grpc/grpc-go · error

rls_csp: error marshaling route lookup config: %v: %v

Error message

rls_csp: error marshaling route lookup config: %v: %v

What it means

Returned when protojson.Marshal of the RouteLookupConfig (extracted from the decoded RouteLookupClusterSpecifier) fails. protojson marshaling fails only on a structurally invalid proto (e.g. an InvalidUTF8 error in a string field or a oneof/required violation), so this indicates a bad RouteLookupConfig payload.

Source

Thrown at internal/xds/clusterspecifier/rls/rls.go:69

	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{
			{
				"cds_experimental": json.RawMessage(`{"isDynamic":true}`),
			},
		},
		ChildPolicyConfigTargetFieldName: "cluster",
	}

	rawJSON, err := json.Marshal(lbCfgJSON)
	if err != nil {
		return nil, fmt.Errorf("rls_csp: error marshaling load balancing config %v: %v", lbCfgJSON, err)
	}

	rlsBB := balancer.Get(internal.RLSLoadBalancingPolicyName)
	if rlsBB == nil {

View on GitHub (pinned to 03255a9237)

Solutions

1. Inspect the %v (the protojson error) — an InvalidUTF8 error points to a specific field.
2. Correct the RouteLookupConfig on the server so all string fields are valid UTF-8.
3. If using a custom RLS config generator, validate strings before serialization.

When it happens

Trigger: The server-provided RouteLookupConfig proto, while decodable as a message, contains values that protojson cannot serialize — most commonly invalid UTF-8 in string fields (grpc_key_builder keys, headers, etc.).

Common situations: A control plane populating RLS config with non-UTF-8 bytes or leaving required-looking fields in an inconsistent state; rare under normal Envoy/Traffic Director output.

Related errors

• rls_csp: error parsing config %v: %v
• rls_csp: error marshaling load balancing config %v: %v
• rls: json unmarshal failed for service config %+v: %v
• rls: bad RouteLookupConfig proto %+v: %v
• rls: failed to parse lookup_service_timeout in route lookup

AI-assisted analysis of grpc/grpc-go@03255a9237 (2026-08-07). Data as JSON: /api/errors/837cec548d6c9b67. Report an issue: GitHub.