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This nifi-utils module should be a general purpose place to store widely and generally useful functions that any component might want to leverage. NO DEPENDENCIES should be added. This module is likely to be leveraged by every extension and should not bring along any other dependencies. The only dependency intended is the nifi-api and even this is expected to be already provided in any case where it would be used. The typical place this util would be found is within a nar and all nars already have nifi-api as a parent dependency. The nifi-api can be thought of as a NiFi Application Container level dependency.

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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
 *
 *     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.nifi.util.concurrency;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class DebugEnabledTimedLock implements DebuggableTimedLock {

    private final Lock lock;
    private final Logger logger;
    private long lockTime = 0L;

    private final Map lockIterations = new HashMap<>();
    private final Map lockNanos = new HashMap<>();

    private final String name;
    private final int iterationFrequency;

    public DebugEnabledTimedLock(final Lock lock, final String name, final int iterationFrequency) {
        this.lock = lock;
        this.name = name;
        this.iterationFrequency = iterationFrequency;
        logger = LoggerFactory.getLogger(TimedLock.class.getName() + "." + name);
    }

    /**
     * @return true if lock obtained; false otherwise
     */
    @Override
    public boolean tryLock() {
        logger.trace("Trying to obtain Lock: {}", name);
        final boolean success = lock.tryLock();
        if (!success) {
            logger.trace("TryLock failed for Lock: {}", name);
            return false;
        }
        logger.trace("TryLock successful");

        return true;
    }

    /**
     * @param timeout duration to wait for lock
     * @param timeUnit unit to understand given duration
     * @return true if lock obtained in time; false otherwise
     */
    @Override
    public boolean tryLock(final long timeout, final TimeUnit timeUnit) {
        logger.trace("Trying to obtain Lock {} with a timeout of {} {}", name, timeout, timeUnit);
        final boolean success;
        try {
            success = lock.tryLock(timeout, timeUnit);
        } catch (final InterruptedException ie) {
            return false;
        }

        if (!success) {
            logger.trace("TryLock failed for Lock {} with a timeout of {} {}", name, timeout, timeUnit);
            return false;
        }
        logger.trace("TryLock successful");
        return true;
    }

    @Override
    public void lock() {
        logger.trace("Obtaining Lock {}", name);
        lock.lock();
        lockTime = System.nanoTime();
        logger.trace("Obtained Lock {}", name);
    }

    /**
     * @param task to release the lock for
     */
    @Override
    public void unlock(final String task) {
        if (lockTime <= 0L) {
            lock.unlock();
            return;
        }

        logger.trace("Releasing Lock {}", name);
        final long nanosLocked = System.nanoTime() - lockTime;

        Long startIterations = lockIterations.get(task);
        if (startIterations == null) {
            startIterations = 0L;
        }
        final long iterations = startIterations + 1L;
        lockIterations.put(task, iterations);

        Long startNanos = lockNanos.get(task);
        if (startNanos == null) {
            startNanos = 0L;
        }
        final long totalNanos = startNanos + nanosLocked;
        lockNanos.put(task, totalNanos);

        lockTime = -1L;

        lock.unlock();
        logger.trace("Released Lock {}", name);

        if (iterations % iterationFrequency == 0) {
            logger.debug("Lock {} held for {} nanos for task: {}; total lock iterations: {}; total lock nanos: {}", name, nanosLocked, task, iterations, totalNanos);
        }
    }

}