Stream reorder example. Issue #179

src/test/java/io/confluent/examples/streams/ReorderIntegrationTest.java

@@ -0,0 +1,239 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.confluent.examples.streams;
+
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.serialization.LongDeserializer;
+import org.apache.kafka.common.serialization.LongSerializer;
+import org.apache.kafka.common.serialization.Serdes;
+import org.apache.kafka.streams.*;
+import org.apache.kafka.streams.kstream.KStream;
+import org.apache.kafka.streams.kstream.Named;
+import org.apache.kafka.streams.kstream.Transformer;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.PunctuationType;
+import org.apache.kafka.streams.processor.TimestampExtractor;
+import org.apache.kafka.streams.state.KeyValueIterator;
+import org.apache.kafka.streams.state.KeyValueStore;
+import org.apache.kafka.streams.state.StoreBuilder;
+import org.apache.kafka.streams.state.Stores;
+import org.junit.Test;
+
+import java.text.ParseException;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Properties;
+
+import static java.time.temporal.ChronoUnit.HOURS;
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+/**
+ * End-to-end integration test that demonstrates how to reorder the stream of incoming messages
+ * by the timestamp embedded in the message payload.
+ * <p>
+ * Makes sense only on per partition basis.
+ * <p>
+ * Reordering occurs within the time windows defined by the {@code grace} constructor parameter.
+ *
+ * Note: This example uses lambda expressions and thus works with Java 8+ only.
+ */
+public class ReorderIntegrationTest {
+
+  public static class ReorderTransformer<K, V>
+      implements Transformer<K, V, KeyValue<K, V>> {
+
+    public interface StoreKeyGenerator<K, V> {
+      K getStoreKey(K key, V val);
+    }
+
+    private final String storeName;
+    private final Duration grace;
+    private KeyValueStore<K, V> reorderStore;
+    private ProcessorContext context;
+    private final StoreKeyGenerator<K,V> storeKeyGenerator;
+
+    public ReorderTransformer(final String storeName, final Duration grace,
+                              final StoreKeyGenerator<K,V> storeKeyGenerator) {
+      this.storeName = storeName;
+      this.grace = grace;
+      this.storeKeyGenerator = storeKeyGenerator;
+    }
+
+    @Override
+    public void init(final ProcessorContext context) {
+      this.reorderStore = context.getStateStore(this.storeName);
+      this.context = context;
+      context.schedule(
+          this.grace,
+          PunctuationType.STREAM_TIME,
+          this::punctuate
+      );
+    }
+
+    /**
+     * 1) read the timestamp from the message value
+     * 2) inserts into a KeyValueStore using (timestamp, message-key) pair
+     * as the key and the message-value as the value, this also provides
+     * de-duplication.
+     *
+     * @param key
+     * @param value
+     * @return
+     */
+    @Override
+    public KeyValue<K, V> transform(final K key, final V value) {
+      // Keys need to contain and be sortable by time
+      final K storeKey = storeKeyGenerator.getStoreKey(key, value);
+      final V storeValue = reorderStore.get(storeKey);
+      if(storeValue == null) {
+        reorderStore.put(storeKey, value);
+      }
+      return null; 	// null suppresses sending to downstream
+    }
+
+    /**
+     * Scheduled to be called automatically when the period
+     * within which message reordering occurs expires.
+     *
+     * Outputs downstream accumulated records sorted by their timestamp.
