@Override
    public void handleSplitRequest(int subtaskId, @Nullable String requesterHostname) {
        if (!context.registeredReaders().containsKey(subtaskId)) {
            // reader failed between sending the request and now. skip this request.
            return;
        }

        readersAwaitingSplit.add(subtaskId);
        assignSplits();
    }
Incremental source enumerator that enumerates receive the split request and assign the split to
source readers.
Copy from com.ververica:flink-cdc-base:2.3.0.
inlong-sort/sort-flink/cdc-base/src/main/java/org/apache/inlong/sort/cdc/base/source/enumerator/IncrementalSourceEnumerator.java