private boolean isTransactional = config.getTransactionalProducer();
    private boolean transactionInProgress = false;
	protected Map<TopicPartition, OffsetAndMetadata> offsetsMap = new HashMap<>();
    private Set<TopicPartition> taskTopicPartitions;
	private KafkaProducer<byte[], byte[]> producer;
    private String connectConsumerGroup;

    @Override
	public void start(Map<String, String> props) {
		config = new MirrorTaskConfig(props);
	    taskTopicPartitions = config.taskTopicPartitions();
        isTransactional = config.transactionalProducer();
	    producer = initProducer(isTransactional);
        connectConsumerGroup = getSourceConsumerGroupId();
		if (isTransactional) {
	        loadContextOffsets();
        }
    }

    @Override
    public void open(Collection<TopicPartition> partitions) {
		if (isTransactional) {
    	    loadContextOffsets();
		}
    }

    private void loadContextOffsets() {
		Map<TopicPartition, OffsetAndMetadata> initOffsetsOnTarget = listTargetConsumerGroupOffsets(connectConsumerGroup);
	
        Set<TopicPartition> assignments = context.assignment();

        // only keep the offsets of the partitions assigned to this task
        Map<TopicPartition, Long> contextOffsets = assignments.stream()
        		                                              .filter(x -> currentOffsets.containsKey(x))
                                                              .collect(Collectors.toMap(
        		                                              x -> x, x -> currentOffsets.get(x)));

        context.offset(contextOffsets);
    }

	protected KafkaProducer<byte[], byte[]> initProducer(boolean isTransactional) {
        Map<String, Object> producerConfig = config.targetProducerConfig();
        if (isTransactional) {
        	String transactionId = getTransactionId();
        	log.info("use transactional producer with Id: {} ", transactionId);
            producerConfig.put(ProducerConfig.ACKS_CONFIG, "all"

    private boolean isTransactional = config.getTransactionalProducer();
    private boolean transactionStart = false;
	protected Map<TopicPartition, OffsetAndMetadata> offsetsMap = new HashMap<>( producerConfig.put(ProducerConfig.ENABLE_IDEMPOTENCE_CONFIG, "true");

	protected KafkaProducer<byte[], byte[]> initProducer(boolean isTransactional) {
   	producerConfig.put(ProducerConfig.TRANSACTIONAL_ID_CONFIG, transactionId);
    Map<String, Object> producerConfig = config	producerConfig.targetProducerConfig(put(ProducerConfig.CLIENT_ID_CONFIG, transactionId);
        if}
 (isTransactional) {
      return  	logMirrorUtils.info("use transactional producer"newProducer(producerConfig);
	}

    /**
     * Per  producerConfig.put(ProducerConfig.ACKS_CONFIG, "all");
            producerConfig.put(ProducerConfig.ENABLE_IDEMPOTENCE_CONFIG, "true");
        	producerConfig.put(ProducerConfig.TRANSACTIONAL_ID_CONFIG, genTransactionId());
        	producerConfig.put(ProducerConfig.CLIENT_ID_CONFIG, "trasactional-producer");some articles, to avoid ProducerFencedException, transaction id is suggested to set application name + hostname
     * Each MirrorSinkTask is also assigned with different set of <topic, partition>. To get unique transaction id,
     * one way }is elseto {
append connector name, hostname and string of  	producerConfig.put(ProducerConfig.CLIENT_ID_CONFIG, "non-trasactional-producer");
 each <topic, partition> pair
     */
    protected String getTransactionId() }{
    	return getHostName() + "-" return+ MirrorUtils.newProducergetUniquePredictableStr(producerConfig);
	    }

    @Override
	public void put(Collection<SinkRecord> records) {
        log.info("receive {} messages from consumer", records.size());
        if (records.size() == 0) {
        	return;
        }
        try {
            sendBatch(records, producer);

        	return;
 } catch (RebalanceException e) {
   }
         producer.close();try {
            sendBatch(records, producer = initProducer(isTransactional);  
        } catch (ResendRecordsExceptionRebalanceException e) {
            abortTransactionproducer.close(producer);
            //TODO: add limited retry
            sendBatch(e.getRemainingRecords(), producer);producer = initProducer(isTransactional);  
        } catch (ThrowableResendRecordsException e) {
            log.error(getHostName() + " terminating on exception: {}", e)abortTransaction(producer);
            return;
   //TODO: add limited retry
     }
    }

