Files.touch causes unnecessary disk contention

When calling Files.touch(foo) on a file that already exists, Guava will call java.io.File#createNewFile() and assume the file already exists if the creation operation fails. But because Java guarantees the existence check and creation are atomic, the existence check lives inside a call to java.io.FileSystem#createFileExclusively, introducing concurrency penalties that might not be needed.

Instead, Guava should skip file.createNewFile() when file.exists() returns true.

[cpovirk]

(Should we just be doing what we do in MoreFiles.touch (taking into account that the File API returns false instead of throwing)?)

[cpovirk]

Sorry, I thought I had seen O_EXCL on the touch strace output, but you’re right. Thanks for all the info. I’m still not sure if we’ll end up doing something about this, but now I understand better.