storm-core/src/jvm/org/apache/storm/windowing/CountTriggerPolicy.java

/**
 * 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.storm.windowing;

import java.util.concurrent.atomic.AtomicInteger;

/**
 * A trigger that tracks event counts and calls back {@link TriggerHandler#onTrigger()}
 * when the count threshold is hit.
 *
 * @param <T> the type of event tracked by this policy.
 */
public class CountTriggerPolicy<T> implements TriggerPolicy<T> {
    private final int count;
    private final AtomicInteger currentCount;
    private final TriggerHandler handler;
    private final EvictionPolicy<T> evictionPolicy;
    private boolean started;

    public CountTriggerPolicy(int count, TriggerHandler handler, EvictionPolicy<T> evictionPolicy) {
        this.count = count;
        this.currentCount = new AtomicInteger();
        this.handler = handler;
        this.evictionPolicy = evictionPolicy;
        this.started = false;
    }

    @Override
    public void track(Event<T> event) {
        if (started && !event.isWatermark()) {
            if (currentCount.incrementAndGet() >= count) {
                evictionPolicy.setContext(new DefaultEvictionContext(System.currentTimeMillis()));
                handler.onTrigger();
            }
        }
    }

    @Override
    public void reset() {
        currentCount.set(0);
    }

    @Override
    public void start() {
        started = true;
    }

    @Override
    public void shutdown() {
        // NOOP
    }

    @Override
    public String toString() {
        return "CountTriggerPolicy{" +
                "count=" + count +
                ", currentCount=" + currentCount +
                ", started=" + started +
                '}';
    }
}