如何在Flink中将Cassandra Sink与TestContainers一起使用

如何解决如何在Flink中将Cassandra Sink与TestContainers一起使用

我正在尝试在使用Cassandra Sink进行测试的简单Flink管道中使用TestContainers来测试DataStreamTestBase：

public class CassandraPojoSinkExampleTest extends DataStreamTestBase {

    @Rule
    public CassandraContainer cassandra = new CassandraContainer<>().withInitScript("testInit3.cql")
            .withCreateContainerCmdModifier(cmd -> cmd.getHostConfig()
                    .withCpuCount(2L));

    @Override
    public void initialize() throws Exception {
        super.initialize();
        testEnv.getConfig().disableObjectReuse();
        testEnv.setStreamTimeCharacteristic(TimeCharacteristic.EventTime);
        testEnv.setRestartStrategy(RestartStrategies.fixedDelayRestart(1,Time.of(1,TimeUnit.SECONDS)));
    }

    @Test
    public void test() throws Throwable {
       ArrayList<Message> messages = new ArrayList<>(20);

            for (long i = 0; i < 20; i++) {
                messages.add(new Message("cassandra-" + i));
            }


        Cluster cluster = cassandra.getCluster();

        try (Session session = cluster.connect()) {

            CassandraPojoSinkExample cassandraPojoSinkExample= new CassandraPojoSinkExample();
            cassandraPojoSinkExample.doIt(cassandra.getHost(),testEnv.fromCollection(messages));

            MappingManager manager= new MappingManager(session);
            Mapper<Message> mapper=manager.mapper(Message.class);
            String word ="cassandra-1";
            Message message= mapper.get(word);
            System.out.println(message);
        }
    }

Flink管道看起来像（它仅陷于doIt方法中）：

public class CassandraPojoSinkExample {
    private static final ArrayList<Message> messages = new ArrayList<>(20);

    static {
        for (long i = 0; i < 20; i++) {
            messages.add(new Message("cassandra-" + i));
        }
    }
    public static void main(String[] args) throws Exception {

        // the main method is not used in tests

        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        DataStreamSource<Message> source = env.fromCollection(messages);

        CassandraPojoSinkExample cassandraPojoSinkExample=new CassandraPojoSinkExample();
        cassandraPojoSinkExample.doIt("127.0.0.1",source);
    }
    public void doIt(String address,DataStreamSource<Message> source) throws Exception {

        CassandraSink.addSink(source)
                .setClusterBuilder(new ClusterBuilder() {
                    @Override
                    protected Cluster buildCluster(Builder builder) {
                        return builder.addContactPoint(address).build();
                    }
                })
                .setMapperOptions(() -> new Mapper.Option[]{Mapper.Option.saveNullFields(true)})
                .build();
    }

运行测试时出现错误：

16:41:57,675 ERROR org.apache.flink.streaming.runtime.tasks.StreamTask           - Error during disposal of stream operator.
java.lang.NullPointerException
    at org.apache.flink.streaming.connectors.cassandra.CassandraSinkBase.checkAsyncErrors(CassandraSinkBase.java:162)
    at org.apache.flink.streaming.connectors.cassandra.CassandraSinkBase.close(CassandraSinkBase.java:96)
    at org.apache.flink.api.common.functions.util.FunctionUtils.closeFunction(FunctionUtils.java:43)
    at org.apache.flink.streaming.api.operators.AbstractUdfStreamOperator.dispose(AbstractUdfStreamOperator.java:117)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.disposeAllOperators(StreamTask.java:651)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.cleanUpInvoke(StreamTask.java:562)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:480)
    at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:708)
    at org.apache.flink.runtime.taskmanager.Task.run(Task.java:533)
    at java.lang.Thread.run(Thread.java:748)
16:41:57,683 INFO  org.apache.flink.runtime.taskmanager.Task                     - Source: Collection Source -> Sink: Cassandra Sink (1/1) (721a02e3c1345d640bf03b67eff0aba7) switched from RUNNING to FAILED.
com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: localhost/127.0.0.1:9042 (com.datastax.driver.core.exceptions.TransportException: [localhost/127.0.0.1] Cannot connect))
    at com.datastax.driver.core.ControlConnection.reconnectInternal(ControlConnection.java:231)
    at com.datastax.driver.core.ControlConnection.connect(ControlConnection.java:77)
    at com.datastax.driver.core.Cluster$Manager.init(Cluster.java:1414)
    at com.datastax.driver.core.Cluster.init(Cluster.java:162)
    at com.datastax.driver.core.Cluster.connectAsync(Cluster.java:333)
    at com.datastax.driver.core.Cluster.connect(Cluster.java:283)
    at org.apache.flink.streaming.connectors.cassandra.CassandraPojoSink.createSession(CassandraPojoSink.java:123)
    at org.apache.flink.streaming.connectors.cassandra.CassandraSinkBase.open(CassandraSinkBase.java:87)
    at org.apache.flink.streaming.connectors.cassandra.CassandraPojoSink.open(CassandraPojoSink.java:106)
    at org.apache.flink.api.common.functions.util.FunctionUtils.openFunction(FunctionUtils.java:36)
    at org.apache.flink.streaming.api.operators.AbstractUdfStreamOperator.open(AbstractUdfStreamOperator.java:102)
    at org.apache.flink.streaming.api.operators.StreamSink.open(StreamSink.java:48)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.initializeStateAndOpen(StreamTask.java:990)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.lambda$beforeInvoke$0(StreamTask.java:453)
    at org.apache.flink.streaming.runtime.tasks.StreamTaskActionExecutor$SynchronizedStreamTaskActionExecutor.runThrowing(StreamTaskActionExecutor.java:94)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.beforeInvoke(StreamTask.java:448)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:460)
    at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:708)
    at org.apache.flink.runtime.taskmanager.Task.run(Task.java:533)
    at java.lang.Thread.run(Thread.java:748)

