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.KeyValueBytesStoreSupplier;
15 import org.apache.kafka.streams.state.QueryableStoreTypes;
16 import org.apache.kafka.streams.state.ReadOnlyKeyValueStore;
19 import java.util.Optional;
20 import java.util.Properties;
24 public class QueryStreamProcessor
26 public static final String STORE_NAME = "rankings-by-username";
28 public final KafkaStreams streams;
29 public final HostInfo hostInfo;
30 public final StoreQueryParameters<ReadOnlyKeyValueStore<String, String>> storeParameters;
31 public final ObjectMapper mapper;
34 public QueryStreamProcessor(
36 HostInfo applicationServer,
37 String usersInputTopic,
38 String rankingInputTopic,
39 KeyValueBytesStoreSupplier storeSupplier,
42 Topology topology = buildTopology(
47 streams = new KafkaStreams(topology, props);
48 hostInfo = applicationServer;
49 storeParameters = StoreQueryParameters.fromNameAndType(STORE_NAME, QueryableStoreTypes.keyValueStore());;
53 static Topology buildTopology(
54 String usersInputTopic,
55 String rankingInputTopic,
56 KeyValueBytesStoreSupplier storeSupplier,
59 StreamsBuilder builder = new StreamsBuilder();
61 KTable<String, String> users = builder.table(usersInputTopic);
62 KStream<String, String> rankings = builder.stream(rankingInputTopic);
65 .join(users, (rankingJson, userJson) ->
69 Ranking ranking = mapper.readValue(rankingJson, Ranking.class);
70 User user = mapper.readValue(userJson, User.class);
72 return mapper.writeValueAsString(
76 ranking.getEntries()));
78 catch (JsonProcessingException e)
80 throw new RuntimeException(e);
83 .toTable(Materialized.as(storeSupplier));
85 Topology topology = builder.build();
86 log.info("\n\n{}", topology.describe());
91 public Optional<URI> getRedirect(String username)
93 KeyQueryMetadata metadata = streams.queryMetadataForKey(STORE_NAME, username, Serdes.String().serializer());
94 HostInfo activeHost = metadata.activeHost();
95 log.debug("Local store for {}: {}, {}:{}", username, metadata.partition(), activeHost.host(), activeHost.port());
97 if (activeHost.equals(this.hostInfo) || activeHost.equals(HostInfo.unavailable()))
99 return Optional.empty();
102 URI location = URI.create("http://" + activeHost.host() + ":" + activeHost.port() + "/" + username);
103 log.debug("Redirecting to {}", location);
104 return Optional.of(location);
107 public Optional<UserRanking> getUserRanking(String username)
111 .ofNullable(streams.store(storeParameters).get(username))
116 return mapper.readValue(json, UserRanking.class);
118 catch (JsonProcessingException e)
120 throw new RuntimeException(e);
128 log.info("Starting Stream-Processor");
135 log.info("Stopping Stream-Processor");