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;
19 import org.springframework.boot.SpringApplication;
20 import org.springframework.context.ConfigurableApplicationContext;
23 import java.util.Optional;
24 import java.util.Properties;
25 import java.util.concurrent.CompletableFuture;
27 import static org.apache.kafka.streams.errors.StreamsUncaughtExceptionHandler.StreamThreadExceptionResponse.SHUTDOWN_CLIENT;
31 public class QueryStreamProcessor
33 public final KafkaStreams streams;
34 public final HostInfo hostInfo;
35 public final String storeName = "rankingsByUsername";
36 public final StoreQueryParameters<ReadOnlyKeyValueStore<String, String>> storeParameters;
37 public final ObjectMapper mapper;
40 public QueryStreamProcessor(
42 HostInfo applicationServer,
43 String usersInputTopic,
44 String rankingInputTopic,
46 ConfigurableApplicationContext context)
48 StreamsBuilder builder = new StreamsBuilder();
50 KTable<String, String> users = builder.table(usersInputTopic);
51 KStream<String, String> rankings = builder.stream(rankingInputTopic);
54 .join(users, (rankingJson, userJson) ->
58 Ranking ranking = mapper.readValue(rankingJson, Ranking.class);
59 User user = mapper.readValue(userJson, User.class);
61 return mapper.writeValueAsString(
65 ranking.getEntries()));
67 catch (JsonProcessingException e)
69 throw new RuntimeException(e);
72 .toTable(Materialized.as(storeName));
74 streams = new KafkaStreams(builder.build(), props);
75 streams.setUncaughtExceptionHandler((Throwable e) ->
77 log.error("Unexpected error!", e);
78 CompletableFuture.runAsync(() ->
80 log.info("Stopping application...");
81 SpringApplication.exit(context, () -> 1);
83 return SHUTDOWN_CLIENT;
86 hostInfo = applicationServer;
87 storeParameters = StoreQueryParameters.fromNameAndType(storeName, QueryableStoreTypes.keyValueStore());;
91 public Optional<URI> getRedirect(String username)
93 KeyQueryMetadata metadata = streams.queryMetadataForKey(storeName, 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");