001/* 002 * Copyright 2002-2016 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.util.backoff; 018 019/** 020 * A simple {@link BackOff} implementation that provides a fixed interval 021 * between two attempts and a maximum number of retries. 022 * 023 * @author Stephane Nicoll 024 * @since 4.1 025 */ 026public class FixedBackOff implements BackOff { 027 028 /** 029 * The default recovery interval: 5000 ms = 5 seconds. 030 */ 031 public static final long DEFAULT_INTERVAL = 5000; 032 033 /** 034 * Constant value indicating an unlimited number of attempts. 035 */ 036 public static final long UNLIMITED_ATTEMPTS = Long.MAX_VALUE; 037 038 private long interval = DEFAULT_INTERVAL; 039 040 private long maxAttempts = UNLIMITED_ATTEMPTS; 041 042 043 /** 044 * Create an instance with an interval of {@value #DEFAULT_INTERVAL} 045 * ms and an unlimited number of attempts. 046 */ 047 public FixedBackOff() { 048 } 049 050 /** 051 * Create an instance. 052 * @param interval the interval between two attempts 053 * @param maxAttempts the maximum number of attempts 054 */ 055 public FixedBackOff(long interval, long maxAttempts) { 056 this.interval = interval; 057 this.maxAttempts = maxAttempts; 058 } 059 060 061 /** 062 * Set the interval between two attempts in milliseconds. 063 */ 064 public void setInterval(long interval) { 065 this.interval = interval; 066 } 067 068 /** 069 * Return the interval between two attempts in milliseconds. 070 */ 071 public long getInterval() { 072 return interval; 073 } 074 075 /** 076 * Set the maximum number of attempts in milliseconds. 077 */ 078 public void setMaxAttempts(long maxAttempts) { 079 this.maxAttempts = maxAttempts; 080 } 081 082 /** 083 * Return the maximum number of attempts in milliseconds. 084 */ 085 public long getMaxAttempts() { 086 return maxAttempts; 087 } 088 089 @Override 090 public BackOffExecution start() { 091 return new FixedBackOffExecution(); 092 } 093 094 095 private class FixedBackOffExecution implements BackOffExecution { 096 097 private long currentAttempts = 0; 098 099 @Override 100 public long nextBackOff() { 101 this.currentAttempts++; 102 if (this.currentAttempts <= getMaxAttempts()) { 103 return getInterval(); 104 } 105 else { 106 return STOP; 107 } 108 } 109 110 @Override 111 public String toString() { 112 final StringBuilder sb = new StringBuilder("FixedBackOff{"); 113 sb.append("interval=").append(FixedBackOff.this.interval); 114 String attemptValue = (FixedBackOff.this.maxAttempts == Long.MAX_VALUE ? 115 "unlimited" : String.valueOf(FixedBackOff.this.maxAttempts)); 116 sb.append(", currentAttempts=").append(this.currentAttempts); 117 sb.append(", maxAttempts=").append(attemptValue); 118 sb.append('}'); 119 return sb.toString(); 120 } 121 } 122 123}