Retry loose object read upon "Stale file handle" exception

When reading loose objects over NFS it is possible that the OS syscall
would fail with ESTALE errors: This happens when the open file
descriptor no longer refers to a valid file.

Notoriously it is possible to hit this scenario when git data is shared
among multiple clients, for example by multiple gerrit instances in HA.

If one of the two clients performs a GC operation that would cause the
packing and then the pruning of loose objects, the other client might
still hold a reference to those objects, which would cause an exception
to bubble up the stack.

The Linux NFS FAQ[1] (at point A.10), suggests that the proper way to
handle such ESTALE scenarios is to:

"[...] close the file or directory where the error occurred, and reopen
it so the NFS client can resolve the pathname again and retrieve the new
file handle."

In case of a stale file handle exception, we now attempt to read the
loose object again (up to 5 times), until we either succeed or encounter
a FileNotFoundException, in which case the search can continue to
Packfiles and alternates.

The limit of 5 provides an arbitrary upper bounds that is consistent to
the one chosen when handling stale file handles for packed-refs
files (see [2] for context).

[1] http://nfs.sourceforge.net/
[2] https://git.eclipse.org/r/c/jgit/jgit/+/54350

Bug: 573791
Change-Id: I9950002f772bbd8afeb9c6108391923be9d0ef51

1 files changed, 1 insertions, 0 deletions

diff --git a/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties b/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
index c5e7dc3efa..2f3520de50 100644
--- a/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
+++ b/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
@@ -416,6 +416,7 @@ logInconsistentFiletimeDiff={}: inconsistent duration from file timestamps on {}
 logLargerFiletimeDiff={}: inconsistent duration from file timestamps on {}, {}: diff = {} > {} (last good value). Aborting measurement.
 logSmallerFiletime={}: got smaller file timestamp on {}, {}: {} < {}. Aborting measurement at resolution {}.
 logXDGConfigHomeInvalid=Environment variable XDG_CONFIG_HOME contains an invalid path {}
+looseObjectHandleIsStale=loose-object {0} file handle is stale. retry {1} of {2}
 maxCountMustBeNonNegative=max count must be >= 0
 mergeConflictOnNonNoteEntries=Merge conflict on non-note entries: base = {0}, ours = {1}, theirs = {2}
 mergeConflictOnNotes=Merge conflict on note {0}. base = {1}, ours = {2}, theirs = {2}