[jira] [Commented] (FOP-3285) NullPointerException in Xerces DOM (fNodeListCache) during concurrent access to newFOP

    [ https://issues.apache.org/jira/browse/FOP-3285?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18040504#comment-18040504 ] 

Manikanta commented on FOP-3285:
--------------------------------

Sorry for the late reply.

I realize that creating a new {{FopFactory}} for every thread would likely fix this, but I want to understand the intended design. Is {{FopFactory}} supposed to be thread-safe? I cannot find any documentation explicitly stating that it must be thread-confined.

Since this issue occurs only intermittently under high load, simply failing to reproduce the crash doesn't prove it is fixed. I need to confirm the root cause to be 100% certain that the solution is robust

> NullPointerException in Xerces DOM (fNodeListCache) during concurrent access to newFOP 
> ---------------------------------------------------------------------------------------
>
>                 Key: FOP-3285
>                 URL: https://issues.apache.org/jira/browse/FOP-3285
>             Project: FOP
>          Issue Type: Bug
>          Components: renderer/pdf
>            Reporter: Manikanta
>            Priority: Major
>
> I am encountering a concurrency issue when using FOP 2.10 in a multi-threaded Spring Boot environment.
> We initialize a singleton FopFactory using FopFactoryBuilder and a DefaultConfigurationBuilder. When multiple threads attempt to create a new FOP object using factory.newFop(...) simultaneously, the application crashes with a NullPointerException inside Xerces.
> Stack Trace:
> Caused by: java.lang.NullPointerException: Cannot read field "fLength" because "this.fNodeListCache" is null
>     at org.apache.xerces.dom.ParentNode.nodeListGetLength(Unknown Source)
>     at org.apache.fop.configuration.DefaultConfiguration.getChildren(DefaultConfiguration.java:138)
>     at org.apache.fop.render.PrintRendererConfigurator.getCustomFontCollection(PrintRendererConfigurator.java:147)
>     ...
> Steps to Reproduce:
> 1. Create a large fop_config.xml with many <font> entries inside a <renderer>.
> 2. Initialize FopFactory once using DefaultConfigurationBuilder  PDF/A3.
> 3. Spawn 20+ threads(more than one is enough IG) that immediately call fopFactory.newFop() and render a PDF.
> Suggested Fix/Workaround:
> Make FopFactory.newFop() threadsafe



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