The head sequence is greater than the committed event index

Error message

The head sequence {} is greater than the committed event index {}

What it means

A warning logged by the HTTP job-event reporter when the ring buffer's current head sequence has advanced past the last event index this handler committed. This means events were added to the ring buffer by another path or the committed index fell behind, so the reporter clamps the committed index forward to avoid re-reading or skipping events. It is a self-healing consistency warning, not a thrown exception.

Solutions

No action needed if infrequent — the handler advances committedEventIndex automatically and continues reporting.
If it fires constantly, verify only one JobEventHttpReportHandler instance is consuming the ring buffer per node.
Check for job restarts or Hazelcast member restarts that reset the handler's committed index; ensure ring buffer data is still valid for the new instance.

Example fix

null

Defensive patterns

Strategy: validation

Validate before calling

if (ringbuffer.headSequence() > committedEventIndex) { log.warn("ringbuffer ahead of committed index; resyncing"); committedEventIndex = ringbuffer.headSequence(); }

Prevention

Run a single ring buffer consumer per node.
Re-initialize committedEventIndex from ringbuffer.headSequence() on handler restart.
Monitor for repeated warnings as a sign of handler churn.

When it happens

Trigger: reportFromRingbuffer() is invoked (from report() or close()) while ringbuffer.headSequence() > committedEventIndex, i.e. the ring buffer contains events beyond the last index this handler processed — typically after a missed batch, a rebalance, or a reset of the handler's in-memory index.

Common situations: Node restart or handler re-creation after Hazelcast membership change where the ring buffer persists but the handler's committedEventIndex starts at 0; concurrent event production during shutdown flushes.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/96c4e70c5321f7b4. Report an issue: GitHub.

Appendix: source

Thrown at seatunnel-engine/seatunnel-engine-server/src/main/java/org/apache/seatunnel/engine/server/event/JobEventHttpReportHandler.java:142

            ringbuffer.addAsync(event, OverflowPolicy.OVERWRITE);
        } catch (HazelcastInstanceNotActiveException e) {
            // Hazelcast is shutting down, keep event in local buffer for best-effort flush.
            log.info("Skip writing event to ringbuffer because Hazelcast instance is not active");
        }
    }

    /**
     * Flushes one batch from the ringbuffer so tests and shutdown hooks can share the same logic.
     */
    @VisibleForTesting
    synchronized void report() throws IOException {
        reportFromRingbuffer();
    }

    private boolean reportFromRingbuffer() throws IOException {
        long headSequence = ringbuffer.headSequence();
        if (headSequence > committedEventIndex) {
            log.warn(
                    "The head sequence {} is greater than the committed event index {}",
                    headSequence,
                    committedEventIndex);
            committedEventIndex = headSequence;
        }
        CompletionStage<ReadResultSet<Event>> completionStage =
                ringbuffer.readManyAsync(
                        committedEventIndex, 0, RingbufferProxy.MAX_BATCH_SIZE, null);
        ReadResultSet<Event> resultSet = completionStage.toCompletableFuture().join();
        if (resultSet.size() <= 0) {
            return false;
        }

        String events = JSON_MAPPER.writeValueAsString(resultSet.iterator());
        if (postEvents(events)) {
            committedEventIndex += resultSet.readCount();
            drainLocalBuffer(resultSet.readCount());
            return true;

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