vitessio/vitess · warning

GetSchema(cluster = %s, keyspace = %s, tablet = %s) failed t

Error message

GetSchema(cluster = %s, keyspace = %s, tablet = %s) failed to acquire schemaReadPool: %w

What it means

For each tablet selected during GetSchema, vtadmin acquires schemaReadPool before issuing Vtctld.GetSchema; an Acquire failure (ctx cancelled/deadline while waiting for a slot) is wrapped with cluster, keyspace, and tablet alias and recorded into the error recorder. It is a resource-limiting failure, not a schema error.

Source

Thrown at go/vt/vtadmin/cluster/cluster.go:1694

	for _, tablet := range tablets {
		wg.Add(1)

		go func(tablet *vtadminpb.Tablet, sizesOnly bool) {
			defer wg.Done()

			span, ctx := trace.NewSpan(ctx, "Vtctld.GetSchema")
			defer span.Finish()
			req := opts.BaseRequest.CloneVT()
			req.TableSizesOnly = sizesOnly
			req.TabletAlias = tablet.Tablet.Alias

			AnnotateSpan(c, span)
			annotateGetSchemaRequest(req, span)
			span.Annotate("keyspace", keyspace)
			span.Annotate("shard", tablet.Tablet.Shard)

			if err := c.schemaReadPool.Acquire(ctx); err != nil {
				err = fmt.Errorf("GetSchema(cluster = %s, keyspace = %s, tablet = %s) failed to acquire schemaReadPool: %w", c.ID, keyspace, tablet.Tablet.Alias, err)
				rec.RecordError(err)
				return
			}

			resp, err := c.Vtctld.GetSchema(ctx, req)
			c.schemaReadPool.Release()

			if err != nil {
				err = fmt.Errorf("GetSchema(cluster = %s, keyspace = %s, tablet = %s) failed: %w", c.ID, keyspace, tablet.Tablet.Alias, err)
				rec.RecordError(err)

				return
			}

			if resp == nil || resp.Schema == nil {
				return
			}

View on GitHub (pinned to 01a25a7d17)

Solutions

1. Increase schemaReadPool size in vtadmin config
2. Check the wrapped cause: DeadlineExceeded indicates sustained pool saturation
3. Reduce the tablet set queried (use narrower opts/tablet filters)
4. Investigate slow tablets (overloaded mysqld, network) that hold pool slots

// Go: check remaining context budget before the fan-out
deadline, ok := ctx.Deadline()
if !ok || time.Until(deadline) < poolWaitBudget {
	return fmt.Errorf("insufficient deadline for schema fan-out")
}

schema, err := c.GetSchema(ctx, req)
if err != nil {
	if strings.Contains(err.Error(), "failed to acquire schemaReadPool") {
		// pool exhaustion: retry with backoff or raise pool size
	}
	return err
}

When it happens

Trigger: Large GetSchema fan-outs across many tablets holding all schemaReadPool slots, with the caller's ctx cancelled or deadline exceeded while a goroutine waits to query a specific tablet.

Common situations: Schema refresh across hundreds of tablets with a small pool; slow/unresponsive tablets making GetSchema calls hold slots for a long time; UI request timeouts cancelling ctx mid-wait.

Related errors

• GetWorkflows(keyspace = %s, active_only = %v) failed to acqu
• GetBackups(%s/%s) failed to acquire backupReadPool: %w
• GetCellInfo(%s) failed to acquire topoReadPool: %w
• GetKeyspace(%s) failed to acquire topoReadPool: %w
• GetKeyspaces() failed to acquire topoReadPool: %w

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/467b99121370dda7. Report an issue: GitHub.