feat: support for tunable retention, grace period for windowed tables

docs-md/concepts/time-and-windows-in-ksqldb-queries.md

@@ -365,4 +365,42 @@ SELECT o.order_id, o.total_amount, o.customer_name, s.shipment_id, s.warehouse
 For more information on joins, see
 [Join Event Streams with ksqlDB](../developer-guide/joins/join-streams-and-tables.md).
 
+### Late Arriving Events
+
+Frequently, events that belong to a window can arrive late, for example, over slow networks, 
+and a grace period may be required to ensure the events are accepted into the window. 
+ksqlDB enables configuring this behavior, for each of the window types. 
+
+For example, to allow events to be accepted for up to two hours after the window ends, 
+you might run a query like:
+
+```sql
+SELECT orderzip_code, TOPK(order_total, 5) FROM orders
+  WINDOW TUMBLING (SIZE 1 HOUR, GRACE PERIOD 2 HOURS) 
+  GROUP BY order_zipcode
+  EMIT CHANGES;
+```
+
+Events that arrive later than the grace period are dropped and not included in the aggregate result.
+
+### Window Retention 
+
+For each window type, you can configure the number of windows in the past that ksqlDB retains. This 
+capability is very useful for interactive applications that use ksqlDB as their primary 
+serving data store.
+
+For example, to retain the computed windowed aggregation results for a week, 
+you might run the following query:
+
+```sql
+SELECT regionid, COUNT(*) FROM pageviews
+  WINDOW HOPPING (SIZE 30 SECONDS, ADVANCE BY 10 SECONDS, RETENTION 7 DAYS, GRACE PERIOD 30 MINUTES)
+  WHERE UCASE(gender)='FEMALE' AND LCASE (regionid) LIKE '%_6'
+  GROUP BY regionid
+  EMIT CHANGES;
+```
+
+Note that the specified retention period should be larger than the sum of window size and any grace
+period.
+
 Page last revised on: {{ git_revision_date }}

ksqldb-engine/src/test/java/io/confluent/ksql/materialization/ks/KsMaterializationFunctionalTest.java

@@ -18,6 +18,7 @@
 import static io.confluent.ksql.serde.FormatFactory.JSON;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.empty;
+import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.hasSize;
 import static org.hamcrest.Matchers.instanceOf;
 import static org.hamcrest.Matchers.is;
@@ -44,17 +45,24 @@
 import io.confluent.ksql.serde.Format;
 import io.confluent.ksql.serde.SerdeOption;
 import io.confluent.ksql.test.util.KsqlIdentifierTestUtil;
+import io.confluent.ksql.util.PageViewDataProvider;
 import io.confluent.ksql.util.PersistentQueryMetadata;
 import io.confluent.ksql.util.QueryMetadata;
 import io.confluent.ksql.util.SchemaUtil;
 import io.confluent.ksql.util.UserDataProvider;
 import java.time.Duration;
+import java.time.Instant;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.Set;
 import java.util.concurrent.TimeUnit;
+import java.util.stream.Collectors;
+import java.util.stream.LongStream;
+import java.util.stream.Stream;
 import kafka.zookeeper.ZooKeeperClientException;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
 import org.apache.kafka.common.serialization.Deserializer;
 import org.apache.kafka.common.serialization.StringDeserializer;
 import org.apache.kafka.connect.data.Struct;
@@ -80,18 +88,26 @@ public class KsMaterializationFunctionalTest {
   private static final String USER_TABLE = "users_table";
   private static final String USER_STREAM = "users_stream";
 
