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source: trunk/src/allmydata/mutable/publish.py

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Last change on this file was fec97256, checked in by Alexandre Detiste <alexandre.detiste@…>, at 2025-01-06T21:51:37Z
trim Python2 syntax
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1	"""
2	Ported to Python 3.
3	"""
4
5	import os, time
6	from io import BytesIO
7	from itertools import count
8	from zope.interface import implementer
9	from twisted.internet import defer
10	from twisted.python import failure
11
12	from allmydata.crypto import aes
13	from allmydata.crypto import rsa
14	from allmydata.interfaces import IPublishStatus, SDMF_VERSION, MDMF_VERSION, \
15	IMutableUploadable
16	from allmydata.util import base32, hashutil, mathutil, log
17	from allmydata.util.dictutil import DictOfSets
18	from allmydata.util.deferredutil import async_to_deferred
19	from allmydata.util.cputhreadpool import defer_to_thread
20	from allmydata import hashtree, codec
21	from allmydata.storage.server import si_b2a
22	from foolscap.api import eventually, fireEventually
23	from allmydata.mutable.common import MODE_WRITE, MODE_CHECK, MODE_REPAIR, \
24	UncoordinatedWriteError, NotEnoughServersError
25	from allmydata.mutable.servermap import ServerMap
26	from allmydata.mutable.layout import get_version_from_checkstring,\
27	unpack_mdmf_checkstring, \
28	unpack_sdmf_checkstring, \
29	MDMFSlotWriteProxy, \
30	SDMFSlotWriteProxy
31
32	from eliot import (
33	Message,
34	start_action,
35	)
36
37	KiB = 1024
38	DEFAULT_MUTABLE_MAX_SEGMENT_SIZE = 128 * KiB
39	PUSHING_BLOCKS_STATE = 0
40	PUSHING_EVERYTHING_ELSE_STATE = 1
41	DONE_STATE = 2
42
43	@implementer(IPublishStatus)
44	class PublishStatus:
45	statusid_counter = count(0)
46	def __init__(self):
47	self.timings = {}
48	self.timings["send_per_server"] = {}
49	self.timings["encrypt"] = 0.0
50	self.timings["encode"] = 0.0
51	self.servermap = None
52	self._problems = {}
53	self.active = True
54	self.storage_index = None
55	self.helper = False
56	self.encoding = ("?", "?")
57	self.size = None
58	self.status = "Not started"
59	self.progress = 0.0
60	self.counter = next(self.statusid_counter)
61	self.started = time.time()
62
63	def add_per_server_time(self, server, elapsed):
64	if server not in self.timings["send_per_server"]:
65	self.timings["send_per_server"][server] = []
66	self.timings["send_per_server"][server].append(elapsed)
67	def accumulate_encode_time(self, elapsed):
68	self.timings["encode"] += elapsed
69	def accumulate_encrypt_time(self, elapsed):
70	self.timings["encrypt"] += elapsed
71
72	def get_started(self):
73	return self.started
74	def get_storage_index(self):
75	return self.storage_index
76	def get_encoding(self):
77	return self.encoding
78	def using_helper(self):
79	return self.helper
80	def get_servermap(self):
81	return self.servermap
82	def get_size(self):
83	return self.size
84	def get_status(self):
85	return self.status
86	def get_progress(self):
87	return self.progress
88	def get_active(self):
89	return self.active
90	def get_counter(self):
91	return self.counter
92	def get_problems(self):
93	return self._problems
94
95	def set_storage_index(self, si):
96	self.storage_index = si
97	def set_helper(self, helper):
98	self.helper = helper
99	def set_servermap(self, servermap):
100	self.servermap = servermap
101	def set_encoding(self, k, n):
102	self.encoding = (k, n)
103	def set_size(self, size):
104	self.size = size
105	def set_status(self, status):
106	self.status = status
107	def set_progress(self, value):
108	self.progress = value
109	def set_active(self, value):
110	self.active = value
111
112	class LoopLimitExceededError(Exception):
113	pass
114
115	class Publish:
116	"""I represent a single act of publishing the mutable file to the grid. I
117	will only publish my data if the servermap I am using still represents
118	the current state of the world.
119
120	To make the initial publish, set servermap to None.
121	"""
122
123	def __init__(self, filenode, storage_broker, servermap):
124	self._node = filenode
125	self._storage_broker = storage_broker
126	self._servermap = servermap
127	self._storage_index = self._node.get_storage_index()
128	self._log_prefix = prefix = si_b2a(self._storage_index)[:5]
129	num = self.log("Publish(%r): starting" % prefix, parent=None)
130	self._log_number = num
131	self._running = True
132	self._first_write_error = None
133	self._last_failure = None
134
135	self._status = PublishStatus()
136	self._status.set_storage_index(self._storage_index)
137	self._status.set_helper(False)
138	self._status.set_progress(0.0)
139	self._status.set_active(True)
140	self._version = self._node.get_version()
141	assert self._version in (SDMF_VERSION, MDMF_VERSION)
142
143
144	def get_status(self):
145	return self._status
146
147	def log(self, args, *kwargs):
148	if 'parent' not in kwargs:
149	kwargs['parent'] = self._log_number
150	if "facility" not in kwargs:
151	kwargs["facility"] = "tahoe.mutable.publish"
152	return log.msg(args, *kwargs)
153
154
155	def update(self, data, offset, blockhashes, version):
156	"""
157	I replace the contents of this file with the contents of data,
158	starting at offset. I return a Deferred that fires with None
159	when the replacement has been completed, or with an error if
160	something went wrong during the process.
161
162	Note that this process will not upload new shares. If the file
163	being updated is in need of repair, callers will have to repair
164	it on their own.
165	"""
166	# How this works:
167	# 1: Make server assignments. We'll assign each share that we know
168	# about on the grid to that server that currently holds that
169	# share, and will not place any new shares.
170	# 2: Setup encoding parameters. Most of these will stay the same
171	# -- datalength will change, as will some of the offsets.
172	# 3. Upload the new segments.
173	# 4. Be done.
174	assert IMutableUploadable.providedBy(data)
175
176	self.data = data
177
178	# XXX: Use the MutableFileVersion instead.
