testing

sdks/java/io/kafka/src/main/java/org/apache/beam/sdk/io/kafka/KafkaUnboundedReader.java

@@ -158,6 +158,7 @@ public boolean advance() throws IOException {
      */
     while (true) {
       if (curBatch.hasNext()) {
+        // data from the next partition?
         PartitionState<K, V> pState = curBatch.next();
 
         if (!pState.recordIter.hasNext()) { // -- (c)
@@ -228,14 +229,16 @@ public boolean advance() throws IOException {
         for (Map.Entry<String, Long> backlogSplit : perPartitionBacklogMetrics.entrySet()) {
           backlogBytesOfSplit.set(backlogSplit.getValue());
         }
-        return true;
+        return true; // record has been read and proccessed, so we return. (only read a record at a time)
 
       } else { // -- (b)
-        nextBatch();
+        nextBatch(); // void, returns nothing, can this be done in the background instead of when we call advance?
 
-        if (!curBatch.hasNext()) {
+        if (!curBatch.hasNext()) { // returns false because nothing returned in time?
           return false;
         }
+        // Gives no such element exception
+        // return true; //? returns, then will call advance again. Whats the difference between repeatedly calling advance vs iterating over constatnly? 
       }
     }
   }