[KAFKA-7304] memory leakage in org.apache.kafka.common.network.Selector

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.1.0, 1.1.1
• Fix Version/s: 2.0.1
• Component/s: core
• Assignee: Rajini Sivaram
• Reporter: Yu Yang
• Created: 17/Aug/18 07:46
• Updated: 13/Feb/22 09:47
• Resolved: 13/Feb/22 09:47

Description

We are testing secured writing to kafka through ssl. Testing at small scale, ssl writing to kafka was fine. However, when we enabled ssl writing at a larger scale (>40k clients write concurrently), the kafka brokers soon hit OutOfMemory issue with 4G memory setting. We have tried with increasing the heap size to 10Gb, but encountered the same issue.

We took a few heap dumps , and found that most of the heap memory is referenced through org.apache.kafka.common.network.Selector objects. There are two Channel maps field in Selector. It seems that somehow the objects is not deleted from the map in a timely manner.

One observation is that the memory leak seems relate to kafka partition leader changes. If there is broker restart etc. in the cluster that caused partition leadership change, the brokers may hit the OOM issue faster.

    private final Map<String, KafkaChannel> channels;
    private final Map<String, KafkaChannel> closingChannels;

Please see the attached images and the following link for sample gc analysis.

http://gceasy.io/my-gc-report.jsp?p=c2hhcmVkLzIwMTgvMDgvMTcvLS1nYy5sb2cuMC5jdXJyZW50Lmd6LS0yLTM5LTM0

the command line for running kafka:

java -Xms10g -Xmx10g -XX:NewSize=512m -XX:MaxNewSize=512m -Xbootclasspath/p:/usr/local/libs/bcp -XX:MetaspaceSize=128m -XX:+UseG1GC -XX:MaxGCPauseMillis=25 -XX:InitiatingHeapOccupancyPercent=35 -XX:G1HeapRegionSize=16M -XX:MinMetaspaceFreeRatio=25 -XX:MaxMetaspaceFreeRatio=75 -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintTenuringDistribution -Xloggc:/var/log/kafka/gc.log -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=40 -XX:GCLogFileSize=50M -Djava.awt.headless=true -Dlog4j.configuration=file:/etc/kafka/log4j.properties -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.port=9999 -Dcom.sun.management.jmxremote.rmi.port=9999 -cp /usr/local/libs/*  kafka.Kafka /etc/kafka/server.properties

We use java 1.8.0_102, and has applied a TLS patch on reducing X509Factory.certCache map size from 750 to 20.

java -version
java version "1.8.0_102"
Java(TM) SE Runtime Environment (build 1.8.0_102-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.102-b14, mixed mode)

Issue Links

• is related to: KAFKA-7453 Enable idle expiry of connections which are never selected
• is related to: KAFKA-7454 Use lazy allocation for SslTransportLayer buffers
• links to: GitHub Pull Request #5601