forked from apache/kafka
/
ExactlyOnceMessageProcessor.java
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/
ExactlyOnceMessageProcessor.java
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package kafka.examples;
import org.apache.kafka.clients.consumer.ConsumerRebalanceListener;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;
import org.apache.kafka.clients.consumer.NoOffsetForPartitionException;
import org.apache.kafka.clients.consumer.OffsetAndMetadata;
import org.apache.kafka.clients.consumer.OffsetOutOfRangeException;
import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.common.KafkaException;
import org.apache.kafka.common.TopicPartition;
import org.apache.kafka.common.errors.AuthorizationException;
import org.apache.kafka.common.errors.FencedInstanceIdException;
import org.apache.kafka.common.errors.OutOfOrderSequenceException;
import org.apache.kafka.common.errors.ProducerFencedException;
import org.apache.kafka.common.errors.SerializationException;
import org.apache.kafka.common.errors.UnsupportedVersionException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Optional;
import java.util.concurrent.CountDownLatch;
import static java.time.Duration.ofMillis;
import static java.util.Collections.emptyList;
import static java.util.Collections.singleton;
/**
* This class implements a read-process-write application.
*/
public class ExactlyOnceMessageProcessor extends Thread implements ConsumerRebalanceListener {
private final String bootstrapServers;
private final String inputTopic;
private final String outputTopic;
private final String groupInstanceId;
private final CountDownLatch latch;
private final String transactionalId;
private volatile boolean closed;
private final KafkaProducer<Integer, String> producer;
private final KafkaConsumer<Integer, String> consumer;
public ExactlyOnceMessageProcessor(String threadName,
String bootstrapServers,
String inputTopic,
String outputTopic,
CountDownLatch latch) {
super(threadName);
this.bootstrapServers = bootstrapServers;
this.inputTopic = inputTopic;
this.outputTopic = outputTopic;
this.transactionalId = "tid-" + threadName;
// It is recommended to have a relatively short txn timeout in order to clear pending offsets faster.
int transactionTimeoutMs = 10_000;
// A unique transactional.id must be provided in order to properly use EOS.
producer = new Producer(
"processor-producer", KafkaProperties.KAFKA_SERVER_URL + ":" + KafkaProperties.KAFKA_SERVER_PORT, outputTopic, true, transactionalId, true, -1, transactionTimeoutMs, null)
.createKafkaProducer();
// Consumer must be in read_committed mode, which means it won't be able to read uncommitted data.
// Consumer could optionally configure groupInstanceId to avoid unnecessary rebalances.
this.groupInstanceId = "giid-" + threadName;
boolean readCommitted = true;
consumer = new Consumer(
"processor-consumer", KafkaProperties.KAFKA_SERVER_URL + ":" + KafkaProperties.KAFKA_SERVER_PORT, inputTopic, "processor-group", Optional.of(groupInstanceId), readCommitted, -1, null)
.createKafkaConsumer();
this.latch = latch;
}
@Override
public void run() {
int processedRecords = 0;
long remainingRecords = Long.MAX_VALUE;
// it is recommended to have a relatively short txn timeout in order to clear pending offsets faster
int transactionTimeoutMs = 10_000;
// consumer must be in read_committed mode, which means it won't be able to read uncommitted data
boolean readCommitted = true;
try (KafkaProducer<Integer, String> producer = new Producer("processor-producer", bootstrapServers, outputTopic,
true, transactionalId, true, -1, transactionTimeoutMs, null).createKafkaProducer();
KafkaConsumer<Integer, String> consumer = new Consumer("processor-consumer", bootstrapServers, inputTopic,
"processor-group", Optional.of(groupInstanceId), readCommitted, -1, null).createKafkaConsumer()) {
// called first and once to fence zombies and abort any pending transaction
producer.initTransactions();
consumer.subscribe(singleton(inputTopic), this);
Utils.printOut("Processing new records");
while (!closed && remainingRecords > 0) {
try {
ConsumerRecords<Integer, String> records = consumer.poll(ofMillis(200));
if (!records.isEmpty()) {
// begin a new transaction session
producer.beginTransaction();
for (ConsumerRecord<Integer, String> record : records) {
// process the record and send downstream
ProducerRecord<Integer, String> newRecord =
new ProducerRecord<>(outputTopic, record.key(), record.value() + "-ok");
producer.send(newRecord);
}
// checkpoint the progress by sending offsets to group coordinator broker
// note that this API is only available for broker >= 2.5
producer.sendOffsetsToTransaction(getOffsetsToCommit(consumer), consumer.groupMetadata());
// commit the transaction including offsets
producer.commitTransaction();
processedRecords += records.count();
}
} catch (AuthorizationException | UnsupportedVersionException | ProducerFencedException
| FencedInstanceIdException | OutOfOrderSequenceException | SerializationException e) {
// we can't recover from these exceptions
Utils.printErr(e.getMessage());
shutdown();
} catch (OffsetOutOfRangeException | NoOffsetForPartitionException e) {
// invalid or no offset found without auto.reset.policy
Utils.printOut("Invalid or no offset found, using latest");
consumer.seekToEnd(emptyList());
consumer.commitSync();
} catch (KafkaException e) {
// abort the transaction and try to continue
Utils.printOut("Aborting transaction: %s", e);
producer.abortTransaction();
}
remainingRecords = getRemainingRecords(consumer);
if (remainingRecords != Long.MAX_VALUE) {
Utils.printOut("Remaining records: %d", remainingRecords);
}
}
} catch (Throwable e) {
Utils.printOut("Unhandled exception");
e.printStackTrace();
}
Utils.printOut("Processed %d records", processedRecords);
shutdown();
}
@Override
public void onPartitionsRevoked(Collection<TopicPartition> partitions) {
Utils.printOut("Revoked partitions: %s", partitions);
}
@Override
public void onPartitionsAssigned(Collection<TopicPartition> partitions) {
Utils.printOut("Assigned partitions: %s", partitions);
}
@Override
public void onPartitionsLost(Collection<TopicPartition> partitions) {
Utils.printOut("Lost partitions: %s", partitions);
}
public void shutdown() {
if (!closed) {
closed = true;
latch.countDown();
}
}
private Map<TopicPartition, OffsetAndMetadata> getOffsetsToCommit(KafkaConsumer<Integer, String> consumer) {
Map<TopicPartition, OffsetAndMetadata> offsets = new HashMap<>();
for (TopicPartition topicPartition : consumer.assignment()) {
offsets.put(topicPartition, new OffsetAndMetadata(consumer.position(topicPartition), null));
}
return offsets;
}
private long getRemainingRecords(KafkaConsumer<Integer, String> consumer) {
final Map<TopicPartition, Long> fullEndOffsets = consumer.endOffsets(new ArrayList<>(consumer.assignment()));
// if we can't detect any end offset, that means we are still not able to fetch offsets
if (fullEndOffsets.isEmpty()) {
return Long.MAX_VALUE;
}
return consumer.assignment().stream().mapToLong(partition -> {
long currentPosition = consumer.position(partition);
if (fullEndOffsets.containsKey(partition)) {
return fullEndOffsets.get(partition) - currentPosition;
} else {
return 0;
}
}).sum();
}
}