I am trying to write a quick sample of streaming word count using Beam APIs and
FlinkBeamRunner.
The problem that I am getting into is that
apply("Write to Kafka", Write.to(UnboundedFlinkSink.of(kafkaSink)))
Does not work in this way - it assumes bounded stream and mine is unbounded.
I have not found any unbounded equivalent for Write, So I tried to implement a
custom ParDo function:
/**
* Write content to Kafka.
*
*/
static class WriteToKafkaFn extends DoFn<Tuple2<String, Integer>,
Tuple2<String, Integer>> {
private FlinkKafkaProducer09<Tuple2<String, Integer>> kafkaSink;
private boolean opened = false;
public WriteToKafkaFn(FlinkKafkaProducer09<Tuple2<String, Integer>>
kafkaSink){
this.kafkaSink = kafkaSink;
}
@ProcessElement
public void processElement(ProcessContext c) {
if(!opened){
kafkaSink.open(new Configuration());
opened = true;
}
Tuple2<String, Integer> record = c.element();
try {
kafkaSink.invoke(record);
}catch(Throwable t){
System.out.println("Error writing record " + record + " to Kafka");
t.printStackTrace();
}
}
}
The problem with this approach is that ParDo is not initialized with Streaming
context, that FlinkKafkaConsumer relies upon, so open fails.
Any suggestions?
