@Override
    protected void recordDropped(SourceRecord record) {
        synchronized (committableRecords) {
            committableRecords.put(record, null);
        }
        transactionBoundaryManager.maybeCommitTransactionForRecord(record);
    }
WorkerTask that uses a {@link SourceTask} to ingest data into Kafka, with support for exactly-once semantics.
connect/runtime/src/main/java/org/apache/kafka/connect/runtime/ExactlyOnceWorkerSourceTask.java