How to acknowledge consume message in kafka using php-rdkafka?

Question

I am using php-rdkafka as php kafka client. I successfully product my test message by using test group.and consume the message by using below code,

$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(), "\n";
        break;
    } else {
        echo $msg->payload, "\n";
    }
  }
}

But when I try to again set message in test group and trying to consume message for test group then I am getting old message as well as new message. So I just want to how can I acknowledge old message so I can get only new message not old one ? Can someone put some shine on this ?

My kafka version is 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($message);
            break;
        case RD_KAFKA_RESP_ERR__PARTITION_EOF:
            echo "No more messages; will wait for more\n";
            break;
        case RD_KAFKA_RESP_ERR__TIMED_OUT:
            echo "Timed out\n";
            break;
        default:
            throw new \Exception($message->errstr(), $message->err);
            break;
    }
}
?>