Github user brkyvz commented on a diff in the pull request:
https://github.com/apache/spark/pull/17539#discussion_r109959911
--- Diff:
examples/src/main/java/org/apache/spark/examples/sql/streaming/JavaStructuredSessionization.java
---
@@ -0,0 +1,258 @@
+/*
+ * 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 org.apache.spark.api.java.function.FlatMapFunction;
+import org.apache.spark.api.java.function.MapFunction;
+import org.apache.spark.api.java.function.MapGroupsWithStateFunction;
+import org.apache.spark.sql.*;
+import org.apache.spark.sql.streaming.GroupState;
+import org.apache.spark.sql.streaming.GroupStateTimeout;
+import org.apache.spark.sql.streaming.StreamingQuery;
+
+import java.io.Serializable;
+import java.sql.Timestamp;
+import java.util.*;
+
+import scala.Tuple2;
+
+/**
+ * Counts words in UTF8 encoded, '\n' delimited text received from the
network.
+ * <p>
+ * Usage: JavaStructuredNetworkWordCount <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.JavaStructuredSessionization
+ * localhost 9999`
+ */
+public final class JavaStructuredSessionization {
+
+ public static void main(String[] args) throws Exception {
+ if (args.length < 2) {
+ System.err.println("Usage: JavaStructuredSessionization <hostname>
<port>");
+ System.exit(1);
+ }
+
+ String host = args[0];
+ int port = Integer.parseInt(args[1]);
+
+ SparkSession spark = SparkSession
+ .builder()
+ .appName("JavaStructuredSessionization")
+ .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();
+
+ FlatMapFunction<LineWithTimestamp, Event> linesToEvents =
+ new FlatMapFunction<LineWithTimestamp, Event>() {
+ @Override
+ public Iterator<Event> call(LineWithTimestamp lineWithTimestamp)
throws Exception {
+ ArrayList<Event> eventList = new ArrayList<Event>();
+ for (String word : lineWithTimestamp.getLine().split(" ")) {
+ eventList.add(new Event(word,
lineWithTimestamp.getTimestamp()));
+ }
+ System.out.println(
+ "Number of events from " + lineWithTimestamp.getLine() + " =
" + eventList.size());
+ return eventList.iterator();
+ }
+ };
+
+ // Split the lines into words, treat words as sessionId of events
+ Dataset<Event> events = lines
+ .withColumnRenamed("value", "line")
+ .as(Encoders.bean(LineWithTimestamp.class))
+ .flatMap(linesToEvents, Encoders.bean(Event.class));
+
+ // Sessionize the events. Track number of events, start and end
timestamps of session, and
+ // and report session updates.
+ //
+ // Step 1: Define the state update function
+ MapGroupsWithStateFunction<String, Event, SessionInfo, SessionUpdate>
stateUpdateFunc =
+ new MapGroupsWithStateFunction<String, Event, SessionInfo,
SessionUpdate>() {
+ @Override public SessionUpdate call(
+ String sessionId, Iterator<Event> events,
GroupState<SessionInfo> state)
+ throws Exception {
+ // If timed out, then remove session and send final update
+ if (state.hasTimedOut()) {
+ SessionUpdate finalUpdate = new SessionUpdate(
+ sessionId, state.get().getDurationMs(),
state.get().getNumEvents(), true);
+ state.remove();
+ return finalUpdate;
+
+ } else {
+ // Find max and min timestamps in events
+ long maxTimestampMs = Long.MIN_VALUE;
+ long minTimestampMs = Long.MAX_VALUE;
+ int numNewEvents = 0;
+ while (events.hasNext()) {
+ Event e = events.next();
+ long timestampMs = e.getTimestamp().getTime();
+ maxTimestampMs = Math.max(timestampMs, maxTimestampMs);
+ minTimestampMs = Math.min(timestampMs, minTimestampMs);
+ numNewEvents += 1;
+ }
+ SessionInfo updatedSession = new SessionInfo();
+
+ // Update start and end timestamps in session
+ if (state.exists()) {
+ SessionInfo oldSession = state.get();
+ updatedSession.setNumEvents(oldSession.numEvents +
numNewEvents);
+
updatedSession.setStartTimestampMs(oldSession.startTimestampMs);
+
updatedSession.setEndTimestampMs(Math.max(oldSession.endTimestampMs,
maxTimestampMs));
+ } else {
+ updatedSession.setNumEvents(numNewEvents);
+ updatedSession.setStartTimestampMs(minTimestampMs);
+ updatedSession.setEndTimestampMs(maxTimestampMs);
+ }
+ state.update(updatedSession);
+ // Set timeout such that the session will be expired if no
data received for 10 seconds
+ state.setTimeoutDuration("10 seconds");
+ return new SessionUpdate(
+ sessionId, state.get().getDurationMs(),
state.get().getNumEvents(), false);
+ }
+ }
+ };
+
+ // Step 2: Apply the state update function to the events streaming
Dataset grouped by sessionId
+ Dataset<SessionUpdate> sessionUpdates = events
+ .groupByKey(
+ new MapFunction<Event, String>() {
+ @Override public String call(Event event) throws Exception {
+ return event.getSessionId();
+ }
+ }, Encoders.STRING())
+ .mapGroupsWithState(
+ stateUpdateFunc,
+ Encoders.bean(SessionInfo.class),
+ Encoders.bean(SessionUpdate.class),
+ GroupStateTimeout.ProcessingTimeTimeout());
+
+ // Start running the query that prints the session updates to the
console
+ StreamingQuery query = sessionUpdates
+ .writeStream()
+ .outputMode("update")
+ .format("console")
+ .start();
+
+ query.awaitTermination();
+ }
+
+ /**
+ * User-defined data type representing the raw lines with timestamps.