179	self.datalength = self._node.get_size()
180	if data.get_size() > self.datalength:
181	self.datalength = data.get_size()
182
183	self.log("starting update")
184	self.log("adding new data of length %d at offset %d" % \
185	(data.get_size(), offset))
186	self.log("new data length is %d" % self.datalength)
187	self._status.set_size(self.datalength)
188	self._status.set_status("Started")
189	self._started = time.time()
190
191	self.done_deferred = defer.Deferred()
192
193	self._writekey = self._node.get_writekey()
194	assert self._writekey, "need write capability to publish"
195
196	# first, which servers will we publish to? We require that the
197	# servermap was updated in MODE_WRITE, so we can depend upon the
198	# serverlist computed by that process instead of computing our own.
199	assert self._servermap
200	assert self._servermap.get_last_update()[0] in (MODE_WRITE, MODE_CHECK, MODE_REPAIR)
201	# we will push a version that is one larger than anything present
202	# in the grid, according to the servermap.
203	self._new_seqnum = self._servermap.highest_seqnum() + 1
204	self._status.set_servermap(self._servermap)
205
206	self.log(format="new seqnum will be %(seqnum)d",
207	seqnum=self._new_seqnum, level=log.NOISY)
208
209	# We're updating an existing file, so all of the following
210	# should be available.
211	self.readkey = self._node.get_readkey()
212	self.required_shares = self._node.get_required_shares()
213	assert self.required_shares is not None
214	self.total_shares = self._node.get_total_shares()
215	assert self.total_shares is not None
216	self._status.set_encoding(self.required_shares, self.total_shares)
217
218	self._pubkey = self._node.get_pubkey()
219	assert self._pubkey
220	self._privkey = self._node.get_privkey()
221	assert self._privkey
222	self._encprivkey = self._node.get_encprivkey()
223
224	sb = self._storage_broker
225	full_serverlist = list(sb.get_servers_for_psi(self._storage_index))
226	self.full_serverlist = full_serverlist # for use later, immutable
227	self.bad_servers = set() # servers who have errbacked/refused requests
228
229	# This will set self.segment_size, self.num_segments, and
230	# self.fec. TODO: Does it know how to do the offset? Probably
231	# not. So do that part next.
232	self.setup_encoding_parameters(offset=offset)
233
234	# if we experience any surprises (writes which were rejected because
235	# our test vector did not match, or shares which we didn't expect to
236	# see), we set this flag and report an UncoordinatedWriteError at the
237	# end of the publish process.
238	self.surprised = False
239
240	# we keep track of three tables. The first is our goal: which share
241	# we want to see on which servers. This is initially populated by the
242	# existing servermap.
243	self.goal = set() # pairs of (server, shnum) tuples
244
245	# the number of outstanding queries: those that are in flight and
246	# may or may not be delivered, accepted, or acknowledged. This is
247	# incremented when a query is sent, and decremented when the response
248	# returns or errbacks.
249	self.num_outstanding = 0
250
251	# the third is a table of successes: share which have actually been
252	# placed. These are populated when responses come back with success.
253	# When self.placed == self.goal, we're done.
254	self.placed = set() # (server, shnum) tuples
255
256	self.bad_share_checkstrings = {}
257
258	# This is set at the last step of the publishing process.
259	self.versioninfo = ""
260
261	# we use the servermap to populate the initial goal: this way we will
262	# try to update each existing share in place. Since we're
263	# updating, we ignore damaged and missing shares -- callers must
264	# do a repair to repair and recreate these.
265	self.goal = set(self._servermap.get_known_shares())
266
267	# shnum -> set of IMutableSlotWriter
268	self.writers = DictOfSets()
269
270	# SDMF files are updated differently.
271	self._version = MDMF_VERSION
272	writer_class = MDMFSlotWriteProxy
273
274	# For each (server, shnum) in self.goal, we make a
275	# write proxy for that server. We'll use this to write
276	# shares to the server.
277	for (server,shnum) in self.goal:
278	write_enabler = self._node.get_write_enabler(server)
279	renew_secret = self._node.get_renewal_secret(server)
280	cancel_secret = self._node.get_cancel_secret(server)
281	secrets = (write_enabler, renew_secret, cancel_secret)
282
283	writer = writer_class(shnum,
284	server.get_storage_server(),
285	self._storage_index,
286	secrets,
287	self._new_seqnum,
288	self.required_shares,
289	self.total_shares,
290	self.segment_size,
291	self.datalength)
292
293	self.writers.add(shnum, writer)
294	writer.server = server
295	known_shares = self._servermap.get_known_shares()
296	assert (server, shnum) in known_shares
297	old_versionid, old_timestamp = known_shares[(server,shnum)]
298	(old_seqnum, old_root_hash, old_salt, old_segsize,
299	old_datalength, old_k, old_N, old_prefix,
300	old_offsets_tuple) = old_versionid
301	writer.set_checkstring(old_seqnum,
302	old_root_hash,
303	old_salt)
304
305	# Our remote shares will not have a complete checkstring until
306	# after we are done writing share data and have started to write
307	# blocks. In the meantime, we need to know what to look for when
308	# writing, so that we can detect UncoordinatedWriteErrors.
309	self._checkstring = self._get_some_writer().get_checkstring()
310
311	# Now, we start pushing shares.
312	self._status.timings["setup"] = time.time() - self._started
313	# First, we encrypt, encode, and publish the shares that we need
314	# to encrypt, encode, and publish.
315
316	# Our update process fetched these for us. We need to update
317	# them in place as publishing happens.
318	self.blockhashes = {} # (shnum, [blochashes])
319	for (i, bht) in list(blockhashes.items()):
320	# We need to extract the leaves from our old hash tree.
321	old_segcount = mathutil.div_ceil(version[4],
322	version[3])
323	h = hashtree.IncompleteHashTree(old_segcount)
324	bht = dict(enumerate(bht))
325	h.set_hashes(bht)
326	leaves = h[h.get_leaf_index(0):]
327	for j in range(self.num_segments - len(leaves)):
328	leaves.append(None)
329
330	assert len(leaves) >= self.num_segments
331	self.blockhashes[i] = leaves
332	# This list will now be the leaves that were set during the
333	# initial upload + enough empty hashes to make it a
334	# power-of-two. If we exceed a power of two boundary, we
335	# should be encoding the file over again, and should not be
336	# here. So, we have
337	#assert len(self.blockhashes[i]) == \
338	# hashtree.roundup_pow2(self.num_segments), \
339	# len(self.blockhashes[i])
340	# XXX: Except this doesn't work. Figure out why.
341
342	# These are filled in later, after we've modified the block hash
343	# tree suitably.
