extras/rya.pcj.fluo/pcj.fluo.app/src/main/java/org/apache/rya/indexing/pcj/fluo/app/export/kafka/KafkaBindingSetExporter.java

/*
 * 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.rya.indexing.pcj.fluo.app.export.kafka;

import static com.google.common.base.Preconditions.checkNotNull;

import java.util.Set;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;

import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.clients.producer.RecordMetadata;
import org.apache.rya.api.client.CreatePCJ.ExportStrategy;
import org.apache.rya.api.client.CreatePCJ.QueryType;
import org.apache.rya.api.log.LogUtils;
import org.apache.rya.api.model.VisibilityBindingSet;
import org.apache.rya.indexing.pcj.fluo.app.export.IncrementalBindingSetExporter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.collect.Sets;

/**
 * Incrementally exports SPARQL query results to Kafka topics.
 */
public class KafkaBindingSetExporter implements IncrementalBindingSetExporter {

    private static final Logger log = LoggerFactory.getLogger(KafkaBindingSetExporter.class);
    private final KafkaProducer<String, VisibilityBindingSet> producer;


    /**
     * Constructs an instance given a Kafka producer.
     *
     * @param producer for sending result set alerts to a broker. (not null) Can be created and configured by
     *            {@link KafkaBindingSetExporterFactory}
     */
    public KafkaBindingSetExporter(final KafkaProducer<String, VisibilityBindingSet> producer) {
        super();
        checkNotNull(producer, "Producer is required.");
        this.producer = producer;
    }

    /**
     * Send the results to the topic using the queryID as the topicname
     */
    @Override
    public void export(final String queryId, final VisibilityBindingSet result) throws ResultExportException {
        checkNotNull(queryId);
        checkNotNull(result);
        try {
            // Send the result to the topic whose name matches the PCJ ID.
            final ProducerRecord<String, VisibilityBindingSet> rec = new ProducerRecord<>(queryId, result);
            final Future<RecordMetadata> future = producer.send(rec);

            // Don't let the export return until the result has been written to the topic. Otherwise we may lose results.
            future.get();
            if(log.isDebugEnabled()) {
                log.debug("Producer successfully sent record with queryId: {} and visbilityBindingSet: \n{}", LogUtils.clean(queryId), LogUtils.clean(result.toString()));
            }
        } catch (final Throwable e) {
            throw new ResultExportException("A result could not be exported to Kafka.", e);
        }
    }

    @Override
    public void close() throws Exception {
        producer.close(5, TimeUnit.SECONDS);
    }

    @Override
    public Set<QueryType> getQueryTypes() {
        return Sets.newHashSet(QueryType.PROJECTION);
    }

    @Override
    public ExportStrategy getExportStrategy() {
        return ExportStrategy.KAFKA;
    }
}