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kabhwan pushed a commit to branch branch-3.2
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The following commit(s) were added to refs/heads/branch-3.2 by this push:
new 9dc8d0c [SPARK-36455][SS] Provide an example of complex session
window via flatMapGroupsWithState
9dc8d0c is described below
commit 9dc8d0c3aeb473c642523d30ef2156c5d1aff68c
Author: Jungtaek Lim <kabhwan.opensou...@gmail.com>
AuthorDate: Mon Aug 9 19:39:49 2021 +0900
[SPARK-36455][SS] Provide an example of complex session window via
flatMapGroupsWithState
### What changes were proposed in this pull request?
This PR proposes to add a new example of complex sessionization, which
leverages flatMapGroupsWithState.
### Why are the changes needed?
We have replaced an example of sessionization from flatMapGroupsWithState
to native support of session window. Given there are still use cases on
sessionization which native support of session window cannot cover, it would be
nice if we can demonstrate such case. It will also be used as an example of
flatMapGroupsWithState.
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
Manually tested. Example data is given in class doc.
Closes #33681 from HeartSaVioR/SPARK-36455.
Authored-by: Jungtaek Lim <kabhwan.opensou...@gmail.com>
Signed-off-by: Jungtaek Lim <kabhwan.opensou...@gmail.com>
(cherry picked from commit 004b87d9a1fbe9063e52523505a247806d50455a)
Signed-off-by: Jungtaek Lim <kabhwan.opensou...@gmail.com>
---
.../JavaStructuredComplexSessionization.java | 461 +++++++++++++++++++++
.../StructuredComplexSessionization.scala | 301 ++++++++++++++
2 files changed, 762 insertions(+)
diff --git
a/examples/src/main/java/org/apache/spark/examples/sql/streaming/JavaStructuredComplexSessionization.java
b/examples/src/main/java/org/apache/spark/examples/sql/streaming/JavaStructuredComplexSessionization.java
new file mode 100644
index 0000000..4c1642c
--- /dev/null
+++
b/examples/src/main/java/org/apache/spark/examples/sql/streaming/JavaStructuredComplexSessionization.java
@@ -0,0 +1,461 @@
+/*
+ * 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,
+ * 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 org.apache.spark.examples.sql.streaming;
+
+import java.io.Serializable;
+import java.sql.Timestamp;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+import org.apache.spark.api.java.function.FlatMapGroupsWithStateFunction;
+import org.apache.spark.api.java.function.MapFunction;
+import org.apache.spark.sql.Dataset;
+import org.apache.spark.sql.Encoders;
+import org.apache.spark.sql.Row;
+import org.apache.spark.sql.SparkSession;
+import org.apache.spark.sql.streaming.GroupState;
+import org.apache.spark.sql.streaming.GroupStateTimeout;
+import org.apache.spark.sql.streaming.OutputMode;
+import org.apache.spark.sql.streaming.StreamingQuery;
+import org.apache.spark.sql.types.StructType;
+
+import static org.apache.spark.sql.types.DataTypes.StringType;
+import static org.apache.spark.sql.types.DataTypes.TimestampType;
+import static org.apache.spark.sql.functions.*;
+
+/**
+ * Sessionize events in UTF8 encoded, '\n' delimited text received from the
network.
+ * Each line composes an event, and the line should match to the json format.
+ * <p>
+ * The schema of the event is following:
+ * - user_id: String
+ * - event_type: String
+ * - timestamp: Long
+ * <p>
+ * The supported types are following:
+ * - NEW_EVENT
+ * - CLOSE_SESSION
+ * <p>
+ * This example focuses to demonstrate the complex sessionization which uses
two conditions
+ * on closing session; conditions are following:
+ * - No further event is provided for the user ID within 5 seconds
+ * - An event having CLOSE_SESSION as event_type is provided for the user ID
+ * <p>
+ * Usage: JavaStructuredComplexSessionization <hostname> <port>
+ * <hostname> and <port> describe the TCP server that Structured Streaming
+ * would connect to receive data.