344	self.sharehash_leaves = None # eventually [sharehashes]
345	self.sharehashes = {} # shnum -> [sharehash leaves necessary to
346	# validate the share]
347
348	self.log("Starting push")
349
350	self._state = PUSHING_BLOCKS_STATE
351	self._push()
352
353	return self.done_deferred
354
355
356	def publish(self, newdata):
357	"""Publish the filenode's current contents. Returns a Deferred that
358	fires (with None) when the publish has done as much work as it's ever
359	going to do, or errbacks with ConsistencyError if it detects a
360	simultaneous write.
361	"""
362
363	# 0. Setup encoding parameters, encoder, and other such things.
364	# 1. Encrypt, encode, and publish segments.
365	assert IMutableUploadable.providedBy(newdata)
366
367	self.data = newdata
368	self.datalength = newdata.get_size()
369	#if self.datalength >= DEFAULT_MUTABLE_MAX_SEGMENT_SIZE:
370	# self._version = MDMF_VERSION
371	#else:
372	# self._version = SDMF_VERSION
373
374	self.log("starting publish, datalen is %s" % self.datalength)
375	self._status.set_size(self.datalength)
376	self._status.set_status("Started")
377	self._started = time.time()
378
379	self.done_deferred = defer.Deferred()
380
381	self._writekey = self._node.get_writekey()
382	assert self._writekey, "need write capability to publish"
383
384	# first, which servers will we publish to? We require that the
385	# servermap was updated in MODE_WRITE, so we can depend upon the
386	# serverlist computed by that process instead of computing our own.
387	if self._servermap:
388	assert self._servermap.get_last_update()[0] in (MODE_WRITE, MODE_CHECK, MODE_REPAIR)
389	# we will push a version that is one larger than anything present
390	# in the grid, according to the servermap.
391	self._new_seqnum = self._servermap.highest_seqnum() + 1
392	else:
393	# If we don't have a servermap, that's because we're doing the
394	# initial publish
395	self._new_seqnum = 1
396	self._servermap = ServerMap()
397	self._status.set_servermap(self._servermap)
398
399	self.log(format="new seqnum will be %(seqnum)d",
400	seqnum=self._new_seqnum, level=log.NOISY)
401
402	# having an up-to-date servermap (or using a filenode that was just
403	# created for the first time) also guarantees that the following
404	# fields are available
405	self.readkey = self._node.get_readkey()
406	self.required_shares = self._node.get_required_shares()
407	assert self.required_shares is not None
408	self.total_shares = self._node.get_total_shares()
409	assert self.total_shares is not None
410	self._status.set_encoding(self.required_shares, self.total_shares)
411
412	self._pubkey = self._node.get_pubkey()
413	assert self._pubkey
414	self._privkey = self._node.get_privkey()
415	assert self._privkey
416	self._encprivkey = self._node.get_encprivkey()
417
418	sb = self._storage_broker
419	full_serverlist = list(sb.get_servers_for_psi(self._storage_index))
420	self.full_serverlist = full_serverlist # for use later, immutable
421	self.bad_servers = set() # servers who have errbacked/refused requests
422
423	# This will set self.segment_size, self.num_segments, and
424	# self.fec.
425	self.setup_encoding_parameters()
426
427	# if we experience any surprises (writes which were rejected because
428	# our test vector did not match, or shares which we didn't expect to
429	# see), we set this flag and report an UncoordinatedWriteError at the
430	# end of the publish process.
431	self.surprised = False
432
433	# we keep track of three tables. The first is our goal: which share
434	# we want to see on which servers. This is initially populated by the
435	# existing servermap.
436	self.goal = set() # pairs of (server, shnum) tuples
437
438	# the number of outstanding queries: those that are in flight and
439	# may or may not be delivered, accepted, or acknowledged. This is
440	# incremented when a query is sent, and decremented when the response
441	# returns or errbacks.
442	self.num_outstanding = 0
443
444	# the third is a table of successes: share which have actually been
445	# placed. These are populated when responses come back with success.
446	# When self.placed == self.goal, we're done.
447	self.placed = set() # (server, shnum) tuples
448
449	self.bad_share_checkstrings = {}
450
451	# This is set at the last step of the publishing process.
452	self.versioninfo = ""
453
454	# we use the servermap to populate the initial goal: this way we will
455	# try to update each existing share in place.
456	self.goal = set(self._servermap.get_known_shares())
457
458	# then we add in all the shares that were bad (corrupted, bad
459	# signatures, etc). We want to replace these.
460	for key, old_checkstring in list(self._servermap.get_bad_shares().items()):
461	(server, shnum) = key
462	self.goal.add( (server,shnum) )
463	self.bad_share_checkstrings[(server,shnum)] = old_checkstring
464
465	# TODO: Make this part do server selection.
466	self.update_goal()
467
468	# shnum -> set of IMutableSlotWriter
469	self.writers = DictOfSets()
470
471	if self._version == MDMF_VERSION:
472	writer_class = MDMFSlotWriteProxy
473	else:
474	writer_class = SDMFSlotWriteProxy
475
476	# For each (server, shnum) in self.goal, we make a
477	# write proxy for that server. We'll use this to write
478	# shares to the server.
479	for (server,shnum) in self.goal:
480	write_enabler = self._node.get_write_enabler(server)
481	renew_secret = self._node.get_renewal_secret(server)
482	cancel_secret = self._node.get_cancel_secret(server)
483	secrets = (write_enabler, renew_secret, cancel_secret)
484
485	writer = writer_class(shnum,
486	server.get_storage_server(),
487	self._storage_index,
488	secrets,
489	self._new_seqnum,
490	self.required_shares,
491	self.total_shares,
492	self.segment_size,
493	self.datalength)
494	self.writers.add(shnum, writer)
495	writer.server = server
496	known_shares = self._servermap.get_known_shares()
497	if (server, shnum) in known_shares:
498	old_versionid, old_timestamp = known_shares[(server,shnum)]
499	(old_seqnum, old_root_hash, old_salt, old_segsize,
500	old_datalength, old_k, old_N, old_prefix,
501	old_offsets_tuple) = old_versionid
502	writer.set_checkstring(old_seqnum,
503	old_root_hash,
504	old_salt)
505	elif (server, shnum) in self.bad_share_checkstrings:
506	old_checkstring = self.bad_share_checkstrings[(server, shnum)]
507	writer.set_checkstring(old_checkstring)
508
509	# Our remote shares will not have a complete checkstring until
510	# after we are done writing share data and have started to write
511	# blocks. In the meantime, we need to know what to look for when
512	# writing, so that we can detect UncoordinatedWriteErrors.
