[GitHub] [tomcat] ChristopherSchultz commented on pull request #456: Document conditions under which the AprLifecycleListener can be used …

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ChristopherSchultz commented on pull request #456:
URL: https://github.com/apache/tomcat/pull/456#issuecomment-954890217


   Something is wrong with the premise, here. I read through [Spring-28472](https://github.com/spring-projects/spring-boot/issues/28472) and looked at the code for `AprLifecycleListener`. `AprLifecycleListener` should not be shutting-down APR twice. In `AprLifecycleListener.lifecycleEvent`, the `Lifecycle.AFTER_DESTROY` handler uses a static lock for cross-thread synchronization and only calls `terminateAPR` if `AprStatus.isAprAvailable` returns `true`. Notably, `terminateAPR` sets `AprStatus.isAprAvailable` to `false`.
   
   I can see a theoretical threading problem because `AprStatus.isAprAvailable` and `AprStatus.setAprAvailable` are not synchronized, but the static class members being set are declared `volatile` and should require threads to reload their values appropriately.
   
   Are you sure it's the shutdown that's causing the failure?
   
   I think I'd rather fix a bug that seems to be hiding, here, rather than document what can and cannot be done (in a way that is very difficult to understand, I have to admit).


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