ClusterJ Performance Problems - Not Dealing Well With NIO Garbage Collection (Doc ID 1988897.1)

Last updated on MARCH 08, 2017

Applies to:

MySQL Cluster - Version 7.3 and later
Information in this document applies to any platform.

Symptoms

On : 7.3 version, Cluster/J

ACTUAL BEHAVIOR
---------------
Observed performance issues with MySQL Cluster accessed by ClusterJ from Java application running on Oracle Java.
Under high load it is easy to fill up all space "available" for Direct Memory, because garbage collector is not deallocating memory used by ByteBuffer in the same pattern as in case of normal Heap space.
This causes System.gc() invoked inside nio package. As a result, gaps were observed in requests processing as System.gc() causes full GC meaning "Stop The World".

EXPECTED BEHAVIOR
-----------------------
Better management of the buffers memory when deallocating direct memory.

STEPS
-----------------------
The issue can be reproduced at will with the following steps:
1. Prepare an application using Cluster/J
2. Put the flag -XX:+DisableExplicitGC to disable System.gc()
3. Start the load and wait until OutofMemoryException is thrown by NIO package.

BUSINESS IMPACT
-----------------------
The issue has the following business impact:
Due to this issue, users cannot get a good performance with direct memory management.

Cause

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