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.storm.kafka.trident; import org.apache.storm.task.OutputCollector; import org.apache.storm.topology.FailedException; import org.apache.commons.lang.Validate; import org.apache.kafka.clients.producer.KafkaProducer; import org.apache.kafka.clients.producer.ProducerRecord; import org.apache.kafka.clients.producer.RecordMetadata; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.apache.storm.kafka.trident.mapper.TridentTupleToKafkaMapper; import org.apache.storm.kafka.trident.selector.KafkaTopicSelector; import org.apache.storm.trident.operation.TridentCollector; import org.apache.storm.trident.state.State; import org.apache.storm.trident.tuple.TridentTuple; import java.util.ArrayList; import java.util.List; import java.util.Properties; import java.util.concurrent.ExecutionException; import java.util.concurrent.Future; public class TridentKafkaState implements State { private static final Logger LOG = LoggerFactory.getLogger(TridentKafkaState.class); private KafkaProducer producer; private OutputCollector collector; private TridentTupleToKafkaMapper mapper; private KafkaTopicSelector topicSelector; public TridentKafkaState withTridentTupleToKafkaMapper(TridentTupleToKafkaMapper mapper) { this.mapper = mapper; return this; } public TridentKafkaState withKafkaTopicSelector(KafkaTopicSelector selector) { this.topicSelector = selector; return this; } @Override public void beginCommit(Long txid) { LOG.debug("beginCommit is Noop."); } @Override public void commit(Long txid) { LOG.debug("commit is Noop."); } public void prepare(Properties options) { Validate.notNull(mapper, "mapper can not be null"); Validate.notNull(topicSelector, "topicSelector can not be null"); producer = new KafkaProducer(options); } public void updateState(List<TridentTuple> tuples, TridentCollector collector) { String topic = null; try { List<Future<RecordMetadata>> futures = new ArrayList<>(tuples.size()); for (TridentTuple tuple : tuples) { topic = topicSelector.getTopic(tuple); if (topic != null) { Future<RecordMetadata> result = producer.send(new ProducerRecord(topic, mapper.getKeyFromTuple(tuple), mapper.getMessageFromTuple(tuple))); futures.add(result); } else { LOG.warn("skipping key = " + mapper.getKeyFromTuple(tuple) + ", topic selector returned null."); } } List<ExecutionException> exceptions = new ArrayList<>(futures.size()); for (Future<RecordMetadata> future : futures) { try { future.get(); } catch (ExecutionException e) { exceptions.add(e); } } if (exceptions.size() > 0) { String errorMsg = "Could not retrieve result for messages " + tuples + " from topic = " + topic + " because of the following exceptions: \n"; for (ExecutionException exception : exceptions) { errorMsg = errorMsg + exception.getMessage() + "\n"; } LOG.error(errorMsg); throw new FailedException(errorMsg); } } catch (Exception ex) { String errorMsg = "Could not send messages " + tuples + " to topic = " + topic; LOG.warn(errorMsg, ex); throw new FailedException(errorMsg, ex); } } }