+ * <p>
+ * To run this on your local machine, you need to first run a Netcat server
+ * `$ nc -lk 9999`
+ * and then run the example
+ * `$ bin/run-example sql.streaming.JavaStructuredComplexSessionization
+ * localhost 9999`
+ * <p>
+ * Here's a set of events for example:
+ *
+ * {"user_id": "user1", "event_type": "NEW_EVENT", "timestamp": 13}
+ * {"user_id": "user1", "event_type": "NEW_EVENT", "timestamp": 10}
+ * {"user_id": "user1", "event_type": "CLOSE_SESSION", "timestamp": 15}
+ * {"user_id": "user1", "event_type": "NEW_EVENT", "timestamp": 17}
+ * {"user_id": "user1", "event_type": "NEW_EVENT", "timestamp": 19}
+ * {"user_id": "user1", "event_type": "NEW_EVENT", "timestamp": 29}
+ *
+ * {"user_id": "user2", "event_type": "NEW_EVENT", "timestamp": 45}
+ *
+ * {"user_id": "user1", "event_type": "NEW_EVENT", "timestamp": 65}
+ *
+ * and results (the output can be split across micro-batches):
+ *
+ * +-----+----------+---------+
+ * | id|durationMs|numEvents|
+ * +-----+----------+---------+
+ * |user1| 5000| 3|
+ * |user1| 7000| 2|
+ * |user1| 5000| 1|
+ * |user2| 5000| 1|
+ * +-----+----------+---------+
+ * (The last event is not reflected into output due to watermark.)
+ * <p>
+ * Note that there're three different sessions for 'user1'. The events in
first two sessions
+ * are occurred within gap duration for nearest events, but they don't compose
a single session
+ * due to the event of CLOSE_SESSION.
+ * <p>
+ * Also note that the implementation is simplified one. This example doesn't
address
+ * - UPDATE MODE (the semantic is not clear for session window with event time
processing)
+ * - partial merge (events in session which are earlier than watermark can be
aggregated)
+ * - other possible optimizations (especially the implementation is ported
from Scala example)
+ */
+public final class JavaStructuredComplexSessionization {
+ public static void main(String[] args) throws Exception {
+ if (args.length < 2) {
+ System.err.println("Usage: JavaStructuredComplexSessionization
<hostname> <port>");
+ System.exit(1);
+ }
+
+ String host = args[0];
+ int port = Integer.parseInt(args[1]);
+
+ SparkSession spark = SparkSession
+ .builder()
+ .appName("JavaStructuredComplexSessionization")
+ .getOrCreate();
+
+ // Create DataFrame representing the stream of input lines from connection
to host:port
+ Dataset<Row> lines = spark
+ .readStream()
+ .format("socket")
+ .option("host", host)
+ .option("port", port)
+ .option("includeTimestamp", true)
+ .load();
+
+ StructType jsonSchema = new StructType()
+ .add("user_id", StringType)
+ .add("event_type", StringType)
+ .add("timestamp", TimestampType);
+
+ long gapDuration = 5 * 1000; // 5 seconds
+
+ // Parse the line into event, as described in classdoc.
+ Dataset<Row> events = lines
+ .select(from_json(col("value"), jsonSchema).as("event"))
+ .selectExpr("event.user_id AS user_id", "event.event_type AS
event_type",
+ "event.timestamp AS timestamp")
+ .withWatermark("timestamp", "10 seconds");
+
+ // Sessionize the events. Track number of events, start and end timestamps
of session,
+ // and report session when session is closed.