我在做什么错了？

解决方法

从上面的堆栈跟踪com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: localhost/127.0.0.1:9042看，cassandra主机似乎不可用。

我会说您需要将端口暴露在外面：

    @Rule
    public CassandraContainer cassandra = new CassandraContainer<>().withInitScript("testInit3.cql")
            .withCreateContainerCmdModifier(cmd -> cmd.getHostConfig()
            .withCpuCount(2L))
            .withExposedPorts(9042);

此外，我将手动通过telnet确保到达相应的主机/端口，以确保该服务已启动。

,

@Mikalai Lushchytski的回答很好，问题出在裸露的港口。

公开的端口也需要通过.setHost()方法传递给addSink。

此外，说实话，我之前已经尝试过此操作，但没有注意到它正在工作，因为问题在于从Cassandra数据库表接收信息。在提供的代码中，我在测试过程中无法从数据库中检索任何行，问题似乎出在DataStreamTestBase和调用方法的顺序上。我通过手动输入数据库并在进行中的测试中提取数据来确认管道的工作。

使用DataStreamTestBase从Cassandra TestContainer正确获取数据库记录的解决方案 是要使用Overrideed executeTest（）方法：

public class CassandraPojoSinkExampleTest extends DataStreamTestBase {
    private static boolean runTestAfterMethod = true;

    @Rule
    public CassandraContainer cassandra = new CassandraContainer<>()
            .withInitScript("testInit3.cql")
            .withExposedPorts(9042);

    @Before
    public void setUp() {
        runTestAfterMethod = true;
    }

    @Override
    public void executeTest() throws Throwable {
        if (runTestAfterMethod) {
            super.executeTest();
        }
    }

    @Override
    public void initialize() throws Exception {
        super.initialize();
        testEnv.getConfig().disableObjectReuse();
        testEnv.setRestartStrategy(RestartStrategies.fixedDelayRestart(1,Time.of(1,TimeUnit.SECONDS)));
    }

    @Test
    public void test() throws Throwable {
        runTestAfterMethod = false;

        ArrayList<Message> messages = new ArrayList<>(20);
        for (long i = 0; i < 20; i++) {
            messages.add(new Message("cassandra-" + i));
        }

        DataStreamSource<Message> source = testEnv.fromCollection(messages);

        CassandraPojoSinkExample cassandraPojoSinkExample = new CassandraPojoSinkExample();
        cassandraPojoSinkExample.doIt(cassandra.getHost(),cassandra.getMappedPort(9042),source);

    try( Session session = cassandra.getCluster().newSession()) {
        testEnv.executeTest();     // Crucial thing

        ResultSet resultSet = session.execute("select * from test.features;");
        List<Row> rows = resultSet.all();
        List<String> actualRecords = new ArrayList<String>();

             if (rows.size() != 0) {
                for (int i = 0; i < 20; i++) {
                    actualRecords.add(rows.get(0).getString(i));
                }
            }

            List<String> expectedRecords = new ArrayList<String>() {
                {
                    for (int i = 0; i < 20; i++) {
                        add("cassandra-" + i);
                    }
                }
            };

            assertTrue("List equality without order",actualRecords.containsAll(expectedRecords)&& actualRecords.containsAll(expectedRecords));
        }
    }
    }

}

通过这种方式，我们确保resultSet不能为空，并且测试将以正确的顺序执行。