Hey folks, with some help from Claes Redestad I've filed an issue with analysis and reproduction of the legendary "zip file closed" error.
https://bugs.openjdk.java.net/browse/JDK-8246714 It turns out that URLClassLoader is just plain broken when used to access jar files (which means this bug affects basically every application out there). Two threads using their own URLClassLoader instances to access the same jar file will likely lead to random errors, due to URLClassLoader improperly closing JarFile instances in the global cache. I'm posting here to bring attention to this issue, because it affects all versions of OpenJDK at least back to Java 7, and the workarounds are gross and only partly effective. We've struggled for years to find the cause of this issue, which occurs randomly in JRuby CI builds and has been reported by numerous users. Maybe we'll finally be able to get this stinker of a bug fixed! - Charlie
