Do we have a support for partitionsFor method in the producer in kafka version 0.8.0? I want to use this method to get the number of partitions given a kafka topic.
If this method is not available in kafka 0.8.0, what is the easiest way to get the number of partitions in the producer in this specific version of kafka?
You can use listTopics() method also
ArrayList<Topics> topicList = new ArrayList<Topics>();
Properties props = new Properties();
Map<String, List<PartitionInfo>> topics;
Topics topic;
InputStream input =
getClass().getClassLoader().getResourceAsStream("kafkaCluster.properties");
try {
props.load(input);
props.put(AdminClientConfig.BOOTSTRAP_SERVERS_CONFIG,
props.getProperty("BOOTSTRAP_SERVERS_CONFIG"));
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<String,
String>(props);
topics = consumer.listTopics();
// System.out.println(topics.get(topics));
for (Map.Entry<String, List<PartitionInfo>> entry :
topics.entrySet()) {
System.out.println("Key = " + entry.getKey() + ", Value = " +
entry.getValue());
topic = new Topics();
topic.setTopic_name(entry.getKey());
topic.setPartitions(Integer.toString(entry.getValue().size()));
topicList.add(topic);
}
} catch (IOException e) {
e.printStackTrace();
}
Why don't you try following approach
https://stackoverflow.com/a/35458605/5922904.
Also ZkUtils have the method getPartitionsForTopics which can also be used. Although I have not tried and tested it myself
Related
My producer can create a topic, but it doesn't seem to store any data inside a broker. I can check that the topic is created with kafka-topics script.
When I tried to consume with kafka-console-consumer, it doesn't consume anything. (I know --from-beginning.)
When I produced with kafka-console-producer, my consumer(kafka-console-consumer) can consume it right away. So there is something wrong with my java code.
And when I run my code with localhost:9092, it worked fine. And when I consume the topic with my consumer code, it was working properly. My producer works with Kafka server on my local machine but doesn't work with another Kafka server on remote machine.
Code :
//this code is inside the main method
Properties properties = new Properties();
//properties.put("bootstrap.servers", "localhost:9092");
//When I used localhost, my consumer code consumes it fine.
properties.put("bootstrap.servers", "192.168.0.30:9092");
properties.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
properties.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
KafkaProducer<String, String> kafkaProducer = new KafkaProducer<String, String>(properties);
ProducerRecord<String, String> record = new ProducerRecord<>("test5", "1111","jin1111");
//topc is created, but consumer can't consume any data.
//I tried putting different values for key and value parameters but no avail.
try {
kafkaProducer.send(record);
System.out.println("complete");
} catch (Exception e) {
e.printStackTrace();
} finally {
kafkaProducer.close();
System.out.println("closed");
}
/*//try{
for(int i = 0; i < 10000; i++){
System.out.println(i);
kafkaProducer.send(new ProducerRecord("test", Integer.toString(i), "message - " + i ));
}*/
My CLI (Putty) :
I want to see my consumer consuming when I run my java code. (Those data shown in the image are from the producer script.)
update
After reading answers and comments, this is what I've tried so far. Still not consuming any messages. I think message produced in this code is not stored in the broker. I tried with the different server, too. The same problem. Topic was created, but no consumer exists in the consumer group list and can't consume. And no data can be consumed with consumer script.
I also tried permission change. (chown) and tried with etc/hosts files. but no luck. I'll keep on trying until I solve this.
public static void main(String[] args){
Properties properties = new Properties();
//properties.put("bootstrap.servers", "localhost:9092");
properties.put("bootstrap.servers", "192.168.0.30:9092");
properties.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
properties.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
properties.put("linger.ms", "1");
properties.put("batch.size", "16384");
properties.put("request.timeout.ms", "30000");
KafkaProducer<String, String> kafkaProducer = new KafkaProducer<String, String>(properties);
ProducerRecord<String, String> record = new ProducerRecord<>("test5", "1111","jin1111");
System.out.println("1");
try {
kafkaProducer.send(record);
//kafkaProducer.send(record).get();
// implement Callback
System.out.println("complete");
kafkaProducer.flush();
System.out.println("flush completed");
} catch (Exception e) {
e.printStackTrace();
} finally {
kafkaProducer.flush();
System.out.println("another flush test");
kafkaProducer.close();
System.out.println("closed");
}
}
When I run this in Eclipse, the console shows :
To complete the ppatierno answer, you should call KafkaProducer.flush() before calling KafkaProducer.close(). This is a blocking call and will not return before all record got sent.
