BE: Messages: Fix first offsets retrieval for compacted topic (#406)

Co-authored-by: iliax <ilya.kuramshin@almatech.dev>

Author: iliax

api/src/main/java/io/kafbat/ui/emitter/OffsetsInfo.java

@@ -6,11 +6,13 @@
 import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
+import java.util.stream.Collectors;
 import lombok.Getter;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.commons.lang3.mutable.MutableLong;
 import org.apache.kafka.clients.consumer.Consumer;
 import org.apache.kafka.common.TopicPartition;
+import org.apache.kafka.common.errors.UnsupportedVersionException;
 
 @Slf4j
 @Getter
@@ -34,7 +36,7 @@ class OffsetsInfo {
 
   OffsetsInfo(Consumer<?, ?> consumer, Collection<TopicPartition> targetPartitions) {
     this.consumer = consumer;
-    this.beginOffsets = consumer.beginningOffsets(targetPartitions);
+    this.beginOffsets = firstOffsetsForPolling(consumer, targetPartitions);
     this.endOffsets = consumer.endOffsets(targetPartitions);
     endOffsets.forEach((tp, endOffset) -> {
       var beginningOffset = beginOffsets.get(tp);
@@ -46,6 +48,28 @@ class OffsetsInfo {
     });
   }
 
+
+  private Map<TopicPartition, Long> firstOffsetsForPolling(Consumer<?, ?> consumer,
+                                                           Collection<TopicPartition> partitions) {
+    try {
+      // we try to use offsetsForTimes() to find earliest offsets, since for
+      // some topics (like compacted) beginningOffsets() ruturning 0 offsets
+      // even when effectively first offset can be very high
+      var offsets = consumer.offsetsForTimes(
+          partitions.stream().collect(Collectors.toMap(p -> p, p -> 0L))
+      );
+      // result of offsetsForTimes() can be null, if message version < 0.10.0
+      if (offsets.entrySet().stream().noneMatch(e -> e.getValue() == null)) {
+        return offsets.entrySet().stream()
+            .collect(Collectors.toMap(Map.Entry::getKey, e -> e.getValue().offset()));
+      }
+    } catch (UnsupportedOperationException | UnsupportedVersionException e) {
+      // offsetsForTimes() not supported
+    }
+    //falling back to beginningOffsets() if offsetsForTimes() not supported
+    return consumer.beginningOffsets(partitions);
+  }
+
   boolean assignedPartitionsFullyPolled() {
     for (var tp : consumer.assignment()) {
       Preconditions.checkArgument(endOffsets.containsKey(tp));

api/src/main/java/io/kafbat/ui/emitter/RangePollingEmitter.java

@@ -3,7 +3,9 @@
 import io.kafbat.ui.model.ConsumerPosition;
 import io.kafbat.ui.model.TopicMessageEventDTO;
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 import java.util.TreeMap;
 import java.util.function.Supplier;
 import lombok.extern.slf4j.Slf4j;
@@ -84,20 +86,22 @@ private List<ConsumerRecord<Bytes, Bytes>> poll(EnhancedConsumer consumer,
     range.forEach((tp, fromTo) -> consumer.seek(tp, fromTo.from));
 
     List<ConsumerRecord<Bytes, Bytes>> result = new ArrayList<>();
-    while (!sink.isCancelled() && consumer.paused().size() < range.size()) {
+    Set<TopicPartition> paused = new HashSet<>();
+    while (!sink.isCancelled() && paused.size() < range.size()) {
       var polledRecords = poll(sink, consumer);
       range.forEach((tp, fromTo) -> {
         polledRecords.records(tp).stream()
             .filter(r -> r.offset() < fromTo.to)
             .forEach(result::add);
 
         //next position is out of target range -> pausing partition
-        if (consumer.position(tp) >= fromTo.to) {
+        if (!paused.contains(tp) && consumer.position(tp) >= fromTo.to) {
+          paused.add(tp);
           consumer.pause(List.of(tp));
         }
       });
     }
-    consumer.resume(consumer.paused());
+    consumer.resume(paused);
     return result;
   }
 }