+package de.juplo.kafka;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.apache.kafka.clients.consumer.Consumer;
+import org.apache.kafka.common.TopicPartition;
+
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.Collection;
+import java.util.Map;
+
+
+@RequiredArgsConstructor
+@Slf4j
+public class ApplicationRebalanceListener implements PollIntervalAwareConsumerRebalanceListener
+{
+ private final ApplicationRecordHandler recordHandler;
+ private final StateRepository stateRepository;
+ private final String id;
+ private final String topic;
+ private final Clock clock;
+ private final Duration commitInterval;
+ private final Consumer<String, String> consumer;
+
+ private Instant lastCommit = Instant.EPOCH;
+ private boolean commitsEnabled = true;
+
+ @Override
+ public void onPartitionsAssigned(Collection<TopicPartition> partitions)
+ {
+ partitions.forEach(tp ->
+ {
+ Integer partition = tp.partition();
+ StateDocument document =
+ stateRepository
+ .findById(Integer.toString(partition))
+ .orElse(new StateDocument(partition));
+ log.info("{} - adding partition: {}, offset={}", id, partition, document.offset);
+ if (document.offset >= 0)
+ {
+ // Only seek, if a stored offset was found
+ // Otherwise: Use initial offset, generated by Kafka
+ consumer.seek(tp, document.offset);
+ }
+ recordHandler.addPartition(partition, document.state);
+ });
+ }
+
+ @Override
+ public void onPartitionsRevoked(Collection<TopicPartition> partitions)
+ {
+ partitions.forEach(tp ->
+ {
+ Integer partition = tp.partition();
+ Long offset = consumer.position(tp);
+ log.info(
+ "{} - removing partition: {}, offset of next message {})",
+ id,
+ partition,
+ offset);
+ if (commitsEnabled)
+ {
+ Map<String, Long> removed = recordHandler.removePartition(partition);
+ stateRepository.save(new StateDocument(partition, removed, offset));
+ }
+ else
+ {
+ log.info("Offset commits are disabled! Last commit: {}", lastCommit);
+ }
+ });
+ }
+
+
+ @Override
+ public void beforeNextPoll()
+ {
+ if (!commitsEnabled)
+ {
+ log.info("Offset commits are disabled! Last commit: {}", lastCommit);
+ return;
+ }
+
+ if (lastCommit.plus(commitInterval).isBefore(clock.instant()))
+ {
+ log.debug("Storing data and offsets, last commit: {}", lastCommit);
+ recordHandler.getState().forEach((partiton, adder) -> stateRepository.save(
+ new StateDocument(
+ partiton,
+ adder.getState(),
+ consumer.position(new TopicPartition(topic, partiton)))));
+ lastCommit = clock.instant();
+ }
+ }
+
+ @Override
+ public void enableCommits()
+ {
+ commitsEnabled = true;
+ }
+
+ @Override
+ public void disableCommits()
+ {
+ commitsEnabled = false;
+ }
+}