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Diffstat (limited to 'soledad/backends/couch.py')
| -rw-r--r-- | soledad/backends/couch.py | 270 |
1 files changed, 270 insertions, 0 deletions
diff --git a/soledad/backends/couch.py b/soledad/backends/couch.py new file mode 100644 index 00000000..b7a77054 --- /dev/null +++ b/soledad/backends/couch.py @@ -0,0 +1,270 @@ +"""A U1DB backend that uses CouchDB as its persistence layer.""" + +# general imports +import uuid +from base64 import b64encode, b64decode +import re +# u1db +from u1db import errors +from u1db.sync import LocalSyncTarget +from u1db.backends.inmemory import InMemoryIndex +from u1db.remote.server_state import ServerState +from u1db.errors import DatabaseDoesNotExist +# couchdb +from couchdb.client import Server, Document as CouchDocument +from couchdb.http import ResourceNotFound +# leap +from leap.soledad.backends.objectstore import ( + ObjectStoreDatabase, + ObjectStoreSyncTarget, +) +from leap.soledad.backends.leap_backend import LeapDocument + +try: + import simplejson as json +except ImportError: + import json # noqa + + +class InvalidURLError(Exception): + """Exception raised when Soledad encounters a malformed URL.""" + pass + + +class CouchDatabase(ObjectStoreDatabase): + """A U1DB backend that uses Couch as its persistence layer.""" + + @classmethod + def open_database(cls, url, create): + """Open a U1DB database using CouchDB as backend.""" + # get database from url + m = re.match('(^https?://[^/]+)/(.+)$', url) + if not m: + raise InvalidURLError + url = m.group(1) + dbname = m.group(2) + server = Server(url=url) + try: + server[dbname] + except ResourceNotFound: + if not create: + raise DatabaseDoesNotExist() + return cls(url, dbname) + + def __init__(self, url, database, replica_uid=None, full_commit=True, + session=None): + """Create a new Couch data container.""" + self._url = url + self._full_commit = full_commit + self._session = session + self._server = Server(url=self._url, + full_commit=self._full_commit, + session=self._session) + self._dbname = database + # this will ensure that transaction and sync logs exist and are + # up-to-date. + try: + self._database = self._server[database] + except ResourceNotFound: + self._server.create(database) + self._database = self._server[database] + super(CouchDatabase, self).__init__(replica_uid=replica_uid, + document_factory=LeapDocument) + + #------------------------------------------------------------------------- + # methods from Database + #------------------------------------------------------------------------- + + def _get_doc(self, doc_id, check_for_conflicts=False): + """Get just the document content, without fancy handling.""" + cdoc = self._database.get(doc_id) + if cdoc is None: + return None + has_conflicts = False + if check_for_conflicts: + has_conflicts = self._has_conflicts(doc_id) + doc = self._factory( + doc_id=doc_id, + rev=cdoc['u1db_rev'], + has_conflicts=has_conflicts) + contents = self._database.get_attachment(cdoc, 'u1db_json') + if contents: + doc.content = json.loads(contents.getvalue()) + else: + doc.make_tombstone() + return doc + + def get_all_docs(self, include_deleted=False): + """Get the JSON content for all documents in the database.""" + generation = self._get_generation() + results = [] + for doc_id in self._database: + if doc_id == self.U1DB_DATA_DOC_ID: + continue + doc = self._get_doc(doc_id, check_for_conflicts=True) + if doc.content is None and not include_deleted: + continue + results.append(doc) + return (generation, results) + + def _put_doc(self, doc): + """Store document in database.""" + # prepare couch's Document + cdoc = CouchDocument() + cdoc['_id'] = doc.doc_id + # we have to guarantee that couch's _rev is cosistent + old_cdoc = self._database.get(doc.doc_id) + if old_cdoc is not None: + cdoc['_rev'] = old_cdoc['_rev'] + # store u1db's rev + cdoc['u1db_rev'] = doc.rev + # save doc in db + self._database.save(cdoc) + # store u1db's content as json string + if not doc.is_tombstone(): + self._database.put_attachment(cdoc, doc.get_json(), + filename='u1db_json') + else: + self._database.delete_attachment(cdoc, 'u1db_json') + + def get_sync_target(self): + """ + Return a SyncTarget object, for another u1db to synchronize with. + """ + return CouchSyncTarget(self) + + def create_index(self, index_name, *index_expressions): + """ + Create a named index, which can then be queried for future lookups. + """ + if index_name in