juplo.de Git - demos/kafka/wordcount/blob - src/main/java/de/juplo/kafka/wordcount/counter/CounterStreamProcessor.java

   1 package de.juplo.kafka.wordcount.counter;
   2
   3 import com.fasterxml.jackson.core.JsonProcessingException;
   4 import com.fasterxml.jackson.databind.ObjectMapper;
   5 import lombok.extern.slf4j.Slf4j;
   6 import org.apache.kafka.clients.consumer.ConsumerConfig;
   7 import org.apache.kafka.common.serialization.Serdes;
   8 import org.apache.kafka.streams.KafkaStreams;
   9 import org.apache.kafka.streams.KeyValue;
  10 import org.apache.kafka.streams.StreamsBuilder;
  11 import org.apache.kafka.streams.StreamsConfig;
  12 import org.apache.kafka.streams.kstream.KStream;
  13 import org.springframework.boot.SpringApplication;
  14 import org.springframework.context.ConfigurableApplicationContext;
  15 import org.springframework.stereotype.Component;
  16
  17 import jakarta.annotation.PostConstruct;
  18 import jakarta.annotation.PreDestroy;
  19 import java.util.Properties;
  20 import java.util.concurrent.CompletableFuture;
  21
  22 import static org.apache.kafka.streams.errors.StreamsUncaughtExceptionHandler.StreamThreadExceptionResponse.SHUTDOWN_CLIENT;
  23
  24
  25 @Slf4j
  26 @Component
  27 public class CounterStreamProcessor
  28 {
  29         public final KafkaStreams streams;
  30
  31
  32         public CounterStreamProcessor(
  33                         CounterApplicationProperties properties,
  34                         ObjectMapper mapper,
  35                         ConfigurableApplicationContext context)
  36         {
  37                 StreamsBuilder builder = new StreamsBuilder();
  38
  39                 KStream<String, String> source = builder.stream(properties.getInputTopic());
  40                 source
  41                                 .map((username, word) ->
  42                                 {
  43                                         try
  44                                         {
  45                                                 String key = mapper.writeValueAsString(Key.of(username, word));
  46                                                 return new KeyValue<>(key, word);
  47                                         }
  48                                         catch (JsonProcessingException e)
  49                                         {
  50                                                 throw new RuntimeException(e);
  51                                         }
  52                                 })
  53                                 .groupByKey()
  54                                 .count()
  55                                 .mapValues(value->Long.toString(value))
  56                                 .toStream()
  57                                 .to(properties.getOutputTopic());
  58
  59                 Properties props = new Properties();
  60                 props.put(StreamsConfig.APPLICATION_ID_CONFIG, properties.getApplicationId());
  61                 props.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, properties.getBootstrapServer());
  62                 props.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName());
  63                 props.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName());
  64                 props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
  65
  66                 streams = new KafkaStreams(builder.build(), props);
  67                 streams.setUncaughtExceptionHandler((Throwable e) ->
  68                 {
  69                         log.error("Unexpected error!", e);
  70                         CompletableFuture.runAsync(() ->
  71                         {
  72                                 log.info("Stopping application...");
  73                                 SpringApplication.exit(context, () -> 1);
  74                         });
  75                         return SHUTDOWN_CLIENT;
  76                 });
  77         }
  78
  79         @PostConstruct
  80         public void start()
  81         {
  82                 log.info("Starting Stream-Processor");
  83                 streams.start();
  84         }
  85
  86         @PreDestroy
  87         public void stop()
  88         {
  89                 log.info("Stopping Stream-Processor");
  90                 streams.close();
  91         }
  92 }