如何使用php-rdkafka在kafka中确认消费消息？

Question

我使用php-rdkafka作为php Kafka客户端，并使用测试组成功地生成了测试消息。我使用下面的代码来使用该消息：

$kafkaConsumer = new RdKafka\Consumer();
$kafkaConsumer->addBrokers("127.0.0.1:9292");
$topic = $kafkaConsumer->newTopic("test");
$topic->consumeStart(0, RD_KAFKA_OFFSET_BEGINNING);

while (true) {
    $msg = $topic->consume(0, 1000);
    if($msg){
    if ($msg->err) {
        echo $msg->errstr(), "
";
        break;
    } else {
        echo $msg->payload, "
";
    }
  }
}

但是，当我再次尝试在测试组中设置消息并尝试使用测试组的消息时，我得到了旧消息和新消息。所以我只想知道如何才能确认旧的信息，这样我才能得到新的信息，而不是旧的信息？有人能给个建议吗？?

我的kafka版本是0.11.0.1。

Answer 1

The method to acknowledge consumed messages in Kafka is to commit its offset. That way when restarting your consumer it can retrieve the last committed offset and restart where it left off.

As suggested in the comments, you need to use RD_KAFKA_OFFSET_STORED to instruct the consumer to retrieve the stored offset.

But you also need to provide a group name by setting the group.id config:

<?php

$conf = new RdKafka\Conf();

// Set the group id. This is required when storing offsets on the broker
$conf->set('group.id', 'myConsumerGroup');

$rk = new RdKafka\Consumer($conf);
$rk->addBrokers("127.0.0.1:9292");

$topicConf = new RdKafka\TopicConf();
$topicConf->set('auto.commit.interval.ms', 100);

// Set where to start consuming messages when there is no initial offset in
// offset store or the desired offset is out of range.
// 'smallest': start from the beginning
$topicConf->set('auto.offset.reset', 'smallest');

$topic = $rk->newTopic("test", $topicConf);

// Start consuming partition 0
$topic->consumeStart(0, RD_KAFKA_OFFSET_STORED);

while (true) {
    $message = $topic->consume(0, 120*10000);
    switch ($message->err) {
        case RD_KAFKA_RESP_ERR_NO_ERROR:
            var_dump($message);
            break;
        case RD_KAFKA_RESP_ERR__PARTITION_EOF:
            echo "No more messages; will wait for more
";
            break;
        case RD_KAFKA_RESP_ERR__TIMED_OUT:
            echo "Timed out
";
            break;
        default:
            throw new \Exception($message->errstr(), $message->err);
            break;
    }
}
?>