+  private static final String PAGE_VIEWS_TOPIC = "page_views_topic";
+  private static final String PAGE_VIEWS_STREAM = "page_views_stream";
+
   private static final Format VALUE_FORMAT = JSON;
   private static final UserDataProvider USER_DATA_PROVIDER = new UserDataProvider();
+  private static final PageViewDataProvider PAGE_VIEW_DATA_PROVIDER = new PageViewDataProvider();
 
   private static final Duration WINDOW_SIZE = Duration.ofSeconds(5);
+  private static final Duration WINDOW_SEGMENT_DURATION = Duration.ofSeconds(60);
+  private static final int NUM_WINDOWS = 4;
+  private static final List<Instant> WINDOW_START_INSTANTS = LongStream.range(1, NUM_WINDOWS + 1)
+      // records have to be apart by at-least a segment for retention to enforced
+      .mapToObj(i -> Instant.ofEpochMilli(i * WINDOW_SEGMENT_DURATION.toMillis()))
+      .collect(Collectors.toList());
 
   private static final Deserializer<String> STRING_DESERIALIZER = new StringDeserializer();
-
   private static final Deserializer<Windowed<String>> TIME_WINDOWED_DESERIALIZER =
       WindowedSerdes
           .timeWindowedSerdeFrom(String.class, WINDOW_SIZE.toMillis())
           .deserializer();
-
   private static final Deserializer<Windowed<String>> SESSION_WINDOWED_DESERIALIZER =
       WindowedSerdes
           .sessionWindowedSerdeFrom(String.class)
@@ -120,13 +136,22 @@ public class KsMaterializationFunctionalTest {
 
   @BeforeClass
   public static void classSetUp() {
-    TEST_HARNESS.ensureTopics(USERS_TOPIC);
+    TEST_HARNESS.ensureTopics(USERS_TOPIC, PAGE_VIEWS_TOPIC);
 
     TEST_HARNESS.produceRows(
         USERS_TOPIC,
         USER_DATA_PROVIDER,
         VALUE_FORMAT
     );
+
+    for (final Instant windowTime : WINDOW_START_INSTANTS) {
+      TEST_HARNESS.produceRows(
+          PAGE_VIEWS_TOPIC,
+          PAGE_VIEW_DATA_PROVIDER,
+          VALUE_FORMAT,
+          windowTime::toEpochMilli
+      );
+    }
   }
 
   @Before
@@ -205,7 +230,7 @@ public void shouldQueryMaterializedTableForAggregatedTable() {
 
     final LogicalSchema schema = schema("KSQL_COL_0", SqlTypes.BIGINT);
 
-    final Map<String, GenericRow> rows = waitForTableRows(STRING_DESERIALIZER, schema);
+    final Map<String, GenericRow> rows = waitForUniqueUserRows(STRING_DESERIALIZER, schema);
 
     // When:
     final Materialization materialization = query.getMaterialization(queryId, contextStacker).get();
@@ -239,7 +264,7 @@ public void shouldQueryMaterializedTableForAggregatedStream() {
 
     final LogicalSchema schema = schema("COUNT", SqlTypes.BIGINT);
 
-    final Map<String, GenericRow> rows = waitForTableRows(STRING_DESERIALIZER, schema);
+    final Map<String, GenericRow> rows = waitForUniqueUserRows(STRING_DESERIALIZER, schema);
 
     // When:
     final Materialization materialization = query.getMaterialization(queryId, contextStacker).get();
@@ -275,7 +300,7 @@ public void shouldQueryMaterializedTableForTumblingWindowed() {
     final LogicalSchema schema = schema("COUNT", SqlTypes.BIGINT);
 
     final Map<Windowed<String>, GenericRow> rows =
-        waitForTableRows(TIME_WINDOWED_DESERIALIZER, schema);
+        waitForUniqueUserRows(TIME_WINDOWED_DESERIALIZER, schema);
 
     // When:
     final Materialization materialization = query.getMaterialization(queryId, contextStacker).get();
@@ -321,7 +346,7 @@ public void shouldQueryMaterializedTableForHoppingWindowed() {
     final LogicalSchema schema = schema("COUNT", SqlTypes.BIGINT);
 
     final Map<Windowed<String>, GenericRow> rows =
-        waitForTableRows(TIME_WINDOWED_DESERIALIZER, schema);
+        waitForUniqueUserRows(TIME_WINDOWED_DESERIALIZER, schema);
 
