001 /** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.camel.processor; 018 019 import org.apache.camel.Exchange; 020 import org.apache.camel.Processor; 021 022 /** 023 * A <a href="http://camel.apache.org/throttler.html">Throttler</a> 024 * will set a limit on the maximum number of message exchanges which can be sent 025 * to a processor within a specific time period. <p/> This pattern can be 026 * extremely useful if you have some external system which meters access; such 027 * as only allowing 100 requests per second; or if huge load can cause a 028 * particular systme to malfunction or to reduce its throughput you might want 029 * to introduce some throttling. 030 * 031 * @version $Revision: 788621 $ 032 */ 033 public class Throttler extends DelayProcessorSupport implements Traceable { 034 private long maximumRequestsPerPeriod; 035 private long timePeriodMillis; 036 private TimeSlot slot; 037 038 public Throttler(Processor processor, long maximumRequestsPerPeriod) { 039 this(processor, maximumRequestsPerPeriod, 1000); 040 } 041 042 public Throttler(Processor processor, long maximumRequestsPerPeriod, long timePeriodMillis) { 043 super(processor); 044 this.maximumRequestsPerPeriod = maximumRequestsPerPeriod; 045 this.timePeriodMillis = timePeriodMillis; 046 } 047 048 @Override 049 public String toString() { 050 return "Throttler[requests: " + maximumRequestsPerPeriod + " per: " + timePeriodMillis + " (ms) to: " 051 + getProcessor() + "]"; 052 } 053 054 public String getTraceLabel() { 055 return "Throttle[" + maximumRequestsPerPeriod + " per: " + timePeriodMillis + "]"; 056 } 057 058 // Properties 059 // ----------------------------------------------------------------------- 060 public long getMaximumRequestsPerPeriod() { 061 return maximumRequestsPerPeriod; 062 } 063 064 /** 065 * Sets the maximum number of requests per time period 066 */ 067 public void setMaximumRequestsPerPeriod(long maximumRequestsPerPeriod) { 068 this.maximumRequestsPerPeriod = maximumRequestsPerPeriod; 069 } 070 071 public long getTimePeriodMillis() { 072 return timePeriodMillis; 073 } 074 075 /** 076 * Sets the time period during which the maximum number of requests apply 077 */ 078 public void setTimePeriodMillis(long timePeriodMillis) { 079 this.timePeriodMillis = timePeriodMillis; 080 } 081 082 // Implementation methods 083 // ----------------------------------------------------------------------- 084 protected void delay(Exchange exchange) throws Exception { 085 TimeSlot slot = nextSlot(); 086 if (!slot.isActive()) { 087 waitUntil(slot.startTime, exchange); 088 } 089 } 090 091 /* 092 * Determine what the next available time slot is for handling an Exchange 093 */ 094 protected synchronized TimeSlot nextSlot() { 095 if (slot == null) { 096 slot = new TimeSlot(); 097 } 098 if (slot.isFull()) { 099 slot = slot.next(); 100 } 101 slot.assign(); 102 return slot; 103 } 104 105 /* 106 * A time slot is capable of handling a number of exchanges within a certain period of time. 107 */ 108 protected class TimeSlot { 109 110 private long capacity = Throttler.this.maximumRequestsPerPeriod; 111 private final long duration = Throttler.this.timePeriodMillis; 112 private final long startTime; 113 114 protected TimeSlot() { 115 this(System.currentTimeMillis()); 116 } 117 118 protected TimeSlot(long startTime) { 119 this.startTime = startTime; 120 } 121 122 protected void assign() { 123 capacity--; 124 } 125 126 /* 127 * Start the next time slot either now or in the future 128 * (no time slots are being created in the past) 129 */ 130 protected TimeSlot next() { 131 return new TimeSlot(Math.max(System.currentTimeMillis(), this.startTime + this.duration)); 132 } 133 134 protected boolean isActive() { 135 return startTime <= System.currentTimeMillis(); 136 } 137 138 protected boolean isFull() { 139 return capacity <= 0; 140 } 141 } 142 }