513	self._checkstring = self._get_some_writer().get_checkstring()
514
515	# Now, we start pushing shares.
516	self._status.timings["setup"] = time.time() - self._started
517	# First, we encrypt, encode, and publish the shares that we need
518	# to encrypt, encode, and publish.
519
520	# This will eventually hold the block hash chain for each share
521	# that we publish. We define it this way so that empty publishes
522	# will still have something to write to the remote slot.
523	self.blockhashes = dict([(i, []) for i in range(self.total_shares)])
524	for i in range(self.total_shares):
525	blocks = self.blockhashes[i]
526	for j in range(self.num_segments):
527	blocks.append(None)
528	self.sharehash_leaves = None # eventually [sharehashes]
529	self.sharehashes = {} # shnum -> [sharehash leaves necessary to
530	# validate the share]
531
532	self.log("Starting push")
533
534	self._state = PUSHING_BLOCKS_STATE
535	self._push()
536
537	return self.done_deferred
538
539	def _get_some_writer(self):
540	return list(list(self.writers.values())[0])[0]
541
542	def _update_status(self):
543	self._status.set_status("Sending Shares: %d placed out of %d, "
544	"%d messages outstanding" %
545	(len(self.placed),
546	len(self.goal),
547	self.num_outstanding))
548	self._status.set_progress(1.0 * len(self.placed) / len(self.goal))
549
550
551	def setup_encoding_parameters(self, offset=0):
552	if self._version == MDMF_VERSION:
553	segment_size = DEFAULT_MUTABLE_MAX_SEGMENT_SIZE # 128 KiB by default
554	else:
555	segment_size = self.datalength # SDMF is only one segment
556	# this must be a multiple of self.required_shares
557	segment_size = mathutil.next_multiple(segment_size,
558	self.required_shares)
559	self.segment_size = segment_size
560
561	# Calculate the starting segment for the upload.
562	if segment_size:
563	# We use div_ceil instead of integer division here because
564	# it is semantically correct.
565	# If datalength isn't an even multiple of segment_size, but
566	# is larger than segment_size, datalength // segment_size
567	# will be the largest number such that num <= datalength and
568	# num % segment_size == 0. But that's not what we want,
569	# because it ignores the extra data. div_ceil will give us
570	# the right number of segments for the data that we're
571	# given.
572	self.num_segments = mathutil.div_ceil(self.datalength,
573	segment_size)
574
575	self.starting_segment = offset // segment_size
576
577	else:
578	self.num_segments = 0
579	self.starting_segment = 0
580
581
582	self.log("building encoding parameters for file")
583	self.log("got segsize %d" % self.segment_size)
584	self.log("got %d segments" % self.num_segments)
585
586	if self._version == SDMF_VERSION:
587	assert self.num_segments in (0, 1) # SDMF
588	# calculate the tail segment size.
589
590	if segment_size and self.datalength:
591	self.tail_segment_size = self.datalength % segment_size
592	self.log("got tail segment size %d" % self.tail_segment_size)
593	else:
594	self.tail_segment_size = 0
595
596	if self.tail_segment_size == 0 and segment_size:
597	# The tail segment is the same size as the other segments.
598	self.tail_segment_size = segment_size
599
600	# Make FEC encoders
601	fec = codec.CRSEncoder()
602	fec.set_params(self.segment_size,
603	self.required_shares, self.total_shares)
604	self.piece_size = fec.get_block_size()
605	self.fec = fec
606
607	if self.tail_segment_size == self.segment_size:
608	self.tail_fec = self.fec
609	else:
610	tail_fec = codec.CRSEncoder()
611	tail_fec.set_params(self.tail_segment_size,
612	self.required_shares,
613	self.total_shares)
614	self.tail_fec = tail_fec
615
616	self._current_segment = self.starting_segment
617	self.end_segment = self.num_segments - 1
618	# Now figure out where the last segment should be.
619	if self.data.get_size() != self.datalength:
620	# We're updating a few segments in the middle of a mutable
621	# file, so we don't want to republish the whole thing.
622	# (we don't have enough data to do that even if we wanted
623	# to)
624	end = self.data.get_size()
625	self.end_segment = end // segment_size
626	if end % segment_size == 0:
627	self.end_segment -= 1
628
629	self.log("got start segment %d" % self.starting_segment)
630	self.log("got end segment %d" % self.end_segment)
631
632
633	def _push(self, ignored=None):
634	"""
635	I manage state transitions. In particular, I see that we still
636	have a good enough number of writers to complete the upload
637	successfully.
638	"""
639	# Can we still successfully publish this file?
640	# TODO: Keep track of outstanding queries before aborting the
641	# process.
642	num_shnums = len(self.writers)
643	if num_shnums < self.required_shares or self.surprised:
644	return self._failure()
645
646	# Figure out what we need to do next. Each of these needs to
647	# return a deferred so that we don't block execution when this
648	# is first called in the upload method.
649	if self._state == PUSHING_BLOCKS_STATE:
650	return self.push_segment(self._current_segment)
651
652	elif self._state == PUSHING_EVERYTHING_ELSE_STATE:
653	return self.push_everything_else()
654
655	# If we make it to this point, we were successful in placing the
656	# file.
657	return self._done()
658
659
660	def push_segment(self, segnum):
661	if self.num_segments == 0 and self._version == SDMF_VERSION:
662	self._add_dummy_salts()
663
664	if segnum > self.end_segment:
665	# We don't have any more segments to push.
666	self._state = PUSHING_EVERYTHING_ELSE_STATE
667	return self._push()
668
669	d = self._encode_segment(segnum)
670	d.addCallback(self._push_segment, segnum)
671	def _increment_segnum(ign):
672	self._current_segment += 1
673	# XXX: I don't think we need to do addBoth here -- any errBacks
674	# should be handled within push_segment.
675	d.addCallback(_increment_segnum)
676	d.addCallback(self._turn_barrier)
677	d.addCallback(self._push)
678	d.addErrback(self._failure)
679
680
681	def _turn_barrier(self, result):
682	"""
683	I help the publish process avoid the recursion limit issues
684	described in #237.
