grpc/grpc-go · error

rls_csp: nil configuration message provided

Error message

rls_csp: nil configuration message provided

What it means

The RLS cluster specifier plugin's ParseClusterSpecifierConfig was called with a nil proto.Message (rls.go:55-56). The parser requires a non-nil configuration to extract the RLS route lookup settings from the xDS resource.

Solutions

1. Ensure the xDS server sends a valid RouteLookupClusterSpecifier proto for RLS cluster resources
2. Check the route configuration on the xDS server for missing RLS config fields
3. Verify the resource type URL matches 'type.googleapis.com/grpc.lookup.v1.RouteLookupClusterSpecifier'

// Guard against nil config before calling ParseClusterSpecifierConfig.
func isNonNilConfig(cfg proto.Message) bool {
    return cfg != nil
}

When it happens

Trigger: clusterspecifier.ParseClusterSpecifierConfig is called with cfg == nil, either directly by test code or through the xDS resource processing pipeline when an RLS cluster specifier resource arrives from the management server with no configuration payload.

Common situations: xDS management server sends an RLS cluster specifier resource with an empty or null config field; route configuration references the RLS cluster specifier type URL but omits the config payload; xDS protocol version mismatch where the server omits a required field.

Related errors

• rls_csp: error marshaling load balancing config
• rls_csp: error marshaling route lookup config
• rls_csp: error parsing config
• rls_csp: error parsing config
• rls_csp: validation error from rls lb policy parsing

AI-assisted analysis of grpc/grpc-go@0c51461d27 (2026-08-11). Data as JSON: /api/errors/92995a119b31712d. Report an issue: GitHub.

Appendix: source

Thrown at internal/xds/clusterspecifier/rls/rls.go:56

type rls struct{}

func (rls) TypeURLs() []string {
	return []string{"type.googleapis.com/grpc.lookup.v1.RouteLookupClusterSpecifier"}
}

// lbConfigJSON is the RLS LB Policies configuration in JSON format.
// RouteLookupConfig will be a raw JSON string from the passed in proto
// configuration, and the other fields will be hardcoded.
type lbConfigJSON struct {
	RouteLookupConfig                json.RawMessage              `json:"routeLookupConfig"`
	ChildPolicy                      []map[string]json.RawMessage `json:"childPolicy"`
	ChildPolicyConfigTargetFieldName string                       `json:"childPolicyConfigTargetFieldName"`
}

func (rls) ParseClusterSpecifierConfig(cfg proto.Message) (clusterspecifier.BalancerConfig, error) {
	if cfg == nil {
		return nil, fmt.Errorf("rls_csp: nil configuration message provided")
	}
	m, ok := cfg.(*anypb.Any)
	if !ok {
		return nil, fmt.Errorf("rls_csp: error parsing config %v: unknown type %T", cfg, cfg)
	}
	rlcs := new(rlspb.RouteLookupClusterSpecifier)

	if err := m.UnmarshalTo(rlcs); err != nil {
		return nil, fmt.Errorf("rls_csp: error parsing config %v: %v", cfg, err)
	}
	rlcJSON, err := protojson.Marshal(rlcs.GetRouteLookupConfig())
	if err != nil {
		return nil, fmt.Errorf("rls_csp: error marshaling route lookup config: %v: %v", rlcs.GetRouteLookupConfig(), err)
	}
	lbCfgJSON := &lbConfigJSON{
		RouteLookupConfig: rlcJSON, // "JSON form of RouteLookupClusterSpecifier.config" - RLS in xDS Design Doc
		ChildPolicy: []map[string]json.RawMessage{
			{

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