I have a job defined to run across approximately 60 build nodes concurrently. If any two of those jobs complete at exactly the same time, one build will fail during link creation, because the links aren't being created atomically:

ln builds/lastStableBuild /jk/jobs/install-system-files-slave/lastStable failed
java.nio.file.FileAlreadyExistsException: /jk/jobs/install-system-files-slave/lastStable
at sun.nio.fs.UnixException.translateToIOException(UnixException.java:88)
at sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:102)
at sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:107)
at sun.nio.fs.UnixFileSystemProvider.createSymbolicLink(UnixFileSystemProvider.java:456)
at java.nio.file.Files.createSymbolicLink(Files.java:996)
at sun.reflect.GeneratedMethodAccessor5497.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at hudson.Util.createSymlinkJava7(Util.java:1202)
at hudson.Util.createSymlink(Util.java:1118)
at hudson.model.Run.createSymlink(Run.java:1865)
at hudson.model.Run.updateSymlinks(Run.java:1847)
at hudson.model.Run.execute(Run.java:1757)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:89)
at hudson.model.Executor.run(Executor.java:240)
Building remotely on d-rg-mt-adm (pack) in workspace /jk/workspace/install-system-files-slave