[jira] [Commented] (LOG4J2-3622) Support for virtual threads

["Volkan Yazici (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LOG4J2-3622?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17622871#comment-17622871 ] 

Volkan Yazici commented on LOG4J2-3622:
---------------------------------------

Thread-locals are used in various places in Log4j for performance purposes. {{ReusableMessageFactory}} is just the tip of the iceberg.

AFAIU, starting with Java 19, [Loom allows TLs to be bound to vthreads|https://blogs.oracle.com/javamagazine/post/java-loom-virtual-threads-platform-threads]:

> ... Virtual threads support thread-local behavior the same way as platform threads, but because virtual threads can be very numerous, thread locals should be used only after careful consideration.
> In fact, as part of Project Loom, many uses of thread locals in the java.base module were removed to reduce the memory footprint when code is running with millions of threads. There is an interesting alternative for some use cases that is currently being explored in a draft JEP for scope-local variables.

I am curious if a vthread can access the TLs of the carrier thread. If possible, this might a quick-and-dirty fix.

Ideally, we should move {{Recycler}} of {{JsonTemplateLayout}} to the {{-core}} for object pooling purposes, replace TL usage with {{Recycler}}s, and provide efficient {{Recycler}} implementations out of box.

> Support for virtual threads
> ---------------------------
>
>                 Key: LOG4J2-3622
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-3622
>             Project: Log4j 2
>          Issue Type: Bug
>          Components: Core
>            Reporter: liuxichen
>            Priority: Critical
>
> I noticed in ReusableMessageFactory threadlocal are used, so If a am using jdk19 virtual threads while logging with threadlocal disabled, UnsupportedOperationException would be thrown, and using log in a lot of virtual threads might create a lot of useless objects, could you  please fix this?



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