } catch (RuntimeException e) { LOG.warn("listener failed", e); }
}

Defensive patterns

Strategy: try-catch

Try / catch

try {
  listener.notify(event);
} catch (RuntimeException e) {
  LOG.warn("listener {} failed; commit unaffected", listenerName, e);
}

Prevention

Wrap listener bodies in try/catch so they never throw
Keep external reporting calls in listeners bounded by timeouts
Match listener code to the current Iceberg event API
Log and alert on listener failures without failing commits

When it happens

Trigger: A RuntimeException is thrown by a listener callback or by commitMetrics()/CommitReport construction while notifyListeners() runs after a commit — commonly a listener that throws unchecked exceptions.

Common situations: Listeners calling external reporting endpoints that fail; listeners written against an older event API; unhandled NPEs in custom listener code when summary fields are absent.

Understand the failure class

Background: 'Something went wrong' / 'Request failed (500)' / 'HTTP error! status: 404' — what failed HTTP requests actually mean and how to find the real cause — this error's family across 28 libraries.

Related errors

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/6f832fc6a81e37ab. Report an issue: GitHub.

Appendix: source

Thrown at core/src/main/java/org/apache/iceberg/SnapshotProducer.java:594

        Listeners.notifyAll(event);

        if (event instanceof CreateSnapshotEvent) {
          CreateSnapshotEvent createSnapshotEvent = (CreateSnapshotEvent) event;

          reporter.report(
              ImmutableCommitReport.builder()
                  .tableName(createSnapshotEvent.tableName())
                  .snapshotId(createSnapshotEvent.snapshotId())
                  .operation(createSnapshotEvent.operation())
                  .sequenceNumber(createSnapshotEvent.sequenceNumber())
                  .metadata(EnvironmentContext.get())
                  .commitMetrics(
                      CommitMetricsResult.from(commitMetrics(), createSnapshotEvent.summary()))
                  .build());
        }
      }
    } catch (RuntimeException e) {
      LOG.warn("Failed to notify listeners", e);
    }
  }

  protected void cleanAll() {
    for (String manifestList : manifestLists) {
      deleteFile(manifestList);
    }
    manifestLists.clear();
    cleanUncommitted(EMPTY_SET);
  }

  protected void deleteFile(String path) {
    deleteFunc.accept(path);
  }

  protected OutputFile manifestListPath() {
    return ops.io()
        .newOutputFile(

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