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   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements. See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You 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,
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  package org.apache.kafka.streams.kstream.internals;
  
  import org.apache.kafka.common.serialization.Serdes;
  import org.apache.kafka.common.utils.LogCaptureAppender;
  import org.apache.kafka.streams.KeyValue;
  import org.apache.kafka.streams.KeyValueTimestamp;
  import org.apache.kafka.streams.StreamsBuilder;
  import org.apache.kafka.streams.StreamsConfig;
  import org.apache.kafka.streams.TestInputTopic;
  import org.apache.kafka.streams.TestOutputTopic;
  import org.apache.kafka.streams.Topology;
  import org.apache.kafka.streams.TopologyConfig;
  import org.apache.kafka.streams.TopologyTestDriver;
  import org.apache.kafka.streams.TopologyTestDriverWrapper;
  import org.apache.kafka.streams.TopologyWrapper;
  import org.apache.kafka.streams.kstream.Consumed;
  import org.apache.kafka.streams.kstream.Grouped;
  import org.apache.kafka.streams.kstream.KTable;
  import org.apache.kafka.streams.kstream.Materialized;
  import org.apache.kafka.streams.kstream.ValueMapper;
  import org.apache.kafka.streams.processor.api.MockProcessorContext;
  import org.apache.kafka.streams.processor.api.Processor;
  import org.apache.kafka.streams.processor.api.Record;
  import org.apache.kafka.streams.state.BuiltInDslStoreSuppliers;
  import org.apache.kafka.streams.state.Stores;
  import org.apache.kafka.streams.test.TestRecord;
  import org.apache.kafka.test.MockApiProcessor;
  import org.apache.kafka.test.MockApiProcessorSupplier;
  import org.apache.kafka.test.MockReducer;
  import org.apache.kafka.test.MockValueJoiner;
  import org.apache.kafka.test.StreamsTestUtils;
  
  import org.junit.jupiter.api.Test;
  
  import java.time.Duration;
  import java.time.Instant;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.HashSet;
  import java.util.Locale;
  import java.util.Properties;
  import java.util.Random;
  import java.util.Set;
  
  import static org.hamcrest.CoreMatchers.equalTo;
  import static org.hamcrest.CoreMatchers.hasItem;
  import static org.hamcrest.MatcherAssert.assertThat;
  import static org.hamcrest.Matchers.is;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertFalse;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  public class KTableKTableLeftJoinTest {
      private final String topic1 = "topic1";
      private final String topic2 = "topic2";
      private final String output = "output";
      private final Consumed<Integer, String> consumed = Consumed.with(Serdes.Integer(), Serdes.String());
      private final Properties props = StreamsTestUtils.getStreamsConfig(Serdes.Integer(), Serdes.String());
  
      private StreamsBuilder createStreamBuilderInMemory() {
          props.put(StreamsConfig.DSL_STORE_SUPPLIERS_CLASS_CONFIG, BuiltInDslStoreSuppliers.InMemoryDslStoreSuppliers.class.getName());
          return new StreamsBuilder(new TopologyConfig(new StreamsConfig(props)));
      }
  
      @Test
      public void testJoin() {
          final StreamsBuilder builder = createStreamBuilderInMemory();
  
          final int[] expectedKeys = new int[] {0, 1, 2, 3};
  
          final KTable<Integer, String> table1 = builder.table(topic1, consumed);
          final KTable<Integer, String> table2 = builder.table(topic2, consumed);
          final KTable<Integer, String> joined = table1.leftJoin(table2, MockValueJoiner.TOSTRING_JOINER);
          joined.toStream().to(output);
  
          final Collection<Set<String>> copartitionGroups =
              TopologyWrapper.getInternalTopologyBuilder(builder.build()).copartitionGroups();
  
          assertEquals(1, copartitionGroups.size());
          assertEquals(new HashSet<>(Arrays.asList(topic1, topic2)), copartitionGroups.iterator().next());
  
          try (final TopologyTestDriver driver = new TopologyTestDriver(builder.build(), props)) {
              final TestInputTopic<Integer, String> inputTopic1 =
                      driver.createInputTopic(topic1, Serdes.Integer().serializer(), Serdes.String().serializer(), Instant.ofEpochMilli(0L), Duration.ZERO);
              final TestInputTopic<Integer, String> inputTopic2 =
                      driver.createInputTopic(topic2, Serdes.Integer().serializer(), Serdes.String().serializer(), Instant.ofEpochMilli(0L), Duration.ZERO);
              final TestOutputTopic<Integer, String> outputTopic =
                      driver.createOutputTopic(output, Serdes.Integer().deserializer(), Serdes.String().deserializer());
  
