def verify_undoable(self, cursor, undo_tid):
"""Raise UndoError if it is not safe to undo the specified txn."""
raise UndoError("Undo is not supported by this storage")
def undo(self, undone_tid, txn):
txn_context = self._txn_container.get(txn)
txn_info, txn_ext = self._getTransactionInformation(undone_tid)
txn_oid_list = txn_info['oids']
# Regroup objects per partition, to ask a minimum set of storage.
partition_oid_dict = {}
for oid in txn_oid_list:
partition = self.pt.getPartition(oid)
try:
oid_list = partition_oid_dict[partition]
except KeyError:
oid_list = partition_oid_dict[partition] = []
oid_list.append(oid)
# Ask storage the undo serial (serial at which object's previous data
# is)
getCellList = self.pt.getCellList
getCellSortKey = self.cp.getCellSortKey
getConnForNode = self.cp.getConnForNode
queue = self._thread_container.queue
ttid = txn_context.ttid
undo_object_tid_dict = {}
snapshot_tid = p64(u64(self.last_tid) + 1)
kw = {
'queue': queue,
'partition_oid_dict': partition_oid_dict,
'undo_object_tid_dict': undo_object_tid_dict,
}
while partition_oid_dict:
for partition, oid_list in partition_oid_dict.iteritems():
cell_list = [
cell for cell in getCellList(partition, readable=True)
# Exclude nodes that may have missed previous resolved
# conflicts. For example, if a network failure happened
# only between the client and the storage, the latter would
# still be readable until we commit.
if txn_context.involved_nodes.get(cell.getUUID(), 0) < 2
]
storage_conn = getConnForNode(
min(cell_list, key=getCellSortKey).getNode())
storage_conn.ask(Packets.AskObjectUndoSerial(
ttid, snapshot_tid, undone_tid, oid_list),
partition=partition,
**kw)
# Wait for all AnswerObjectUndoSerial. We might get
# OidNotFoundError, meaning that objects in transaction's oid_list
# do not exist any longer. This is the symptom of a pack, so forbid
# undoing transaction when it happens.
try:
self.waitResponses(queue)
except NEOStorageNotFoundError:
self.dispatcher.forget_queue(queue)
raise UndoError('non-undoable transaction')
# Send undo data to all storage nodes.
for oid in txn_oid_list:
current_serial, undo_serial, is_current = undo_object_tid_dict[oid]
if is_current:
data = None
else:
# Serial being undone is not the latest version for this
# object. This is an undo conflict, try to resolve it.
try:
# Load the latest version we are supposed to see
if current_serial == ttid:
# XXX: see TODO below
data = txn_context.cache_dict[oid]
else:
data = self.load(oid, current_serial)[0]
# Load the version we were undoing to
undo_data = self.load(oid, undo_serial)[0]
except NEOStorageNotFoundError:
raise UndoError('Object not found while resolving undo '
'conflict')
# Resolve conflict
try:
data = txn_context.Storage.tryToResolveConflict(
oid, current_serial, undone_tid, undo_data, data)
except ConflictError:
raise UndoError('Some data were modified by a later ' \
'transaction', oid)
undo_serial = None
# TODO: The situation is similar to deadlock avoidance.
# Reenable the cache size limit to avoid OOM when there's
# a huge amount conflicting data, and get the data back
# from the storage when it's not in cache_dict anymore.
txn_context.cache_size = -float('inf')
self._store(txn_context, oid, current_serial, data, undo_serial)
self.waitStoreResponses(txn_context)
return None, txn_oid_list
