chen.guo.X.storm.example.tools.NthLastModifiedTimeTracker.java Source code

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Here is the source code for chen.guo.X.storm.example.tools.NthLastModifiedTimeTracker.java

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/**
 * 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
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * 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 chen.guo.X.storm.example.tools;

import org.apache.commons.collections.buffer.CircularFifoBuffer;
import org.apache.storm.utils.Time;

/**
 * This class tracks the last ${numTimesToTrack} modifications in a rolling fashion.
 */
public class NthLastModifiedTimeTracker {

    private static final int MILLIS_IN_SEC = 1000;

    /**
     * CircularFifoBuffer of length(3) behavior:
     * add(1) => 1
     * add(2) => 1,2
     * add(3) => 1,2,3
     * add(4) => 2,3,4
     * get()  => 2,3,4
     * remove() => 3,4
     * add(5) => 3,4,5
     */
    private final CircularFifoBuffer lastModifiedTimesMillis;

    public NthLastModifiedTimeTracker(int numTimesToTrack) {
        if (numTimesToTrack < 1) {
            throw new IllegalArgumentException(
                    "numTimesToTrack must be greater than zero (you requested " + numTimesToTrack + ")");
        }
        lastModifiedTimesMillis = new CircularFifoBuffer(numTimesToTrack);
        long nowCached = Time.currentTimeMillis();
        for (int i = 0; i < lastModifiedTimesMillis.maxSize(); i++) {
            lastModifiedTimesMillis.add(nowCached);
        }
    }

    public int secondsSinceOldestModification() {
        long modifiedTimeMillis = (Long) lastModifiedTimesMillis.get();
        return (int) ((Time.currentTimeMillis() - modifiedTimeMillis) / MILLIS_IN_SEC);
    }

    public void markAsModified() {
        lastModifiedTimesMillis.add(Time.currentTimeMillis());
    }
}