Java tutorial
/* * 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.tinkerpop.gremlin.server; import io.netty.bootstrap.ServerBootstrap; import io.netty.buffer.PooledByteBufAllocator; import io.netty.channel.Channel; import io.netty.channel.ChannelFuture; import io.netty.channel.ChannelFutureListener; import io.netty.channel.ChannelOption; import io.netty.channel.EventLoopGroup; import io.netty.channel.epoll.EpollEventLoopGroup; import io.netty.channel.epoll.EpollServerSocketChannel; import io.netty.channel.nio.NioEventLoopGroup; import io.netty.channel.socket.nio.NioServerSocketChannel; import io.netty.util.concurrent.GenericFutureListener; import io.netty.util.internal.logging.InternalLoggerFactory; import io.netty.util.internal.logging.Slf4JLoggerFactory; import org.apache.commons.lang3.SystemUtils; import org.apache.tinkerpop.gremlin.server.op.OpLoader; import org.apache.tinkerpop.gremlin.server.util.LifeCycleHook; import org.apache.tinkerpop.gremlin.server.util.MetricManager; import org.apache.tinkerpop.gremlin.server.util.ServerGremlinExecutor; import org.apache.tinkerpop.gremlin.server.util.ThreadFactoryUtil; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.io.IOException; import java.lang.reflect.UndeclaredThrowableException; import java.util.concurrent.CompletableFuture; import java.util.concurrent.CountDownLatch; import java.util.concurrent.ExecutorService; import java.util.concurrent.ThreadFactory; import java.util.concurrent.TimeUnit; /** * Start and stop Gremlin Server. * * @author Stephen Mallette (http://stephen.genoprime.com) */ public class GremlinServer { static { // hook slf4j up to netty internal logging InternalLoggerFactory.setDefaultFactory(new Slf4JLoggerFactory()); } private static final String SERVER_THREAD_PREFIX = "gremlin-server-"; private static final Logger logger = LoggerFactory.getLogger(GremlinServer.class); private final Settings settings; private Channel ch; private CompletableFuture<Void> serverStopped = null; private CompletableFuture<ServerGremlinExecutor<EventLoopGroup>> serverStarted = null; private final EventLoopGroup bossGroup; private final EventLoopGroup workerGroup; private final ExecutorService gremlinExecutorService; private final ServerGremlinExecutor<EventLoopGroup> serverGremlinExecutor; private final boolean isEpollEnabled; /** * Construct a Gremlin Server instance from {@link Settings}. */ public GremlinServer(final Settings settings) { this.settings = settings; this.isEpollEnabled = settings.useEpollEventLoop && SystemUtils.IS_OS_LINUX; if (settings.useEpollEventLoop && !SystemUtils.IS_OS_LINUX) { logger.warn("cannot use epoll in non-linux env, falling back to NIO"); } Runtime.getRuntime() .addShutdownHook(new Thread(() -> this.stop().join(), SERVER_THREAD_PREFIX + "shutdown")); final ThreadFactory threadFactoryBoss = ThreadFactoryUtil.create("boss-%d"); // if linux os use epoll else fallback to nio based eventloop // epoll helps in reducing GC and has better performance // http://netty.io/wiki/native-transports.html if (isEpollEnabled) { bossGroup = new EpollEventLoopGroup(settings.threadPoolBoss, threadFactoryBoss); } else { bossGroup = new NioEventLoopGroup(settings.threadPoolBoss, threadFactoryBoss); } final ThreadFactory threadFactoryWorker = ThreadFactoryUtil.create("worker-%d"); if (isEpollEnabled) { workerGroup = new EpollEventLoopGroup(settings.threadPoolWorker, threadFactoryWorker); } else { workerGroup = new NioEventLoopGroup(settings.threadPoolWorker, threadFactoryWorker); } serverGremlinExecutor = new ServerGremlinExecutor<>(settings, null, workerGroup, EventLoopGroup.class); gremlinExecutorService = serverGremlinExecutor.getGremlinExecutorService(); // force an early load of the OpLoader (even if not used by a Channelizer). this is an expensive operation // as it uses ServiceLoader and if left uninitialized puts a burden on the first client request that passes // through an OpProcessor OpLoader.getProcessors(); } /** * Construct a Gremlin Server instance from the {@link ServerGremlinExecutor} which internally carries some * pre-constructed objects used by the server as well as the {@link Settings} object itself. This constructor * is useful when Gremlin Server is being used in an embedded style and there is a need to share thread pools * with the hosting application. * * @deprecated As of release 3.1.1-incubating, not replaced. * @see <a href="https://issues.apache.org/jira/browse/TINKERPOP-912">TINKERPOP-912</a> */ @Deprecated public GremlinServer(final ServerGremlinExecutor<EventLoopGroup> serverGremlinExecutor) { this.serverGremlinExecutor = serverGremlinExecutor; this.settings = serverGremlinExecutor.getSettings(); this.isEpollEnabled = settings.useEpollEventLoop && SystemUtils.IS_OS_LINUX; if (settings.useEpollEventLoop && !SystemUtils.IS_OS_LINUX) { logger.warn("cannot use epoll in non-linux env, falling back to NIO"); } Runtime.getRuntime() .addShutdownHook(new Thread(() -> this.stop().join(), SERVER_THREAD_PREFIX + "shutdown")); final ThreadFactory threadFactoryBoss = ThreadFactoryUtil.create("boss-%d"); if (isEpollEnabled) { bossGroup = new EpollEventLoopGroup(settings.threadPoolBoss, threadFactoryBoss); } else { bossGroup = new NioEventLoopGroup(settings.threadPoolBoss, threadFactoryBoss); } workerGroup = serverGremlinExecutor.getScheduledExecutorService(); gremlinExecutorService = serverGremlinExecutor.getGremlinExecutorService(); } /** * Start Gremlin Server with {@link Settings} provided to the constructor. */ public synchronized CompletableFuture<ServerGremlinExecutor<EventLoopGroup>> start() throws Exception { if (serverStarted != null) { // server already started - don't get it rolling again return serverStarted; } serverStarted = new CompletableFuture<>(); final CompletableFuture<ServerGremlinExecutor<EventLoopGroup>> serverReadyFuture = serverStarted; try { final ServerBootstrap b = new ServerBootstrap(); // when high value is reached then the channel becomes non-writable and stays like that until the // low value is so that there is time to recover b.childOption(ChannelOption.WRITE_BUFFER_LOW_WATER_MARK, settings.writeBufferLowWaterMark); b.childOption(ChannelOption.WRITE_BUFFER_HIGH_WATER_MARK, settings.writeBufferHighWaterMark); b.childOption(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT); // fire off any lifecycle scripts that were provided by the user. hooks get initialized during // ServerGremlinExecutor initialization serverGremlinExecutor.getHooks().forEach(hook -> { logger.info("Executing start up {}", LifeCycleHook.class.getSimpleName()); try { hook.onStartUp(new LifeCycleHook.Context(logger)); } catch (UnsupportedOperationException uoe) { // if the user doesn't implement onStartUp the scriptengine will throw // this exception. it can safely be ignored. } }); final Channelizer channelizer = createChannelizer(settings); channelizer.init(serverGremlinExecutor); b.group(bossGroup, workerGroup).childHandler(channelizer); if (isEpollEnabled) { b.channel(EpollServerSocketChannel.class); } else { b.channel(NioServerSocketChannel.class); } // bind to host/port and wait for channel to be ready b.bind(settings.host, settings.port).addListener(new ChannelFutureListener() { @Override public void operationComplete(final ChannelFuture channelFuture) throws Exception { if (channelFuture.isSuccess()) { ch = channelFuture.channel(); logger.info( "Gremlin Server configured with worker thread pool of {}, gremlin pool of {} and boss thread pool of {}.", settings.threadPoolWorker, settings.gremlinPool, settings.threadPoolBoss); logger.info("Channel started at port {}.", settings.port); serverReadyFuture.complete(serverGremlinExecutor); } else { serverReadyFuture.completeExceptionally(new IOException(String.format( "Could not bind to %s and %s - perhaps something else is bound to that address.", settings.host, settings.port))); } } }); } catch (Exception ex) { logger.error("Gremlin Server Error", ex); serverReadyFuture.completeExceptionally(ex); } return serverStarted; } private static Channelizer createChannelizer(final Settings settings) throws Exception { try { final Class clazz = Class.forName(settings.channelizer); final Object o = clazz.newInstance(); return (Channelizer) o; } catch (ClassNotFoundException fnfe) { logger.error("Could not find {} implementation defined by the 'channelizer' setting as: {}", Channelizer.class.getName(), settings.channelizer); throw new RuntimeException(fnfe); } catch (Exception ex) { logger.error( "Class defined by the 'channelizer' setting as: {} could not be properly instantiated as a {}", settings.channelizer, Channelizer.class.getName()); throw new RuntimeException(ex); } } /** * Stop Gremlin Server and free the port binding. Note that multiple calls to this method will return the * same instance of the {@link java.util.concurrent.CompletableFuture}. */ public synchronized CompletableFuture<Void> stop() { if (serverStopped != null) { // shutdown has started so don't fire it off again return serverStopped; } serverStopped = new CompletableFuture<>(); final CountDownLatch servicesLeftToShutdown = new CountDownLatch(3); // release resources in the OpProcessors (e.g. kill sessions) OpLoader.getProcessors().entrySet().forEach(kv -> { logger.info("Shutting down OpProcessor[{}]", kv.getKey()); try { kv.getValue().close(); } catch (Exception ex) { logger.warn( "Shutdown will continue but, there