     // When:
     final Materialization materialization = query.getMaterialization(queryId, contextStacker).get();
@@ -365,7 +390,7 @@ public void shouldQueryMaterializedTableForSessionWindowed() {
     final LogicalSchema schema = schema("COUNT", SqlTypes.BIGINT);
 
     final Map<Windowed<String>, GenericRow> rows =
-        waitForTableRows(SESSION_WINDOWED_DESERIALIZER, schema);
+        waitForUniqueUserRows(SESSION_WINDOWED_DESERIALIZER, schema);
 
     // When:
     final Materialization materialization = query.getMaterialization(queryId, contextStacker).get();
@@ -396,6 +421,103 @@ public void shouldQueryMaterializedTableForSessionWindowed() {
     });
   }
 
+  @Test(expected = IllegalArgumentException.class)
+  public void shouldFailQueryWithRetentionSmallerThanGracePeriod() {
+    // Given:
+    executeQuery("CREATE TABLE " + output + " AS"
+            + " SELECT COUNT(*) AS COUNT FROM " + PAGE_VIEWS_STREAM
+            + " WINDOW TUMBLING (SIZE " + WINDOW_SEGMENT_DURATION.getSeconds() + " SECONDS,"
+            + " RETENTION " + (WINDOW_SEGMENT_DURATION.getSeconds() * 2) + " SECONDS)"
+            + " GROUP BY PAGEID;"
+    );
+  }
+
+  @Test
+  public void shouldQueryTumblingWindowMaterializedTableWithRetention() {
+    // Given:
+    final PersistentQueryMetadata query = executeQuery(
+        "CREATE TABLE " + output + " AS"
+            + " SELECT COUNT(*) AS COUNT FROM " + PAGE_VIEWS_STREAM
+            + " WINDOW TUMBLING (SIZE " + WINDOW_SEGMENT_DURATION.getSeconds() + " SECONDS,"
+            + " RETENTION " + (WINDOW_SEGMENT_DURATION.getSeconds() * 2) + " SECONDS,"
+            + " GRACE PERIOD 0 SECONDS)"
+            + " GROUP BY PAGEID;"
+    );
+
+    final List<ConsumerRecord<Windowed<String>, GenericRow>> rows =
+        waitForPageViewRows(TIME_WINDOWED_DESERIALIZER, query.getPhysicalSchema());
+
+    // When:
+    final Materialization materialization = query.getMaterialization(queryId, contextStacker).get();
+
+    // Then:
+    assertThat(materialization.windowType(), is(Optional.of(WindowType.TUMBLING)));
+    final MaterializedWindowedTable table = materialization.windowed();
+    final Set<Optional<Window>> expectedWindows = Stream.of(
+        Window.of(WINDOW_START_INSTANTS.get(1), WINDOW_START_INSTANTS.get(1).plusSeconds(WINDOW_SEGMENT_DURATION.getSeconds())),
+        Window.of(WINDOW_START_INSTANTS.get(2), WINDOW_START_INSTANTS.get(2).plusSeconds(WINDOW_SEGMENT_DURATION.getSeconds())),
+        Window.of(WINDOW_START_INSTANTS.get(3), WINDOW_START_INSTANTS.get(3).plusSeconds(WINDOW_SEGMENT_DURATION.getSeconds()))
+    ).map(Optional::of).collect(Collectors.toSet());
+    verifyRetainedWindows(rows, table, query, expectedWindows);
+  }
+
+  @Test
+  public void shouldQueryHoppingWindowMaterializedTableWithRetention() {
+    // Given:
+    final PersistentQueryMetadata query = executeQuery(
+        "CREATE TABLE " + output + " AS"
+            + " SELECT COUNT(*) AS COUNT FROM " + PAGE_VIEWS_STREAM
+            + " WINDOW HOPPING (SIZE " + WINDOW_SEGMENT_DURATION.getSeconds() + " SECONDS,"
