/**
 * Copyright 2018, OpenCensus Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/// <reference types="node" />
import { CoreTracerBase } from './tracer-base';
import * as types from './types';
/**
 * This class represents a tracer with Continuation Local Storage (CLS).
 *
 * CLS helps keep tracking the root span over function calls automatically.
 * It is capable of storing, propagating and retrieving arbitrary
 * continuation-local data (also called "context").
 * CLS comes with some performance overhead, you can read more about it here:
 * https://github.com/othiym23/node-continuation-local-storage/issues/59
 */
export declare class CoreTracer extends CoreTracerBase implements types.Tracer {
    /** Manage context automatic propagation */
    private contextManager;
    /** Constructs a new TraceImpl instance. */
    constructor();
    /** Gets the current root span. */
    get currentRootSpan(): types.Span;
    /** Sets the current root span. */
    set currentRootSpan(root: types.Span);
    /** Sets the current root span. */
    setCurrentRootSpan(root: types.Span): void;
    /**
     * Starts a root span.
     * @param options A TraceOptions object to start a root span.
     * @param fn A callback function to run after starting a root span.
     */
    startRootSpan<T>(options: types.TraceOptions, fn: (root: types.Span) => T): T;
    /** Notifies listeners of the span start. */
    onStartSpan(span: types.Span): void;
    /** Notifies listeners of the span end. */
    onEndSpan(span: types.Span): void;
    /** Clears the current root span. */
    clearCurrentTrace(): void;
    /**
     * Starts a span.
     * @param [options] A SpanOptions object to start a child span.
     */
    startChildSpan(options?: types.SpanOptions): types.Span;
    /**
     * Binds the trace context to the given function.
     * This is necessary in order to create child spans correctly in functions
     * that are called asynchronously (for example, in a network response
     * handler).
     * @param fn A function to which to bind the trace context.
     */
    wrap<T>(fn: types.Func<T>): types.Func<T>;
    /**
     * Binds the trace context to the given event emitter.
     * This is necessary in order to create child spans correctly in event
     * handlers.
     * @param emitter An event emitter whose handlers should have
     *     the trace context binded to them.
     */
    wrapEmitter(emitter: NodeJS.EventEmitter): void;
}