content: /*
   * Tencent is pleased to support the open source community by making Angel available.
   *
   * Copyright (C) 2017-2018 THL A29 Limited, a Tencent company. All rights reserved.
   *
   * 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
   *
   * https://opensource.org/licenses/Apache-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.tencent.angel.io.retry;
  
  
  /**
   * <p>
   * Specifies a policy for retrying method failures. Implementations of this interface should be
   * immutable.
   * </p>
   */
  public interface RetryPolicy {
  
    /**
     * Returned by {@link RetryPolicy#shouldRetry(Exception, int, int, boolean)}.
     */
    public static class RetryAction {
  
      // A few common retry policies, with no delays.
      public static final RetryAction FAIL = new RetryAction(RetryDecision.FAIL);
      public static final RetryAction RETRY = new RetryAction(RetryDecision.RETRY);
      public static final RetryAction FAILOVER_AND_RETRY =
        new RetryAction(RetryDecision.FAILOVER_AND_RETRY);
  
      public final RetryDecision action;
      public final long delayMillis;
      public final String reason;
  
      public RetryAction(RetryDecision action) {
        this(action, 0, null);
      }
  
      public RetryAction(RetryDecision action, long delayTime) {
        this(action, delayTime, null);
      }
  
      public RetryAction(RetryDecision action, long delayTime, String reason) {
        this.action = action;
        this.delayMillis = delayTime;
        this.reason = reason;
      }
  
      @Override public String toString() {
        return getClass().getSimpleName() + "(action=" + action + ", delayMillis=" + delayMillis
          + ", reason=" + reason + ")";
      }
  
      public enum RetryDecision {
        FAIL, RETRY, FAILOVER_AND_RETRY
      }
    }
  
    /**
     * <p>
     * Determines whether the framework should retry a method for the given exception, and the number
     * of retries that have been made for that operation so far.
     * </p>
     *
     * @param e                        The exception that caused the method to fail
     * @param retries                  The number of times the method has been retried
     * @param failovers                The number of times the method has failed over to a different backend
     *                                 implementation
     * @param isIdempotentOrAtMostOnce <code>true</code> if the method is {@link Idempotent} or
     *                                 {@link AtMostOnce} and so can reasonably be retried on failover when we don't know if
     *                                 the previous attempt reached the server or not
     * @return <code>true</code> if the method should be retried, <code>false</code> if the method
     * should not be retried but shouldn't fail with an exception (only for void methods)
     * @throws Exception The re-thrown exception <code>e</code> indicating that the method failed and
     *                   should not be retried further
     */
    public RetryAction shouldRetry(Exception e, int retries, int failovers,
      boolean isIdempotentOrAtMostOnce) throws Exception;
  }
  