1 package de.juplo.kafka.wordcount.query;
3 import com.fasterxml.jackson.core.JsonProcessingException;
4 import com.fasterxml.jackson.databind.ObjectMapper;
5 import jakarta.annotation.PostConstruct;
6 import jakarta.annotation.PreDestroy;
7 import lombok.extern.slf4j.Slf4j;
8 import org.apache.kafka.common.serialization.Serdes;
9 import org.apache.kafka.streams.KafkaStreams;
10 import org.apache.kafka.streams.KeyQueryMetadata;
11 import org.apache.kafka.streams.StoreQueryParameters;
12 import org.apache.kafka.streams.StreamsBuilder;
13 import org.apache.kafka.streams.kstream.KStream;
14 import org.apache.kafka.streams.kstream.KTable;
15 import org.apache.kafka.streams.kstream.Materialized;
16 import org.apache.kafka.streams.state.HostInfo;
17 import org.apache.kafka.streams.state.QueryableStoreTypes;
18 import org.apache.kafka.streams.state.ReadOnlyKeyValueStore;
21 import java.util.Optional;
22 import java.util.Properties;
26 public class QueryStreamProcessor
28 public static final String STORE_NAME = "rankings-by-username";
30 public final KafkaStreams streams;
31 public final HostInfo hostInfo;
32 public final StoreQueryParameters<ReadOnlyKeyValueStore<String, String>> storeParameters;
33 public final ObjectMapper mapper;
36 public QueryStreamProcessor(
38 HostInfo applicationServer,
39 String usersInputTopic,
40 String rankingInputTopic,
43 StreamsBuilder builder = new StreamsBuilder();
45 KTable<String, String> users = builder.table(usersInputTopic);
46 KStream<String, String> rankings = builder.stream(rankingInputTopic);
49 .join(users, (rankingJson, userJson) ->
53 Ranking ranking = mapper.readValue(rankingJson, Ranking.class);
54 User user = mapper.readValue(userJson, User.class);
56 return mapper.writeValueAsString(
60 ranking.getEntries()));
62 catch (JsonProcessingException e)
64 throw new RuntimeException(e);
67 .toTable(Materialized.as(STORE_NAME));
69 streams = new KafkaStreams(builder.build(), props);
70 hostInfo = applicationServer;
71 storeParameters = StoreQueryParameters.fromNameAndType(STORE_NAME, QueryableStoreTypes.keyValueStore());;
75 public Optional<URI> getRedirect(String username)
77 KeyQueryMetadata metadata = streams.queryMetadataForKey(STORE_NAME, username, Serdes.String().serializer());
78 HostInfo activeHost = metadata.activeHost();
79 log.debug("Local store for {}: {}, {}:{}", username, metadata.partition(), activeHost.host(), activeHost.port());
81 if (activeHost.equals(this.hostInfo) || activeHost.equals(HostInfo.unavailable()))
83 return Optional.empty();
86 URI location = URI.create("http://" + activeHost.host() + ":" + activeHost.port() + "/" + username);
87 log.debug("Redirecting to {}", location);
88 return Optional.of(location);
91 public Optional<UserRanking> getUserRanking(String username)
95 .ofNullable(streams.store(storeParameters).get(username))
100 return mapper.readValue(json, UserRanking.class);
102 catch (JsonProcessingException e)
104 throw new RuntimeException(e);
112 log.info("Starting Stream-Processor");
119 log.info("Stopping Stream-Processor");