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 java.util.concurrent.TimeUnit;
020
021 import org.apache.camel.Exchange;
022 import org.apache.camel.Processor;
023 import org.apache.commons.logging.Log;
024 import org.apache.commons.logging.LogFactory;
025
026 /**
027 * A <code>SamplingThrottler</code> is a special kind of throttler. It also
028 * limits the number of exchanges sent to a downstream endpoint. It differs from
029 * a normal throttler in that it will not queue exchanges above the threshold
030 * for a given period. Instead these exchanges will be stopped, precluding them
031 * from being processed at all by downstream consumers.
032 * <p/>
033 * This kind of throttling can be useful for taking a sample from
034 * an exchange stream, rough consolidation of noisy and bursty exchange traffic
035 * or where queuing of throttled exchanges is undesirable.
036 *
037 * @version $Revision: 885283 $
038 */
039 public class SamplingThrottler extends DelegateProcessor {
040 protected final transient Log log = LogFactory.getLog(getClass());
041 private long samplePeriod;
042 private long periodInNanos;
043 private TimeUnit units;
044 private long timeOfLastExchange;
045 private StopProcessor stopper = new StopProcessor();
046 private Object calculationLock = new Object();
047 private SampleStats sampled = new SampleStats();
048
049 public SamplingThrottler(Processor processor, long samplePeriod, TimeUnit units) {
050 super(processor);
051
052 if (samplePeriod <= 0) {
053 throw new IllegalArgumentException("A positive value is required for the sampling period");
054 }
055 if (units == null) {
056 throw new IllegalArgumentException("A invalid null value was supplied for the units of the sampling period");
057 }
058 this.samplePeriod = samplePeriod;
059 this.units = units;
060 periodInNanos = units.toNanos(samplePeriod);
061 }
062
063 @Override
064 public String toString() {
065 return "SamplingThrottler[1 exchange per: " + samplePeriod + " " + units.toString().toLowerCase() + " -> " + getProcessor() + "]";
066 }
067
068 public String getTraceLabel() {
069 return "samplingThrottler[1 exchange per: " + samplePeriod + " " + units.toString().toLowerCase() + "]";
070 }
071
072 public void process(Exchange exchange) throws Exception {
073 boolean doSend = false;
074
075 synchronized (calculationLock) {
076 long now = System.nanoTime();
077 if (now >= timeOfLastExchange + periodInNanos) {
078 doSend = true;
079 if (log.isTraceEnabled()) {
080 log.trace(sampled.sample());
081 }
082 timeOfLastExchange = now;
083 } else {
084 if (log.isTraceEnabled()) {
085 log.trace(sampled.drop());
086 }
087 }
088 }
089
090 if (doSend) {
091 super.process(exchange);
092 } else {
093 stopper.process(exchange);
094 }
095 }
096
097 private static class SampleStats {
098 private long droppedThisPeriod;
099 private long totalDropped;
100 private long totalSampled;
101 private long totalThisPeriod;
102
103 String drop() {
104 droppedThisPeriod++;
105 totalThisPeriod++;
106 totalDropped++;
107 return getDroppedLog();
108 }
109
110 String sample() {
111 totalThisPeriod = 1; // a new period, reset to 1
112 totalSampled++;
113 droppedThisPeriod = 0;
114 return getSampledLog();
115 }
116
117 String getSampledLog() {
118 return String.format("Sampled %d of %d total exchanges", totalSampled, totalSampled + totalDropped);
119 }
120
121 String getDroppedLog() {
122 return String.format("Dropped %d of %d exchanges in this period, totalling %d dropped of %d exchanges overall.",
123 droppedThisPeriod, totalThisPeriod, totalDropped, totalSampled + totalDropped);
124 }
125 }
126
127 }