Description Alexander Schubert 2020-06-11 06:43:51 EDT

Created attachment 283228 [details]
Java snippet to reproduce problem

When using JGit concurrently in the same application, JGit often fails with the following error:

java.util.concurrent.RejectedExecutionException: Task java.util.concurrent.CompletableFuture$AsyncSupply@41727a4c rejected from java.util.concurrent.ThreadPoolExecutor@1f27645f[Running, pool size = 5, active threads = 5, queued tasks = 0, completed tasks = 0]
	at java.util.concurrent.CompletableFuture.asyncSupplyStage(CompletableFuture.java:1604)
	at java.util.concurrent.CompletableFuture.supplyAsync(CompletableFuture.java:1830)
	at org.eclipse.jgit.util.FS$FileStoreAttributes.getFileStoreAttributes(FS.java:329)
	at org.eclipse.jgit.util.FS$FileStoreAttributes.get(FS.java:296)
	at org.eclipse.jgit.util.FS.getFileStoreAttributes(FS.java:767)
	at org.eclipse.jgit.internal.storage.file.FileSnapshot.<init>(FileSnapshot.java:224)
	at org.eclipse.jgit.internal.storage.file.FileSnapshot.<init>(FileSnapshot.java:205)
	at org.eclipse.jgit.internal.storage.file.FileSnapshot.save(FileSnapshot.java:102)
	at org.eclipse.jgit.internal.storage.file.FileRepository.<init>(FileRepository.java:209)
	at org.eclipse.jgit.storage.file.FileRepositoryBuilder.build(FileRepositoryBuilder.java:55)
	at Reproducer.lambda$null$0(Reproducer.java:21)

This worked fine until 5.6.1.202002131546-r and started failing on later versions, so I believe this is a regression.

I've attached a small Java snippet to reproduce the problem. Note that it requires an existing working directory of a Git repository to be passed as an argument. Also, it's not completely reliable in reproducing the problem. Disabling JIT compilation in the JVM ('-Xint' for OpenJDK) to change the performance characteristics increased the chances of hitting the problem for me.