WIP: Dirty in-place implementation

[demos/kafka/wordcount] / src / main / java / de / juplo / kafka / wordcount / top10 / Top10StreamProcessor.java

diff --git a/src/main/java/de/juplo/kafka/wordcount/top10/Top10StreamProcessor.java b/src/main/java/de/juplo/kafka/wordcount/top10/Top10StreamProcessor.java
index aa21c4a..2bc1da7 100644 (file)
--- a/src/main/java/de/juplo/kafka/wordcount/top10/Top10StreamProcessor.java
+++ b/src/main/java/de/juplo/kafka/wordcount/top10/Top10StreamProcessor.java
@@ -10,11 +10,9 @@ import io.confluent.kafka.streams.serdes.avro.SpecificAvroSerializer;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.kafka.clients.consumer.ConsumerConfig;
 import org.apache.kafka.common.serialization.Serdes;
-import org.apache.kafka.streams.KafkaStreams;
-import org.apache.kafka.streams.KeyValue;
-import org.apache.kafka.streams.StreamsBuilder;
-import org.apache.kafka.streams.StreamsConfig;
+import org.apache.kafka.streams.*;
 import org.apache.kafka.streams.kstream.Consumed;
+import org.apache.kafka.streams.kstream.Grouped;
 import org.apache.kafka.streams.kstream.Materialized;
 import org.apache.kafka.streams.kstream.Produced;
 import org.springframework.boot.SpringApplication;
@@ -23,6 +21,9 @@ import org.springframework.stereotype.Component;
 
 import javax.annotation.PostConstruct;
 import javax.annotation.PreDestroy;
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
 import java.util.Properties;
 import java.util.concurrent.CompletableFuture;
 import java.util.regex.Pattern;
@@ -51,14 +52,44 @@ public class Top10StreamProcessor
                                .map((key, count) -> new KeyValue<>(
                                                key.getUsername(),
                                                Entry.newBuilder().setWord(key.getWord()).setCount(count).build()))
-                               .groupByKey()
+                               .groupByKey(Grouped.keySerde(Serdes.String()))
                                .aggregate(
-                                               () -> Ranking.newBuilder().build(),
-                                               (username, entry, ranking) -> {
-                                                       ranking.getEntries().add(entry);
+                                               () -> Ranking.newBuilder().setEntries(new LinkedList<Entry>()).build(),
+                                               (username, newEntry, ranking) -> {
+                                                       List<Entry> entries = new LinkedList<>(ranking.getEntries());
+
+                                                       if (entries.isEmpty())
+                                                       {
+                                                               entries.add(newEntry);
+                                                       }
+                                                       else
+                                                       {
+                                                               for (int i = 0; i < entries.size(); i++)
+                                                               {
+                                                                       Entry entry = entries.get(i);
+                                                                       if (entry.getCount() <= newEntry.getCount())
+                                                                       {
+                                                                               entries.add(i, newEntry);
+                                                                               for (int j = i + 1; j < entries.size(); j++)
+                                                                               {
+                                                                                       entry = entries.get(j);
+                                                                                       if (entry.getWord().equals(newEntry.getWord()))
+                                                                                       {
+                                                                                               entries.remove(j);
+                                                                                               break;
+                                                                                       }
+                                                                               }
+                                                                               if (entries.size() > 10)
+                                                                               {
+                                                                                       entries = entries.subList(0, 10);
+                                                                               }
+                                                                       }
+                                                               }
+                                                       }
+
+                                                       ranking.setEntries(entries);
                                                        return ranking;
-                                               },
-                                               Materialized.with(Serdes.String(), null))
+                                               })
                                .toStream()
                                .to(properties.getOutputTopic(), Produced.keySerde(Serdes.String()));
 
@@ -70,7 +101,10 @@ public class Top10StreamProcessor
                props.put(AbstractKafkaSchemaSerDeConfig.SCHEMA_REGISTRY_URL_CONFIG, properties.getSchemaRegistry());
                props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
 
-               streams = new KafkaStreams(builder.build(), props);
+               Topology topology = builder.build();
+               log.info("Topology:\n-----------------\n\n{}-----------------", topology.describe());
+
+               streams = new KafkaStreams(topology, props);
                streams.setUncaughtExceptionHandler((Throwable e) ->
                {
                        log.error("Unexpected error!", e);