+            + " ADVANCE BY " + WINDOW_SEGMENT_DURATION.getSeconds() + " SECONDS, "
+            + " RETENTION " + WINDOW_SEGMENT_DURATION.getSeconds() + " SECONDS,"
+            + " GRACE PERIOD 0 SECONDS"
+            + ") GROUP BY PAGEID;"
+    );
+
+    final List<ConsumerRecord<Windowed<String>, GenericRow>> rows =
+        waitForPageViewRows(TIME_WINDOWED_DESERIALIZER, query.getPhysicalSchema());
+
+    // When:
+    final Materialization materialization = query.getMaterialization(queryId, contextStacker).get();
+
+    // Then:
+    assertThat(materialization.windowType(), is(Optional.of(WindowType.HOPPING)));
+    final MaterializedWindowedTable table = materialization.windowed();
+    final Set<Optional<Window>> expectedWindows = Stream.of(
+        Window.of(WINDOW_START_INSTANTS.get(2), WINDOW_START_INSTANTS.get(2).plusSeconds(WINDOW_SEGMENT_DURATION.getSeconds())),
+        Window.of(WINDOW_START_INSTANTS.get(3), WINDOW_START_INSTANTS.get(3).plusSeconds(WINDOW_SEGMENT_DURATION.getSeconds()))
+    ).map(Optional::of).collect(Collectors.toSet());
+    verifyRetainedWindows(rows, table, query, expectedWindows);
+  }
+
+  @Test
+  public void shouldQuerySessionWindowMaterializedTableWithRetention() {
+    // Given:
+    final PersistentQueryMetadata query = executeQuery(
+        "CREATE TABLE " + output + " AS"
+            + " SELECT COUNT(*) AS COUNT FROM " + PAGE_VIEWS_STREAM
+            + " WINDOW SESSION (" + WINDOW_SEGMENT_DURATION.getSeconds()/2 + " SECONDS,"
+            + " RETENTION " + WINDOW_SEGMENT_DURATION.getSeconds() + " SECONDS,"
+            + " GRACE PERIOD 0 SECONDS"
+            + ") GROUP BY USERID;"
+    );
+
+    final List<ConsumerRecord<Windowed<String>, GenericRow>> rows =
+        waitForPageViewRows(SESSION_WINDOWED_DESERIALIZER, query.getPhysicalSchema());
+
+    // When:
+    final Materialization materialization = query.getMaterialization(queryId, contextStacker).get();
+
+    // Then:
+    assertThat(materialization.windowType(), is(Optional.of(WindowType.SESSION)));
+    final MaterializedWindowedTable table = materialization.windowed();
+    final Set<Optional<Window>> expectedWindows = Stream.of(
+        Window.of(WINDOW_START_INSTANTS.get(2), WINDOW_START_INSTANTS.get(2)),
+        Window.of(WINDOW_START_INSTANTS.get(3), WINDOW_START_INSTANTS.get(3))
+    ).map(Optional::of).collect(Collectors.toSet());
+    verifyRetainedWindows(rows, table, query, expectedWindows);
+  }
+
   @Test
   public void shouldQueryMaterializedTableWithKeyFieldsInProjection() {
     // Given:
@@ -405,14 +527,13 @@ public void shouldQueryMaterializedTableWithKeyFieldsInProjection() {
             + " GROUP BY USERID;"
     );
 
-
     final LogicalSchema schema = schema(
         "USERID", SqlTypes.STRING,
         "KSQL_COL_1", SqlTypes.BIGINT,
         "USERID_2", SqlTypes.STRING
     );
 
-    final Map<String, GenericRow> rows = waitForTableRows(STRING_DESERIALIZER, schema);
+    final Map<String, GenericRow> rows = waitForUniqueUserRows(STRING_DESERIALIZER, schema);
 
 
     // When:
@@ -434,7 +555,7 @@ public void shouldQueryMaterializedTableWithKeyFieldsInProjection() {
   }
 
