[PATCH 0/3] reftable: graceful concurrent writes

Hi,

the reftable backend cannot properly handle concurrent writes due to two reasons:

  - It will bail out immediately when it sees a locked "tables.list"
    file. This is being addressed by introducing a configurable locking
    timeout, similar to how we have it for both loose and packed refs.

  - It will bail out when it notices that its stack is out-of-date after
    having locked the "tables.list" file. This is addressed by reloading
    the stack as requested after locking it, which is fine because our
    transactional API would verify queued ref updates against their
    expected state after the lock was acquired anyway.

So with this patch series we can now spawn concurrent writers and they are expected to succeed, which is demonstrated by the test added by the last patch.

Thanks!

Patrick

Patrick Steinhardt (3):
  refs/reftable: introduce "reftable.lockTimeout"
  reftable/stack: allow locking of outdated stacks
  refs/reftable: reload locked stack when preparing transaction

 Documentation/config/reftable.txt |  7 ++++
 refs/reftable-backend.c           |  9 ++++-
 reftable/reftable-stack.h         | 13 +++++-
 reftable/reftable-writer.h        |  8 ++++
 reftable/stack.c                  | 38 ++++++++++++------
 t/t0610-reftable-basics.sh        | 58 ++++++++++++++++++++++++++
 t/unit-tests/t-reftable-stack.c   | 67 ++++++++++++++++++++++++++++++-
 7 files changed, 181 insertions(+), 19 deletions(-)