net.osomahe.esk.eventstore.control.TopicService Maven / Gradle / Ivy

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CDI extension for Java EE 8 application using Apache Kafka as Event Store
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package net.osomahe.esk.eventstore.control;

import static org.apache.kafka.clients.consumer.ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG;
import static org.apache.kafka.clients.consumer.ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG;

import java.util.Map;
import java.util.Properties;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;

import javax.ejb.ConcurrencyManagement;
import javax.ejb.ConcurrencyManagementType;
import javax.ejb.Singleton;
import javax.inject.Inject;

import org.apache.kafka.clients.consumer.KafkaConsumer;
import org.apache.kafka.common.serialization.StringDeserializer;

import net.osomahe.esk.config.boundary.ConfigurationBoundary;
import net.osomahe.esk.eventstore.entity.EventStoreEvent;
import net.osomahe.esk.eventstore.entity.TopicName;


/**
 * Provides operations with kafka topics.
 *
 * @author Antonin Stoklasek
 */
@Singleton
@ConcurrencyManagement(ConcurrencyManagementType.BEAN)
public class TopicService {
    private final Map mapPartitionCount = new ConcurrentHashMap<>();

    private static final String DEFAULT_TOPIC = "eventstore";

    @Inject
    private ConfigurationBoundary config;

    /**
     * Provides topic name for given {@link EventStoreEvent}.
     *
     * @param eventClass event for which the topic name is requested
     * @return topic name
     */
    public String getTopicName(Class eventClass) {
        TopicName topicName = eventClass.getAnnotation(TopicName.class);
        if (topicName == null) {
            return DEFAULT_TOPIC;
        }
        return topicName.value();
    }

    /**
     * Provides how many partitions does topic for given event have.
     *
     * @param eventClass class of the event
     * @return number of topic's partitions
     */
    public int getPartitionCount(Class eventClass) {
        return getPartitionCount(getTopicName(eventClass));
    }

    /**
     * Provides how many partitions does given topic.
     *
     * @param topicName name of the topic
     * @return number of topic's partitions
     */
    public synchronized int getPartitionCount(String topicName) {
        if (mapPartitionCount.containsKey(topicName)) {
            return mapPartitionCount.get(topicName);
        }
        Integer count = loadPartitionCount(topicName);
        mapPartitionCount.put(topicName, count);
        return count;
    }

    private Integer loadPartitionCount(String topicName) {
        Properties props = this.config.getKafkaConsumerConfig();
        props.put(KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
        props.put(VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
        KafkaConsumer consumer = new KafkaConsumer(props);
        try {
            return consumer.partitionsFor(topicName).size();
        } finally {
            consumer.close(10, TimeUnit.SECONDS);
        }
    }

}