self._indexes: + if self._indexes[index_name]._definition == list( + index_expressions): + return + raise errors.IndexNameTakenError + index = InMemoryIndex(index_name, list(index_expressions)) + for doc_id in self._database: + if doc_id == self.U1DB_DATA_DOC_ID: + continue + doc = self._get_doc(doc_id) + if doc.content is not None: + index.add_json(doc_id, doc.get_json()) + self._indexes[index_name] = index + # save data in object store + self._store_u1db_data() + + def close(self): + """Release any resources associated with this database.""" + # TODO: fix this method so the connection is properly closed and + # test_close (+tearDown, which deletes the db) works without problems. + self._url = None + self._full_commit = None + self._session = None + #self._server = None + self._database = None + return True + + def sync(self, url, creds=None, autocreate=True): + """Synchronize documents with remote replica exposed at url.""" + from u1db.sync import Synchronizer + return Synchronizer(self, CouchSyncTarget(url, creds=creds)).sync( + autocreate=autocreate) + + #------------------------------------------------------------------------- + # methods from ObjectStoreDatabase + #------------------------------------------------------------------------- + + def _init_u1db_data(self): + if self._replica_uid is None: + self._replica_uid = uuid.uuid4().hex + doc = self._factory(doc_id=self.U1DB_DATA_DOC_ID) + doc.content = {'transaction_log': [], + 'conflicts': b64encode(json.dumps({})), + 'other_generations': {}, + 'indexes': b64encode(json.dumps({})), + 'replica_uid': self._replica_uid} + self._put_doc(doc) + + def _fetch_u1db_data(self): + # retrieve u1db data from couch db + cdoc = self._database.get(self.U1DB_DATA_DOC_ID) + jsonstr = self._database.get_attachment(cdoc, 'u1db_json').getvalue() + content = json.loads(jsonstr) + # set u1db database info + #self._sync_log = content['sync_log'] + self._transaction_log = content['transaction_log'] + self._conflicts = json.loads(b64decode(content['conflicts'])) + self._other_generations = content['other_generations'] + self._indexes = self._load_indexes_from_json( + b64decode(content['indexes'])) + self._replica_uid = content['replica_uid'] + # save couch _rev + self._couch_rev = cdoc['_rev'] + + def _store_u1db_data(self): + doc = self._factory(doc_id=self.U1DB_DATA_DOC_ID) + doc.content = { + 'transaction_log': self._transaction_log, + # Here, the b64 encode ensures that document content + # does not cause strange behaviour in couchdb because + # of encoding. + 'conflicts': b64encode(json.dumps(self._conflicts)), + 'other_generations': self._other_generations, + 'indexes': b64encode(self._dump_indexes_as_json()), + 'replica_uid': self._replica_uid, + '_rev': self._couch_rev} + self._put_doc(doc) + + #------------------------------------------------------------------------- + # Couch specific methods + #------------------------------------------------------------------------- + + def delete_database(self): + """Delete a U1DB CouchDB database.""" + del(self._server[self._dbname]) + + def _dump_indexes_as_json(self): + indexes = {} + for name, idx in self._indexes.iteritems(): + indexes[name] = {} + for attr in ['name', 'definition', 'values']: + indexes[name][attr] = getattr(idx, '_' + attr) + return json.dumps(indexes) + + def _load_indexes_from_json(self, indexes): + dict = {} + for name, idx_dict in json.loads(indexes).iteritems(): + idx = InMemoryIndex(name, idx_dict['definition']) + idx._values = idx_dict['values'] + dict[name] = idx + return dict + + +class CouchSyncTarget(ObjectStoreSyncTarget): + pass + + +class CouchServerState(ServerState): + """Inteface of the WSGI server with the CouchDB backend.""" + + def __init__(self, couch_url): + self.couch_url = couch_url + + def open_database(self, dbname): + """Open a database at the given location.""" + # TODO: open couch + from leap.soledad.backends.couch import CouchDatabase + return CouchDatabase.open_database(self.couch_url + '/' + dbname, + create=False) + + def ensure_database(self, dbname): + """Ensure database at the given location.""" + from leap.soledad.backends.couch import CouchDatabase + db = CouchDatabase.open_database(self.couch_url + '/' + dbname, + create=True) + return db, db._replica_uid + + def delete_database(self, dbname): + """Delete database at the given location.""" + from leap.soledad.backends.couch import CouchDatabase + CouchDatabase.delete_database(self.couch_url + '/' + dbname) |