core/src/main/java/com/android/volley/RetryPolicy.java

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * 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.
 */

package com.android.volley;

/**
 * Retry policy for a request.
 *
 * <p>A retry policy can control two parameters:
 *
 * <ul>
 *   <li>The number of tries. This can be a simple counter or more complex logic based on the type
 *       of error passed to {@link #retry(VolleyError)}, although {@link #getCurrentRetryCount()}
 *       should always return the current retry count for logging purposes.
 *   <li>The request timeout for each try, via {@link #getCurrentTimeout()}. In the common case that
 *       a request times out before the response has been received from the server, retrying again
 *       with a longer timeout can increase the likelihood of success (at the expense of causing the
 *       user to wait longer, especially if the request still fails).
 * </ul>
 *
 * <p>Note that currently, retries triggered by a retry policy are attempted immediately in sequence
 * with no delay between them (although the time between tries may increase if the requests are
 * timing out and {@link #getCurrentTimeout()} is returning increasing values).
 *
 * <p>By default, Volley uses {@link DefaultRetryPolicy}.
 */
public interface RetryPolicy {

    /** Returns the current timeout (used for logging). */
    int getCurrentTimeout();

    /** Returns the current retry count (used for logging). */
    int getCurrentRetryCount();

    /**
     * Prepares for the next retry by applying a backoff to the timeout.
     *
     * @param error The error code of the last attempt.
     * @throws VolleyError In the event that the retry could not be performed (for example if we ran
     *     out of attempts), the passed in error is thrown.
     */
    void retry(VolleyError error) throws VolleyError;
}