+ FlatMapGroupsWithStateFunction<String, Row, Sessions, Session>
stateUpdateFunc =
+ new FlatMapGroupsWithStateFunction<String, Row, Sessions, Session>() {
+ private Iterator<Session> handleEvict(String userId,
GroupState<Sessions> state) {
+ Sessions sessions = state.get();
+
+ List<SessionAcc> evicted = new ArrayList<>();
+ List<SessionAcc> kept = new ArrayList<>();
+
+ // we sorted sessions by timestamp
+ sessions.getSessions().forEach(session -> {
+ if (session.endTime().getTime() < state.getCurrentWatermarkMs())
{
+ evicted.add(session);
+ } else {
+ kept.add(session);
+ }
+ });
+
+ if (kept.isEmpty()) {
+ state.remove();
+ } else {
+ state.update(Sessions.newInstance(kept));
+ // trigger timeout at the end time of the first session
+ state.setTimeoutTimestamp(kept.get(0).endTime().getTime());
+ }
+
+ return evicted.stream()
+ .map(sessionAcc -> Session.newInstance(
+ userId,
+ sessionAcc.endTime().getTime() -
sessionAcc.startTime().getTime(),
+ sessionAcc.getEvents().size()))
+ .iterator();
+ }
+
+ private void mergeSessions(List<SessionAcc> sessionAccs,
GroupState<Sessions> state) {
+ // we sorted sessionAccs by timestamp
+
+ int curIdx = 0;
+ while (curIdx < sessionAccs.size() - 1) {
+ SessionAcc curSession = sessionAccs.get(curIdx);
+ SessionAcc nextSession = sessionAccs.get(curIdx + 1);
+
+ // Current session and next session can be merged
+ if (curSession.endTime().getTime() >
nextSession.startTime().getTime()) {
+ List<SessionEvent> accumulatedEvents = new
ArrayList<>(curSession.getEvents());
+ accumulatedEvents.addAll(nextSession.getEvents());
+ accumulatedEvents.sort(
+ Comparator.comparingLong(e ->
e.getStartTimestamp().getTime()));
+
+ List<SessionAcc> newSessions = new ArrayList<>();
+ List<SessionEvent> eventsForCurSession = new ArrayList<>();
+ for (SessionEvent event : accumulatedEvents) {
+ eventsForCurSession.add(event);
+ if (event.eventType == EventTypes.CLOSE_SESSION) {
+ SessionAcc newSessionAcc =
SessionAcc.newInstance(eventsForCurSession);
+ newSessions.add(newSessionAcc);
+ eventsForCurSession = new ArrayList<>();
+ }
+ }
+ if (!eventsForCurSession.isEmpty()) {
+ SessionAcc newSessionAcc =
SessionAcc.newInstance(eventsForCurSession);
+ newSessions.add(newSessionAcc);
+ }
+
+ // replace current session and next session with new session(s)
+ sessionAccs.remove(curIdx + 1);
+ sessionAccs.set(curIdx, newSessions.get(0));
+ if (newSessions.size() > 1) {
+ sessionAccs.addAll(curIdx + 1,
+
newSessions.stream().skip(1).collect(Collectors.toList()));
+ }
+
+ // move the cursor to the last new session(s)
+ curIdx += newSessions.size() - 1;
+ } else {
+ // move to the next session
+ curIdx++;
+ }
+ }
+
+ // update state
+ state.update(Sessions.newInstance(sessionAccs));
+ }
+
+ @Override
+ public Iterator<Session> call(
+ String userId, Iterator<Row> events, GroupState<Sessions> state)
{
+
+ if (state.hasTimedOut() && state.exists()) {
+ return handleEvict(userId, state);
+ }
+
+ // convert each event as individual session
+ Stream<Row> stream = StreamSupport.stream(
+ Spliterators.spliteratorUnknownSize(
+ events,
+ Spliterator.ORDERED), false);
+ List<SessionAcc> sessionsFromEvents = stream.map(r -> {
+ SessionEvent event = SessionEvent.newInstance(userId,
r.getString(1),
+ r.getTimestamp(2), gapDuration);
+ return SessionAcc.newInstance(event);
+ }).collect(Collectors.toList());
+
+ if (sessionsFromEvents.isEmpty()) {
+ return Collections.emptyIterator();
+ }
+
+ // sort sessions via start timestamp
+ List<SessionAcc> allSessions = new ArrayList<>(sessionsFromEvents);
+ if (state.exists()) {
+ allSessions.addAll(state.get().getSessions());
+ }
+ allSessions.sort(Comparator.comparingLong(s ->
s.startTime().getTime()));
+
+ // merge sessions
+ mergeSessions(allSessions, state);
+
+ // we still need to handle eviction here
+ return handleEvict(userId, state);