              // push two items to the primary stream. the other table is empty
              for (int i = 0; i < 2; i++) {
                  inputTopic1.pipeInput(expectedKeys[i], "X" + expectedKeys[i], 5L + i);
              }
              // pass tuple with null key, it will be discarded in join process
              inputTopic1.pipeInput(null, "SomeVal", 42L);
              // left: X0:0 (ts: 5), X1:1 (ts: 6)
              // right:
              assertOutputKeyValueTimestamp(outputTopic, 0, "X0+null", 5L);
              assertOutputKeyValueTimestamp(outputTopic, 1, "X1+null", 6L);
              assertTrue(outputTopic.isEmpty());
  
              // push two items to the other stream. this should produce two items.
              for (int i = 0; i < 2; i++) {
                  inputTopic2.pipeInput(expectedKeys[i], "Y" + expectedKeys[i], 10L * i);
              }
              // pass tuple with null key, it will be discarded in join process
              inputTopic2.pipeInput(null, "AnotherVal", 73L);
              // left: X0:0 (ts: 5), X1:1 (ts: 6)
              // right: Y0:0 (ts: 0), Y1:1 (ts: 10)
              assertOutputKeyValueTimestamp(outputTopic, 0, "X0+Y0", 5L);
              assertOutputKeyValueTimestamp(outputTopic, 1, "X1+Y1", 10L);
              assertTrue(outputTopic.isEmpty());
  
              // push all four items to the primary stream. this should produce four items.
              for (final int expectedKey : expectedKeys) {
                  inputTopic1.pipeInput(expectedKey, "XX" + expectedKey, 7L);
              }
              // left: XX0:0 (ts: 7), XX1:1 (ts: 7), XX2:2 (ts: 7), XX3:3 (ts: 7)
              // right: Y0:0 (ts: 0), Y1:1 (ts: 10)
              assertOutputKeyValueTimestamp(outputTopic, 0, "XX0+Y0", 7L);
              assertOutputKeyValueTimestamp(outputTopic, 1, "XX1+Y1", 10L);
              assertOutputKeyValueTimestamp(outputTopic, 2, "XX2+null", 7L);
              assertOutputKeyValueTimestamp(outputTopic, 3, "XX3+null", 7L);
              assertTrue(outputTopic.isEmpty());
  
              // push all items to the other stream. this should produce four items.
              for (final int expectedKey : expectedKeys) {
                  inputTopic2.pipeInput(expectedKey, "YY" + expectedKey, expectedKey * 5L);
              }
              // left: XX0:0 (ts: 7), XX1:1 (ts: 7), XX2:2 (ts: 7), XX3:3 (ts: 7)
              // right: YY0:0 (ts: 0), YY1:1 (ts: 5), YY2:2 (ts: 10), YY3:3 (ts: 15)
              assertOutputKeyValueTimestamp(outputTopic, 0, "XX0+YY0", 7L);
              assertOutputKeyValueTimestamp(outputTopic, 1, "XX1+YY1", 7L);
              assertOutputKeyValueTimestamp(outputTopic, 2, "XX2+YY2", 10L);
              assertOutputKeyValueTimestamp(outputTopic, 3, "XX3+YY3", 15L);
              assertTrue(outputTopic.isEmpty());
  
