I am learning kafka following Apache kafka document. I started it with default configuration.
bin/zookeeper-server-start.sh config/zookeeper.properties
bin/kafka-server-start.sh config/server.properties &
I ran the kafka-console-producer.sh and kafka-console-consumer.sh to produce and consume message, and it was successful. I wrote a java code using producer API to produce message, which is OK. This is verified by kafka-console-consumer.sh. The code is same as Apache Kafka guide:
Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("acks", "all");
props.put("retries", 0);
props.put("batch.size", 16384);
props.put("linger.ms", 1);
props.put("buffer.memory", 33554432);
props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
Producer<String, String> producer = new KafkaProducer<>(props);
for(int i = 0; i < 100; i++)
producer.send(new ProducerRecord<String, String>("my-topic", Integer.toString(i), Integer.toString(i)));
producer.close();
Although producer code works, consumer code doesn't work. There's no Exception, but it just blocks at consumer.poll(100). The code is from Apache Kafka documentation:
Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("group.id", "test");
props.put("enable.auto.commit", "true");
props.put("auto.commit.interval.ms", "1000");
props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
KafkaConsumer<String, String> consumer = new KafkaConsumer<>(props);
consumer.subscribe(Arrays.asList("my-topic"));
while (true) {
ConsumerRecords<String, String> records = consumer.poll(100);
for (ConsumerRecord<String, String> record : records)
System.out.printf("offset = %d, key = %s, value = %s%n", record.offset(), record.key(), record.value());
}
By the way, the example of kafka-console-consumer.sh in Apache Kafka document is successful in consuming message, which is produced to topic "test" by producer :
bin/kafka-console-consumer.sh --zookeeper localhost:2181 --topic test --from-beginning
But if I don't connect to zookeeper, but connect to kafka broker directly, then also it doesn't work with no wrong and no exception, it just blocks.
bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic test --from-beginning
The kafka version and API version is 0.11.0.0
Why they can't consume messages?