+ */
+ public static class LineWithTimestamp implements Serializable {
+ private String line;
+ private Timestamp timestamp;
+
+ public Timestamp getTimestamp() { return timestamp; }
+ public void setTimestamp(Timestamp timestamp) { this.timestamp =
timestamp; }
+
+ public String getLine() { return line; }
+ public void setLine(String sessionId) { this.line = sessionId; }
+ }
+
+ /**
+ * User-defined data type representing the input events
+ */
+ public static class Event implements Serializable {
+ private String sessionId;
+ private Timestamp timestamp;
+
+ public Event() { }
+ public Event(String sessionId, Timestamp timestamp) {
+ this.sessionId = sessionId;
+ this.timestamp = timestamp;
+ }
+
+ public Timestamp getTimestamp() { return timestamp; }
+ public void setTimestamp(Timestamp timestamp) { this.timestamp =
timestamp; }
+
+ public String getSessionId() { return sessionId; }
+ public void setSessionId(String sessionId) { this.sessionId =
sessionId; }
+ }
+
+ /**
+ * User-defined data type for storing a session information as state in
mapGroupsWithState.
+ */
+ public static class SessionInfo implements Serializable {
+ private int numEvents = 0;
+ private long startTimestampMs = -1;
+ private long endTimestampMs = -1;
+
+ public int getNumEvents() { return numEvents; }
+ public void setNumEvents(int numEvents) { this.numEvents = numEvents; }
+
+ public long getStartTimestampMs() { return startTimestampMs; }
+ public void setStartTimestampMs(long startTimestampMs) {
+ this.startTimestampMs = startTimestampMs;
+ }
+
+ public long getEndTimestampMs() { return endTimestampMs; }
+ public void setEndTimestampMs(long endTimestampMs) {
this.endTimestampMs = endTimestampMs; }
+
+ public long getDurationMs() { return endTimestampMs -
startTimestampMs; }
+ @Override public String toString() {
+ return "SessionInfo(numEvents = " + numEvents +
+ ", timestamps = " + startTimestampMs + " to " + endTimestampMs +
")";
+ }
+ }
+
+ /**
+ * User-defined data type representing the update information returned
by mapGroupsWithState.
+ */
+ public static class SessionUpdate implements Serializable {
+ private String id;
+ private long durationMs;
+ private int numEvents;
+ private boolean expired;
+
+ public SessionUpdate() { }
+
+ public SessionUpdate(String id, long durationMs, int numEvents,
boolean expired) {
+ this.id = id;
+ this.durationMs = durationMs;
+ this.numEvents = numEvents;
+ this.expired = expired;
+ }
+
+ public String getId() { return id; }
+ public void setId(String id) { this.id = id; }
+
+ public long getDurationMs() { return durationMs; }
+ public void setDurationMs(long durationMs) { this.durationMs =
durationMs; }
+
+ public int getNumEvents() { return numEvents; }
+ public void setNumEvents(int numEvents) { this.numEvents = numEvents; }
+
+ public boolean isExpired() { return expired; }
+ public void setExpired(boolean expired) { this.expired = expired; }
+ }
+}
+
--- End diff --
nit: extra lines
---
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