685	"""
686	return fireEventually(result)
687
688
689	def _add_dummy_salts(self):
690	"""
691	SDMF files need a salt even if they're empty, or the signature
692	won't make sense. This method adds a dummy salt to each of our
693	SDMF writers so that they can write the signature later.
694	"""
695	salt = os.urandom(16)
696	assert self._version == SDMF_VERSION
697
698	for shnum, writers in self.writers.items():
699	for writer in writers:
700	writer.put_salt(salt)
701
702
703	@async_to_deferred
704	async def _encode_segment(self, segnum):
705	"""
706	I encrypt and encode the segment segnum.
707	"""
708	started = time.time()
709
710	if segnum + 1 == self.num_segments:
711	segsize = self.tail_segment_size
712	else:
713	segsize = self.segment_size
714
715
716	self.log("Pushing segment %d of %d" % (segnum + 1, self.num_segments))
717	data = self.data.read(segsize)
718	if not isinstance(data, bytes):
719	# XXX: Why does this return a list?
720	data = b"".join(data)
721
722	assert len(data) == segsize, len(data)
723
724	self._status.set_status("Encrypting")
725
726	def encrypt(readkey):
727	salt = os.urandom(16)
728	key = hashutil.ssk_readkey_data_hash(salt, readkey)
729	encryptor = aes.create_encryptor(key)
730	crypttext = aes.encrypt_data(encryptor, data)
731	assert len(crypttext) == len(data)
732	return salt, crypttext
733
734	salt, crypttext = await defer_to_thread(encrypt, self.readkey)
735
736	now = time.time()
737	self._status.accumulate_encrypt_time(now - started)
738	started = now
739
740	# now apply FEC
741	if segnum + 1 == self.num_segments:
742	fec = self.tail_fec
743	else:
744	fec = self.fec
745
746	self._status.set_status("Encoding")
747	crypttext_pieces = [None] * self.required_shares
748	piece_size = fec.get_block_size()
749	for i in range(len(crypttext_pieces)):
750	offset = i * piece_size
751	piece = crypttext[offset:offset+piece_size]
752	piece = piece + b"\x00"*(piece_size - len(piece)) # padding
753	crypttext_pieces[i] = piece
754	assert len(piece) == piece_size
755
756	res = await fec.encode(crypttext_pieces)
757	elapsed = time.time() - started
758	self._status.accumulate_encode_time(elapsed)
759	return (res, salt)
760
761	@async_to_deferred
762	async def _push_segment(self, encoded_and_salt, segnum):
763	"""
764	I push (data, salt) as segment number segnum.
765	"""
766	results, salt = encoded_and_salt
767	shares, shareids = results
768	self._status.set_status("Pushing segment")
769	for i in range(len(shares)):
770	sharedata = shares[i]
771	shareid = shareids[i]
772	if self._version == MDMF_VERSION:
773	hashed = salt + sharedata
774	else:
775	hashed = sharedata
776	block_hash = await defer_to_thread(hashutil.block_hash, hashed)
777	self.blockhashes[shareid][segnum] = block_hash
778	# find the writer for this share
779	writers = self.writers[shareid]
780	for writer in writers:
781	writer.put_block(sharedata, segnum, salt)
782
783
784	def push_everything_else(self):
785	"""
786	I put everything else associated with a share.
787	"""
788	self._pack_started = time.time()
789	self.push_encprivkey()
790	self.push_blockhashes()
791	self.push_sharehashes()
792	self.push_toplevel_hashes_and_signature()
793	d = self.finish_publishing()
794	def _change_state(ignored):
795	self._state = DONE_STATE
796	d.addCallback(_change_state)
797	d.addCallback(self._push)
798	return d
799
800
801	def push_encprivkey(self):
802	encprivkey = self._encprivkey
803	self._status.set_status("Pushing encrypted private key")
804	for shnum, writers in self.writers.items():
805	for writer in writers:
806	writer.put_encprivkey(encprivkey)
807
808
809	def push_blockhashes(self):
810	self.sharehash_leaves = [None] * len(self.blockhashes)
811	self._status.set_status("Building and pushing block hash tree")
812	for shnum, blockhashes in list(self.blockhashes.items()):
813	t = hashtree.HashTree(blockhashes)
814	self.blockhashes[shnum] = list(t)
815	# set the leaf for future use.
816	self.sharehash_leaves[shnum] = t[0]
817
818	writers = self.writers[shnum]
819	for writer in writers:
820	writer.put_blockhashes(self.blockhashes[shnum])
821
822
823	def push_sharehashes(self):
824	self._status.set_status("Building and pushing share hash chain")
825	share_hash_tree = hashtree.HashTree(self.sharehash_leaves)
826	for shnum in range(len(self.sharehash_leaves)):
827	needed_indices = share_hash_tree.needed_hashes(shnum)
828	self.sharehashes[shnum] = dict( [ (i, share_hash_tree[i])
829	for i in needed_indices] )
830	writers = self.writers[shnum]
831	for writer in writers:
832	writer.put_sharehashes(self.sharehashes[shnum])
833	self.root_hash = share_hash_tree[0]
834
835
836	def push_toplevel_hashes_and_signature(self):
837	# We need to to three things here:
838	# - Push the root hash and salt hash
839	# - Get the checkstring of the resulting layout; sign that.
840	# - Push the signature
841	self._status.set_status("Pushing root hashes and signature")
842	for shnum in range(self.total_shares):
843	writers = self.writers[shnum]
844	for writer in writers:
845	writer.put_root_hash(self.root_hash)
846	self._update_checkstring()
847	self._make_and_place_signature()
848
849
850	def _update_checkstring(self):
851	"""
852	After putting the root hash, MDMF files will have the
853	checkstring written to the storage server. This means that we
854	can update our copy of the checkstring so we can detect
855	uncoordinated writes. SDMF files will have the same checkstring,
856	so we need not do anything.
