Merge "Adjust AsyncTask.THREAD_POOL_EXECUTOR config"

import android.annotation.WorkerThread;

import java.util.ArrayDeque;

import java.util.concurrent.BlockingQueue;

import java.util.concurrent.Callable;

import java.util.concurrent.CancellationException;

import java.util.concurrent.ExecutionException;

import java.util.concurrent.Executor;

import java.util.concurrent.FutureTask;

import java.util.concurrent.LinkedBlockingQueue;

import java.util.concurrent.RejectedExecutionHandler;

import java.util.concurrent.SynchronousQueue;

import java.util.concurrent.ThreadFactory;

import java.util.concurrent.ThreadPoolExecutor;

import java.util.concurrent.TimeUnit;

public abstract class AsyncTask<Params, Progress, Result> {

    private static final String LOG_TAG = "AsyncTask";

    private static final int CPU_COUNT = Runtime.getRuntime().availableProcessors();

    // We want at least 2 threads and at most 4 threads in the core pool,

    // preferring to have 1 less than the CPU count to avoid saturating

    // the CPU with background work

    private static final int CORE_POOL_SIZE = Math.max(2, Math.min(CPU_COUNT - 1, 4));

    private static final int MAXIMUM_POOL_SIZE = CPU_COUNT * 2 + 1;

    private static final int KEEP_ALIVE_SECONDS = 30;

    // We keep only a single pool thread around all the time.

    // We let the pool grow to a fairly large number of threads if necessary,

    // but let them time out quickly. In the unlikely case that we run out of threads,

    // we fall back to a simple unbounded-queue executor.

    // This combination ensures that:

    // 1. We normally keep few threads (1) around.

    // 2. We queue only after launching a significantly larger, but still bounded, set of threads.

    // 3. We keep the total number of threads bounded, but still allow an unbounded set

    //    of tasks to be queued.

    private static final int CORE_POOL_SIZE = 1;

    private static final int MAXIMUM_POOL_SIZE = 20;

    private static final int BACKUP_POOL_SIZE = 5;

    private static final int KEEP_ALIVE_SECONDS = 3;

    private static final ThreadFactory sThreadFactory = new ThreadFactory() {

        private final AtomicInteger mCount = new AtomicInteger(1);

        }

    };

    private static final BlockingQueue<Runnable> sPoolWorkQueue =

            new LinkedBlockingQueue<Runnable>(128);

    // Used only for rejected executions.

    // Initialization protected by sRunOnSerialPolicy lock.

    private static ThreadPoolExecutor sBackupExecutor;

    private static LinkedBlockingQueue<Runnable> sBackupExecutorQueue;

    private static final RejectedExecutionHandler sRunOnSerialPolicy =

            new RejectedExecutionHandler() {

        public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {

            android.util.Log.w(LOG_TAG, "Exceeded ThreadPoolExecutor pool size");

            // As a last ditch fallback, run it on an executor with an unbounded queue.

            // Create this executor lazily, hopefully almost never.

            synchronized (this) {

                if (sBackupExecutor == null) {

                    sBackupExecutorQueue = new LinkedBlockingQueue<Runnable>();

                    sBackupExecutor = new ThreadPoolExecutor(

                            BACKUP_POOL_SIZE, BACKUP_POOL_SIZE, KEEP_ALIVE_SECONDS,

                            TimeUnit.SECONDS, sBackupExecutorQueue, sThreadFactory);

                    sBackupExecutor.allowCoreThreadTimeOut(true);

                }

            }

            sBackupExecutor.execute(r);

        }

    };

    /**

     * An {@link Executor} that can be used to execute tasks in parallel.

    static {

        ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(

                CORE_POOL_SIZE, MAXIMUM_POOL_SIZE, KEEP_ALIVE_SECONDS, TimeUnit.SECONDS,

                sPoolWorkQueue, sThreadFactory);

        threadPoolExecutor.allowCoreThreadTimeOut(true);

                new SynchronousQueue<Runnable>(), sThreadFactory);

        threadPoolExecutor.setRejectedExecutionHandler(sRunOnSerialPolicy);

        THREAD_POOL_EXECUTOR = threadPoolExecutor;

    }