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/*******************************************************************************
* ============LICENSE_START==================================================
* * org.onap.dmaap
* * ===========================================================================
* * Copyright © 2017 AT&T Intellectual Property. 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
* *
* * 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.
* * ============LICENSE_END====================================================
* *
* * ECOMP is a trademark and service mark of AT&T Intellectual Property.
* *
******************************************************************************/
package org.onap.dmaap.datarouter.node;
import java.util.*;
/**
* Execute an operation no more frequently than a specified interval
*/
public abstract class RateLimitedOperation implements Runnable {
private boolean marked; // a timer task exists
private boolean executing; // the operation is currently in progress
private boolean remark; // a request was made while the operation was in progress
private Timer timer;
private long last; // when the last operation started
private long mininterval;
/**
* Create a rate limited operation
* @param mininterval The minimum number of milliseconds after the last execution starts before a new execution can begin
* @param timer The timer used to perform deferred executions
*/
public RateLimitedOperation(long mininterval, Timer timer) {
this.timer = timer;
this.mininterval = mininterval;
}
private class deferred extends TimerTask {
public void run() {
execute();
}
}
private synchronized void unmark() {
marked = false;
}
private void execute() {
unmark();
request();
}
/**
* Request that the operation be performed by this thread or at a later time by the timer
*/
public void request() {
if (premark()) {
return;
}
do {
run();
} while (demark());
}
private synchronized boolean premark() {
if (executing) {
// currently executing - wait until it finishes
remark = true;
return(true);
}
if (marked) {
// timer currently running - will run when it expires
return(true);
}
long now = System.currentTimeMillis();
if (last + mininterval > now) {
// too soon - schedule a timer
marked = true;
timer.schedule(new deferred(), last + mininterval - now);
return(true);
}
last = now;
executing = true;
// start execution
return(false);
}
private synchronized boolean demark() {
executing = false;
if (remark) {
remark = false;
return(!premark());
}
return(false);
}
}
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