857	"""
858	self._checkstring = self._get_some_writer().get_checkstring()
859
860
861	def _make_and_place_signature(self):
862	"""
863	I create and place the signature.
864	"""
865	started = time.time()
866	self._status.set_status("Signing prefix")
867	signable = self._get_some_writer().get_signable()
868	self.signature = rsa.sign_data(self._privkey, signable)
869
870	for (shnum, writers) in self.writers.items():
871	for writer in writers:
872	writer.put_signature(self.signature)
873	self._status.timings['sign'] = time.time() - started
874
875
876	def finish_publishing(self):
877	# We're almost done -- we just need to put the verification key
878	# and the offsets
879	started = time.time()
880	self._status.set_status("Pushing shares")
881	self._started_pushing = started
882	ds = []
883	verification_key = rsa.der_string_from_verifying_key(self._pubkey)
884
885	for (shnum, writers) in list(self.writers.copy().items()):
886	for writer in writers:
887	writer.put_verification_key(verification_key)
888	self.num_outstanding += 1
889	def _no_longer_outstanding(res):
890	self.num_outstanding -= 1
891	return res
892
893	d = writer.finish_publishing()
894	d.addBoth(_no_longer_outstanding)
895	d.addErrback(self._connection_problem, writer)
896	d.addCallback(self._got_write_answer, writer, started)
897	ds.append(d)
898	self._record_verinfo()
899	self._status.timings['pack'] = time.time() - started
900	return defer.DeferredList(ds)
901
902
903	def _record_verinfo(self):
904	self.versioninfo = self._get_some_writer().get_verinfo()
905
906
907	def _connection_problem(self, f, writer):
908	"""
909	We ran into a connection problem while working with writer, and
910	need to deal with that.
911	"""
912	self.log("found problem: %s" % str(f))
913	self._last_failure = f
914	self.writers.discard(writer.shnum, writer)
915
916
917	def log_goal(self, goal, message=""):
918	logmsg = [message]
919	for (shnum, server) in sorted([(s,p) for (p,s) in goal], key=lambda t: (id(t[0]), id(t[1]))):
920	logmsg.append("sh%d to [%r]" % (shnum, server.get_name()))
921	self.log("current goal: %s" % (", ".join(logmsg)), level=log.NOISY)
922	self.log("we are planning to push new seqnum=#%d" % self._new_seqnum,
923	level=log.NOISY)
924
925	def update_goal(self):
926	self.log_goal(self.goal, "before update: ")
927
928	# first, remove any bad servers from our goal
929	self.goal = set([ (server, shnum)
930	for (server, shnum) in self.goal
931	if server not in self.bad_servers ])
932
933	# find the homeless shares:
934	homefull_shares = set([shnum for (server, shnum) in self.goal])
935	homeless_shares = set(range(self.total_shares)) - homefull_shares
936	homeless_shares = sorted(list(homeless_shares))
937	# place them somewhere. We prefer unused servers at the beginning of
938	# the available server list.
939
940	if not homeless_shares:
941	return
942
943	# if an old share X is on a node, put the new share X there too.
944	# TODO: 1: redistribute shares to achieve one-per-server, by copying
945	# shares from existing servers to new (less-crowded) ones. The
946	# old shares must still be updated.
947	# TODO: 2: move those shares instead of copying them, to reduce future
948	# update work
949
950	# this is a bit CPU intensive but easy to analyze. We create a sort
951	# order for each server. If the server is marked as bad, we don't
952	# even put them in the list. Then we care about the number of shares
953	# which have already been assigned to them. After that we care about
954	# their permutation order.
955	old_assignments = DictOfSets()
956	for (server, shnum) in self.goal:
957	old_assignments.add(server, shnum)
958
959	serverlist = []
960
961	action = start_action(
962	action_type=u"mutable:upload:update_goal",
963	homeless_shares=len(homeless_shares),
964	)
965	with action:
966	for i, server in enumerate(self.full_serverlist):
967	serverid = server.get_serverid()
968	if server in self.bad_servers:
969	Message.log(
970	message_type=u"mutable:upload:bad-server",
971	server_id=serverid,
972	)
973	continue
974	# if we have >= 1 grid-managers, this checks that we have
975	# a valid certificate for this server
976	if not server.upload_permitted():
977	Message.log(
978	message_type=u"mutable:upload:no-gm-certs",
979	server_id=serverid,
980	)
981	continue
982
983	entry = (len(old_assignments.get(server, [])), i, serverid, server)
984	serverlist.append(entry)
985	serverlist.sort()
986
987	if not serverlist:
988	raise NotEnoughServersError("Ran out of non-bad servers, "
989	"first_error=%s" %
990	str(self._first_write_error),
991	self._first_write_error)
992
993	# we then index this serverlist with an integer, because we may have
994	# to wrap. We update the goal as we go.
995	i = 0
996	for shnum in homeless_shares:
997	(ignored1, ignored2, ignored3, server) = serverlist[i]
998	# if we are forced to send a share to a server that already has
999	# one, we may have two write requests in flight, and the
1000	# servermap (which was computed before either request was sent)
1001	# won't reflect the new shares, so the second response will be
1002	# surprising. There is code in _got_write_answer() to tolerate
1003	# this, otherwise it would cause the publish to fail with an
1004	# UncoordinatedWriteError. See #546 for details of the trouble
1005	# this used to cause.
1006	self.goal.add( (server, shnum) )
1007	i += 1
1008	if i >= len(serverlist):
1009	i = 0
1010	self.log_goal(self.goal, "after update: ")
1011
1012
1013	def _got_write_answer(self, answer, writer, started):
1014	if not answer:
1015	# SDMF writers only pretend to write when readers set their
1016	# blocks, salts, and so on -- they actually just write once,
1017	# at the end of the upload process. In fake writes, they
1018	# return defer.succeed(None). If we see that, we shouldn't
1019	# bother checking it.
1020	return
1021
1022	server = writer.server
1023	lp = self.log("_got_write_answer from %r, share %d" %
1024	(server.get_name(), writer.shnum))
1025
1026	now = time.time()
1027	elapsed = now - started
1028
1029	self._status.add_per_server_time(server, elapsed)
1030
1031	wrote, read_data = answer
1032
1033	surprise_shares = set(read_data.keys()) - set([writer.shnum])
1034
1035	# We need to remove from surprise_shares any shares that we are
1036	# knowingly also writing to that server from other writers.
1037
1038	# TODO: Precompute this.
1039	shares = []
1040	for shnum, writers in self.writers.items():
1041	shares.extend([x.shnum for x in writers if x.server == server])
1042	known_shnums = set(shares)
1043	surprise_shares -= known_shnums
1044	self.log("found the following surprise shares: %s" %
1045	str(surprise_shares))
1046
1047	# Now surprise shares contains all of the shares that we did not
1048	# expect to be there.
1049
1050	surprised = False
1051	for shnum in surprise_shares:
1052	# read_data is a dict mapping shnum to checkstring (SIGNED_PREFIX)
1053	checkstring = read_data[shnum][0]
1054	# What we want to do here is to see if their (seqnum,
1055	# roothash, salt) is the same as our (seqnum, roothash,
1056	# salt), or the equivalent for MDMF. The best way to do this
1057	# is to store a packed representation of our checkstring
1058	# somewhere, then not bother unpacking the other
1059	# checkstring.