              // push all four items to the primary stream. this should produce four items.
              for (final int expectedKey : expectedKeys) {
                  inputTopic1.pipeInput(expectedKey, "XXX" + expectedKey, 6L);
              }
              // left: XXX0:0 (ts: 6), XXX1:1 (ts: 6), XXX2:2 (ts: 6), XXX3:3 (ts: 6)
              // right: YY0:0 (ts: 0), YY1:1 (ts: 5), YY2:2 (ts: 10), YY3:3 (ts: 15)
              assertOutputKeyValueTimestamp(outputTopic, 0, "XXX0+YY0", 6L);
              assertOutputKeyValueTimestamp(outputTopic, 1, "XXX1+YY1", 6L);
              assertOutputKeyValueTimestamp(outputTopic, 2, "XXX2+YY2", 10L);
              assertOutputKeyValueTimestamp(outputTopic, 3, "XXX3+YY3", 15L);
              assertTrue(outputTopic.isEmpty());
  
              // push two items with null to the other stream as deletes. this should produce two item.
              inputTopic2.pipeInput(expectedKeys[0], null, 5L);
              inputTopic2.pipeInput(expectedKeys[1], null, 7L);
              // left: XXX0:0 (ts: 6), XXX1:1 (ts: 6), XXX2:2 (ts: 6), XXX3:3 (ts: 6)
              // right: YY2:2 (ts: 10), YY3:3 (ts: 15)
              assertOutputKeyValueTimestamp(outputTopic, 0, "XXX0+null", 6L);
              assertOutputKeyValueTimestamp(outputTopic, 1, "XXX1+null", 7L);
              assertTrue(outputTopic.isEmpty());
  
              // push all four items to the primary stream. this should produce four items.
              for (final int expectedKey : expectedKeys) {
                  inputTopic1.pipeInput(expectedKey, "XXXX" + expectedKey, 13L);
              }
              // left: XXXX0:0 (ts: 13), XXXX1:1 (ts: 13), XXXX2:2 (ts: 13), XXXX3:3 (ts: 13)
              // right: YY2:2 (ts: 10), YY3:3 (ts: 15)
              assertOutputKeyValueTimestamp(outputTopic, 0, "XXXX0+null", 13L);
              assertOutputKeyValueTimestamp(outputTopic, 1, "XXXX1+null", 13L);
              assertOutputKeyValueTimestamp(outputTopic, 2, "XXXX2+YY2", 13L);
              assertOutputKeyValueTimestamp(outputTopic, 3, "XXXX3+YY3", 15L);
              assertTrue(outputTopic.isEmpty());
  
              // push three items to the primary stream with null. this should produce four items.
              inputTopic1.pipeInput(expectedKeys[0], null, 0L);
              inputTopic1.pipeInput(expectedKeys[1], null, 42L);
              inputTopic1.pipeInput(expectedKeys[2], null, 5L);
              inputTopic1.pipeInput(expectedKeys[3], null, 20L);
              // left:
              // right: YY2:2 (ts: 10), YY3:3 (ts: 15)
              assertOutputKeyValueTimestamp(outputTopic, 0, null, 0L);
              assertOutputKeyValueTimestamp(outputTopic, 1, null, 42L);
              assertOutputKeyValueTimestamp(outputTopic, 2, null, 10L);
              assertOutputKeyValueTimestamp(outputTopic, 3, null, 20L);
              assertTrue(outputTopic.isEmpty());
          }
      }
  
      @Test
      public void testNotSendingOldValue() {
          final StreamsBuilder builder = createStreamBuilderInMemory();
  
          final int[] expectedKeys = new int[] {0, 1, 2, 3};
  
          final KTable<Integer, String> table1;
          final KTable<Integer, String> table2;
          final KTable<Integer, String> joined;
          final MockApiProcessorSupplier<Integer, String, Void, Void> supplier = new MockApiProcessorSupplier<>();
  
          table1 = builder.table(topic1, consumed);
          table2 = builder.table(topic2, consumed);
          joined = table1.leftJoin(table2, MockValueJoiner.TOSTRING_JOINER);
  
          final Topology topology = builder.build().addProcessor("proc", supplier, ((KTableImpl<?, ?, ?>) joined).name);
  
