| /** |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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 org.apache.camel.processor; |
| |
| import java.util.concurrent.ScheduledExecutorService; |
| |
| import org.apache.camel.Exchange; |
| import org.apache.camel.Processor; |
| |
| /** |
| * A <a href="http://camel.apache.org/throttler.html">Throttler</a> |
| * will set a limit on the maximum number of message exchanges which can be sent |
| * to a processor within a specific time period. <p/> This pattern can be |
| * extremely useful if you have some external system which meters access; such |
| * as only allowing 100 requests per second; or if huge load can cause a |
| * particular system to malfunction or to reduce its throughput you might want |
| * to introduce some throttling. |
| * |
| * @version |
| */ |
| public class Throttler extends DelayProcessorSupport implements Traceable { |
| private long maximumRequestsPerPeriod; |
| private long timePeriodMillis; |
| private volatile TimeSlot slot; |
| |
| public Throttler(Processor processor, long maximumRequestsPerPeriod) { |
| this(processor, maximumRequestsPerPeriod, 1000, null); |
| } |
| |
| public Throttler(Processor processor, long maximumRequestsPerPeriod, long timePeriodMillis, ScheduledExecutorService executorService) { |
| super(processor, executorService); |
| this.maximumRequestsPerPeriod = maximumRequestsPerPeriod; |
| this.timePeriodMillis = timePeriodMillis; |
| } |
| |
| @Override |
| public String toString() { |
| return "Throttler[requests: " + maximumRequestsPerPeriod + " per: " + timePeriodMillis + " (ms) to: " |
| + getProcessor() + "]"; |
| } |
| |
| public String getTraceLabel() { |
| return "throttle[" + maximumRequestsPerPeriod + " per: " + timePeriodMillis + "]"; |
| } |
| |
| // Properties |
| // ----------------------------------------------------------------------- |
| public long getMaximumRequestsPerPeriod() { |
| return maximumRequestsPerPeriod; |
| } |
| |
| /** |
| * Sets the maximum number of requests per time period |
| */ |
| public void setMaximumRequestsPerPeriod(long maximumRequestsPerPeriod) { |
| this.maximumRequestsPerPeriod = maximumRequestsPerPeriod; |
| } |
| |
| public long getTimePeriodMillis() { |
| return timePeriodMillis; |
| } |
| |
| /** |
| * Sets the time period during which the maximum number of requests apply |
| */ |
| public void setTimePeriodMillis(long timePeriodMillis) { |
| this.timePeriodMillis = timePeriodMillis; |
| } |
| |
| // Implementation methods |
| // ----------------------------------------------------------------------- |
| |
| protected long calculateDelay(Exchange exchange) { |
| TimeSlot slot = nextSlot(); |
| if (!slot.isActive()) { |
| long delay = slot.startTime - currentSystemTime(); |
| return delay; |
| } else { |
| return 0; |
| } |
| } |
| |
| /* |
| * Determine what the next available time slot is for handling an Exchange |
| */ |
| protected synchronized TimeSlot nextSlot() { |
| if (slot == null) { |
| slot = new TimeSlot(); |
| } |
| if (slot.isFull()) { |
| slot = slot.next(); |
| } |
| slot.assign(); |
| return slot; |
| } |
| |
| /* |
| * A time slot is capable of handling a number of exchanges within a certain period of time. |
| */ |
| protected class TimeSlot { |
| |
| private volatile long capacity = Throttler.this.maximumRequestsPerPeriod; |
| private final long duration = Throttler.this.timePeriodMillis; |
| private final long startTime; |
| |
| protected TimeSlot() { |
| this(System.currentTimeMillis()); |
| } |
| |
| protected TimeSlot(long startTime) { |
| this.startTime = startTime; |
| } |
| |
| protected void assign() { |
| capacity--; |
| } |
| |
| /* |
| * Start the next time slot either now or in the future |
| * (no time slots are being created in the past) |
| */ |
| protected TimeSlot next() { |
| return new TimeSlot(Math.max(System.currentTimeMillis(), this.startTime + this.duration)); |
| } |
| |
| protected boolean isActive() { |
| return startTime <= System.currentTimeMillis(); |
| } |
| |
| protected boolean isFull() { |
| return capacity <= 0; |
| } |
| } |
| } |