1060	if checkstring == self._checkstring:
1061	# they have the right share, somehow
1062
1063	if (server,shnum) in self.goal:
1064	# and we want them to have it, so we probably sent them a
1065	# copy in an earlier write. This is ok, and avoids the
1066	# #546 problem.
1067	continue
1068
1069	# They aren't in our goal, but they are still for the right
1070	# version. Somebody else wrote them, and it's a convergent
1071	# uncoordinated write. Pretend this is ok (don't be
1072	# surprised), since I suspect there's a decent chance that
1073	# we'll hit this in normal operation.
1074	continue
1075
1076	else:
1077	# the new shares are of a different version
1078	if server in self._servermap.get_reachable_servers():
1079	# we asked them about their shares, so we had knowledge
1080	# of what they used to have. Any surprising shares must
1081	# have come from someone else, so UCW.
1082	surprised = True
1083	else:
1084	# we didn't ask them, and now we've discovered that they
1085	# have a share we didn't know about. This indicates that
1086	# mapupdate should have wokred harder and asked more
1087	# servers before concluding that it knew about them all.
1088
1089	# signal UCW, but make sure to ask this server next time,
1090	# so we'll remember to update it if/when we retry.
1091	surprised = True
1092	# TODO: ask this server next time. I don't yet have a good
1093	# way to do this. Two insufficient possibilities are:
1094	#
1095	# self._servermap.add_new_share(server, shnum, verinfo, now)
1096	# but that requires fetching/validating/parsing the whole
1097	# version string, and all we have is the checkstring
1098	# self._servermap.mark_bad_share(server, shnum, checkstring)
1099	# that will make publish overwrite the share next time,
1100	# but it won't re-query the server, and it won't make
1101	# mapupdate search further
1102
1103	# TODO later: when publish starts, do
1104	# servermap.get_best_version(), extract the seqnum,
1105	# subtract one, and store as highest-replaceable-seqnum.
1106	# Then, if this surprise-because-we-didn't-ask share is
1107	# of highest-replaceable-seqnum or lower, we're allowed
1108	# to replace it: send out a new writev (or rather add it
1109	# to self.goal and loop).
1110
1111	surprised = True
1112
1113	if surprised:
1114	self.log("they had shares %s that we didn't know about" %
1115	(list(surprise_shares),),
1116	parent=lp, level=log.WEIRD, umid="un9CSQ")
1117	self.surprised = True
1118
1119	if not wrote:
1120	# TODO: there are two possibilities. The first is that the server
1121	# is full (or just doesn't want to give us any room), which means
1122	# we shouldn't ask them again, but is not an indication of an
1123	# uncoordinated write. The second is that our testv failed, which
1124	# does indicate an uncoordinated write. We currently don't have
1125	# a way to tell these two apart (in fact, the storage server code
1126	# doesn't have the option of refusing our share).
1127	#
1128	# If the server is full, mark the server as bad (so we don't ask
1129	# them again), but don't set self.surprised. The loop() will find
1130	# a new server.
1131	#
1132	# If the testv failed, log it, set self.surprised, but don't
1133	# bother adding to self.bad_servers .
1134
1135	self.log("our testv failed, so the write did not happen",
1136	parent=lp, level=log.WEIRD, umid="8sc26g")
1137	self.surprised = True
1138	self.bad_servers.add(server) # don't ask them again
1139	# use the checkstring to add information to the log message
1140	unknown_format = False
1141	for (shnum,readv) in list(read_data.items()):
1142	checkstring = readv[0]
1143	version = get_version_from_checkstring(checkstring)
1144	if version == MDMF_VERSION:
1145	(other_seqnum,
1146	other_roothash) = unpack_mdmf_checkstring(checkstring)
1147	elif version == SDMF_VERSION:
1148	(other_seqnum,
1149	other_roothash,
1150	other_IV) = unpack_sdmf_checkstring(checkstring)
1151	else:
1152	unknown_format = True
1153	expected_version = self._servermap.version_on_server(server,
1154	shnum)
1155	if expected_version:
1156	(seqnum, root_hash, IV, segsize, datalength, k, N, prefix,
1157	offsets_tuple) = expected_version
1158	msg = ("somebody modified the share on us:"
1159	" shnum=%d: I thought they had #%d:R=%r," %
1160	(shnum,
1161	seqnum, base32.b2a(root_hash)[:4]))
1162	if unknown_format:
1163	msg += (" but I don't know how to read share"
1164	" format %d" % version)
1165	else:
1166	msg += " but testv reported #%d:R=%r" % \
1167	(other_seqnum, base32.b2a(other_roothash)[:4])
1168	self.log(msg, parent=lp, level=log.NOISY)
1169	# if expected_version==None, then we didn't expect to see a
1170	# share on that server, and the 'surprise_shares' clause
1171	# above will have logged it.
1172	return
1173
1174	# and update the servermap
1175	# self.versioninfo is set during the last phase of publishing.
1176	# If we get there, we know that responses correspond to placed
1177	# shares, and can safely execute these statements.
1178	if self.versioninfo:
1179	self.log("wrote successfully: adding new share to servermap")
1180	self._servermap.add_new_share(server, writer.shnum,
1181	self.versioninfo, started)
1182	self.placed.add( (server, writer.shnum) )
1183	self._update_status()
1184	# the next method in the deferred chain will check to see if
1185	# we're done and successful.
1186	return
1187
1188
1189	def _done(self):
1190	if not self._running:
1191	return
1192	self._running = False
1193	now = time.time()
1194	self._status.timings["total"] = now - self._started
1195
1196	elapsed = now - self._started_pushing
1197	self._status.timings['push'] = elapsed
1198
1199	self._status.set_active(False)
1200	self.log("Publish done, success")
1201	self._status.set_status("Finished")
1202	self._status.set_progress(1.0)
1203	# Get k and segsize, then give them to the caller.
1204	hints = {}
1205	hints['segsize'] = self.segment_size
1206	hints['k'] = self.required_shares
1207	self._node.set_downloader_hints(hints)
1208	eventually(self.done_deferred.callback, None)
1209
1210	def _failure(self, f=None):
1211	if f:
1212	self._last_failure = f
1213
1214	if not self.surprised:
1215	# We ran out of servers
1216	msg = "Publish ran out of good servers"
1217	if self._last_failure:
1218	msg += ", last failure was: %s" % str(self._last_failure)
1219	self.log(msg)
1220	e = NotEnoughServersError(msg)
1221
1222	else:
1223	# We ran into shares that we didn't recognize, which means
1224	# that we need to return an UncoordinatedWriteError.
