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make sure we have a excl. lock when starting a transaction 

if we don't, we try to upgrade the lock.
this is to support old clients talking to a new server and also
to avoid bad consequences from coding mistakes for new clients.
This commit is contained in:
Thomas Waldmann 2016-07-23 14:13:32 +02:00
parent 26007c0162
commit 2a355e547e
1 changed files with 17 additions and 8 deletions
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25
borg/repository.py
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@ -207,14 +207,23 @@ class Repository:
def prepare_txn(self, transaction_id, do_cleanup=True):
self._active_txn = True
try:
self.lock.upgrade()
except (LockError, LockErrorT):
# if upgrading the lock to exclusive fails, we do not have an
# active transaction. this is important for "serve" mode, where
# the repository instance lives on - even if exceptions happened.
self._active_txn = False
raise
if not self.lock.got_exclusive_lock():
if self.exclusive is not None:
# self.exclusive is either True or False, thus a new client is active here.
# if it is False and we get here, the caller did not use exclusive=True although
# it is needed for a write operation. if it is True and we get here, something else
# went very wrong, because we should have a exclusive lock, but we don't.
raise AssertionError("bug in code, exclusive lock should exist here")
# if we are here, this is an old client talking to a new server (expecting lock upgrade).
# or we are replaying segments and might need a lock upgrade for that.
try:
self.lock.upgrade()
except (LockError, LockErrorT):
# if upgrading the lock to exclusive fails, we do not have an
# active transaction. this is important for "serve" mode, where
# the repository instance lives on - even if exceptions happened.
self._active_txn = False
raise
if not self.index or transaction_id is None:
self.index = self.open_index(transaction_id)
if transaction_id is None: