grpctransport: ServerURI is not set in ServerIdentifier

Error message

grpctransport: ServerURI is not set in ServerIdentifier

What it means

Returned by (*Builder).Build when clients.ServerIdentifier.ServerURI is the empty string (grpc_transport.go:91). Build requires a non-empty target URI because it is passed directly to grpc.NewClient; an empty URI is treated as a configuration error rather than a dial error.

Solutions

Inspect the bootstrap configuration and ensure every xds_server / lrs_server has a non-empty server_uri.
If building ServerIdentifier in code, validate ServerURI before calling Build.
Log the offending ServerIdentifier at the call site to pinpoint which entry is empty.

Example fix

// before
si := clients.ServerIdentifier{} // ServerURI empty
tr, err := builder.Build(si)

// after
if si.ServerURI == "" {
    return fmt.Errorf("server URI required for %v", si)
}
tr, err := builder.Build(si)

Defensive patterns

Strategy: validation

Validate before calling

func validServerIdentifier(si clients.ServerIdentifier) error {
    if si.ServerURI == "" {
        return errors.New("ServerURI must be set")
    }
    return nil
}
// call before builder.Build(si)

Try / catch

tr, err := builder.Build(si)
if err != nil && strings.Contains(err.Error(), "ServerURI is not set") {
    // bootstrap is missing server_uri; fail fast with context
}

Prevention

Validate bootstrap JSON with a schema check that requires server_uri on every xds_server.
Build ServerIdentifier in one helper and unit-test it.
Log the ServerIdentifier at debug level before Build to catch empty fields.

When it happens

Trigger: Calling builder.Build(si) where si.ServerURI == "". Common when the ServerIdentifier is constructed from a bootstrap xds_server entry whose server_uri field is missing.

Common situations: Bootstrap configuration JSON is missing the "server_uri" field on an xds_server; a templated config left the URI blank; the LRS server config reuses an xDS server entry without copying the URI; programmatic bootstrap assembly bug.

Related errors

AI-assisted analysis of grpc/grpc-go@0c51461d27 (2026-08-11). Data as JSON: /api/errors/34249a342e6a46fc. Report an issue: GitHub.

Appendix: source

Thrown at internal/xds/clients/grpctransport/grpc_transport.go:91

}

// NewBuilder provides a builder for creating gRPC-based Transports using
// the credentials from provided map of credentials names to
// credentials.Bundle.
func NewBuilder(configs map[string]Config) *Builder {
	return &Builder{
		configs:     configs,
		connections: make(map[clients.ServerIdentifier]*grpc.ClientConn),
		refs:        make(map[clients.ServerIdentifier]int),
	}
}

// Build returns a gRPC-based clients.Transport.
//
// The Extension field of the ServerIdentifier must be a ServerIdentifierExtension.
func (b *Builder) Build(si clients.ServerIdentifier) (clients.Transport, error) {
	if si.ServerURI == "" {
		return nil, fmt.Errorf("grpctransport: ServerURI is not set in ServerIdentifier")
	}
	if si.Extensions == nil {
		return nil, fmt.Errorf("grpctransport: Extensions is not set in ServerIdentifier")
	}
	sce, ok := si.Extensions.(ServerIdentifierExtension)
	if !ok {
		return nil, fmt.Errorf("grpctransport: Extensions field is %T, but must be %T in ServerIdentifier", si.Extensions, ServerIdentifierExtension{})
	}

	config, ok := b.configs[sce.ConfigName]
	if !ok {
		return nil, fmt.Errorf("grpctransport: unknown config name %q specified in ServerIdentifierExtension", sce.ConfigName)
	}
	if config.Credentials == nil {
		return nil, fmt.Errorf("grpctransport: config %q has nil credentials bundle", sce.ConfigName)
	}

	b.mu.Lock()

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