+ }
+ };
+
+ Dataset<Session> sessionUpdates = events
+ .groupByKey((MapFunction<Row, String>) event -> event.getString(0),
Encoders.STRING())
+ .flatMapGroupsWithState(
+ stateUpdateFunc,
+ OutputMode.Append(),
+ Encoders.bean(Sessions.class),
+ Encoders.bean(Session.class),
+ GroupStateTimeout.EventTimeTimeout());
+
+ // Start running the query that prints the session updates to the console
+ StreamingQuery query = sessionUpdates
+ .writeStream()
+ .outputMode("append")
+ .format("console")
+ .start();
+
+ query.awaitTermination();
+ }
+
+ public static class Sessions {
+ private List<SessionAcc> sessions;
+
+ public List<SessionAcc> getSessions() {
+ return sessions;
+ }
+
+ public void setSessions(List<SessionAcc> sessions) {
+ // `sessions` should not be empty, and be sorted by start time
+ if (sessions.isEmpty()) {
+ throw new IllegalArgumentException("events should not be empty!");
+ }
+
+ List<SessionAcc> sorted = new ArrayList<>(sessions);
+ sorted.sort(Comparator.comparingLong(session ->
session.startTime().getTime()));
+
+ this.sessions = sorted;
+ }
+
+ public static Sessions newInstance(List<SessionAcc> sessions) {
+ Sessions instance = new Sessions();
+ instance.setSessions(sessions);
+ return instance;
+ }
+ }
+
+ public enum EventTypes {
+ NEW_EVENT, CLOSE_SESSION;
+ }
+
+ public static class SessionEvent implements Serializable {
+ private String userId;
+ private EventTypes eventType;
+ private Timestamp startTimestamp;
+ private Timestamp endTimestamp;
+
+ public String getUserId() {
+ return userId;
+ }
+
+ public void setUserId(String userId) {
+ this.userId = userId;
+ }
+
+ public EventTypes getEventType() {
+ return eventType;
+ }
+
+ public void setEventType(EventTypes eventType) {
+ this.eventType = eventType;
+ }
+
+ public Timestamp getStartTimestamp() {
+ return startTimestamp;
+ }
+
+ public void setStartTimestamp(Timestamp startTimestamp) {
+ this.startTimestamp = startTimestamp;
+ }
+
+ public Timestamp getEndTimestamp() {
+ return endTimestamp;
+ }
+
+ public void setEndTimestamp(Timestamp endTimestamp) {
+ this.endTimestamp = endTimestamp;
+ }
+
+ public static SessionEvent newInstance(String userId, String eventTypeStr,
+ Timestamp startTimestamp, long
gapDuration) {
+ SessionEvent instance = new SessionEvent();
+ instance.setUserId(userId);
+ instance.setEventType(EventTypes.valueOf(eventTypeStr));
+ instance.setStartTimestamp(startTimestamp);
+
+ if (instance.getEventType() == EventTypes.CLOSE_SESSION) {
+ instance.setEndTimestamp(instance.getStartTimestamp());
+ } else {
+ instance.setEndTimestamp(
+ new Timestamp(instance.getStartTimestamp().getTime() +
gapDuration));
+ }
+
+ return instance;
+ }
+ }
+
+ public static class SessionAcc implements Serializable {
+ private List<SessionEvent> events;
+
+ public Timestamp startTime() {
+ return events.get(0).startTimestamp;
+ }
+
+ public Timestamp endTime() {
+ return events.get(events.size() - 1).getEndTimestamp();
+ }
+
+ public List<SessionEvent> getEvents() {
+ return events;
+ }
+
+ public void setEvents(List<SessionEvent> events) {
+ // `events` should not be empty, and be sorted by start time
+ if (events.isEmpty()) {
+ throw new IllegalArgumentException("events should not be empty!");
+ }
+
+ List<SessionEvent> sorted = new ArrayList<>(events);
+ sorted.sort(Comparator.comparingLong(event ->
event.startTimestamp.getTime()));
+
+ boolean eventCloseSessionExistBeforeLastEvent = sorted
+ .stream()
+ .limit(sorted.size() - 1)
+ .anyMatch(e -> e.eventType == EventTypes.CLOSE_SESSION);
+
+ if (eventCloseSessionExistBeforeLastEvent) {
+ throw new IllegalStateException("CLOSE_SESSION event cannot be placed
except " +
+ "the last event!");
+ }
+
+ this.events = sorted;
+ }
+
+ public static SessionAcc newInstance(SessionEvent event) {
