summaryrefslogtreecommitdiff
path: root/backends/objectstore.py
blob: 03694532970910e94c670db9b58aece0f5dc43e5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
from u1db.backends import CommonBackend
from u1db import errors, Document, vectorclock

class ObjectStore(CommonBackend):
    """
    A backend for storing u1db data in an object store.
    """

    def __init__(self, replica_uid=None):
        # This initialization method should be called after the connection
        # with the database is established in each implementation, 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._conflict_log = ConflictLog(self._factory)
        self._replica_uid = replica_uid
        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 _update_gen_and_transaction_log(self, doc_id):
        new_gen = self._get_generation() + 1
        trans_id = self._allocate_transaction_id()
        self._transaction_log.append((new_gen, doc_id, trans_id))
        self._set_u1db_data()

    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_and_update_indexes(old_doc, doc)
        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_and_update_indexes(old_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):
        self._get_u1db_data()
        conflict_docs = self._conflict_log.get_conflicts(doc_id)
        if not conflict_docs:
            return []
        this_doc = self._get_doc(doc_id)
        this_doc.has_conflicts = True
        return [this_doc] + list(conflict_docs)

    def resolve_doc(self, doc, conflicted_doc_revs):
        cur_doc = self._get_doc(doc.doc_id)
        new_rev = self._ensure_maximal_rev(cur_doc.rev,
                                           conflicted_doc_revs)
        superseded_revs = set(conflicted_doc_revs)
        doc.rev = new_rev
        if cur_doc.rev in superseded_revs:
            self._put_and_update_indexes(cur_doc, doc)
        else:
            self._add_conflict(doc.doc_id, new_rev, doc.get_json())
        self._delete_conflicts(doc, superseded_revs)

    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):
        return self._do_set_replica_gen_and_trans_id(
                 other_replica_uid,
                 other_generation,
                 other_transaction_id)

    def _do_set_replica_gen_and_trans_id(self, other_replica_uid,
                                         other_generation, other_transaction_id):
        self._sync_log.set_replica_gen_and_trans_id(other_replica_uid,
                                                    other_generation,
                                                    other_transaction_id)
        self._set_u1db_data()

    def _get_transaction_log(self):
        self._get_u1db_data()
        return self._transaction_log.get_transaction_log()

    #-------------------------------------------------------------------------
    # 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):
        self._get_u1db_data()
        return self._conflict_log.has_conflicts(doc_id)

    def _put_and_update_indexes(self, old_doc, doc):
        # for now we ignore indexes as this backend is used to store encrypted
        # blobs of data in the server.
        self._put_doc(doc)
        self._update_gen_and_transaction_log(doc.doc_id)

    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.
        """
        NotImplementedError(self._initialize)

    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.
        """
        NotImplementedError(self._set_u1db_data)

    def _set_replica_uid(self, replica_uid):
        self._replica_uid = replica_uid
        self._set_u1db_data()

    def _get_replica_uid(self):
        return self._replica_uid

    replica_uid = property(
        _get_replica_uid, _set_replica_uid, doc="Replica UID of the database")


    #-------------------------------------------------------------------------
    # The methods below were cloned from u1db sqlite backend. They should at
    # least exist and raise a NotImplementedError exception in CommonBackend
    # (should we maybe fill a bug in u1db bts?).
    #-------------------------------------------------------------------------

    def _add_conflict(self, doc_id, my_doc_rev, my_content):
        self._conflict_log.append((doc_id, my_doc_rev, my_content))
        self._set_u1db_data()

    def _delete_conflicts(self, doc, conflict_revs):
        deleting = [(doc.doc_id, c_rev) for c_rev in conflict_revs]
        self._conflict_log.delete_conflicts(deleting)
        self._set_u1db_data()
        doc.has_conflicts = self._has_conflicts(doc.doc_id)

    def _prune_conflicts(self, doc, doc_vcr):
        if self._has_conflicts(doc.doc_id):
            autoresolved = False
            c_revs_to_prune = []
            for c_doc in self._conflict_log.get_conflicts(doc.doc_id):
                c_vcr = vectorclock.VectorClockRev(c_doc.rev)
                if doc_vcr.is_newer(c_vcr):
                    c_revs_to_prune.append(c_doc.rev)
                elif doc.same_content_as(c_doc):
                    c_revs_to_prune.append(c_doc.rev)
                    doc_vcr.maximize(c_vcr)
                    autoresolved = True
            if autoresolved:
                doc_vcr.increment(self._replica_uid)
                doc.rev = doc_vcr.as_str()
            self._delete_conflicts(doc, c_revs_to_prune)

    def _force_doc_sync_conflict(self, doc):
        my_doc = self._get_doc(doc.doc_id)
        self._prune_conflicts(doc, vectorclock.VectorClockRev(doc.rev))
        self._add_conflict(doc.doc_id, my_doc.rev, my_doc.get_json())
        doc.has_conflicts = True
        self._put_and_update_indexes(my_doc, doc)


