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[SPARK-36314][SS] Update Sessionization examples to use native support of session window

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### What changes were proposed in this pull request?

This PR proposes to update Sessionization examples to use native support of session window. It also adds the example for PySpark as native support of session window is available to PySpark as well.

### Why are the changes needed?

We should guide the simplest way to achieve the same workload. I'll provide another example for cases we can't do with native support of session window.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Manually tested.

Closes #33548 from HeartSaVioR/SPARK-36314.

Authored-by: Jungtaek Lim <kabhwan.opensource@gmail.com>
Signed-off-by: Liang-Chi Hsieh <viirya@gmail.com>
(cherry picked from commit 1fafa8e191)
Signed-off-by: Liang-Chi Hsieh <viirya@gmail.com>
This commit is contained in:
Jungtaek Lim 2021-07-27 20:10:02 -07:00 committed by Liang-Chi Hsieh
parent 0e9e737a84
commit 16c6009957
3 changed files with 112 additions and 252 deletions
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193
examples/src/main/java/org/apache/spark/examples/sql/streaming/JavaStructuredSessionization.java
View file

@ -16,22 +16,15 @@
*/ */
package org.apache.spark.examples.sql.streaming; 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.*;
import org.apache.spark.sql.streaming.GroupState;
import org.apache.spark.sql.streaming.GroupStateTimeout;
import org.apache.spark.sql.streaming.StreamingQuery; import org.apache.spark.sql.streaming.StreamingQuery;
import java.io.Serializable; import static org.apache.spark.sql.functions.*;
import java.sql.Timestamp;
import java.util.*;
/** /**
* Counts words in UTF8 encoded, '\n' delimited text received from the network. * Counts words in UTF8 encoded, '\n' delimited text received from the network.
* <p> * <p>
* Usage: JavaStructuredNetworkWordCount <hostname> <port> * Usage: JavaStructuredSessionization <hostname> <port>
* <hostname> and <port> describe the TCP server that Structured Streaming * <hostname> and <port> describe the TCP server that Structured Streaming
* would connect to receive data. * would connect to receive data.
* <p> * <p>
@ -66,86 +59,20 @@ public final class JavaStructuredSessionization {
.option("includeTimestamp", true) .option("includeTimestamp", true)
.load(); .load();
FlatMapFunction<LineWithTimestamp, Event> linesToEvents = // Split the lines into words, retaining timestamps
new FlatMapFunction<LineWithTimestamp, Event>() { // split() splits each line into an array, and explode() turns the array into multiple rows
@Override // treat words as sessionId of events
public Iterator<Event> call(LineWithTimestamp lineWithTimestamp) { Dataset<Row> events = lines
ArrayList<Event> eventList = new ArrayList<>(); .selectExpr("explode(split(value, ' ')) AS sessionId", "timestamp AS eventTime");
for (String word : lineWithTimestamp.getLine().split(" ")) {
eventList.add(new Event(word, lineWithTimestamp.getTimestamp()));
}
return eventList.iterator();
}
};
// Split the lines into words, treat words as sessionId of events // Sessionize the events. Track number of events, start and end timestamps of session,
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. // and report session updates.
// Dataset<Row> sessionUpdates = events
// Step 1: Define the state update function .groupBy(session_window(col("eventTime"), "10 seconds").as("session"), col("sessionId"))
MapGroupsWithStateFunction<String, Event, SessionInfo, SessionUpdate> stateUpdateFunc = .agg(count("*").as("numEvents"))
new MapGroupsWithStateFunction<String, Event, SessionInfo, SessionUpdate>() { .selectExpr("sessionId", "CAST(session.start AS LONG)", "CAST(session.end AS LONG)",
@Override public SessionUpdate call( "CAST(session.end AS LONG) - CAST(session.start AS LONG) AS durationMs",
String sessionId, Iterator<Event> events, GroupState<SessionInfo> state) { "numEvents");
// If timed out, then remove session and send final update
if (state.hasTimedOut()) {
SessionUpdate finalUpdate = new SessionUpdate(
sessionId, state.get().calculateDuration(), 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().calculateDuration(), 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) {
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 // Start running the query that prints the session updates to the console
StreamingQuery query = sessionUpdates StreamingQuery query = sessionUpdates
@ -156,96 +83,4 @@ public final class JavaStructuredSessionization {
query.awaitTermination(); 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 calculateDuration() { 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; }
}
} }

87
examples/src/main/python/sql/streaming/structured_sessionization.py Normal file
View file

