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.handler; import org.apache.tinkerpop.gremlin.driver.Tokens; import org.apache.tinkerpop.gremlin.driver.message.RequestMessage; import org.apache.tinkerpop.gremlin.driver.message.ResponseMessage; import org.apache.tinkerpop.gremlin.driver.message.ResponseStatusCode; import org.apache.tinkerpop.gremlin.server.Settings; import io.netty.channel.ChannelHandler; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.ChannelOutboundHandlerAdapter; import io.netty.channel.ChannelPromise; import io.netty.util.ReferenceCountUtil; import io.netty.util.concurrent.EventExecutorGroup; import io.netty.util.concurrent.Future; import org.apache.commons.lang.time.StopWatch; import org.javatuples.Pair; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.util.ArrayList; import java.util.Iterator; import java.util.List; import java.util.concurrent.Callable; import java.util.concurrent.TimeoutException; /** * This handler helps in scenarios where iteration is not being already handled later in the Netty pipeline. It is * important that if this handler is used at all, that it not block, thus ensure that if {@link Iterator} instances * are passed to it, they do not contain large result sets or iterates over objects that require network calls. * * @author Stephen Mallette (http://stephen.genoprime.com) * @deprecated As of release 3.1.1-incubating, not directly replaced. */ @Deprecated @ChannelHandler.Sharable public class IteratorHandler extends ChannelOutboundHandlerAdapter { private static final Logger logger = LoggerFactory.getLogger(IteratorHandler.class); private final Settings settings; public IteratorHandler(final Settings settings) { this.settings = settings; } @Override public void write(final ChannelHandlerContext ctx, final Object msg, final ChannelPromise promise) throws Exception { if (msg instanceof Pair) { try { final Pair pair = (Pair) msg; final Iterator itty = (Iterator) pair.getValue1(); final RequestMessage requestMessage = (RequestMessage) pair.getValue0(); // the batch size can be overriden by the request final int resultIterationBatchSize = (Integer) requestMessage.optionalArgs(Tokens.ARGS_BATCH_SIZE) .orElse(settings.resultIterationBatchSize); // timer for the total serialization time final StopWatch stopWatch = new StopWatch(); final EventExecutorGroup executorService = ctx.executor(); final Future<?> iteration = executorService.submit((Callable<Void>) () -> { logger.debug("Preparing to iterate results from - {} - in thread [{}]", requestMessage, Thread.currentThread().getName()); stopWatch.start(); List<Object> aggregate = new ArrayList<>(resultIterationBatchSize); while (itty.hasNext()) { aggregate.add(itty.next()); // send back a page of results if batch size is met or if it's the end of the results being // iterated if (aggregate.size() == resultIterationBatchSize || !itty.hasNext()) { final ResponseStatusCode code = itty.hasNext() ? ResponseStatusCode.PARTIAL_CONTENT : ResponseStatusCode.SUCCESS; ctx.writeAndFlush( ResponseMessage.build(requestMessage).code(code).result(aggregate).create()); aggregate = new ArrayList<>(resultIterationBatchSize); } stopWatch.split(); if (stopWatch.getSplitTime() > settings.serializedResponseTimeout) throw new TimeoutException( "Serialization of the entire response exceeded the serializeResponseTimeout setting"); stopWatch.unsplit(); } return null; }); iteration.addListener(f -> { stopWatch.stop(); if (!f.isSuccess()) { final String errorMessage = String.format( "Response iteration and serialization exceeded the configured threshold for request [%s] - %s", msg, f.cause().getMessage()); logger.warn(errorMessage); ctx.writeAndFlush( ResponseMessage.build(requestMessage).code(ResponseStatusCode.SERVER_ERROR_TIMEOUT) .statusMessage(errorMessage).create()); } }); } finally { ReferenceCountUtil.release(msg); } } else { ctx.write(msg, promise); } } }