#----------------------------------------------------------------------------
# U1DB's Transaction, Sync, and conflict Logs
#----------------------------------------------------------------------------

class SimpleList(object):
    def __init__(self):
        self._log = []

    def _set_log(self, log):
        self._log = log

    def _get_log(self):
        return self._log

    log = property(
        _get_log, _set_log, doc="Log contents.")

    def append(self, msg):
        self._log.append(msg)

    def reduce(self, func, initializer=None):
        return reduce(func, self._log, initializer)

    def map(self, func):
        return map(func, self._get_log())

    def filter(self, func):
        return filter(func, self._get_log())


class TransactionLog(SimpleList):
    """
    An ordered list of (generation, doc_id, transaction_id) tuples.
    """

    def _set_log(self, log):
        self._log = log

    def _get_log(self):
        return sorted(self._log, reverse=True)

    log = property(
        _get_log, _set_log, doc="Log contents.")

    def get_generation(self):
        """
        Return the current generation.
        """
        gens = self.map(lambda x: x[0])
        if not gens:
            return 0
        return max(gens)

    def get_generation_info(self):
        """
        Return the current generation and transaction id.
        """
        if not self._log:
            return(0, '')
        info = self.map(lambda x: (x[0], x[2]))
        return reduce(lambda x, y: x if (x[0] > y[0]) else y, info)

    def get_trans_id_for_gen(self, gen):
        """
        Get the transaction id corresponding to a particular generation.
        """
        log = self.reduce(lambda x, y: y if y[0] == gen else x)
        if log is None:
            return None
        return log[2]

    def whats_changed(self, old_generation):
        """
        Return a list of documents that have changed since old_generation.
        """
        results = self.filter(lambda x: x[0] > old_generation)
        seen = set()
        changes = []
        newest_trans_id = ''
        for generation, doc_id, trans_id in results:
            if doc_id not in seen:
                changes.append((doc_id, generation, trans_id))
                seen.add(doc_id)
        if changes:
            cur_gen = changes[0][1]  # max generation
            newest_trans_id = changes[0][2]
            changes.reverse()
        else:
            results = self._get_log()
            if not results:
                cur_gen = 0
                newest_trans_id = ''
            else:
                cur_gen, _, newest_trans_id = results[0]

        return cur_gen, newest_trans_id, changes


    def get_transaction_log(self):
        """
        Return only a list of (doc_id, transaction_id)
        """
        return map(lambda x: (x[1], x[2]), sorted(self._log))


class SyncLog(SimpleList):
    """
    A list of (replica_id, generation, transaction_id) tuples.
    """

    def find_by_replica_uid(self, replica_uid):
        if not self._get_log():
            return ()
        return self.reduce(lambda x, y: y if y[0] == replica_uid else x)

    def get_replica_gen_and_trans_id(self, other_replica_uid):
        """
        Return the last known generation and transaction id for the other db
        replica.
        """
        info = self.find_by_replica_uid(other_replica_uid)
        if not info:
            return (0, '')
        return (info[1], info[2])

    def set_replica_gen_and_trans_id(self, other_replica_uid,
                                      other_generation, other_transaction_id):
        """
        Set the last-known generation and transaction id for the other
        database replica.
        """
        self._log = self.filter(lambda x: x[0] != other_replica_uid)
        self.append((other_replica_uid, other_generation,
                     other_transaction_id))

class ConflictLog(SimpleList):
    """
    A list of (doc_id, my_doc_rev, my_content) tuples.
    """

    def __init__(self, factory):
        super(ConflictLog, self).__init__()
        self._factory = factory
    
    def delete_conflicts(self, conflicts):
        for conflict in conflicts:
            self._log = self.filter(lambda x:
                         x[0] != conflict[0] or x[1] != conflict[1])

    def get_conflicts(self, doc_id):
        conflicts = self.filter(lambda x: x[0] == doc_id)
        if not conflicts:
            return []
        return reversed(map(lambda x: self._factory(doc_id, x[1], x[2]),
                            conflicts))

    def has_conflicts(self, doc_id):
        return bool(self.filter(lambda x: x[0] == doc_id))