/*
 * 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.cassandra.concurrent;

import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicInteger;

import com.google.common.annotations.VisibleForTesting;

import io.netty.util.concurrent.FastThreadLocal;
import io.netty.util.concurrent.FastThreadLocalThread;

This class is an implementation of the ThreadFactory interface. This
is useful to give Java threads meaningful names which is useful when using
a tool like JConsole.
/**
 * This class is an implementation of the <i>ThreadFactory</i> interface. This
 * is useful to give Java threads meaningful names which is useful when using
 * a tool like JConsole.
 */

public class NamedThreadFactory implements ThreadFactory
{
    private static volatile String globalPrefix;
    public static void setGlobalPrefix(String prefix) { globalPrefix = prefix; }

    public final String id;
    private final int priority;
    private final ClassLoader contextClassLoader;
    private final ThreadGroup threadGroup;
    protected final AtomicInteger n = new AtomicInteger(1);

    public NamedThreadFactory(String id)
    {
        this(id, Thread.NORM_PRIORITY);
    }

    public NamedThreadFactory(String id, int priority)
    {
        this(id, priority, null, null);
    }

    public NamedThreadFactory(String id, int priority, ClassLoader contextClassLoader, ThreadGroup threadGroup)
    {
        this.id = id;
        this.priority = priority;
        this.contextClassLoader = contextClassLoader;
        this.threadGroup = threadGroup;
    }

    public Thread newThread(Runnable runnable)
    {
        String name = id + ':' + n.getAndIncrement();
        Thread thread = createThread(threadGroup, runnable, name, true);
        thread.setPriority(priority);
        if (contextClassLoader != null)
            thread.setContextClassLoader(contextClassLoader);
        return thread;
    }

    
Ensures that FastThreadLocal.remove() is called when the Runnable.run() method of the given Runnable instance completes to ensure cleanup of FastThreadLocal instances. This is especially important for direct byte buffers allocated locally for a thread. /**
     * Ensures that {@link FastThreadLocal#remove() FastThreadLocal.remove()} is called when the {@link Runnable#run()}
     * method of the given {@link Runnable} instance completes to ensure cleanup of {@link FastThreadLocal} instances.
     * This is especially important for direct byte buffers allocated locally for a thread.
     */
    public static Runnable threadLocalDeallocator(Runnable r)
    {
        return () ->
        {
            try
            {
                r.run();
            }
            finally
            {
                FastThreadLocal.removeAll();
            }
        };
    }

    private static final AtomicInteger threadCounter = new AtomicInteger();

    @VisibleForTesting
    public static Thread createThread(Runnable runnable)
    {
        return createThread(null, runnable, "anonymous-" + threadCounter.incrementAndGet());
    }

    public static Thread createThread(Runnable runnable, String name)
    {
        return createThread(null, runnable, name);
    }

    public static Thread createThread(Runnable runnable, String name, boolean daemon)
    {
        return createThread(null, runnable, name, daemon);
    }

    public static Thread createThread(ThreadGroup threadGroup, Runnable runnable, String name)
    {
        return createThread(threadGroup, runnable, name, false);
    }

    public static Thread createThread(ThreadGroup threadGroup, Runnable runnable, String name, boolean daemon)
    {
        String prefix = globalPrefix;
        Thread thread = new FastThreadLocalThread(threadGroup, threadLocalDeallocator(runnable), prefix != null ? prefix + name : name);
        thread.setDaemon(daemon);
        return thread;
    }
}