+     *
+     * 1) read the entire store
+     * 2) send the fetched messages in order using context.forward() and delete
+     * them from the store
+     *
+     * @param timestamp – stream time of the punctuate function call
+     */
+    void punctuate(final long timestamp) {
+      try(KeyValueIterator<K, V> it = reorderStore.all()) {
+        while (it.hasNext()) {
+          final KeyValue<K, V> kv = it.next();
+          context.forward(kv.key, kv.value);
+          reorderStore.delete(kv.key);
+        }
+      }
+    }
+
+    @Override
+    public void close() {
+    }
+  }
+
+
+  public static class TestTimestampExtractor implements TimestampExtractor {
+    @Override
+    public long extract(final ConsumerRecord<Object, Object> record, final long partitionTime) {
+      return (long) record.value();
+    }
+  }
+
+  private static long ts(final String timeString) throws ParseException {
+    return Instant.parse(timeString).toEpochMilli();
+  }
+
+  @Test
+  public void shouldReorderTheInput() throws ParseException {
+
+    //  Input not ordered by time
+    final List<Long> inputValues = Arrays.asList(
+        ts("2021-11-03T23:00:00Z"),    // stream time calibration
+        ts("2021-11-04T01:05:00Z"),    // 10 hours interval border is at "2021-11-04T00:00:00Z"
+        ts("2021-11-04T01:10:00Z"),
+        ts("2021-11-04T01:40:00Z"),
+        ts("2021-11-04T02:25:00Z"),
+        ts("2021-11-04T01:20:00Z"),
+        ts("2021-11-04T02:45:00Z"),
+        ts("2021-11-04T02:00:00Z"),
+        ts("2021-11-04T03:00:00Z"),
+        ts("2021-11-04T02:40:00Z"),
+        ts("2021-11-04T02:20:00Z"),    // 10 hours interval border is at "2021-11-04T10:00:00Z"
+        ts("2021-11-05T00:00:00Z")     // stream time calibration
+    );
+
+    //  Expected ordered by time
+    final List<Long> expectedValues = Arrays.asList(
+        ts("2021-11-03T23:00:00Z"),    // stream time calibration
+        ts("2021-11-04T01:05:00Z"),
+        ts("2021-11-04T01:10:00Z"),
+        ts("2021-11-04T01:20:00Z"),
+        ts("2021-11-04T01:40:00Z"),
+        ts("2021-11-04T02:00:00Z"),
+        ts("2021-11-04T02:20:00Z"),
+        ts("2021-11-04T02:25:00Z"),
+        ts("2021-11-04T02:40:00Z"),
+        ts("2021-11-04T02:45:00Z"),
+        ts("2021-11-04T03:00:00Z"),
+        ts("2021-11-05T00:00:00Z")     // stream time calibration
+    );
+
+    //
+    // Step 1: Configure and start the processor topology.
+    //
+    final StreamsBuilder builder = new StreamsBuilder();
+
+    final Properties streamsConfiguration = new Properties();
+    streamsConfiguration.put(StreamsConfig.APPLICATION_ID_CONFIG, "reorder-integration-test");
+    streamsConfiguration.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "dummy config");
+    streamsConfiguration.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName());
+    streamsConfiguration.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.Long().getClass().getName());
+    streamsConfiguration.put(StreamsConfig.DEFAULT_TIMESTAMP_EXTRACTOR_CLASS_CONFIG, TestTimestampExtractor.class.getName());
+
+    final String inputTopic = "inputTopic";
+    final String outputTopic = "outputTopic";
+    final String persistentStore = "reorderStore";
+    final String transformerName = "reorderTransformer";
+
+    final StoreBuilder<KeyValueStore<String, Long>> countStoreSupplier =
+        Stores.keyValueStoreBuilder(
+            Stores.persistentKeyValueStore(persistentStore),
+            Serdes.String(),
+            Serdes.Long());
+
+    final KStream<String, Long> stream = builder.stream(inputTopic);
+    final KStream<String, Long> reordered = stream
+      .transform(() -> new ReorderTransformer<>(persistentStore,
+          Duration.of(10, HOURS), (k,v) -> String.format("key-%d", v)),
+          Named.as(transformerName));
+    reordered.to(outputTopic);
+
+    final Topology topology = builder.build();
+    topology.addStateStore(countStoreSupplier, transformerName);
+
+    try (final TopologyTestDriver topologyTestDriver = new TopologyTestDriver(topology, streamsConfiguration)) {
+      //
+      // Step 2: Setup input and output topics.
+      //
+      final TestInputTopic<String, Long> input = topologyTestDriver
+        .createInputTopic(inputTopic,
+                          new Serdes.StringSerde().serializer(),
+                          new LongSerializer());
+      final TestOutputTopic<String, Long> output = topologyTestDriver
+        .createOutputTopic(outputTopic,
+                          new Serdes.StringSerde().deserializer(),
+                          new LongDeserializer());
+
+      //
+      // Step 3: Produce some input data to the input topic.
+      //
+      input.pipeValueList(inputValues);
+
+      //
+      // Step 4: Verify the application's output data.
+      //
+      assertThat(output.readValuesToList(), equalTo(expectedValues));
+    }
+  }
+}