          try (final TopologyTestDriver driver = new TopologyTestDriver(topology, props)) {
              final TestInputTopic<Integer, String> inputTopic1 =
                      driver.createInputTopic(topic1, Serdes.Integer().serializer(), Serdes.String().serializer(), Instant.ofEpochMilli(0L), Duration.ZERO);
              final TestInputTopic<Integer, String> inputTopic2 =
                      driver.createInputTopic(topic2, Serdes.Integer().serializer(), Serdes.String().serializer(), Instant.ofEpochMilli(0L), Duration.ZERO);
              final MockApiProcessor<Integer, String, Void, Void> proc = supplier.theCapturedProcessor();
  
              assertTrue(((KTableImpl<?, ?, ?>) table1).sendingOldValueEnabled());
              assertFalse(((KTableImpl<?, ?, ?>) table2).sendingOldValueEnabled());
              assertFalse(((KTableImpl<?, ?, ?>) joined).sendingOldValueEnabled());
  
              // push two items to the primary stream. the other table is empty
              for (int i = 0; i < 2; i++) {
                  inputTopic1.pipeInput(expectedKeys[i], "X" + expectedKeys[i], 5L + i);
              }
              // pass tuple with null key, it will be discarded in join process
              inputTopic1.pipeInput(null, "SomeVal", 42L);
              // left: X0:0 (ts: 5), X1:1 (ts: 6)
              // right:
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>("X0+null", null), 5),
                  new KeyValueTimestamp<>(1, new Change<>("X1+null", null), 6));
  
              // push two items to the other stream. this should produce two items.
              for (int i = 0; i < 2; i++) {
                  inputTopic2.pipeInput(expectedKeys[i], "Y" + expectedKeys[i], 10L * i);
              }
              // pass tuple with null key, it will be discarded in join process
              inputTopic2.pipeInput(null, "AnotherVal", 73L);
              // left: X0:0 (ts: 5), X1:1 (ts: 6)
              // right: Y0:0 (ts: 0), Y1:1 (ts: 10)
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>("X0+Y0", null), 5),
                  new KeyValueTimestamp<>(1, new Change<>("X1+Y1", null), 10));
  
              // push all four items to the primary stream. this should produce four items.
              for (final int expectedKey : expectedKeys) {
                  inputTopic1.pipeInput(expectedKey, "XX" + expectedKey, 7L);
              }
              // left: XX0:0 (ts: 7), XX1:1 (ts: 7), XX2:2 (ts: 7), XX3:3 (ts: 7)
              // right: Y0:0 (ts: 0), Y1:1 (ts: 10)
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>("XX0+Y0", null), 7),
                  new KeyValueTimestamp<>(1, new Change<>("XX1+Y1", null), 10),
                  new KeyValueTimestamp<>(2, new Change<>("XX2+null", null), 7),
                  new KeyValueTimestamp<>(3, new Change<>("XX3+null", null), 7));
  
              // push all items to the other stream. this should produce four items.
              for (final int expectedKey : expectedKeys) {
                  inputTopic2.pipeInput(expectedKey, "YY" + expectedKey, expectedKey * 5L);
              }
              // left: XX0:0 (ts: 7), XX1:1 (ts: 7), XX2:2 (ts: 7), XX3:3 (ts: 7)
              // right: YY0:0 (ts: 0), YY1:1 (ts: 5), YY2:2 (ts: 10), YY3:3 (ts: 15)
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>("XX0+YY0", null), 7),
                  new KeyValueTimestamp<>(1, new Change<>("XX1+YY1", null), 7),
                  new KeyValueTimestamp<>(2, new Change<>("XX2+YY2", null), 10),
                  new KeyValueTimestamp<>(3, new Change<>("XX3+YY3", null), 15));
  
