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https://issues.apache.org/jira/browse/DERBY-7001?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Leo Peng updated DERBY-7001:
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Attachment: OutOfMemoryError.png
> Derby JDBC driver classs loader leak
> ------------------------------------
>
> Key: DERBY-7001
> URL: https://issues.apache.org/jira/browse/DERBY-7001
> Project: Derby
> Issue Type: Bug
> Components: JDBC
> Affects Versions: 10.12.1.1
> Reporter: Leo Peng
> Priority: Major
> Attachments: DerbyProfile.png, DerbyTest.zip, MySqlProfile .png,
> OutOfMemoryError.png
>
>
> We had a customer facing Metaspace out of memory issue. After investigation.
> I found that the Derby JDBC driver may have a class loader leak problem. The
> reason is that I use same code doing the same thing with Derby and MySql,
> however, the statistics showed that there is a lot of difference. What I did
> was using Derby or MySql to create some tables and then do 200k queries on
> those tables. and collect some statistics from them.
> When using Derby as the data source, it is very easy to run out of Metaspace.
> Derby loads a large number of classes and committed Metaspace keeps
> increasing until full, at the same time, the GC operations are very frequent.
> On the contrary, when using MySql as the data source, it uses steady
> Metaspace during the process and no extra class loaded to JVM and no GCs.
> Another thing I found was that it took Derby more than 10 minutes to run 200k
> queries while it only costs MySql less than a second.
> Please see the attached screenshot profiles for more details.
> The JVM arguments I was using:
> {noformat}
> -XX:MaxMetaspaceSize=96m
> -XX:+HeapDumpOnOutOfMemoryError
> -XX:HeapDumpPath=C:/heapdump
> -verbose:gc
> -verbose:class
> {noformat}
> Some GCs when using Derby
> {noformat}
> [GC (Allocation Failure) 134632K->12584K(245760K), 0.0063202 secs]
> [GC (Metadata GC Threshold) 32171K->12432K(241152K), 0.0045418 secs]
> [Full GC (Metadata GC Threshold) 12432K->8691K(238592K), 0.0405280 secs]
> [GC (Allocation Failure) 128499K->12435K(237056K), 0.0074788 secs]
> [GC (Metadata GC Threshold) 38054K->12531K(234496K), 0.0053295 secs]
> [Full GC (Metadata GC Threshold) 12531K->8719K(232448K), 0.0366468 secs]
> [GC (Allocation Failure) 122895K->12271K(229376K), 0.0087422 secs]
> [GC (Metadata GC Threshold) 43475K->12799K(224768K), 0.0055041 secs]
> [Full GC (Metadata GC Threshold) 12799K->8738K(223744K), 0.0333892 secs]
> [GC (Allocation Failure) 117794K->12258K(223232K), 0.0060031 secs]
> [GC (Metadata GC Threshold) 48433K->12674K(221184K), 0.0050477 secs]
> [Full GC (Metadata GC Threshold) 12674K->8759K(219136K), 0.0339425 secs]
> [GC (Allocation Failure) 112695K->12183K(216064K), 0.0066411 secs]
> [GC (Metadata GC Threshold) 54733K->12623K(212992K), 0.0052730 secs]
> [Full GC (Metadata GC Threshold) 12623K->8778K(210432K), 0.0387252 secs]
> {noformat}
> I also attached the Java testing project for your reference.
>
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