lianetm commented on code in PR #18336:
URL: https://github.com/apache/kafka/pull/18336#discussion_r1900988248
##########
clients/src/main/java/org/apache/kafka/clients/consumer/KafkaConsumer.java:
##########
@@ -70,8 +70,12 @@
* <h3>Offsets and Consumer Position</h3>
* Kafka maintains a numerical offset for each record in a partition. This
offset acts as a unique identifier of
* a record within that partition, and also denotes the position of the
consumer in the partition. For example, a consumer
- * which is at position 5 has consumed records with offsets 0 through 4 and
will next receive the record with offset 5. There
- * are actually two notions of position relevant to the user of the consumer:
+ * which is at position 5 has consumed records with offsets 0 through 4 and
will next receive the record with offset 5.
+ * Note that offsets are not guaranteed to be consecutive (eg., for compacted
topic, or—independent of "read_committed"
+ * mode— transactional topics). For example, if the consumer did read a
record with offset 4, but 5 is not an offset
+ * with a record, it's position might advance to 6 (or higher) directly.
Similarly, if the consumer's position is 5,
+ * but there is no record with offset 5, the consumer will return the record
with the next higher offset.
+ * There are actually two notions of position relevant to the user of the
consumer:
Review Comment:
Related to this but on ln 84 right below (sorry couldn't add comment there):
```
The {@link #commitSync() committed position} is the last offset that has
been stored securely
```
shouldn't that refer to committed(..) instead?
```
The {@link #committed(Set) committed position} is the last offset that has
been stored securely
```
##########
clients/src/main/java/org/apache/kafka/clients/consumer/KafkaConsumer.java:
##########
@@ -266,8 +270,7 @@
* for (ConsumerRecord<String, String> record :
partitionRecords) {
* System.out.println(record.offset() + ": " +
record.value());
* }
- * long lastOffset =
partitionRecords.get(partitionRecords.size() - 1).offset();
- * consumer.commitSync(Collections.singletonMap(partition, new
OffsetAndMetadata(lastOffset + 1)));
+ * consumer.commitSync(Collections.singletonMap(partition,
partitionRecords.nextOffsets().get(partition));
Review Comment:
and missing parenthesis, I guess we should end with :
```suggestion
* consumer.commitSync(Collections.singletonMap(partition,
records.nextOffsets().get(partition)));
```
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