vitessio/vitess · error

either source or target shards are missing

Error message

either source or target shards are missing

What it means

Validation of a VReplication workflow (e.g. MoveTables completion validation) requires both source and target shard lists to be non-empty so their sharding key ranges can be parsed. If either list is empty, getSourceAndTargetKeyRanges rejects the call before any shard comparison is possible.

Source

Thrown at go/vt/vtctl/workflow/utils.go:443

	if len(targets) == 0 {
		return nil, fmt.Errorf("%w in keyspace %s for %s", ErrNoStreams, targetKeyspace, workflow)
	}

	return &TargetInfo{
		Targets:         targets,
		Frozen:          frozen,
		OptCells:        optCells,
		OptTabletTypes:  optTabletTypes,
		WorkflowType:    workflowType,
		WorkflowSubType: workflowSubType,
		Options:         &options,
	}, nil
}

func getSourceAndTargetKeyRanges(sourceShards, targetShards []string) (*topodatapb.KeyRange, *topodatapb.KeyRange, error) {
	if len(sourceShards) == 0 || len(targetShards) == 0 {
		return nil, nil, errors.New("either source or target shards are missing")
	}

	getKeyRange := func(shard string) (*topodatapb.KeyRange, error) {
		krs, err := key.ParseShardingSpec(shard)
		if err != nil {
			return nil, err
		}
		return krs[0], nil
	}

	// Happily string sorting of shards also sorts them in the ascending order of key
	// ranges in vitess.
	sort.Strings(sourceShards)
	sort.Strings(targetShards)
	getFullKeyRange := func(shards []string) (*topodatapb.KeyRange, error) {
		// Expect sorted shards.
		kr1, err := getKeyRange(shards[0])
		if err != nil {

View on GitHub (pinned to 01a25a7d17)

Solutions

1. Verify the workflow was created correctly with explicit source/target shards (MoveTables --source or same-keyspace shard specs)
2. Check the keyspace actually has shards in topology (vtctldclient GetTablets / GetShards) before validating completion
3. Fix the caller so it only invokes isPartialMoveTables after ShardSet is populated

Example fix

// before: empty shard list
sourceShards := []string{}
kr, _, err := getSourceAndTargetKeyRanges(sourceShards, targetShards)
// after: guard at the caller
if len(sourceShards) == 0 || len(targetShards) == 0 {
    return fmt.Errorf("workflow has no source/target shards loaded")
}
kr, _, err := getSourceAndTargetKeyRanges(sourceShards, targetShards)

if len(workflow.SourceShards) == 0 || len(workflow.TargetShards) == 0 {
    return errors.New("workflow must have non-empty source and target shard sets before validation")
}

When it happens

Trigger: Calling isPartialMoveTables / workflow validation with an empty sourceShards or targetShards slice — typically the ShardSet was never populated on the workflow, or a caller passed empty shard specs.

Common situations: Programmatic use of the workflow API with shards not yet loaded from topology, a MoveTables workflow created against a keyspace with zero shards, or a typo/mis-configuration leaving the shard list unset.

Related errors

• validateWorkflowName.VReplicationExec: <dynamic validation.m
• malformed spec: doesn't define a range: %q
• invalid value for on-ddl: %v
• invalid action for Migrate: %s
• VReplication streams must have named workflows for migration

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/8b645f367d8f706f. Report an issue: GitHub.