/**
 * @license
 * Copyright 2019 Google LLC
 *
 * 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.
 */
/**
 * The maximum milliseconds to increase to.
 *
 * <p>Visible for testing
 */
export declare const MAX_VALUE_MILLIS: number;
/**
 * The percentage of backoff time to randomize by.
 * See
 * http://go/safe-client-behavior#step-1-determine-the-appropriate-retry-interval-to-handle-spike-traffic
 * for context.
 *
 * <p>Visible for testing
 */
export declare const RANDOM_FACTOR = 0.5;
/**
 * Based on the backoff method from
 * https://github.com/google/closure-library/blob/master/closure/goog/math/exponentialbackoff.js.
 * Extracted here so we don't need to pass metadata and a stateful ExponentialBackoff object around.
 */
export declare function calculateBackoffMillis(backoffCount: number, intervalMillis?: number, backoffFactor?: number): number;