AHeise commented on code in PR #25456:
URL: https://github.com/apache/flink/pull/25456#discussion_r1805994539
##########
flink-runtime/src/main/java/org/apache/flink/streaming/api/connector/sink2/GlobalCommitterOperator.java:
##########
@@ -47,10 +47,50 @@
import java.util.Collections;
import java.util.List;
+import static
org.apache.flink.streaming.api.connector.sink2.CommittableMessage.EOI;
import static org.apache.flink.util.Preconditions.checkNotNull;
-class GlobalCommitterOperator<CommT, GlobalCommT> extends
AbstractStreamOperator<Void>
- implements OneInputStreamOperator<CommittableMessage<CommT>, Void>,
BoundedOneInput {
+/**
+ * Implements the {@code GlobalCommitter}.
+ *
+ * <p>This operator usually trails behind a {@code CommitterOperator}. In this
case, the global
+ * committer will receive committables from the committer operator through
{@link
+ * #processElement(StreamRecord)}. Once all committables from all subtasks
have been received, the
+ * global committer will commit them.
+ *
+ * <p>That means that the global committer will not wait for {@link
+ * #notifyCheckpointComplete(long)}. In many cases, it receives the callback
before the actual
+ * committables anyway. So it would effectively globally commit one checkpoint
later.
+ *
+ * <p>However, we can leverage the following observation: the global committer
will only receive
+ * committables iff the respective checkpoint was completed and upstream
committers received the
+ * {@link #notifyCheckpointComplete(long)}. So by waiting for all committables
of a given
+ * checkpoint, we implicitly know that the checkpoint was successful and the
global committer is
+ * supposed to globally commit.
+ *
+ * <p>Note that committables of checkpoint X are not checkpointed in X because
the global committer
+ * is trailing behind the checkpoint. They are replayed from the committer
state in case of an
+ * error. The state only includes incomplete checkpoints coming from upstream
committers not
+ * receiving {@link #notifyCheckpointComplete(long)}. All committables
received are successful.
+ *
+ * <p>In rare cases, the GlobalCommitterOperator may be connected to a writer
directly. In this
Review Comment:
Yes, you are right. I'll clarify the comment - the good already acknowledges
that.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: issues-unsubscr...@flink.apache.org
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org
