单元测试之embedded-kafka

在项目中，团队也使用了Kafka作为消息中间件。 经过了嵌入式redis选型的问题之后，笔者在嵌入式kafka选型时就更倾向于还在持续更新，并且维护人员是一个团队而不是个人或者松散的组织。 最终，笔者选择了来自salesforce的开源项目

com.salesforce.kafka.test
    kafka-junit
    3.0.1

以下是在项目自带的测试用例代码上稍加修改的案例。

package com.salesforce.kafka.test.junit4;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertTrue;

import java.util.Collection;
import java.util.Properties;
import java.util.Set;
import java.util.stream.Collectors;

import org.apache.kafka.common.Node;
import org.junit.ClassRule;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.salesforce.kafka.test.KafkaBroker;
import com.salesforce.kafka.test.KafkaTestServer;

public class KafkaBrokerTest {
    private static final Logger logger = LoggerFactory.getLogger(KafkaBrokerTest.class);

    /**
     * Validate that we started 2 brokers.
     * @throws Exception 
     */
    @Test
    public void testTwoBrokersStarted() throws Exception {
        Properties overrideProperties = new Properties();
        overrideProperties.put("broker.id", "1");
        overrideProperties.put("port", "6666");
        KafkaTestServer server1= new KafkaTestServer(overrideProperties);
        server1.start();
       String string= server1.getKafkaBrokers().getBrokerById(1).getConnectString();
        logger.info("\n"+string+"\n");
         
        overrideProperties.put("broker.id", "2");
        overrideProperties.put("port", "8888");
        KafkaTestServer server2= new KafkaTestServer(overrideProperties);
        server2.start();
       String string2= server2.getKafkaBrokers().getBrokerById(2).getConnectString();
        logger.info("\n"+string2+"\n");

    }

}

问题

从上述案例中可以看出，在实际的kafka使用中，IP+端口号是每个kafka broker都不一样的。但是在salesforce/kafka-core中提供的KafkaTestCluster类中，其并没有给外部来指定某个broker port的机会。

 /**
     * Starts the cluster.
     * @throws Exception on startup errors.
     * @throws TimeoutException When the cluster fails to start up within a timely manner.
     */
    public void start() throws Exception, TimeoutException {
        // Ensure zookeeper instance has been started.
        zkTestServer.start();

        // If we have no brokers defined yet...
        if (brokers.isEmpty()) {
            // Loop over brokers, starting with brokerId 1.
            for (int brokerId = 1; brokerId <= numberOfBrokers; brokerId++) {
                // Create properties for brokers
                final Properties brokerProperties = new Properties();

                // Add user defined properties.
                brokerProperties.putAll(overrideBrokerProperties);

                // Set broker.id
                brokerProperties.put("broker.id", String.valueOf(brokerId));

                // Create new KafkaTestServer and add to our broker list
                brokers.add(
                    new KafkaTestServer(brokerProperties, zkTestServer)
                );
            }
        }

        // Loop over each broker and start it
        for (final KafkaTestServer broker : brokers) {
            broker.start();
        }

        // Block until the cluster is 'up' or the timeout is exceeded.
        waitUntilClusterReady(10_000L);
    }

这在某些需要预先指定IP+端口号的场景中还是有一些麻烦的。需要后续进行处理。例如，给这个类新增一个构造方法，利用以下的List ,把已经完成初始化的List brokers 作为入参传递进去。

private final List brokers = new ArrayList<>();

新增构造方法：

public KafkaTestCluster(final List brokers)