tree 5d435cb7c5c1f5500b0cebe73e2fbc0c9aa50227
parent 5188c231043982c83f5bfbb5b0a7a8bde58cfe42
author Dave Borowitz <dborowitz@google.com> 1501102401 -0400
committer Dave Borowitz <dborowitz@google.com> 1501242805 -0400

RefDirectory: Retry acquiring ref locks with backoff

If a repo frequently uses PackedBatchRefUpdates, there is likely to be
contention on the packed-refs file, so it's not appropriate to fail
immediately the first time we fail to acquire a lock. Add some logic to
RefDirectory to support general retrying of lock acquisition.

Currently, there is a hard-coded wait starting at 100ms and backing off
exponentially to 1600ms, for about 3s of total wait. This is no worse
than the hard-coded backoff that JGit does elsewhere, e.g. in
FileUtils#delete. One can imagine a scheme that uses per-repository
configuration of backoff, and the current interface would support this
without changing any callers.

Change-Id: I4764e11270d9336882483eb698f67a78a401c251