/**
     * @param errorHandler Notified when some async activity fails. Must be thread-safe.
     */
    public MessageHub(String displayName, ExecutorFactory executorFactory, Action<? super Throwable> errorHandler) {
        this.displayName = displayName;
        this.errorHandler = errorHandler;
        workers = executorFactory.create(displayName + " workers");
    }

    /**

        private final TransformErrorHandler errorHandler;

        InstrumentingScriptClassLoader(ScriptSource scriptSource, ClassLoader parent, TransformedClassPath classPath, HashCode implementationHash) {
            super(scriptSource, parent, classPath, implementationHash);
            replacer = new TransformReplacer(classPath);
            errorHandler = new TransformErrorHandler(getName());
        }

import java.util.concurrent.LinkedBlockingQueue

@Timeout(60)
class MessageHubTest extends ConcurrentSpec {
    final Action<Throwable> errorHandler = Mock()
    final MessageHub hub = new MessageHub("<hub>", executorFactory, errorHandler)

    def cleanup() {
        hub.stop()
    }

    def "creates a separate dispatcher for each outgoing type"() {
        when:

	// If the backend is unreachable, the optional ErrorHandler is
	// called without any call to ModifyResponse.
	//
	// If ModifyResponse returns an error, ErrorHandler is called
	// with its error value. If ErrorHandler is nil, its default
	// implementation is used.
	ModifyResponse func(*http.Response) error

	// ErrorHandler is an optional function that handles errors

	})
	writeJSON(w, configs, req)
}

// SidecarScope debugging
func (s *DiscoveryServer) sidecarz(w http.ResponseWriter, req *http.Request) {
	proxyID, con := s.getDebugConnection(req)
	if con == nil {
		s.errorHandler(w, proxyID, con)
		return
	}
	writeJSON(w, con.proxy.SidecarScope, req)
}

// Resource debugging.
func (s *DiscoveryServer) resourcez(w http.ResponseWriter, req *http.Request) {

	}
}

// ErrorHandlers is a list of functions which will be invoked when a nonreturnable
// error occurs.
// TODO(lavalamp): for testability, this and the below HandleError function
// should be packaged up into a testable and reusable object.
var ErrorHandlers = []ErrorHandler{
	logError,
	func(_ context.Context, _ error, _ string, _ ...interface{}) {

    // a value of `configuration.getAttributes()`.
    // TODO:configuration-cache find a way to clean up this #23732
    private Provider<AttributeContainer> zConfigurationAttributes;
    private ResolutionErrorRenderer errorHandler;
    private String configurationName;
    private String configurationDescription;

    /**
     * The root component of the dependency graph to be inspected.
     *
     * @since 7.5
     */

	"go/token"
	"path/filepath"
	"strconv"
	"unicode"
	"unicode/utf8"
)

// An ErrorHandler may be provided to [Scanner.Init]. If a syntax error is
// encountered and a handler was installed, the handler is called with a
// position and an error message. The position points to the beginning of
// the offending token.
type ErrorHandler func(pos token.Position, msg string)

// A Scanner holds the scanner's internal state while processing

		t.Run(test.name, func(t *testing.T) {
			var (
				errorHandlerCallCountGot int
				rwGot                    http.ResponseWriter
				requestGot               *http.Request
			)

			errorHandler := http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
				http.Error(rw, "error serving request", http.StatusBadRequest)

				errorHandlerCallCountGot++
				requestGot = req
				rwGot = rw
			})

			v.SetComplex(s.scanComplex(verb, v.Type().Bits()))
		default:
			s.errorString("can't scan type: " + val.Type().String())
		}
	}
}

// errorHandler turns local panics into error returns.
func errorHandler(errp *error) {
	if e := recover(); e != nil {
		if se, ok := e.(scanError); ok { // catch local error
			*errp = se.err