private SourceRecord normalizeHeartbeatRecord(SourceRecord heartbeatRecord) {
        final Struct heartbeatValue = new Struct(HEARTBEAT_VALUE_SCHEMA);
        heartbeatValue.put(TIMESTAMP_KEY_FIELD, Instant.now().toEpochMilli());

        return new SourceRecord(
                heartbeatRecord.sourcePartition(),
                heartbeatRecord.sourceOffset(),
                heartbeatRecord.topic(),
                heartbeatRecord.keySchema(),
                heartbeatRecord.key(),
                HEARTBEAT_VALUE_SCHEMA,
                heartbeatValue);
    }
The task to work for fetching data of MongoDB stream split .
Copy from com.ververica:flink-connector-mongodb-cdc:2.3.0.
inlong-sort/sort-flink/sort-flink-v1.13/sort-connectors/mongodb-cdc/src/main/java/org/apache/inlong/sort/cdc/mongodb/source/reader/fetch/MongoDBStreamFetchTask.java