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/*
 *      Copyright (C) 2012-2015 DataStax Inc.
 *
 *   Licensed 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 com.datastax.driver.core;

import com.datastax.driver.$internal.com.google.common.util.concurrent.ThreadFactoryBuilder;
import io.netty.util.concurrent.DefaultThreadFactory;

import java.util.concurrent.*;

/**
 * A set of hooks that allow clients to customize the driver's internal executors.
 * 

* The methods in this class are invoked when the cluster initializes. To customize the behavior, extend the class and * override the appropriate methods. *

* This is mainly intended to allow customization and instrumentation of driver threads. Each method must return a * newly-allocated executor; don't use a shared executor, as this could introduce unintended consequences like deadlocks * (we're working to simplify the driver's architecture and reduce the number of executors in a future release). The * default implementations use unbounded queues, which is appropriate when the driver is properly configured; the only * reason you would want to use bounded queues is to limit memory consumption in case of a bug or bad configuration. In * that case, make sure to use a {@link RejectedExecutionHandler} that throws, such as * {@link java.util.concurrent.ThreadPoolExecutor.AbortPolicy}; a blocking handler could introduce deadlocks. *

* Netty uses a separate pool for I/O operations, that can be configured via {@link NettyOptions}. */ public class ThreadingOptions { // Kept for backward compatibility, but this should be customized via this class now private static final int NON_BLOCKING_EXECUTOR_SIZE = SystemProperties.getInt( "com.datastax.driver.NON_BLOCKING_EXECUTOR_SIZE", Runtime.getRuntime().availableProcessors()); private static final int DEFAULT_THREAD_KEEP_ALIVE_SECONDS = 30; /** * Builds a thread factory for the threads created by a given executor. *

* This is used by the default implementations in this class, and also internally to create the Netty I/O pool. * * @param clusterName the name of the cluster, as specified by * {@link com.datastax.driver.core.Cluster.Builder#withClusterName(String)}. * @param executorName a name that identifies the executor. * @return the thread factory. */ public ThreadFactory createThreadFactory(String clusterName, String executorName) { return new ThreadFactoryBuilder() .setNameFormat(clusterName + "-" + executorName + "-%d") // Back with Netty's thread factory in order to create FastThreadLocalThread instances. This allows // an optimization around ThreadLocals (we could use DefaultThreadFactory directly but it creates // slightly different thread names, so keep we keep a ThreadFactoryBuilder wrapper for backward // compatibility). .setThreadFactory(new DefaultThreadFactory("ignored name")) .build(); } /** * Builds the main internal executor, used for tasks such as scheduling speculative executions, triggering * registered {@link SchemaChangeListener}s, reacting to node state changes, and metadata updates. *

* The default implementation sets the pool size to the number of available cores. * * @param clusterName the name of the cluster, as specified by * {@link com.datastax.driver.core.Cluster.Builder#withClusterName(String)}. * @return the executor. */ public ExecutorService createExecutor(String clusterName) { ThreadPoolExecutor executor = new ThreadPoolExecutor( NON_BLOCKING_EXECUTOR_SIZE, NON_BLOCKING_EXECUTOR_SIZE, DEFAULT_THREAD_KEEP_ALIVE_SECONDS, TimeUnit.SECONDS, new LinkedBlockingQueue(), createThreadFactory(clusterName, "worker")); executor.allowCoreThreadTimeOut(true); return executor; } /** * Builds the executor used to block on new connections before they are added to a pool. *

* The default implementation uses 2 threads. * * @param clusterName the name of the cluster, as specified by * {@link com.datastax.driver.core.Cluster.Builder#withClusterName(String)}. * @return the executor. */ public ExecutorService createBlockingExecutor(String clusterName) { ThreadPoolExecutor executor = new ThreadPoolExecutor( 2, 2, DEFAULT_THREAD_KEEP_ALIVE_SECONDS, TimeUnit.SECONDS, new LinkedBlockingQueue(), createThreadFactory(clusterName, "blocking-task-worker")); executor.allowCoreThreadTimeOut(true); return executor; } /** * Builds the executor when reconnection attempts will be scheduled. *

* The default implementation uses 2 threads. * * @param clusterName the name of the cluster, as specified by * {@link com.datastax.driver.core.Cluster.Builder#withClusterName(String)}. * @return the executor. */ public ScheduledExecutorService createReconnectionExecutor(String clusterName) { return new ScheduledThreadPoolExecutor(2, createThreadFactory(clusterName, "reconnection")); } /** * Builds the executor to handle host state notifications from Cassandra. *

* This executor must have exactly one thread so that notifications are processed in order. * * @param clusterName the name of the cluster, as specified by * {@link com.datastax.driver.core.Cluster.Builder#withClusterName(String)}. * @return the executor. */ public ScheduledExecutorService createScheduledTasksExecutor(String clusterName) { return new ScheduledThreadPoolExecutor(1, createThreadFactory(clusterName, "scheduled-task-worker")); } /** * Builds the executor for an internal maintenance task used to clean up closed connections. *

* A single scheduled task runs on this executor, so there is no reason to use more than one thread. * * @param clusterName the name of the cluster, as specified by * {@link com.datastax.driver.core.Cluster.Builder#withClusterName(String)}. * @return the executor. */ public ScheduledExecutorService createReaperExecutor(String clusterName) { return new ScheduledThreadPoolExecutor(1, createThreadFactory(clusterName, "connection-reaper")); } }





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