+ return newInstance(Collections.singletonList(event));
+ }
+
+ public static SessionAcc newInstance(List<SessionEvent> events) {
+ SessionAcc instance = new SessionAcc();
+ instance.setEvents(events);
+ return instance;
+ }
+ }
+
+ public static class Session implements Serializable {
+ private String id;
+ private long duration;
+ private int numEvents;
+
+ public String getId() {
+ return id;
+ }
+
+ public void setId(String id) {
+ this.id = id;
+ }
+
+ public long getDuration() {
+ return duration;
+ }
+
+ public void setDuration(long duration) {
+ this.duration = duration;
+ }
+
+ public int getNumEvents() {
+ return numEvents;
+ }
+
+ public void setNumEvents(int numEvents) {
+ this.numEvents = numEvents;
+ }
+
+ public static Session newInstance(String id, long duration, int numEvents)
{
+ Session instance = new Session();
+ instance.setId(id);
+ instance.setDuration(duration);
+ instance.setNumEvents(numEvents);
+ return instance;
+ }
+ }
+}
diff --git
a/examples/src/main/scala/org/apache/spark/examples/sql/streaming/StructuredComplexSessionization.scala
b/examples/src/main/scala/org/apache/spark/examples/sql/streaming/StructuredComplexSessionization.scala
new file mode 100644
index 0000000..f25ba29
--- /dev/null
+++
b/examples/src/main/scala/org/apache/spark/examples/sql/streaming/StructuredComplexSessionization.scala
@@ -0,0 +1,301 @@
+/*
+ * 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,
+ * 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.
+ */
+
+// scalastyle:off println
+package org.apache.spark.examples.sql.streaming
+
+import java.sql.Timestamp
+
+import scala.collection.mutable
+
+import org.apache.spark.sql.SparkSession
+import org.apache.spark.sql.functions._
+import org.apache.spark.sql.streaming._
+import org.apache.spark.sql.types.{StringType, StructType, TimestampType}
+
+
+/**
+ * Sessionize events in UTF8 encoded, '\n' delimited text received from the
network.
+ * Each line composes an event, and the line should match to the json format.
+ *
+ * The schema of the event is following:
+ * - user_id: String
+ * - event_type: String
+ * - timestamp: Long
+ *
+ * The supported types are following:
+ * - NEW_EVENT
+ * - CLOSE_SESSION
+ *
+ * This example focuses to demonstrate the complex sessionization which uses
two conditions
+ * on closing session; conditions are following:
+ * - No further event is provided for the user ID within 5 seconds
+ * - An event having CLOSE_SESSION as event_type is provided for the user ID
+ *
+ * Usage: StructuredComplexSessionization <hostname> <port>
+ * <hostname> and <port> describe the TCP server that Structured Streaming
+ * would connect to receive data.
+ *
+ * To run this on your local machine, you need to first run a Netcat server
+ * `$ nc -lk 9999`
+ * and then run the example
+ * `$ bin/run-example sql.streaming.StructuredComplexSessionization
+ * localhost 9999`
+ *
+ * Here's a set of events for example:
+ *
+ * {"user_id": "user1", "event_type": "NEW_EVENT", "timestamp": 13}
+ * {"user_id": "user1", "event_type": "NEW_EVENT", "timestamp": 10}
+ * {"user_id": "user1", "event_type": "CLOSE_SESSION", "timestamp": 15}
+ * {"user_id": "user1", "event_type": "NEW_EVENT", "timestamp": 17}
+ * {"user_id": "user1", "event_type": "NEW_EVENT", "timestamp": 19}
+ * {"user_id": "user1", "event_type": "NEW_EVENT", "timestamp": 29}
+ *
+ * {"user_id": "user2", "event_type": "NEW_EVENT", "timestamp": 45}
+ *
+ * {"user_id": "user1", "event_type": "NEW_EVENT", "timestamp": 65}
+ *
+ * and results (the output can be split across micro-batches):
+ *
+ * +-----+----------+---------+
+ * | id|durationMs|numEvents|
+ * +-----+----------+---------+
+ * |user1| 5000| 3|
+ * |user1| 7000| 2|
+ * |user1| 5000| 1|
+ * |user2| 5000| 1|
+ * +-----+----------+---------+
+ * (The last event is not reflected into output due to watermark.)