              // push all four items to the primary stream. this should produce four items.
              for (final int expectedKey : expectedKeys) {
                  inputTopic1.pipeInput(expectedKey, "XXX" + expectedKey, 6L);
              }
              // left: XXX0:0 (ts: 6), XXX1:1 (ts: 6), XXX2:2 (ts: 6), XXX3:3 (ts: 6)
              // right: YY0:0 (ts: 0), YY1:1 (ts: 5), YY2:2 (ts: 10), YY3:3 (ts: 15)
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>("XXX0+YY0", null), 6),
                  new KeyValueTimestamp<>(1, new Change<>("XXX1+YY1", null), 6),
                  new KeyValueTimestamp<>(2, new Change<>("XXX2+YY2", null), 10),
                  new KeyValueTimestamp<>(3, new Change<>("XXX3+YY3", null), 15));
  
              // push two items with null to the other stream as deletes. this should produce two item.
              inputTopic2.pipeInput(expectedKeys[0], null, 5L);
              inputTopic2.pipeInput(expectedKeys[1], null, 7L);
              // left: XXX0:0 (ts: 6), XXX1:1 (ts: 6), XXX2:2 (ts: 6), XXX3:3 (ts: 6)
              // right: YY2:2 (ts: 10), YY3:3 (ts: 15)
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>("XXX0+null", null), 6),
                  new KeyValueTimestamp<>(1, new Change<>("XXX1+null", null), 7));
  
              // push all four items to the primary stream. this should produce four items.
              for (final int expectedKey : expectedKeys) {
                  inputTopic1.pipeInput(expectedKey, "XXXX" + expectedKey, 13L);
              }
              // left: XXXX0:0 (ts: 13), XXXX1:1 (ts: 13), XXXX2:2 (ts: 13), XXXX3:3 (ts: 13)
              // right: YY2:2 (ts: 10), YY3:3 (ts: 15)
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>("XXXX0+null", null), 13),
                  new KeyValueTimestamp<>(1, new Change<>("XXXX1+null", null), 13),
                  new KeyValueTimestamp<>(2, new Change<>("XXXX2+YY2", null), 13),
                  new KeyValueTimestamp<>(3, new Change<>("XXXX3+YY3", null), 15));
  
              // push four items to the primary stream with null. this should produce four items.
              inputTopic1.pipeInput(expectedKeys[0], null, 0L);
              inputTopic1.pipeInput(expectedKeys[1], null, 42L);
              inputTopic1.pipeInput(expectedKeys[2], null, 5L);
              inputTopic1.pipeInput(expectedKeys[3], null, 20L);
              // left:
              // right: YY2:2 (ts: 10), YY3:3 (ts: 15)
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>(null, null), 0),
                  new KeyValueTimestamp<>(1, new Change<>(null, null), 42),
                  new KeyValueTimestamp<>(2, new Change<>(null, null), 10),
                  new KeyValueTimestamp<>(3, new Change<>(null, null), 20));
          }
      }
  
      @Test
      public void testSendingOldValue() {
          final StreamsBuilder builder = createStreamBuilderInMemory();
  
          final int[] expectedKeys = new int[] {0, 1, 2, 3};
  
          final KTable<Integer, String> table1;
          final KTable<Integer, String> table2;
          final KTable<Integer, String> joined;
          final MockApiProcessorSupplier<Integer, String, Void, Void> supplier = new MockApiProcessorSupplier<>();
  
          table1 = builder.table(topic1, consumed);
          table2 = builder.table(topic2, consumed);
          joined = table1.leftJoin(table2, MockValueJoiner.TOSTRING_JOINER);
  
          ((KTableImpl<?, ?, ?>) joined).enableSendingOldValues(true);
  
          assertThat(((KTableImpl<?, ?, ?>) table1).sendingOldValueEnabled(), is(true));
          assertThat(((KTableImpl<?, ?, ?>) table2).sendingOldValueEnabled(), is(true));
          assertThat(((KTableImpl<?, ?, ?>) joined).sendingOldValueEnabled(), is(true));
  
          final Topology topology = builder.build().addProcessor("proc", supplier, ((KTableImpl<?, ?, ?>) joined).name);
  