   @Test
-  public void shouldQueryMaterializedTableWitMultipleAggregationColumns() {
+  public void shouldQueryMaterializedTableWithMultipleAggregationColumns() {
     // Given:
     final PersistentQueryMetadata query = executeQuery(
         "CREATE TABLE " + output + " AS"
@@ -447,7 +568,7 @@ public void shouldQueryMaterializedTableWitMultipleAggregationColumns() {
         "SUM", SqlTypes.BIGINT
     );
 
-    final Map<String, GenericRow> rows = waitForTableRows(STRING_DESERIALIZER, schema);
+    final Map<String, GenericRow> rows = waitForUniqueUserRows(STRING_DESERIALIZER, schema);
 
     // When:
     final Materialization materialization = query.getMaterialization(queryId, contextStacker).get();
@@ -481,7 +602,7 @@ public void shouldIgnoreHavingClause() {
 
     final LogicalSchema schema = schema("COUNT", SqlTypes.BIGINT);
 
-    final Map<String, GenericRow> rows = waitForTableRows(STRING_DESERIALIZER, schema);
+    final Map<String, GenericRow> rows = waitForUniqueUserRows(STRING_DESERIALIZER, schema);
 
     // When:
     final Materialization materialization = query.getMaterialization(queryId, contextStacker).get();
@@ -502,7 +623,26 @@ public void shouldIgnoreHavingClause() {
     });
   }
 
-  private <T> Map<T, GenericRow> waitForTableRows(
+  private void verifyRetainedWindows(
+      final List<ConsumerRecord<Windowed<String>, GenericRow>> rows,
+      final MaterializedWindowedTable table,
+      final PersistentQueryMetadata query,
+      final Set<Optional<Window>> expectedWindows
+  ) {
+    rows.forEach(record -> {
+      final Struct key = asKeyStruct(record.key().key(), query.getPhysicalSchema());
+      final List<WindowedRow> resultAtWindowStart = table.get(key, Range.all());
+      assertThat("Should have fewer windows retained",
+          resultAtWindowStart,
+          hasSize(expectedWindows.size()));
+      final Set<Optional<Window>> actualWindows = resultAtWindowStart.stream()
+          .map(WindowedRow::window)
+          .collect(Collectors.toSet());
+      assertThat("Should retain the latest windows", actualWindows, equalTo(expectedWindows));
+    });
+  }
+
+  private <T> Map<T, GenericRow> waitForUniqueUserRows(
       final Deserializer<T> keyDeserializer,
       final LogicalSchema aggregateSchema
   ) {
@@ -515,6 +655,18 @@ private <T> Map<T, GenericRow> waitForTableRows(
     );
   }
 
+  private <T> List<ConsumerRecord<T, GenericRow>> waitForPageViewRows(
+      final Deserializer<T> keyDeserializer,
+      final PhysicalSchema aggregateSchema) {
+    return TEST_HARNESS.verifyAvailableRows(
+        output.toUpperCase(),
+        hasSize(PAGE_VIEW_DATA_PROVIDER.data().size() * NUM_WINDOWS),
+        VALUE_FORMAT,
+        aggregateSchema,
+        keyDeserializer
+    );
+  }
+
   private PersistentQueryMetadata executeQuery(final String statement) {
     return executeQuery(ksqlContext, statement);
   }
@@ -601,6 +753,16 @@ private static void initializeKsql(final TestKsqlContext ksqlContext) {
         + "    key = '" + USER_DATA_PROVIDER.key() + "'"
         + ");"
     );
+
+    ksqlContext.sql("CREATE STREAM " + PAGE_VIEWS_STREAM + " "
+        + " (" + PAGE_VIEW_DATA_PROVIDER.ksqlSchemaString() + ")"
+        + " WITH ("
+        + "    kafka_topic='" + PAGE_VIEWS_TOPIC + "', "
+        + "    value_format='" + VALUE_FORMAT.name() + "', "
+        + "    key = '" + PAGE_VIEW_DATA_PROVIDER.key() + "'"
+        + ");"
+    );
+
   }
 }