1 files changed, 102 insertions, 0 deletions
diff --git a/datarouter-node/src/main/java/com/att/research/datarouter/node/RateLimitedOperation.java b/datarouter-node/src/main/java/com/att/research/datarouter/node/RateLimitedOperation.java
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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 com.att.research.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);
+	}
+}