          try (final TopologyTestDriver driver = new TopologyTestDriverWrapper(topology, props)) {
              final TestInputTopic<Integer, String> inputTopic1 =
                      driver.createInputTopic(topic1, Serdes.Integer().serializer(), Serdes.String().serializer(), Instant.ofEpochMilli(0L), Duration.ZERO);
              final TestInputTopic<Integer, String> inputTopic2 =
                      driver.createInputTopic(topic2, Serdes.Integer().serializer(), Serdes.String().serializer(), Instant.ofEpochMilli(0L), Duration.ZERO);
              final MockApiProcessor<Integer, String, Void, Void> proc = supplier.theCapturedProcessor();
  
              assertTrue(((KTableImpl<?, ?, ?>) table1).sendingOldValueEnabled());
              assertTrue(((KTableImpl<?, ?, ?>) table2).sendingOldValueEnabled());
              assertTrue(((KTableImpl<?, ?, ?>) joined).sendingOldValueEnabled());
  
              // push two items to the primary stream. the other table is empty
              for (int i = 0; i < 2; i++) {
                  inputTopic1.pipeInput(expectedKeys[i], "X" + expectedKeys[i], 5L + i);
              }
              // pass tuple with null key, it will be discarded in join process
              inputTopic1.pipeInput(null, "SomeVal", 42L);
              // left: X0:0 (ts: 5), X1:1 (ts: 6)
              // right:
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>("X0+null", null), 5),
                  new KeyValueTimestamp<>(1, new Change<>("X1+null", null), 6));
  
              // push two items to the other stream. this should produce two items.
              for (int i = 0; i < 2; i++) {
                  inputTopic2.pipeInput(expectedKeys[i], "Y" + expectedKeys[i], 10L * i);
              }
              // pass tuple with null key, it will be discarded in join process
              inputTopic2.pipeInput(null, "AnotherVal", 73L);
              // left: X0:0 (ts: 5), X1:1 (ts: 6)
              // right: Y0:0 (ts: 0), Y1:1 (ts: 10)
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>("X0+Y0", "X0+null"), 5),
                  new KeyValueTimestamp<>(1, new Change<>("X1+Y1", "X1+null"), 10));
  
              // push all four items to the primary stream. this should produce four items.
              for (final int expectedKey : expectedKeys) {
                  inputTopic1.pipeInput(expectedKey, "XX" + expectedKey, 7L);
              }
              // left: XX0:0 (ts: 7), XX1:1 (ts: 7), XX2:2 (ts: 7), XX3:3 (ts: 7)
              // right: Y0:0 (ts: 0), Y1:1 (ts: 10)
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>("XX0+Y0", "X0+Y0"), 7),
                  new KeyValueTimestamp<>(1, new Change<>("XX1+Y1", "X1+Y1"), 10),
                  new KeyValueTimestamp<>(2, new Change<>("XX2+null", null), 7),
                  new KeyValueTimestamp<>(3, new Change<>("XX3+null", null), 7));
  
              // push all items to the other stream. this should produce four items.
              for (final int expectedKey : expectedKeys) {
                  inputTopic2.pipeInput(expectedKey, "YY" + expectedKey, expectedKey * 5L);
              }
              // left: XX0:0 (ts: 7), XX1:1 (ts: 7), XX2:2 (ts: 7), XX3:3 (ts: 7)
              // right: YY0:0 (ts: 0), YY1:1 (ts: 5), YY2:2 (ts: 10), YY3:3 (ts: 15)
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>("XX0+YY0", "XX0+Y0"), 7),
                  new KeyValueTimestamp<>(1, new Change<>("XX1+YY1", "XX1+Y1"), 7),
                  new KeyValueTimestamp<>(2, new Change<>("XX2+YY2", "XX2+null"), 10),
                  new KeyValueTimestamp<>(3, new Change<>("XX3+YY3", "XX3+null"), 15));
              // push all four items to the primary stream. this should produce four items.
              for (final int expectedKey : expectedKeys) {
                  inputTopic1.pipeInput(expectedKey, "XXX" + expectedKey, 6L);
              }
              // left: XXX0:0 (ts: 6), XXX1:1 (ts: 6), XXX2:2 (ts: 6), XXX3:3 (ts: 6)
              // right: YY0:0 (ts: 0), YY1:1 (ts: 5), YY2:2 (ts: 10), YY3:3 (ts: 15)
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>("XXX0+YY0", "XX0+YY0"), 6),
                  new KeyValueTimestamp<>(1, new Change<>("XXX1+YY1", "XX1+YY1"), 6),
                  new KeyValueTimestamp<>(2, new Change<>("XXX2+YY2", "XX2+YY2"), 10),
                  new KeyValueTimestamp<>(3, new Change<>("XXX3+YY3", "XX3+YY3"), 15));
  