    private void sendBatch(Collection<SinkRecord> records, KafkaProducer<byte[], byte[]>sendBatch(e.getRemainingRecords(), producer);
  {
      } catch try(Throwable e) {
            Map<TopicPartition, List<SinkRecord> remainingRecordsMap = new HashMap<>(log.error(getHostName() + " terminating on exception: {}", e);
            offsetsMap.clear()return;
        }
    beginTransaction(producer);}

    private void sendBatch(Collection<SinkRecord> records,     SinkRecord record;KafkaProducer<byte[], byte[]> producer) {
        try {
   for ((record = records.peek()) != null) {
   Map<TopicPartition, List<SinkRecord> remainingRecordsMap = new HashMap<>();
        ProducerRecord<byte[], byte[]> producerRecord = convertToProducerRecordoffsetsMap.clear(record);
                offsetsMap.compute(new TopicPartition(record.topic(), record.kafkaPartition()),beginTransaction(producer);
            SinkRecord record;
          (tp, curOffsetMetadata) ->
  for ((record = records.peek()) != null) {
                ProducerRecord<byte[], byte[]> producerRecord = convertToProducerRecord(record);
             (curOffsetMetadata == null ||  offsetsMap.compute(new TopicPartition(record.kafkaOffsettopic(), > curOffsetMetadatarecord.offsetkafkaPartition()),
                       (tp,                ?curOffsetMetadata) ->
                               (curOffsetMetadata == null || record.kafkaOffset()    new OffsetAndMetadata(record.kafkaOffset> curOffsetMetadata.offset())
                                       : curOffsetMetadata);?
                Future<RecordMetadata> future = producer.send(producerRecord, (recordMetadata, e) -> {
                    ifnew (e != null) {
OffsetAndMetadata(record.kafkaOffset())
                              log.error("{} failed to send record to {}: ", MirrorSinkTask.this, producerRecord.topic(), e : curOffsetMetadata);
                Future<RecordMetadata> future = producer.send(producerRecord, (recordMetadata, e) -> {
     log.debug("{} Failed record: {}", MirrorSinkTask.this, producerRecord);
          if (e != null) {
          throw new KafkaException(e);
            log.error("{} failed to send record to {}:  } else {", MirrorSinkTask.this, producerRecord.topic(), e);
                        log.infodebug("{} WroteFailed record successfully: topic {} partition {} offset {}", //log.trace
MirrorSinkTask.this, producerRecord);
                         		MirrorSinkTask.this,throw new KafkaException(e);
                    } else {
          recordMetadata.topic(), recordMetadata.partition(),
              log.info("{} Wrote record successfully: topic {} partition {} offset {}", //log.trace
            recordMetadata.offset());
            		MirrorSinkTask.this,
            commitRecord(record, recordMetadata);
                    }recordMetadata.topic(), recordMetadata.partition(),
                });
                futuresrecordMetadata.addoffset(future));
                records.poll();
         commitRecord(record, recordMetadata);
  }

        } catch (KafkaException e) {
      }
      // Any unsent messages are added to the remaining remainingRecordsMap for re-send });
            for (SinkRecord record = recordsfutures.polladd(future);
 record != null; record = records.poll()) {
            	addConsumerRecordToTopicPartitionRecordsMap(record, remainingRecordsMaprecords.poll();
        } finally {  //TODO: may add more exception handling case
      }

        } catch (KafkaException e) {
      for (Future<RecordMetadata> future : futures) {
 // Any unsent messages are added to the remaining remainingRecordsMap for re-send
    try {
       for (SinkRecord record = records.poll(); record        future.get();!= null; record = records.poll()) {
                } catch (Exception e) {	addConsumerRecordToTopicPartitionRecordsMap(record, remainingRecordsMap);
        } finally {  //TODO: may add more exception handling case
  SinkRecord record = futureMap.get(future);
       for (Future<RecordMetadata> future : futures) {
        // Any record failed to send, add to thetry remainingRecordsMap{
                    addConsumerRecordToTopicPartitionRecordsMap(record, remainingRecordsMapfuture.get();
                }
 catch (Exception e) {
        }
         }