+ *
+ * Note that there're three different sessions for 'user1'. The events in
first two sessions
+ * are occurred within gap duration for nearest events, but they don't compose
a single session
+ * due to the event of CLOSE_SESSION.
+ *
+ * Also note that the implementation is simplified one. This example doesn't
address
+ * - UPDATE MODE (the semantic is not clear for session window with event time
processing)
+ * - partial merge (events in session which are earlier than watermark can be
aggregated)
+ * - other possible optimizations
+ */
+object StructuredComplexSessionization {
+
+ def main(args: Array[String]): Unit = {
+ if (args.length < 2) {
+ System.err.println("Usage: StructuredComplexSessionization <hostname>
<port>")
+ System.exit(1)
+ }
+
+ val host = args(0)
+ val port = args(1).toInt
+
+ val spark = SparkSession
+ .builder
+ .appName("StructuredComplexSessionization")
+ .getOrCreate()
+
+ import spark.implicits._
+
+ // Create DataFrame representing the stream of input lines from connection
to host:port
+ val lines = spark.readStream
+ .format("socket")
+ .option("host", host)
+ .option("port", port)
+ .load()
+
+ val jsonSchema = new StructType()
+ .add("user_id", StringType, nullable = false)
+ .add("event_type", StringType, nullable = false)
+ .add("timestamp", TimestampType, nullable = false)
+
+ val gapDuration: Long = 5 * 1000 // 5 seconds
+
+ // Parse the line into event, as described in classdoc.
+ val events = lines
+ .select(from_json(col("value"), jsonSchema).as("event"))
+ .selectExpr("event.user_id AS user_id", "event.event_type AS event_type",
+ "event.timestamp AS timestamp")
+ .withWatermark("timestamp", "10 seconds")
+ .as[(String, String, Timestamp)]
+
+ // Sessionize the events. Track number of events, start and end timestamps
of session,
+ // and report session when session is closed.
+ val sessionUpdates = events
+ .groupByKey(event => event._1)
+ .flatMapGroupsWithState[List[SessionAcc], Session](OutputMode.Append(),
+ GroupStateTimeout.EventTimeTimeout) {
+
+ case (userId: String, events: Iterator[(String, String, Timestamp)],
+ state: GroupState[List[SessionAcc]]) =>
+
+ def handleEvict(sessions: List[SessionAcc]): Iterator[Session] = {
+ // we sorted sessions by timestamp
+ val (evicted, kept) = sessions.span {
+ s => s.endTime.getTime < state.getCurrentWatermarkMs()
+ }
+
+ if (kept.isEmpty) {
+ state.remove()
+ } else {
+ state.update(kept)
+ // trigger timeout at the end time of the first session
+ state.setTimeoutTimestamp(kept.head.endTime.getTime)
+ }
+
+ evicted.map { sessionAcc =>
+ Session(userId, sessionAcc.endTime.getTime -
sessionAcc.startTime.getTime,
+ sessionAcc.events.length)
+ }.iterator
+ }
+
+ def mergeSessions(sessions: List[SessionAcc]): Unit = {
+ // we sorted sessions by timestamp
+ val updatedSessions = new mutable.ArrayBuffer[SessionAcc]()
+ updatedSessions ++= sessions
+
+ var curIdx = 0
+ while (curIdx < updatedSessions.length - 1) {
+ val curSession = updatedSessions(curIdx)
+ val nextSession = updatedSessions(curIdx + 1)
+
+ // Current session and next session can be merged
+ if (curSession.endTime.getTime > nextSession.startTime.getTime) {
+ val accumulatedEvents =
+ (curSession.events ++
nextSession.events).sortBy(_.startTimestamp.getTime)
+
+ val newSessions = new mutable.ArrayBuffer[SessionAcc]()
+ var eventsForCurSession = new
mutable.ArrayBuffer[SessionEvent]()
+ accumulatedEvents.foreach { event =>