              // push two items with null to the other stream as deletes. this should produce two item.
              inputTopic2.pipeInput(expectedKeys[0], null, 5L);
              inputTopic2.pipeInput(expectedKeys[1], null, 7L);
              // left: XXX0:0 (ts: 6), XXX1:1 (ts: 6), XXX2:2 (ts: 6), XXX3:3 (ts: 6)
              // right: YY2:2 (ts: 10), YY3:3 (ts: 15)
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>("XXX0+null", "XXX0+YY0"), 6),
                  new KeyValueTimestamp<>(1, new Change<>("XXX1+null", "XXX1+YY1"), 7));
  
              // push all four items to the primary stream. this should produce four items.
              for (final int expectedKey : expectedKeys) {
                  inputTopic1.pipeInput(expectedKey, "XXXX" + expectedKey, 13L);
              }
              // left: XXXX0:0 (ts: 13), XXXX1:1 (ts: 13), XXXX2:2 (ts: 13), XXXX3:3 (ts: 13)
              // right: YY2:2 (ts: 10), YY3:3 (ts: 15)
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>("XXXX0+null", "XXX0+null"), 13),
                  new KeyValueTimestamp<>(1, new Change<>("XXXX1+null", "XXX1+null"), 13),
                  new KeyValueTimestamp<>(2, new Change<>("XXXX2+YY2", "XXX2+YY2"), 13),
                  new KeyValueTimestamp<>(3, new Change<>("XXXX3+YY3", "XXX3+YY3"), 15));
              // push four items to the primary stream with null. this should produce four items.
              inputTopic1.pipeInput(expectedKeys[0], null, 0L);
              inputTopic1.pipeInput(expectedKeys[1], null, 42L);
              inputTopic1.pipeInput(expectedKeys[2], null, 5L);
              inputTopic1.pipeInput(expectedKeys[3], null, 20L);
              // left:
              // right: YY2:2 (ts: 10), YY3:3 (ts: 15)
              proc.checkAndClearProcessResult(new KeyValueTimestamp<>(0, new Change<>(null, "XXXX0+null"), 0),
                  new KeyValueTimestamp<>(1, new Change<>(null, "XXXX1+null"), 42),
                  new KeyValueTimestamp<>(2, new Change<>(null, "XXXX2+YY2"), 10),
                  new KeyValueTimestamp<>(3, new Change<>(null, "XXXX3+YY3"), 20));
          }
      }
  
      /**
       * This test was written to reproduce https://issues.apache.org/jira/browse/KAFKA-4492
       * It is based on a fairly complicated join used by the developer that reported the bug.
       * Before the fix this would trigger an IllegalStateException.
       */
      @Test
      public void shouldNotThrowIllegalStateExceptionWhenMultiCacheEvictions() {
          final String agg = "agg";
          final String tableOne = "tableOne";
          final String tableTwo = "tableTwo";
          final String tableThree = "tableThree";
          final String tableFour = "tableFour";
          final String tableFive = "tableFive";
          final String tableSix = "tableSix";
          final String[] inputs = {agg, tableOne, tableTwo, tableThree, tableFour, tableFive, tableSix};
  
          final StreamsBuilder builder = createStreamBuilderInMemory();
          final Consumed<Long, String> consumed = Consumed.with(Serdes.Long(), Serdes.String());
          final KTable<Long, String> aggTable = builder
              .table(agg, consumed, Materialized.as(Stores.inMemoryKeyValueStore("agg-base-store")))
              .groupBy(KeyValue::new, Grouped.with(Serdes.Long(), Serdes.String()))
              .reduce(
                  MockReducer.STRING_ADDER,
                  MockReducer.STRING_ADDER,
                  Materialized.as(Stores.inMemoryKeyValueStore("agg-store")));
  
