考虑以下代码:

public static long Offset = 0L;
FetchRequest req = new FetchRequest(KafkaProperties.topic, 0, Offset,10485760);
ByteBufferMessageSet messageSet = simpleConsumer.fetch(req);


问题是如何获取最后的偏移量并设置变量Offset以便从Kafka读取下一批数据?


更新:
当我打印数据时:

for (MessageAndOffset messageAndOffset : messageSet) {
            System.out.println(messageAndOffset);
}


输出将如下所示:

MessageAndOffset(message(magic = 1, attributes = 0, crc = 2000130375, payload = java.nio.HeapByteBuffer[pos=0 lim=176 cap=176]),296215)
MessageAndOffset(message(magic = 1, attributes = 0, crc = 956398356, payload = java.nio.HeapByteBuffer[pos=0 lim=196 cap=196]),298144)
....
....
MessageAndOffset(message(magic = 1, attributes = 0, crc = 396743887, payload = java.nio.HeapByteBuffer[pos=0 lim=179 cap=179]),299136)


docs说最后一个数字是偏移量

MessageAndOffset(message: Message, offset: Long)


在上述情况下,我最后一次读取的偏移量为299136

最佳答案

这样的帮助吗?一件坏事是它会永远循环。

    long offset = 0;

    while (true) {
        FetchRequest fetchrequest = new FetchRequest(topicName, 0, offset, 10485760);

        ByteBufferMessageSet messages = consumer.fetch(fetchrequest);
        for (MessageAndOffset msg : messages) {
            System.out.println("consumed: " + Utils.toString(msg.message().payload(), "UTF-8"));
            offset = msg.offset();
        }

    }


同样在0.8 Kafka SimpleConsumer example中,它们具有如下所示的内容

    long numRead = 0;
    for (MessageAndOffset messageAndOffset : fetchResponse.messageSet(a_topic, a_partition)) {
          long currentOffset = messageAndOffset.offset();
          if (currentOffset < readOffset) {
             System.out.println("Found an old offset: " + currentOffset + " Expecting: " + readOffset);
             continue;
          }
          readOffset = messageAndOffset.nextOffset();
          ByteBuffer payload = messageAndOffset.message().payload();

          byte[] bytes = new byte[payload.limit()];
          payload.get(bytes);
          System.out.println(String.valueOf(messageAndOffset.offset()) + ": " + new String(bytes, "UTF-8"));
          numRead++;
          a_maxReads--;
    }


但是他们还提到应用程序希望将a_maxread(要读取的最大邮件数)参数作为参数传递,因此我们不会永远循环。我是kafka的新手,不确定是否是您要找的东西。

10-07 19:06
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