vamossagar12 commented on code in PR #13801:
URL: https://github.com/apache/kafka/pull/13801#discussion_r1463150319


##########
connect/runtime/src/main/java/org/apache/kafka/connect/storage/ConnectorOffsetBackingStore.java:
##########
@@ -279,15 +290,54 @@ public Future<Void> set(Map<ByteBuffer, ByteBuffer> 
values, Callback<Void> callb
             throw new IllegalStateException("At least one non-null offset 
store must be provided");
         }
 
-        return primaryStore.set(values, (primaryWriteError, ignored) -> {
+        List<ByteBuffer> partitionsWithTombstoneOffsets = 
values.entrySet().stream()
+                .filter(offsetEntry -> offsetEntry.getValue() == null)
+                .map(Map.Entry::getKey).collect(Collectors.toList());
+
+        Map<ByteBuffer, ByteBuffer> tombstoneOffsets = new HashMap<>();
+        for (ByteBuffer partition : partitionsWithTombstoneOffsets) {
+            tombstoneOffsets.put(partition, null);
+        }
+        Map<ByteBuffer, ByteBuffer> regularOffsets = values.entrySet().stream()
+                .filter(offsetEntry -> offsetEntry.getValue() != null)
+                .collect(Collectors.toMap(Map.Entry::getKey, 
Map.Entry::getValue));
+
+        // If the supplied offsets contain tombstone values, then tombstone 
offsets are extracted first,
+        // written to the secondary store in a synchronous manner and then to 
the primary store.
+        // This is because, if a tombstone offset is successfully written to 
the per-connector offsets topic,
+        // but cannot be written to the global offsets topic, then the global 
offsets topic will still contain that
+        // source offset, but the per-connector topic will not. Due to the 
fallback-on-global logic used by the worker,
+        // if a task requests offsets for one of the tombstoned partitions, 
the worker will provide it with the
+        // offsets present in the global offsets topic, instead of indicating 
to the task that no offsets can be found.
+        CompletableFuture<Void> offsetWriteFuture = 
CompletableFuture.completedFuture(null);
+        if (secondaryStore != null && !tombstoneOffsets.isEmpty()) {
+            offsetWriteFuture.thenAccept(v -> {

Review Comment:
   I have actually removed the chaining using `CompletableFuture` and 
simplified the logic. I just wait on the secondary store write directly (with 
or without a timeout) and if the execution fails or the wait itself fails, I 
update the callback and return the same exception (because it's already 
completed).
   
   ```
   if (secondaryStore != null && !tombstoneOffsets.isEmpty()) {
               Future<Void> secondaryWriteFuture = 
secondaryStore.set(tombstoneOffsets, (t, r) -> { });
               try {
                   if (exactlyOnce) {
                       secondaryWriteFuture.get();
                   } else {
                       secondaryWriteFuture.get(offsetFlushTimeoutMs, 
TimeUnit.MILLISECONDS);
                   }
                   log.debug("Successfully flushed tombstone offsets to 
secondary store");
               } catch (ExecutionException e) {
                   log.error("{} Failed to flush tombstone offsets to secondary 
store", this, e.getCause());
                   callback.onCompletion(e.getCause(), null);
                   return secondaryWriteFuture;
               } catch (Throwable e) {
                   log.error("{} Failed to flush tombstone offsets to secondary 
store", this, e);
                   callback.onCompletion(e, null);
                   return secondaryWriteFuture;
               }
           }
   ```
   
   With this,  there are no changes (apart from using `regularOffsets` when 
writing to secondary store) from the primary store. Let me know what you think 
about this.



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