failed to automatically buffer and retry failed request duri

Error message

failed to automatically buffer and retry failed request during failover. original err (type=%T): %v

What it means

This error is produced by TabletGateway.withRetry when buffering a failed PRIMARY query during a failover fails: WaitForFailoverEnd returns a bufferErr (e.g. the failover buffer is full, the buffer's redis/go-mem-manager is unavailable, or buffering was denied) and the gateway wraps it together with the original query error. The message preserves both the failover-buffer failure and the original error (with its Go type) that triggered the buffering attempt.

Source

Thrown at go/vt/vtgate/tabletgateway.go:373

		// Check if we should buffer PRIMARY queries which failed due to an ongoing failover.
		// Note: We only buffer once and only "!inTransaction" queries i.e.
		// a) no transaction is necessary (e.g. critical reads) or
		// b) no transaction was created yet.
		if gw.buffer != nil && !bufferedOnce && !opts.InTransaction && target.TabletType == topodatapb.TabletType_PRIMARY {
			// The next call blocks if we should buffer during a failover.
			retryDone, bufferErr := gw.buffer.WaitForFailoverEnd(ctx, target.Keyspace, target.Shard, gw.kev, err)

			// Request may have been buffered.
			if retryDone != nil {
				// We're going to retry this request as part of a buffer drain.
				// Notify the buffer after we retried.
				defer retryDone()
				bufferedOnce = true
			}

			if bufferErr != nil {
				err = vterrors.Wrapf(bufferErr,
					"failed to automatically buffer and retry failed request during failover. original err (type=%T): %v",
					err, err)
				break
			}
		}

		tablets := gw.hc.GetHealthyTabletStats(target)
		if len(tablets) == 0 {
			// if we have a keyspace event watcher, check if the reason why our primary is not available is that it's currently being resharded
			// or if a reparent operation is in progress.
			// We only check for whether reshard is ongoing or primary is serving or not, only if the target is primary. We don't want to buffer
			// replica queries, so it doesn't make any sense to check for resharding or reparenting in that case.
			if kev := gw.kev; kev != nil && target.TabletType == topodatapb.TabletType_PRIMARY {
				if kev.TargetIsBeingResharded(ctx, target) {
					log.V(2).Info(fmt.Sprintf("current keyspace is being resharded, retrying: %s: %s", target.Keyspace, debug.Stack()))
					err = vterrors.Errorf(vtrpcpb.Code_CLUSTER_EVENT, buffer.ClusterEventReshardingInProgress)
					continue
				}
				primary, shouldBuffer := kev.ShouldStartBufferingForTarget(ctx, target)

View on GitHub (pinned to 01a25a7d17)

Solutions

Inspect the wrapped 'original err' in the message — it is the root query failure (often a reparent-in-progress cluster event) — and resolve the underlying failover issue.
Check vtgate logs for buffer errors ('failed to buffer' / buffer full) and tune buffer settings (size/drain concurrency) if overflow is recurring.
Retry the request after the failover completes; the error is typically transient for non-transactional reads.
Verify vtgate and the buffer are healthy (vtgate restart during the event can abort buffering); pin to a stable vtgate instance or enable client-side retry with backoff for retryable codes (CLUSTER_EVENT).

Example fix

// before: single-shot query, fails during reparent
err := execute(ctx, target, query)
// after: retry retryable cluster-event failures with backoff
err := executeWithRetry(ctx, target, query, func(err error) bool {
    code := vterrors.Code(err)
    return code == vtrpcpb.Code_CLUSTER_EVENT || code == vtrpcpb.Code_UNAVAILABLE
})

Defensive patterns

Strategy: retry

Validate before calling

// Check failover state before issuing PRIMARY queries
if kev, _ := keyspaceEvents.Get(ctx, target.Keyspace); kev != nil && kev.IsReparenting() {
    return ErrFailoverInProgress // delay or route elsewhere
}

Try / catch

err := exec.Query(ctx, target, query)
if err != nil {
    code := vterrors.Code(err)
    if code == vtrpcpb.Code_CLUSTER_EVENT || code == vtrpcpb.Code_UNAVAILABLE {
        // failover-related; retry with backoff after reparent completes
        return retryWithBackoff(ctx, query, 3)
    }
    return err
}

Prevention

Size the failover buffer for peak PRIMARY traffic so buffering requests are not rejected.
Avoid restarting vtgate during planned reparents; keep buffer configuration stable.
Enable client-side retries only for retryable codes (CLUSTER_EVENT, UNAVAILABLE) and never for transactions already in flight.
Monitor buffer usage metrics and alert on capacity or drain-latency issues before failures occur.

When it happens

Trigger: A non-transactional query targeting a PRIMARY tablet fails (e.g. during reparent), the gateway's failover buffer is enabled (gw.buffer != nil), the request has not been buffered yet, and gw.buffer.WaitForFailoverEnd returns an error — e.g. buffer capacity exceeded, buffer shut down mid-wait, or context cancelled while waiting for failover end.

Common situations: Keyspace reparenting while vtgate buffering is enabled and the buffer overflows or is disabled/restarted; vtgate shutdown concurrent with a failover; misconfigured buffer settings (too small) during heavy failover traffic; clients seeing wrapped errors like 'failed to automatically buffer and retry ... original err (type=*vterrors.VtError): ...'.

Related errors

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/4429b8be1e5acd4d. Report an issue: GitHub.