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import uuid
from u1db.backends import CommonBackend
from u1db import errors, Document
from soledad.util import SyncLog, TransactionLog
class ObjectStore(CommonBackend):
"""
A backend for storing u1db data in an object store.
"""
def __init__(self):
# This initialization method should be called after the connection
# with the database is established, so it can ensure that u1db data is
# configured and up-to-date.
self.set_document_factory(Document)
self._sync_log = SyncLog()
self._transaction_log = TransactionLog()
self._ensure_u1db_data()
#-------------------------------------------------------------------------
# implemented methods from Database
#-------------------------------------------------------------------------
def set_document_factory(self, factory):
self._factory = factory
def set_document_size_limit(self, limit):
raise NotImplementedError(self.set_document_size_limit)
def whats_changed(self, old_generation=0):
self._get_u1db_data()
return self._transaction_log.whats_changed(old_generation)
def get_doc(self, doc_id, include_deleted=False):
doc = self._get_doc(doc_id, check_for_conflicts=True)
if doc is None:
return None
if doc.is_tombstone() and not include_deleted:
return None
return doc
def _put_doc(self, doc):
raise NotImplementedError(self._put_doc)
def put_doc(self, doc):
# consistency check
if doc.doc_id is None:
raise errors.InvalidDocId()
self._check_doc_id(doc.doc_id)
self._check_doc_size(doc)
# check if document exists
old_doc = self._get_doc(doc.doc_id, check_for_conflicts=True)
if old_doc and old_doc.has_conflicts:
raise errors.ConflictedDoc()
if old_doc and doc.rev is None and old_doc.is_tombstone():
new_rev = self._allocate_doc_rev(old_doc.rev)
else:
if old_doc is not None:
if old_doc.rev != doc.rev:
raise errors.RevisionConflict()
else:
if doc.rev is not None:
raise errors.RevisionConflict()
new_rev = self._allocate_doc_rev(doc.rev)
doc.rev = new_rev
self._put_doc(doc)
# update u1db generation and logs
new_gen = self._get_generation() + 1
trans_id = self._allocate_transaction_id()
self._transaction_log.append((new_gen, doc.doc_id, trans_id))
self._set_u1db_data()
return doc.rev
def delete_doc(self, doc):
old_doc = self._get_doc(doc.doc_id, check_for_conflicts=True)
if old_doc is None:
raise errors.DocumentDoesNotExist
if old_doc.rev != doc.rev:
raise errors.RevisionConflict()
if old_doc.is_tombstone():
raise errors.DocumentAlreadyDeleted
if old_doc.has_conflicts:
raise errors.ConflictedDoc()
new_rev = self._allocate_doc_rev(doc.rev)
doc.rev = new_rev
doc.make_tombstone()
self._put_doc(doc)
return new_rev
# start of index-related methods: these are not supported by this backend.
def create_index(self, index_name, *index_expressions):
return False
def delete_index(self, index_name):
return False
def list_indexes(self):
return []
def get_from_index(self, index_name, *key_values):
return []
def get_range_from_index(self, index_name, start_value=None,
end_value=None):
return []
def get_index_keys(self, index_name):
return []
# end of index-related methods: these are not supported by this backend.
def get_doc_conflicts(self, doc_id):
return []
def resolve_doc(self, doc, conflicted_doc_revs):
raise NotImplementedError(self.resolve_doc)
def _get_replica_gen_and_trans_id(self, other_replica_uid):
self._get_u1db_data()
return self._sync_log.get_replica_gen_and_trans_id(other_replica_uid)
def _set_replica_gen_and_trans_id(self, other_replica_uid,
other_generation, other_transaction_id):
self._get_u1db_data()
self._sync_log.set_replica_gen_and_trans_id(other_replica_uid,
other_generation,
other_transaction_id)
self._set_u1db_data()
#-------------------------------------------------------------------------
# implemented methods from CommonBackend
#-------------------------------------------------------------------------
def _get_generation(self):
self._get_u1db_data()
return self._transaction_log.get_generation()
def _get_generation_info(self):
self._get_u1db_data()
return self._transaction_log.get_generation_info()
def _has_conflicts(self, doc_id):
# Documents never have conflicts on server.
return False
def _put_and_update_indexes(self, doc_id, old_doc, new_rev, content):
raise NotImplementedError(self._put_and_update_indexes)
def _get_trans_id_for_gen(self, generation):
self._get_u1db_data()
trans_id = self._transaction_log.get_trans_id_for_gen(generation)
if trans_id is None:
raise errors.InvalidGeneration
return trans_id
#-------------------------------------------------------------------------
# methods specific for object stores
#-------------------------------------------------------------------------
def _ensure_u1db_data(self):
"""
Guarantee that u1db data (logs and replica info) exists in store.
"""
if not self._is_initialized():
self._initialize()
self._get_u1db_data()
U1DB_DATA_DOC_ID = 'u1db_data'
def _is_initialized(self):
"""
Verify if u1db data exists in store.
"""
doc = self._get_doc(self.U1DB_DATA_DOC_ID)
if not self._get_doc(self.U1DB_DATA_DOC_ID):
return False
return True
def _initialize(self):
"""
Create u1db data object in store.
"""
self._replica_uid = uuid.uuid4().hex
doc = self._factory(doc_id=self.U1DB_DATA_DOC_ID)
doc.content = { 'transaction_log' : [],
'sync_log' : [],
'replica_uid' : self._replica_uid }
self._put_doc(doc)
def _get_u1db_data(self, u1db_data_doc_id):
"""
Fetch u1db configuration data from backend storage.
"""
NotImplementedError(self._get_u1db_data)
def _set_u1db_data(self):
"""
Save u1db configuration data on backend storage.
"""
doc = self._factory(doc_id=self.U1DB_DATA_DOC_ID)
doc.content = { 'transaction_log' : self._transaction_log.log,
'sync_log' : self._sync_log.log,
'replica_uid' : self._replica_uid,
'_rev' : self._couch_rev}
self._put_doc(doc)
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