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[demos/kafka/training] / src / main / java / de / juplo / kafka / ApplicationRebalanceListener.java

diff --git a/src/main/java/de/juplo/kafka/ApplicationRebalanceListener.java b/src/main/java/de/juplo/kafka/ApplicationRebalanceListener.java
new file mode 100644 (file)
index 0000000..2fccb4f
--- /dev/null
+++ b/src/main/java/de/juplo/kafka/ApplicationRebalanceListener.java
@@ -0,0 +1,83 @@
+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, Long> consumer;
+
+  private Instant lastCommit = Instant.EPOCH;
+
+  @Override
+  public void onPartitionsAssigned(Collection<TopicPartition> partitions)
+  {
+    partitions.forEach(tp ->
+    {
+      Integer partition = tp.partition();
+      Long offset = consumer.position(tp);
+      log.info("{} - adding partition: {}, offset={}", id, partition, offset);
+      StateDocument document =
+          stateRepository
+              .findById(Integer.toString(partition))
+              .orElse(new StateDocument(partition));
+      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 newOffset = consumer.position(tp);
+      log.info(
+          "{} - removing partition: {}, offset of next message {})",
+          id,
+          partition,
+          newOffset);
+      Map<String, Long> removed = recordHandler.removePartition(partition);
+      stateRepository.save(new StateDocument(partition, removed, consumer.position(tp)));
+    });
+  }
+
+
+  @Override
+  public void beforeNextPoll()
+  {
+    if (lastCommit.plus(commitInterval).isBefore(clock.instant()))
+    {
+      log.debug("Storing data and offsets, last commit: {}", lastCommit);
+      recordHandler.getState().forEach((partiton, state) -> stateRepository.save(
+          new StateDocument(
+              partiton,
+              state,
+              consumer.position(new TopicPartition(topic, partiton)))));
+      lastCommit = clock.instant();
+    }
+  }
+}