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.*;
10 import org.apache.kafka.streams.kstream.KStream;
11 import org.apache.kafka.streams.kstream.KTable;
12 import org.apache.kafka.streams.kstream.Materialized;
13 import org.apache.kafka.streams.state.HostInfo;
14 import org.apache.kafka.streams.state.QueryableStoreTypes;
15 import org.apache.kafka.streams.state.ReadOnlyKeyValueStore;
18 import java.util.Optional;
19 import java.util.Properties;
23 public class QueryStreamProcessor
25 public static final String STORE_NAME = "rankings-by-username";
27 public final KafkaStreams streams;
28 public final HostInfo hostInfo;
29 public final StoreQueryParameters<ReadOnlyKeyValueStore<String, String>> storeParameters;
30 public final ObjectMapper mapper;
33 public QueryStreamProcessor(
35 HostInfo applicationServer,
36 String usersInputTopic,
37 String rankingInputTopic,
40 Topology topology = buildTopology(usersInputTopic, rankingInputTopic, mapper);
41 streams = new KafkaStreams(topology, props);
42 hostInfo = applicationServer;
43 storeParameters = StoreQueryParameters.fromNameAndType(STORE_NAME, QueryableStoreTypes.keyValueStore());;
47 static Topology buildTopology(
48 String usersInputTopic,
49 String rankingInputTopic,
52 StreamsBuilder builder = new StreamsBuilder();
54 KTable<String, String> users = builder.table(usersInputTopic);
55 KStream<String, String> rankings = builder.stream(rankingInputTopic);
58 .join(users, (rankingJson, userJson) ->
62 Ranking ranking = mapper.readValue(rankingJson, Ranking.class);
63 User user = mapper.readValue(userJson, User.class);
65 return mapper.writeValueAsString(
69 ranking.getEntries()));
71 catch (JsonProcessingException e)
73 throw new RuntimeException(e);
76 .toTable(Materialized.as(STORE_NAME));
78 Topology topology = builder.build();
79 log.info("\n\n{}", topology.describe());
84 public Optional<URI> getRedirect(String username)
86 KeyQueryMetadata metadata = streams.queryMetadataForKey(STORE_NAME, username, Serdes.String().serializer());
87 HostInfo activeHost = metadata.activeHost();
88 log.debug("Local store for {}: {}, {}:{}", username, metadata.partition(), activeHost.host(), activeHost.port());
90 if (activeHost.equals(this.hostInfo) || activeHost.equals(HostInfo.unavailable()))
92 return Optional.empty();
95 URI location = URI.create("http://" + activeHost.host() + ":" + activeHost.port() + "/" + username);
96 log.debug("Redirecting to {}", location);
97 return Optional.of(location);
100 public Optional<UserRanking> getUserRanking(String username)
104 .ofNullable(streams.store(storeParameters).get(username))
109 return mapper.readValue(json, UserRanking.class);
111 catch (JsonProcessingException e)
113 throw new RuntimeException(e);
121 log.info("Starting Stream-Processor");
128 log.info("Stopping Stream-Processor");