Yannick
My guess is that your main method exits and the application ends before the message is sent by the Kafka client.
The send method is not sync. The client buffers messages and send them after reaching a timeout named linger time (see linger.ms) or the buffer is filled to a specific size (see batch.size parameter for example). The default linger time is anyway 0.
So what your main method does is providing the message to the send method but then it exits and the underlying thread in the Kafka client isn't able to send the message.
I finally figured out. If you experienced similar problem, there are things you can do.
In your server.properties, uncomment these and put the ip and port.
(There seems to be a problem with the port, so I changed it.)
listeners=PLAINTEXT://192.168.0.30:9093
advertised.listeners=PLAINTEXT://192.168.0.30:9093
(Before restarting your broker with your changed server.properties, you might want to clean all existing log.dir. Try this, if nothing works)
Some other things you might want to consider :
change your log.dir. Usually the default path is tmp, but sometimes there is a noexec setting, so configure to a different location
check your etc/hosts
check your permission : And use chown and chmod
change zookeeper port and kafka port if necessary.
change broker.id
My working producer code :
public class Producer1 {
public static void main(String[] args){
Properties properties = new Properties();
properties.put("bootstrap.servers", "192.168.0.30:9093");
properties.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
properties.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
KafkaProducer<String, String> kafkaProducer = new KafkaProducer<String, String>(properties);
ProducerRecord<String, String> record = new ProducerRecord<>("test", "1","jin");
try {
kafkaProducer.send(record);
System.out.println("complete");
} catch (Exception e) {
e.printStackTrace();
} finally {
kafkaProducer.close();
System.out.println("closed");
}
}
}
working Consumer code:
public class Consumer1 {
public static void main(String[] args) {
Properties props = new Properties();
props.put("bootstrap.servers", "192.168.0.30:9093");
props.put("group.id", "jin");
props.put("auto.offset.reset", "earliest");
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<String, String>(props);
consumer.subscribe(Collections.singletonList("test"));
try {
while (true) {
ConsumerRecords<String, String> records = consumer.poll(Duration.ofMillis(1000));
for (ConsumerRecord<String, String> record : records){
System.out.printf("offset = %d, key = %s, value = %s", record.offset(), record.key(), record.value());
}
}
} catch (Exception e){
e.printStackTrace();
} finally {
consumer.close();
System.out.println("closed");
}
}
}
Console :
in consumer when subscribed to a topic and start consuming messages it read the messages from the the beginning is there any way to read only unread messages ? this is the code i used for consuming the messages.
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("session.timeout.ms", "30000");
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<String, String>(props);
//Kafka Consumer subscribes list of topics here.
consumer.subscribe(Arrays.asList(topicName));
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());
}
Turn off auto.commit and manually commit each message offset after your app has successfully read it. That way if the app crashes it will restart at exactly the last committed offset.
i have try your code, and it read only unread messages. what's your client version and server version?
I want to have a Kafka Consumer which starts from the latest message in a topic.
Here is the java code:
private static Properties properties = new Properties();
private static KafkaConsumer<String, String> consumer;
static
{
properties.setProperty("bootstrap.servers","localhost");
properties.setProperty("enable.auto.commit", "true");
properties.setProperty("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
properties.setProperty("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
properties.setProperty("group.id", "test");
properties.setProperty("auto.offset.reset", "latest");
consumer = new KafkaConsumer<>(properties);
consumer.subscribe(Collections.singletonList("mytopic"));
}
#Override
public StreamHandler call() throws Exception
{
while (true)
{
ConsumerRecords<String, String> consumerRecords = consumer.poll(200);
Iterable<ConsumerRecord<String, String>> records = consumerRecords.records("mytopic");
for(ConsumerRecord<String, String> rec : records)
{
System.out.println(rec.value());
}
}
}
Although the value for auto.offset.reset is latest, but the consumer starts form messages which belong to 2 days ago and then it catches up with the latest messages.
