Very slow producer

Hi,

I’m writing my own producer to read from text files, and send line by line to Kafka cluster. I notice that the producer is extremely slow. It's currently sending at ~57KB/node/s. This is like 50-100 times slower than using bin/kafka-console-producer.sh

Here’s my producer:
final File dir = new File(dataDir);
List<File> files = new ArrayList<>(Arrays.asList(dir.listFiles()));
int key = 0;
for (final File file : files) {
try {
BufferedReader br = new BufferedReader(new FileReader(file));
for (String line = br.readLine(); line != null; line = br.readLine()) {
KeyedMessage<String, String> data = new KeyedMessage<>(topic, Integer.toString(key++), line);
producer.send(data);

} catch (IOException e) {
e.printStackTrace();

And partitioner:
public int partition(Object key, int numPartitions) {
String stringKey = (String)key;
return Integer.parseInt(stringKey) % numPartitions;

The only difference between kafka-console-producer.sh code and my code is that I use a custom partitioner. I have no idea why it’s so slow.

Best regards,Huy, Le Van