@ -0,0 +1,87 @@
#
# 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.
#
r"""
Counts words in UTF8 encoded, '\n' delimited text received from the network over a
sliding window of configurable duration.
Usage: structured_sessionization.py <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/spark-submit
examples/src/main/python/sql/streaming/structured_sessionization.py
localhost 9999`
"""
import sys
from pyspark.sql import SparkSession
from pyspark.sql.functions import explode
from pyspark.sql.functions import split
from pyspark.sql.functions import count, session_window
if __name__ == "__main__":
if len(sys.argv) != 3 and len(sys.argv) != 2:
msg = "Usage: structured_sessionization.py <hostname> <port> "
print(msg, file=sys.stderr)
sys.exit(-1)
host = sys.argv[1]
port = int(sys.argv[2])
spark = SparkSession\
.builder\
.appName("StructuredSessionization")\
.getOrCreate()
# Create DataFrame representing the stream of input lines from connection to host:port
lines = spark\
.readStream\
.format('socket')\
.option('host', host)\
.option('port', port)\
.option('includeTimestamp', 'true')\
.load()
# Split the lines into words, retaining timestamps
# split() splits each line into an array, and explode() turns the array into multiple rows
# treat words as sessionId of events
events = lines.select(
explode(split(lines.value, ' ')).alias('sessionId'),
lines.timestamp.alias('eventTime')
)
# Group the data by window and word and compute the count of each group
windowedCounts = events \
.groupBy(session_window(events.eventTime, "10 seconds").alias('session'),
events.sessionId) \
.agg(count("*").alias("numEvents")) \
.selectExpr("sessionId", "CAST(session.start AS LONG)", "CAST(session.end AS LONG)",
"CAST(session.end AS LONG) - CAST(session.start AS LONG) AS durationMs",
"numEvents")
# Start running the query that prints the session updates to the console
query = windowedCounts\
.writeStream\
.outputMode('update')\
.format('console')\
.start()
query.awaitTermination()

84
examples/src/main/scala/org/apache/spark/examples/sql/streaming/StructuredSessionization.scala
View file

@ -18,16 +18,14 @@
// scalastyle:off println // scalastyle:off println
package org.apache.spark.examples.sql.streaming package org.apache.spark.examples.sql.streaming
import java.sql.Timestamp
import org.apache.spark.sql.SparkSession import org.apache.spark.sql.SparkSession
import org.apache.spark.sql.streaming._ import org.apache.spark.sql.functions.{count, session_window}
/** /**
* Counts words in UTF8 encoded, '\n' delimited text received from the network. * Counts words in UTF8 encoded, '\n' delimited text received from the network.
* *
* Usage: MapGroupsWithState <hostname> <port> * Usage: StructuredSessionization <hostname> <port>
* <hostname> and <port> describe the TCP server that Structured Streaming * <hostname> and <port> describe the TCP server that Structured Streaming
* would connect to receive data. * would connect to receive data.
* *
@ -63,46 +61,20 @@ object StructuredSessionization {
.option("includeTimestamp", true) .option("includeTimestamp", true)
.load() .load()
// Split the lines into words, treat words as sessionId of events // Split the lines into words, retaining timestamps
// split() splits each line into an array, and explode() turns the array into multiple rows
// treat words as sessionId of events
val events = lines val events = lines
.as[(String, Timestamp)] .selectExpr("explode(split(value, ' ')) AS sessionId", "timestamp AS eventTime")
.flatMap { case (line, timestamp) =>
line.split(" ").map(word => Event(sessionId = word, timestamp))
}
// Sessionize the events. Track number of events, start and end timestamps of session, // Sessionize the events. Track number of events, start and end timestamps of session,
// and report session updates. // and report session updates.
val sessionUpdates = events val sessionUpdates = events
.groupByKey(event => event.sessionId) .groupBy(session_window($"eventTime", "10 seconds") as 'session, 'sessionId)
.mapGroupsWithState[SessionInfo, SessionUpdate](GroupStateTimeout.ProcessingTimeTimeout) { .agg(count("*").as("numEvents"))
.selectExpr("sessionId", "CAST(session.start AS LONG)", "CAST(session.end AS LONG)",
case (sessionId: String, events: Iterator[Event], state: GroupState[SessionInfo]) => "CAST(session.end AS LONG) - CAST(session.start AS LONG) AS durationMs",
"numEvents")
// If timed out, then remove session and send final update
if (state.hasTimedOut) {
val finalUpdate =
SessionUpdate(sessionId, state.get.durationMs, state.get.numEvents, expired = true)
state.remove()
finalUpdate
} else {
// Update start and end timestamps in session
val timestamps = events.map(_.timestamp.getTime).toSeq
val updatedSession = if (state.exists) {
val oldSession = state.get
SessionInfo(
oldSession.numEvents + timestamps.size,
oldSession.startTimestampMs,
math.max(oldSession.endTimestampMs, timestamps.max))
} else {
SessionInfo(timestamps.size, timestamps.min, timestamps.max)
}
state.update(updatedSession)
// Set timeout such that the session will be expired if no data received for 10 seconds
state.setTimeoutDuration("10 seconds")
SessionUpdate(sessionId, state.get.durationMs, state.get.numEvents, expired = false)
}
}
// Start running the query that prints the session updates to the console // Start running the query that prints the session updates to the console
val query = sessionUpdates val query = sessionUpdates
@ -114,38 +86,4 @@ object StructuredSessionization {
query.awaitTermination() query.awaitTermination()
} }
} }
/** User-defined data type representing the input events */
case class Event(sessionId: String, timestamp: Timestamp)
/**
* User-defined data type for storing a session information as state in mapGroupsWithState.
*
* @param numEvents total number of events received in the session
* @param startTimestampMs timestamp of first event received in the session when it started
* @param endTimestampMs timestamp of last event received in the session before it expired
*/
case class SessionInfo(
numEvents: Int,
startTimestampMs: Long,
endTimestampMs: Long) {
/** Duration of the session, between the first and last events */
def durationMs: Long = endTimestampMs - startTimestampMs
}
/**
* User-defined data type representing the update information returned by mapGroupsWithState.
*
* @param id Id of the session
* @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
* @param expired Is the session active or expired
*/
case class SessionUpdate(
id: String,
durationMs: Long,
numEvents: Int,
expired: Boolean)
// scalastyle:on println // scalastyle:on println