   SinkRecord record     if (isTransactional && remainingRecordsMap.size() == 0) {
= futureMap.get(future);
                 producer.sendOffsetsToTransaction(offsetsMap, consumerGroupId);
  // Any record failed to send, add to the remainingRecordsMap
  commitTransaction(producer);
         }

        if addConsumerRecordToTopicPartitionRecordsMap(record, remainingRecordsMap.size();
 > 0) {
            // For}
 transaction case, all records should be put into remainingRecords, as the whole}
 transaction should be redone
     }

       Collection<SinkRecord> recordsToReSend;
 if (isTransactional && remainingRecordsMap.size() == 0) {
     if (isTransactional) {
      producer.sendOffsetsToTransaction(offsetsMap, consumerGroupId);
         // Transactional: retry all records, the transaction will have cancelled all of our outputs. commitTransaction(producer);
         }

        if (remainingRecordsMap.size() > 0) {
     recordsToReSend = records;
     // For transaction case, all records should }be elseput {
into remainingRecords, as the whole transaction should be redone
        // Non-transactional: only retry failed records, others already were finished and sent.
Collection<SinkRecord> recordsToReSend;
            if (isTransactional) {
        recordsToReSend = remainingRecordsMap;
      // transactional: retry all records, as }
the transaction will cancel all successful and failed records.
    throw new ResendRecordsException(recordsToReSend);
        }
  recordsToReSend = }records;

    @Override
    public Map<TopicPartition, OffsetAndMetadata> preCommit(Map<TopicPartition, OffsetAndMetadata>} offsets)else {
    	//   if transactional, return empty Map intentionally to disable the offset commit by commitOffsets() in "WorkerSinkTask.java"
        // so that the transactional producer is able to commit the consumer offsets in a transaction
    	if (isTransactional) 
    		return new HashMap<TopicPartition, OffsetAndMetadata>();
    	else // otherwise, return offsetsMap to let commitOffsets() in "WorkerSinkTask.java" to commit offsets
    		return offsetsMap;	// non-transactional: only retry failed records, others were finished and sent.
                recordsToReSend = remainingRecordsMap;
            }
            throw new ResendRecordsException(recordsToReSend);
        }
    }

    // This commitRecord() follows the same logics as commitRecord() in MirrorSourceTask, to 
    public void commitRecord(SinkRecord record, RecordMetadata metadata) {
        try {
            if (stopping) {
                return;
            }
            if (!metadata.hasOffset()) {
                log.error("RecordMetadata has no offset -- can't sync offsets for {}.", record.topic());
                return;
            }
            TopicPartition topicPartition = new TopicPartition(record.topic(), record.kafkaPartition());
            long latency = System.currentTimeMillis() - record.timestamp();
            metrics.countRecord(topicPartition);
            metrics.replicationLatency(topicPartition, latency);
            TopicPartition sourceTopicPartition = MirrorUtils.unwrapPartition(record.sourcePartition());
            long upstreamOffset = MirrorUtils.unwrapOffset(record.sourceOffset());
            long downstreamOffset = metadata.offset();
            maybeSyncOffsets(sourceTopicPartition, upstreamOffset, downstreamOffset);
        } catch (Throwable e) {
            log.warn("Failure committing record.", e);
        }
    }

    private void beginTransaction(KafkaProducer<byte[], byte[]> producer) {
        if (isTransactional) {
            producer.beginTransaction();
            transactionStarttransactionInProgress = true;
        }
    }
	
    private void initTransactions(KafkaProducer<byte[], byte[]> producer) {
        if (isTransactional) {
            producer.initTransactions();
        }
    }
    
    private void commitTransaction(KafkaProducer<byte[], byte[]> producer) {
        if (isTransactional) {
            producer.commitTransaction();
            transactionStarttransactionInProgress = false;
        }
    }
    
    private void abortTransaction(KafkaProducer<byte[], byte[]> producer) {
        if (isTransactional && transactionStarttransactionInProgress) {
            producer.abortTransaction();
            transactionStarttransactionInProgress = false;
        }
    }

    public static class ResendRecordsException extends Exception {
        private Collection<SinkRecord> remainingRecords;

        public ResendRecordsException(Collection<SinkRecord> remainingRecords) {
            super(cause);
            this.remainingRecords = remainingRecords;
        }

        public Collection<SinkRecord> getRemainingRecords() {
            return remainingRecords;
        }
    }
            return remainingRecords;
        }
    }