grpc/grpc-go · error

rls_csp: error parsing config %v: unknown type %T

Error message

rls_csp: error parsing config %v: unknown type %T

What it means

Returned by ParseClusterSpecifierConfig when cfg is non-nil but not a *anypb.Any. The clusterspecifier framework always wraps configs as *anypb.Any, so reaching this branch means the framework or a custom caller bypassed that contract.

Source

Thrown at internal/xds/clusterspecifier/rls/rls.go:60

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

View on GitHub (pinned to 03255a9237)

Solutions

1. When calling ParseClusterSpecifierConfig directly, wrap the proto with anypb.New first.
2. If this surfaces through the normal xDS path, it is a framework bug — report it with the resource that triggered it.

Example fix

// before
b, err := rls{}.ParseClusterSpecifierConfig(rlcs) // *RouteLookupClusterSpecifier

// after
any, _ := anypb.New(rlcs)
b, err := rls{}.ParseClusterSpecifierConfig(any)

func isAnyProto(m proto.Message) (*anypb.Any, bool) {
    a, ok := m.(*anypb.Any)
    return a, ok
}

When it happens

Trigger: A direct call to ParseClusterSpecifierConfig with a concrete proto type (e.g. *rlspb.RouteLookupClusterSpecifier) instead of *anypb.Any, or a framework integration bug that does not Any-wrap.

Common situations: Unit tests or custom clusterspecifier plumbing that invoke the parser directly with a raw proto; normal xDS-driven parsing always supplies *anypb.Any.

Related errors

• rls_csp: nil configuration message provided
• rls_csp: error parsing config %v: %v
• rls_csp: error marshaling route lookup config: %v: %v
• rls_csp: error marshaling load balancing config %v: %v
• RLS LB policy not registered

AI-assisted analysis of grpc/grpc-go@03255a9237 (2026-08-07). Data as JSON: /api/errors/df2b7e46195eb861. Report an issue: GitHub.