--buffer-keyspace-shards=%v also requires that --enable_buff

Error message

--buffer-keyspace-shards=%v also requires that --enable_buffer is set

What it means

Listing keyspace/shards in --buffer-keyspace-shards only makes sense when buffering is actually enabled with --enable_buffer. verifyFlags rejects a non-empty --buffer-keyspace-shards when buffering is disabled, because the list would silently do nothing.

Source

Thrown at go/vt/vtgate/buffer/flags.go:84

	if bufferWindow < 1*time.Second {
		return fmt.Errorf("--buffer-window must be >= 1s (specified value: %v)", bufferWindow)
	}
	if bufferWindow > bufferMaxFailoverDuration {
		return fmt.Errorf("--buffer-window must be <= --buffer-max-failover-duration: %v vs. %v", bufferWindow, bufferMaxFailoverDuration)
	}
	if bufferSize < 1 {
		return fmt.Errorf("--buffer-size must be >= 1 (specified value: %d)", bufferSize)
	}
	if bufferMinTimeBetweenFailovers < 1*time.Second {
		return fmt.Errorf("--buffer-min-time-between-failovers must be >= 1s (specified value: %v)", bufferMinTimeBetweenFailovers)
	}

	if bufferDrainConcurrency < 1 {
		return fmt.Errorf("--buffer-drain-concurrency must be >= 1 (specified value: %d)", bufferDrainConcurrency)
	}

	if bufferKeyspaceShards != "" && !bufferEnabled {
		return fmt.Errorf("--buffer-keyspace-shards=%v also requires that --enable_buffer is set", bufferKeyspaceShards)
	}
	if bufferEnabled && bufferEnabledDryRun && bufferKeyspaceShards == "" {
		return errors.New("both the dry-run mode and actual buffering is enabled. To avoid ambiguity, keyspaces and shards for actual buffering must be explicitly listed in --buffer-keyspace-shards")
	}

	keyspaces, shards := keyspaceShardsToSets(bufferKeyspaceShards)
	for s := range shards {
		keyspace, _, err := topoproto.ParseKeyspaceShard(s)
		if err != nil {
			return err
		}
		if keyspaces[keyspace] {
			return fmt.Errorf("--buffer-keyspace-shards has overlapping entries (keyspace only vs. keyspace/shard): %v vs. %v Please remove one or the other", keyspace, s)
		}
	}

	return nil
}

View on GitHub (pinned to 01a25a7d17)

Solutions

Add --enable_buffer so the keyspace/shard list takes effect
Or remove --buffer-keyspace-shards if buffering is intentionally disabled
Check flag-precedence automation that may strip --enable_buffer while keeping other buffer flags

Example fix

// before
vtgate --buffer-keyspace-shards=commerce/-80
// after
vtgate --enable_buffer --buffer-keyspace-shards=commerce/-80

Defensive patterns

Strategy: validation

Validate before calling

if bufferKeyspaceShards != "" && !bufferEnabled {
    return fmt.Errorf("--buffer-keyspace-shards=%v also requires --enable_buffer", bufferKeyspaceShards)
}

Prevention

When disabling buffering, remove all related flags, not just --enable_buffer
Keep buffer flags in one config block toggled together
Grep deploy manifests for orphaned buffer flags after config changes

When it happens

Trigger: Starting vtgate with --buffer-keyspace-shards=ks1/-shard1 but without --enable_buffer (or with it explicitly false).

Common situations: Disabling buffering during an incident by removing --enable_buffer but leaving the shard list; stale configs where the enable flag was dropped but the list kept.

Understand the failure class

Background: "unknown output mode", "invalid value for flag", "expects true/false": fixing invalid flag value errors in CLI tools — this error's family across 24 libraries.

Related errors

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/a7ab97d55d43cd33. Report an issue: GitHub.