com.microsoft.azure.servicebus.Timer Maven / Gradle / Ivy

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/*
 * Copyright (c) Microsoft. All rights reserved.
 * Licensed under the MIT license. See LICENSE file in the project root for full license information.
 */
package com.microsoft.azure.servicebus;

import java.time.Duration;
import java.util.HashSet;
import java.util.Locale;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * An abstraction for a Scheduler functionality - which can later be replaced by a light-weight Thread
 */
final class Timer
{
	private static ScheduledThreadPoolExecutor executor = null;

	private static final Logger TRACE_LOGGER = Logger.getLogger(ClientConstants.SERVICEBUS_CLIENT_TRACE);
	private static final HashSet references = new HashSet();
	private static final Object syncReferences = new Object();

	private Timer() 
	{
	}

	/**
	 * @param runFrequency implemented only for TimeUnit granularity - Seconds
	 */
	public static ScheduledFuture schedule(Runnable runnable, Duration runFrequency, TimerType timerType)
	{
		switch (timerType)
		{
		case OneTimeRun:
			return executor.schedule(runnable, runFrequency.toMillis(), TimeUnit.MILLISECONDS);

		case RepeatRun:
			return executor.scheduleWithFixedDelay(runnable, runFrequency.toMillis(), runFrequency.toMillis(), TimeUnit.MILLISECONDS);

		default:
			throw new UnsupportedOperationException("Unsupported timer pattern.");
		}
	}

	static void register(final String clientId)
	{
		synchronized (syncReferences)
		{
			if (references.size() == 0 && (executor == null || executor.isShutdown()))
			{
				final int corePoolSize = Math.max(Runtime.getRuntime().availableProcessors(), 4);
				if (TRACE_LOGGER.isLoggable(Level.FINE))
				{
					TRACE_LOGGER.log(Level.FINE, 
							String.format(Locale.US, "Starting ScheduledThreadPoolExecutor with coreThreadPoolSize: %s", corePoolSize));
				}

				executor = new ScheduledThreadPoolExecutor(corePoolSize);
			}

			references.add(clientId);
		}
	}

	static void unregister(final String clientId)
	{
		synchronized (syncReferences)
		{
			if (references.remove(clientId) && references.size() == 0 && executor != null)
			{
				if (TRACE_LOGGER.isLoggable(Level.FINE))
				{
					TRACE_LOGGER.log(Level.FINE, "Shuting down ScheduledThreadPoolExecutor.");
				}

				executor.shutdownNow();
			}
		}
	}
}