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https://issues.apache.org/jira/browse/SPARK-33635?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17256046#comment-17256046
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David Wyles commented on SPARK-33635:
-------------------------------------
[~gsomogyi] I now have my results.
I was so unhappy about these results I ran all the tests again, the only thing
that changed between them is the version of spark running on the cluster,
everything else was static - the data input from kafka was an unchanging static
set of data.
Input-> *672733262* rows
+*Spark 2.4.5*:+
*440* seconds - *1,528,939* rows per second.
+*Spark 3.0.1*:+
*990* seconds - *679,528* rows per seconds.
These are multiple runs (I even took the best from sprak 3.0.1)
I also captured the event logs between these two versions of spark - should
anyone find them useful.
So, no matter what I do, I can only conclude that Spark 2.4.5 was a lot faster
in this test case (In my production use case I'm just writing to parquet files
in hdfs - which is where I noticed the degredation in performant).
Is Spark SQL reading the source data twice, just as it would if there was a
"order by" in the query?
Sample code used:
val spark =
SparkSession.builder.appName("Kafka Read Performance")
.config("spark.executor.memory","16g")
.config("spark.cores.max", "10")
.config("spark.eventLog.enabled","true")
.config("spark.eventLog.dir","file:///tmp/spark-events")
.config("spark.eventLog.overwrite","true")
.getOrCreate()
import spark.implicits._
val *startTime* = System.nanoTime()
val df =
spark
.read
.format("kafka")
.option("kafka.bootstrap.servers", config.brokers)
.option("subscribe", config.inTopic)
.option("startingOffsets", "earliest")
.option("endingOffsets", "latest")
.option("failOnDataLoss","false")
.load()
df
.write
.format("kafka")
.option("kafka.bootstrap.servers", config.brokers)
.option("topic", config.outTopic)
.mode(SaveMode.Append)
.save()
val *endTime* = System.nanoTime()
val elapsedSecs = (endTime - startTime) / 1E9
// static input sample was used, fixed row count.
println(s"Took $elapsedSecs secs")
spark.stop()
> Performance regression in Kafka read
> ------------------------------------
>
> Key: SPARK-33635
> URL: https://issues.apache.org/jira/browse/SPARK-33635
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 3.0.0, 3.0.1
> Environment: A simple 5 node system. A simple data row of csv data in
> kafka, evenly distributed between the partitions.
> Open JDK 1.8.0.252
> Spark in stand alone - 5 nodes, 10 workers (2 worker per node, each locked to
> a distinct NUMA group)
> kafka (v 2.3.1) cluster - 5 nodes (1 broker per node).
> Centos 7.7.1908
> 1 topic, 10 partiions, 1 hour queue life
> (this is just one of clusters we have, I have tested on all of them and
> theyall exhibit the same performance degredation)
> Reporter: David Wyles
> Priority: Major
>
> I have observed a slowdown in the reading of data from kafka on all of our
> systems when migrating from spark 2.4.5 to Spark 3.0.0 (and Spark 3.0.1)
> I have created a sample project to isolate the problem as much as possible,
> with just a read all data from a kafka topic (see
> [https://github.com/codegorillauk/spark-kafka-read] ).
> With 2.4.5, across multiple runs,
> I get a stable read rate of 1,120,000 (1.12 mill) rows per second
> With 3.0.0 or 3.0.1, across multiple runs,
> I get a stable read rate of 632,000 (0.632 mil) rows per second
> The represents a *44% loss in performance*. Which is, a lot.
> I have been working though the spark-sql-kafka-0-10 code base, but change for
> spark 3 have been ongoing for over a year and its difficult to pin point an
> exact change or reason for the degradation.
> I am happy to help fix this problem, but will need some assitance as I am
> unfamiliar with the spark-sql-kafka-0-10 project.
>
> A sample of the data my test reads (note: its not parsing csv - this is just
> test data)
>
> 1606921800000,001e0610e532,lightsense,tsl250rd,intensity,21853,53.262,acceleration_z,651,ep,290,commit,913,pressure,138,pm1,799,uv_intensity,823,idletime,-372,count,-72,ir_intensity,185,concentration,-61,flags,-532,tx,694.36,ep_heatsink,-556.92,acceleration_x,-221.40,fw,910.53,sample_flow_rate,-959.60,uptime,-515.15,pm10,-768.03,powersupply,214.72,magnetic_field_y,-616.04,alphasense,606.73,AoT_Chicago,053,Racine
> Ave & 18th St Chicago IL,41.857959,-87.65642700000002,AoT Chicago (S)
> [C],2017/12/15 00:00:00,
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