What am I missing?
Have you run this same code before with the same group.id? The auto.offset.reset parameter is only used if there is not an existing offset already stored for your consumer. So if you've run the example previously, say two days ago, and then you run it again, it will start from the last consumed position.
Use seekToEnd() if you would like to manually go to the end of the topic.
See https://stackoverflow.com/a/32392174/1392894 for a slightly more thorough discussion of this.
If you want to manually control the position of your offsets you need to set enable.auto.commit = false.
If you want to position all offsets to the end of each partition then call seekToEnd()
https://kafka.apache.org/0102/javadoc/org/apache/kafka/clients/consumer/KafkaConsumer.html#seekToEnd(java.util.Collection)
I am trying to send Integer value through Kafka producer using the kafka provided API IntegerSerializer,but the integer value is not getting parsed correctly and it displayed in form of random unknown symbol on the Kafka consumer console.
public static void main(String[] args) throws Exception{
int i;
// Check arguments length value
if(args.length == 0){
System.out.println("Enter topic name");
return;
}
//Assign topicName to string variable
String topicName = args[0].toString();
// create instance for properties to access producer configs
Properties props = new Properties();
//Assign localhost id
props.put("bootstrap.servers", "localhost:9092");
//Set acknowledgements for producer requests.
props.put("acks", "all");
//If the request fails, the producer can automatically retry,
props.put("retries", "0");
//Specify buffer size in config
props.put("batch.size"," 16384");
//Reduce the no of requests less than 0
props.put("linger.ms", "1");
//The buffer.memory controls the total amount of memory available to the producer for buffering.
props.put("buffer.memory", "33554432");
props.put("key.serializer",
"org.apache.kafka.common.serialization.StringSerializer");
props.put("value.serializer",
"org.apache.kafka.common.serialization.IntegerSerializer");
KafkaProducer<String,Integer> producerRcrd = new KafkaProducer<String,Integer>(props);
producerRcrd.send(new ProducerRecord<String,Integer>(topicName, "Key1",100));
System.out.println("Message sent successfully");
producerRcrd.flush();
producerRcrd.close();
}
}
Then it is not showing 100 on Kafka-consumer console.
Appending
--property key.deserializer=org.apache.kafka.common.serialization.StringDeserializer --property value.deserializer=org.apache.kafka.common.serialization.IntegerDeserializer
to kafka-console-consumer.sh, having console message formatter know how to deserialize your message body.
I'm constructing messages using below code...
Producer<String, String> producer = new kafka.javaapi.producer.Producer<String, String>(producerConfig);
KeyedMessage<String, String> keyedMsg = new KeyedMessage<String, String>(topic, "device-420", "{message:'hello world'}");
producer.send(keyedMsg);
And Consuming using following code block...
//Key = topic name, Value = No. of threads for topic
Map<String, Integer> topicCount = new HashMap<String, Integer>();
topicCount.put(topic, 1);
//ConsumerConnector creates the message stream for each topic
Map<String, List<KafkaStream<byte[], byte[]>>> consumerStreams = consumerConnector.createMessageStreams(topicCount);
// Get Kafka stream for topic
List<KafkaStream<byte[], byte[]>> kStreamList = consumerStreams.get(topic);
// Iterate stream using ConsumerIterator
for (final KafkaStream<byte[], byte[]> kStreams : kStreamList) {
ConsumerIterator<byte[], byte[]> consumerIte = kStreams.iterator();
while (consumerIte.hasNext()) {
MessageAndMetadata<byte[], byte[]> msg = consumerIte.next();
System.out.println(topic.toUpperCase() + ">"
+ " Partition:" + msg.partition()
+ " | Key:"+ new String(msg.key())
+ " | Offset:" + msg.offset()
+ " | Message:"+ new String(msg.message()));
}
}
Everything is working fine because I'm reading data topic wise. So I want to know that Is there any way to to consume data using message key i.e. device-420 in this example?
Short answer: no.
The smallest granularity in Kafka is a partition. You can write a client that reads only from a single partition. However, a partition can contain multiple keys and you need to consume all the keys contained in this partition.