          final KTable<Long, String> one = builder.table(tableOne, consumed);
          final KTable<Long, String> two = builder.table(tableTwo, consumed);
          final KTable<Long, String> three = builder.table(tableThree, consumed);
          final KTable<Long, String> four = builder.table(tableFour, consumed);
          final KTable<Long, String> five = builder.table(tableFive, consumed);
          final KTable<Long, String> six = builder.table(tableSix, consumed);
  
          final ValueMapper<String, String> mapper = value -> value.toUpperCase(Locale.ROOT);
  
          final KTable<Long, String> seven = one.mapValues(mapper);
  
          final KTable<Long, String> eight = six.leftJoin(seven, MockValueJoiner.TOSTRING_JOINER);
  
          aggTable
              .leftJoin(one, MockValueJoiner.TOSTRING_JOINER)
              .leftJoin(two, MockValueJoiner.TOSTRING_JOINER)
              .leftJoin(three, MockValueJoiner.TOSTRING_JOINER)
              .leftJoin(four, MockValueJoiner.TOSTRING_JOINER)
              .leftJoin(five, MockValueJoiner.TOSTRING_JOINER)
              .leftJoin(eight, MockValueJoiner.TOSTRING_JOINER)
              .mapValues(mapper);
  
          try (final TopologyTestDriver driver = new TopologyTestDriver(builder.build(), props)) {
              final String[] values = {
                  "a", "AA", "BBB", "CCCC", "DD", "EEEEEEEE", "F", "GGGGGGGGGGGGGGG", "HHH", "IIIIIIIIII",
                  "J", "KK", "LLLL", "MMMMMMMMMMMMMMMMMMMMMM", "NNNNN", "O", "P", "QQQQQ", "R", "SSSS",
                  "T", "UU", "VVVVVVVVVVVVVVVVVVV"
              };
  
              TestInputTopic<Long, String> inputTopic;
              final Random random = new Random();
              for (int i = 0; i < 1000; i++) {
                  for (final String input : inputs) {
                      final Long key = (long) random.nextInt(1000);
                      final String value = values[random.nextInt(values.length)];
                      inputTopic = driver.createInputTopic(input, Serdes.Long().serializer(), Serdes.String().serializer());
                      inputTopic.pipeInput(key, value);
                  }
              }
          }
      }
  
      @Test
      public void shouldLogAndMeterSkippedRecordsDueToNullLeftKey() {
          final StreamsBuilder builder = createStreamBuilderInMemory();
  
          @SuppressWarnings("unchecked")
          final Processor<String, Change<String>, String, Change<Object>> join = new KTableKTableLeftJoin<>(
              (KTableImpl<String, String, String>) builder.table("left", Consumed.with(Serdes.String(), Serdes.String())),
              (KTableImpl<String, String, String>) builder.table("right", Consumed.with(Serdes.String(), Serdes.String())),
              null
          ).get();
  
          final MockProcessorContext<String, Change<Object>> context = new MockProcessorContext<>(props);
          context.setRecordMetadata("left", -1, -2);
          join.init(context);
  
          try (final LogCaptureAppender appender = LogCaptureAppender.createAndRegister(KTableKTableLeftJoin.class)) {
              join.process(new Record<>(null, new Change<>("new", "old"), 0));
  
              assertThat(
                  appender.getMessages(),
                  hasItem("Skipping record due to null key. topic=[left] partition=[-1] offset=[-2]")
              );
          }
      }
  
      private void assertOutputKeyValueTimestamp(final TestOutputTopic<Integer, String> outputTopic,
                                                 final Integer expectedKey,
                                                 final String expectedValue,
                                                 final long expectedTimestamp) {
          assertThat(outputTopic.readRecord(), equalTo(new TestRecord<>(expectedKey, expectedValue, null, expectedTimestamp)));
      }
  }
  