C0urante commented on code in PR #13948:
URL: https://github.com/apache/kafka/pull/13948#discussion_r1262996406


##########
connect/api/src/main/java/org/apache/kafka/connect/source/SourceTask.java:
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@@ -105,9 +105,11 @@ public void initialize(SourceTaskContext context) {
     public abstract List<SourceRecord> poll() throws InterruptedException;
 
     /**
-     * <p>
-     * Commit the offsets, up to the offsets that have been returned by {@link 
#poll()}. This
-     * method should block until the commit is complete.
+     * This method is invoked periodically when offsets are committed for this 
source task. Note that the offsets
+     * being committed won't necessarily correspond to the latest offsets 
returned by this source task via
+     * {@link #poll()}. When exactly-once support is disabled, offsets are 
committed periodically and asynchronously
+     * (i.e. on a separate thread from the one which calls {@link #poll()}). 
When exactly-once support is enabled,
+     * offsets are committed on transaction commits (also see {@link 
TransactionBoundary}).

Review Comment:
   I don't love how we're outlining differences in behavior when exactly-once 
support is enabled/disabled; it adds to the cognitive load and may tempt 
connector developers to write connectors that are designed to work exclusively 
with one mode or the other.
   
   Could it be enough to leave this bit out and rely on the "Note that the 
offsets being committed won't necessarily correspond to the latest offsets 
returned by this source task via `poll`" part? We can also refer people to 
[SourceTask::commitRecord](https://kafka.apache.org/35/javadoc/org/apache/kafka/connect/source/SourceTask.html#commitRecord(org.apache.kafka.connect.source.SourceRecord,org.apache.kafka.clients.producer.RecordMetadata))
 for fine-grained tracking of records (though there's also no guarantee that 
all records that have been ack'd in that method will have their offsets 
committed before a call to `SourceTask::commit`).



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