was an error encountered while closing " + kv.getKey(), ex); } }); // it's possible that a channel might not be initialized in the first place if bind() fails because // of port conflict. in that case, there's no need to wait for the channel to close. if (null == ch) servicesLeftToShutdown.countDown(); else ch.close().addListener(f -> servicesLeftToShutdown.countDown()); logger.info("Shutting down thread pools."); try { gremlinExecutorService.shutdown(); } finally { logger.debug("Shutdown Gremlin thread pool."); } try { workerGroup.shutdownGracefully() .addListener((GenericFutureListener) f -> servicesLeftToShutdown.countDown()); } finally { logger.debug("Shutdown Worker thread pool."); } try { bossGroup.shutdownGracefully() .addListener((GenericFutureListener) f -> servicesLeftToShutdown.countDown()); } finally { logger.debug("Shutdown Boss thread pool."); } // channel is shutdown as are the thread pools - time to kill graphs as nothing else should be acting on them new Thread(() -> { serverGremlinExecutor.getHooks().forEach(hook -> { logger.info("Executing shutdown {}", LifeCycleHook.class.getSimpleName()); try { hook.onShutDown(new LifeCycleHook.Context(logger)); } catch (UnsupportedOperationException | UndeclaredThrowableException uoe) { // if the user doesn't implement onShutDown the scriptengine will throw // this exception. it can safely be ignored. } }); try { gremlinExecutorService.awaitTermination(30000, TimeUnit.MILLISECONDS); } catch (InterruptedException ie) { logger.warn( "Timeout waiting for Gremlin thread pool to shutdown - continuing with shutdown process."); } try { servicesLeftToShutdown.await(30000, TimeUnit.MILLISECONDS); } catch (InterruptedException ie) { logger.warn( "Timeout waiting for boss/worker thread pools to shutdown - continuing with shutdown process."); } serverGremlinExecutor.getGraphManager().getGraphs().forEach((k, v) -> { logger.debug("Closing Graph instance [{}]", k); try { v.close(); } catch (Exception ex) { logger.warn(String.format("Exception while closing Graph instance [%s]", k), ex); } finally { logger.info("Closed Graph instance [{}]", k); } }); logger.info("Gremlin Server - shutdown complete"); serverStopped.complete(null); }, SERVER_THREAD_PREFIX + "stop").start(); return serverStopped; } public ServerGremlinExecutor<EventLoopGroup> getServerGremlinExecutor() { return serverGremlinExecutor; } public static void main(final String[] args) throws Exception { // add to vm options: -Dlog4j.configuration=file:conf/log4j.properties printHeader(); final String file; if (args.length > 0) file = args[0]; else file = "conf/gremlin-server.yaml"; final Settings settings; try { settings = Settings.read(file); } catch (Exception ex) { logger.error("Configuration file at {} could not be found or parsed properly. [{}]", file, ex.getMessage()); return; } logger.info("Configuring Gremlin Server from {}", file); settings.optionalMetrics().ifPresent(GremlinServer::configureMetrics); final GremlinServer server = new GremlinServer(settings); server.start().exceptionally(t -> { logger.error("Gremlin Server was unable to start and will now begin shutdown: {}", t.getMessage()); server.stop().join(); return null; }).join(); } public static String getHeader() { final StringBuilder builder = new StringBuilder(); builder.append("\r\n"); builder.append(" \\,,,/\r\n"); builder.append(" (o o)\r\n"); builder.append("-----oOOo-(3)-oOOo-----\r\n"); return builder.toString(); } private static void configureMetrics(final Settings.ServerMetrics settings) { final MetricManager metrics = MetricManager.INSTANCE; settings.optionalConsoleReporter().ifPresent(config -> { if (config.enabled) metrics.addConsoleReporter(config.interval); }); settings.optionalCsvReporter().ifPresent(config -> { if (config.enabled) metrics.addCsvReporter(config.interval, config.fileName); }); settings.optionalJmxReporter().ifPresent(config -> { if (config.enabled) metrics.addJmxReporter(config.domain, config.agentId); }); settings.optionalSlf4jReporter().ifPresent(config -> { if (config.enabled) metrics.addSlf4jReporter(config.interval, config.loggerName); }); settings.optionalGangliaReporter().ifPresent(config -> { if (config.enabled) { try { metrics.addGangliaReporter(config.host, config.port, config.optionalAddressingMode(), config.ttl, config.protocol31, config.hostUUID, config.spoof, config.interval); } catch (IOException ioe) { logger.warn("Error configuring the Ganglia Reporter.", ioe); } } }); settings.optionalGraphiteReporter().ifPresent(config -> { if (config.enabled) metrics.addGraphiteReporter(config.host, config.port, config.prefix, config.interval); }); } private static void printHeader() { logger.info(getHeader()); } }