1225	self.log("Publish failed with UncoordinatedWriteError")
1226	e = UncoordinatedWriteError()
1227	f = failure.Failure(e)
1228	eventually(self.done_deferred.callback, f)
1229
1230
1231	@implementer(IMutableUploadable)
1232	class MutableFileHandle:
1233	"""
1234	I am a mutable uploadable built around a filehandle-like object,
1235	usually either a BytesIO instance or a handle to an actual file.
1236	"""
1237
1238	def __init__(self, filehandle):
1239	# The filehandle is defined as a generally file-like object that
1240	# has these two methods. We don't care beyond that.
1241	assert hasattr(filehandle, "read")
1242	assert hasattr(filehandle, "close")
1243
1244	self._filehandle = filehandle
1245	# We must start reading at the beginning of the file, or we risk
1246	# encountering errors when the data read does not match the size
1247	# reported to the uploader.
1248	self._filehandle.seek(0)
1249
1250	# We have not yet read anything, so our position is 0.
1251	self._marker = 0
1252
1253
1254	def get_size(self):
1255	"""
1256	I return the amount of data in my filehandle.
1257	"""
1258	if not hasattr(self, "_size"):
1259	old_position = self._filehandle.tell()
1260	# Seek to the end of the file by seeking 0 bytes from the
1261	# file's end
1262	self._filehandle.seek(0, os.SEEK_END)
1263	self._size = self._filehandle.tell()
1264	# Restore the previous position, in case this was called
1265	# after a read.
1266	self._filehandle.seek(old_position)
1267	assert self._filehandle.tell() == old_position
1268
1269	assert hasattr(self, "_size")
1270	return self._size
1271
1272
1273	def pos(self):
1274	"""
1275	I return the position of my read marker -- i.e., how much data I
1276	have already read and returned to callers.
1277	"""
1278	return self._marker
1279
1280
1281	def read(self, length):
1282	"""
1283	I return some data (up to length bytes) from my filehandle.
1284
1285	In most cases, I return length bytes, but sometimes I won't --
1286	for example, if I am asked to read beyond the end of a file, or
1287	an error occurs.
1288	"""
1289	results = self._filehandle.read(length)
1290	self._marker += len(results)
1291	return [results]
1292
1293
1294	def close(self):
1295	"""
1296	I close the underlying filehandle. Any further operations on the
1297	filehandle fail at this point.
1298	"""
1299	self._filehandle.close()
1300
1301
1302	class MutableData(MutableFileHandle):
1303	"""
1304	I am a mutable uploadable built around a string, which I then cast
1305	into a BytesIO and treat as a filehandle.
1306	"""
1307
1308	def __init__(self, s):
1309	# Take a string and return a file-like uploadable.
1310	assert isinstance(s, bytes)
1311
1312	MutableFileHandle.__init__(self, BytesIO(s))
1313
1314
1315	@implementer(IMutableUploadable)
1316	class TransformingUploadable:
1317	"""
1318	I am an IMutableUploadable that wraps another IMutableUploadable,
1319	and some segments that are already on the grid. When I am called to
1320	read, I handle merging of boundary segments.
1321	"""
1322
1323
1324	def __init__(self, data, offset, segment_size, start, end):
1325	assert IMutableUploadable.providedBy(data)
1326
1327	self._newdata = data
1328	self._offset = offset
1329	self._segment_size = segment_size
1330	self._start = start
1331	self._end = end
1332
1333	self._read_marker = 0
1334
1335	self._first_segment_offset = offset % segment_size
1336
1337	num = self.log("TransformingUploadable: starting", parent=None)
1338	self._log_number = num
1339	self.log("got fso: %d" % self._first_segment_offset)
1340	self.log("got offset: %d" % self._offset)
1341
1342
1343	def log(self, args, *kwargs):
1344	if 'parent' not in kwargs:
1345	kwargs['parent'] = self._log_number
1346	if "facility" not in kwargs:
1347	kwargs["facility"] = "tahoe.mutable.transforminguploadable"
1348	return log.msg(args, *kwargs)
1349
1350
1351	def get_size(self):
1352	return self._offset + self._newdata.get_size()
1353
1354
1355	def read(self, length):
1356	# We can get data from 3 sources here.
1357	# 1. The first of the segments provided to us.
1358	# 2. The data that we're replacing things with.
1359	# 3. The last of the segments provided to us.
1360
1361	# are we in state 0?
1362	self.log("reading %d bytes" % length)
1363
1364	old_start_data = b""
1365	old_data_length = self._first_segment_offset - self._read_marker
1366	if old_data_length > 0:
1367	if old_data_length > length:
1368	old_data_length = length
1369	self.log("returning %d bytes of old start data" % old_data_length)
1370
1371	old_data_end = old_data_length + self._read_marker
1372	old_start_data = self._start[self._read_marker:old_data_end]
1373	length -= old_data_length
1374	else:
1375	# otherwise calculations later get screwed up.
1376	old_data_length = 0
1377
1378	# Is there enough new data to satisfy this read? If not, we need
1379	# to pad the end of the data with data from our last segment.
1380	old_end_length = length - \
1381	(self._newdata.get_size() - self._newdata.pos())
1382	old_end_data = b""
1383	if old_end_length > 0:
1384	self.log("reading %d bytes of old end data" % old_end_length)
1385
1386	# TODO: We're not explicitly checking for tail segment size
1387	# here. Is that a problem?
1388	old_data_offset = (length - old_end_length + \
1389	old_data_length) % self._segment_size
1390	self.log("reading at offset %d" % old_data_offset)
1391	old_end = old_data_offset + old_end_length
1392	old_end_data = self._end[old_data_offset:old_end]
1393	length -= old_end_length
1394	assert length == self._newdata.get_size() - self._newdata.pos()
1395
1396	self.log("reading %d bytes of new data" % length)
1397	new_data = self._newdata.read(length)
1398	new_data = b"".join(new_data)
1399
1400	self._read_marker += len(old_start_data + new_data + old_end_data)
1401
1402	return old_start_data + new_data + old_end_data
1403
1404	def close(self):
1405	pass

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