Flink源码阅读:如何使用FlinkKafkaProducer将数据在Kafka的多个partition中均匀分布

使Flink输出的数据在多个partition中均匀分布

FlinkKafkaProducerBase的子类可以使用默认的KafkaPartitioner FixedPartitioner(只向partition 0中写数据)也可以使用自己定义的Partitioner(继承KafkaPartitioner),我觉得实现比较复杂.

构造FlinkKafkaProducerBase的子类的2种情况

    public FlinkKafkaProducer09(String topicId, SerializationSchema serializationSchema, 
Properties producerConfig) {
    this(topicId, new KeyedSerializationSchemaWrapper<>(serializationSchema), 
                producerConfig, new FixedPartitioner());
    }

    public FlinkKafkaProducer09(String topicId, SerializationSchema serializationSchema, 
Properties producerConfig, KafkaPartitioner customPartitioner) {
    this(topicId, new KeyedSerializationSchemaWrapper<>(serializationSchema), 
            producerConfig, customPartitioner);

    }

默认的FixedPartitioner

public class FixedPartitioner<T> extends KafkaPartitioner<T> implements Serializable {
    private static final long serialVersionUID = 1627268846962918126L;

    private int targetPartition = -1;

    @Override
    public void open(int parallelInstanceId, int parallelInstances, int[] partitions) {
        if (parallelInstanceId < 0 || parallelInstances <= 0 || 
                    partitions.length == 0) {
            throw new IllegalArgumentException();
        }

        this.targetPartition = partitions[parallelInstanceId % partitions.length];
    }

    @Override
    public int partition(T next, byte[] serializedKey, byte[] serializedValue, 
            int numPartitions) {
        if (targetPartition >= 0) {
            return targetPartition;
        } else {
            throw new RuntimeException("The partitioner has not been initialized properly");
        }
    }
}

在构造FlinkKafkaProducerBase的子类时,可以传递一个值为null的KafkaPartitioner,这样就可以使用Kafka Client默认的Partitioner,默认的Paritioner就是将数据均匀分配到各个partition中.

protected FlinkKafkaProducerBase createSink(String topic, KeyedSerializationSchema
 deserializationSchema, Properties properties) {
        String classFullName = "";
        if (kafkaVersion.startsWith("0.8")) {
            classFullName = 
"org.apache.flink.streaming.connectors.kafka.FlinkKafkaProducer08";
        } else if (kafkaVersion.startsWith("0.9")) {
            classFullName = 
"org.apache.flink.streaming.connectors.kafka.FlinkKafkaProducer09";
        } else if (kafkaVersion.startsWith("0.10")) {
            classFullName = 
"org.apache.flink.streaming.connectors.kafka.FlinkKafkaProducer09";
        } else {
            throw new RuntimeException("not support the "+
                        "version kafka = " + kafkaVersion);
        }
        FlinkKafkaProducerBase sink = null;
        try {
            Class clazz = Class.forName(classFullName);
            Constructor constructor = clazz.getConstructor(String.class, 
KeyedSerializationSchema.class, Properties.class, KafkaPartitioner.class);
            sink = (FlinkKafkaProducerBase) constructor.newInstance(topic, 
deserializationSchema, properties,(KafkaPartitioner)null);
        } catch (Throwable e) {
            e.printStackTrace();
        }
        return sink;
    }

Kafka Client中默认的Partitioner

public class DefaultPartitioner implements Partitioner {

    private final ConcurrentMap topicCounterMap = 
            new ConcurrentHashMap<>();

    public void configure(Map configs) {}

    public int partition(String topic, Object key, byte[] keyBytes, Object value, 
        byte[] valueBytes, Cluster cluster) {
        List partitions = cluster.partitionsForTopic(topic);
        int numPartitions = partitions.size();
        if (keyBytes == null) {
            int nextValue = nextValue(topic);
            List availablePartitions = 
                cluster.availablePartitionsForTopic(topic);
            if (availablePartitions.size() > 0) {
                int part = Utils.toPositive(nextValue) % availablePartitions.size();
                return availablePartitions.get(part).partition();
            } else {
                // no partitions are available, give a non-available partition
                return Utils.toPositive(nextValue) % numPartitions;
            }
        } else {
            // hash the keyBytes to choose a partition
            return Utils.toPositive(Utils.murmur2(keyBytes)) % numPartitions;
        }
    }

    private int nextValue(String topic) {
        AtomicInteger counter = topicCounterMap.get(topic);
        if (null == counter) {
            counter = new AtomicInteger(ThreadLocalRandom.current().nextInt());
            AtomicInteger currentCounter = topicCounterMap.putIfAbsent(topic, counter);
            if (currentCounter != null) {
                counter = currentCounter;
            }
        }
        return counter.getAndIncrement();
    }

    public void close() {}
}

调用过程

在调用FlinkKafkaProducerBase中的invoke方法时,会判断partitioner是否为空,如果为空则构建一个partition属性为空的ProducerRecord对象,否则使用partitioner获得partition构造ProducerRecord对象.

    public void invoke(IN next) throws Exception {
        // propagate asynchronous errors
        checkErroneous();

        byte[] serializedKey = schema.serializeKey(next);
        byte[] serializedValue = schema.serializeValue(next);
        String targetTopic = schema.getTargetTopic(next);
        if (targetTopic == null) {
            targetTopic = defaultTopicId;
        }

        ProducerRecord<byte[], byte[]> record;
        if (partitioner == null) {
            record = new ProducerRecord<>(targetTopic, serializedKey, 
                            serializedValue);
        } else {
            record = new ProducerRecord<>(targetTopic, 
                        partitioner.partition(next, serializedKey, serializedValue, 
                        partitions.length), serializedKey, serializedValue);
        }
        if (flushOnCheckpoint) {
            synchronized (pendingRecordsLock) {
                pendingRecords++;
            }
        }
        producer.send(record, callback);
    }

在调用KafkaProducer的send方法的时候,方法里面会调用partition方法决定数据放到哪个分区,如果ProducerRecord的partition属性存在并且合法,则使用该值,否则使用KafkaProducer中的partitioner进行分区

private int partition(ProducerRecord record, byte[] serializedKey , 
        byte[] serializedValue, Cluster cluster) {
        Integer partition = record.partition();
        if (partition != null) {
            List partitions = cluster.partitionsForTopic(record.topic());
            int numPartitions = partitions.size();
            // they have given us a partition, use it
            if (partition < 0 || partition >= numPartitions)
                throw new IllegalArgumentException("Invalid partition given with record: " + 
                                                    partition
                                                   + " is not in the range [0..."
                                                   + numPartitions
                                                   + "].");
            return partition;
        }
        return this.partitioner.partition(record.topic(), record.key(), 
            serializedKey, record.value(), serializedValue,cluster);
    }

KafkaProducer的partitioner是通过读取配置获取的,默认为DefaultPartitioner,可以在properties中put partitioner.class指定要使用的partitioner

this.partitioner = config.getConfiguredInstance(
ProducerConfig.PARTITIONER_CLASS_CONFIG, Partitioner.class);