+ eventsForCurSession += event
+ if (event.eventType == EventTypes.CLOSE_SESSION) {
+ newSessions += SessionAcc(eventsForCurSession.toList)
+ eventsForCurSession = new
mutable.ArrayBuffer[SessionEvent]()
+ }
+ }
+ if (eventsForCurSession.nonEmpty) {
+ newSessions += SessionAcc(eventsForCurSession.toList)
+ }
+
+ // replace current session and next session with new session(s)
+ updatedSessions.remove(curIdx + 1)
+ updatedSessions(curIdx) = newSessions.head
+ if (newSessions.length > 1) {
+ updatedSessions.insertAll(curIdx + 1, newSessions.tail)
+ }
+
+ // move the cursor to the last new session(s)
+ curIdx += newSessions.length - 1
+ } else {
+ // move to the next session
+ curIdx += 1
+ }
+ }
+
+ // update state
+ state.update(updatedSessions.toList)
+ }
+
+ if (state.hasTimedOut && state.exists) {
+ handleEvict(state.get.sortBy(_.startTime.getTime))
+ } else {
+ // convert each event as individual session
+ val sessionsFromEvents = events.map { case (userId, eventType,
timestamp) =>
+ val e = SessionEvent(userId, eventType, timestamp, gapDuration)
+ SessionAcc(List(e))
+ }.toList
+ if (sessionsFromEvents.nonEmpty) {
+ val sessionsFromState = if (state.exists) {
+ state.get
+ } else {
+ List.empty
+ }
+
+ // sort sessions via start timestamp, and merge
+ mergeSessions((sessionsFromEvents ++
sessionsFromState).sortBy(_.startTime.getTime))
+ // we still need to handle eviction here
+ handleEvict(state.get.sortBy(_.startTime.getTime))
+ } else {
+ Iterator.empty
+ }
+ }
+ }
+
+ // Start running the query that prints the session updates to the console
+ val query = sessionUpdates
+ .writeStream
+ .outputMode("append")
+ .format("console")
+ .start()
+
+ query.awaitTermination()
+ }
+}
+
+object EventTypes extends Enumeration {
+ type EventTypes = Value
+ val NEW_EVENT, CLOSE_SESSION = Value
+}
+
+case class SessionEvent(
+ userId: String,
+ eventType: EventTypes.Value,
+ startTimestamp: Timestamp,
+ endTimestamp: Timestamp)
+
+object SessionEvent {
+ def apply(
+ userId: String,
+ eventTypeStr: String,
+ timestamp: Timestamp,
+ gapDuration: Long): SessionEvent = {
+ val eventType = EventTypes.withName(eventTypeStr)
+ val endTime = if (eventType == EventTypes.CLOSE_SESSION) {
+ timestamp
+ } else {
+ new Timestamp(timestamp.getTime + gapDuration)
+ }
+ SessionEvent(userId, eventType, timestamp, endTime)
+ }
+}
+
+case class SessionAcc(events: List[SessionEvent]) {
+ private val sortedEvents: List[SessionEvent] =
events.sortBy(_.startTimestamp.getTime)
+
+ require(!sortedEvents.dropRight(1).exists(_.eventType ==
EventTypes.CLOSE_SESSION),
+ "CLOSE_SESSION event cannot be placed except the last event!")
+
+ def eventsAsSorted: List[SessionEvent] = sortedEvents
+ def startTime: Timestamp = sortedEvents.head.startTimestamp
+ def endTime: Timestamp = sortedEvents.last.endTimestamp
+
+ override def toString: String = {
+ s"SessionAcc(events: $events / sorted: $sortedEvents / " +
+ s"start time: $startTime / endTime: $endTime)"
+ }
+}
+
+/**
+ * User-defined data type representing the session information returned by
flatMapGroupsWithState.
+ *
+ * @param id Id of the user
+ * @param durationMs Duration the session was active, that is, from first
event to its expiry
+ * @param numEvents Number of events received by the session while it was
active
+ */
+case class Session(
+ id: String,
+ durationMs: Long,
+ numEvents: Int)
+
+// scalastyle:on println
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