From: Brian Warner Date: Fri, 6 Apr 2007 04:17:42 +0000 (-0700) Subject: rename encode_new.py to encode.py, now that there isn't an old one anymore X-Git-Url: https://git.rkrishnan.org/pf/content/it.html?a=commitdiff_plain;h=919ca3e9029f84d347eb18976aad426f5c3a5ea9;p=tahoe-lafs%2Ftahoe-lafs.git rename encode_new.py to encode.py, now that there isn't an old one anymore --- diff --git a/src/allmydata/encode.py b/src/allmydata/encode.py new file mode 100644 index 00000000..a0e92922 --- /dev/null +++ b/src/allmydata/encode.py @@ -0,0 +1,284 @@ +# -*- test-case-name: allmydata.test.test_encode -*- + +from zope.interface import implements +from twisted.internet import defer +from twisted.python import log +from allmydata.chunk import HashTree, roundup_pow2 +from allmydata.Crypto.Cipher import AES +from allmydata.util import mathutil, hashutil +from allmydata.util.assertutil import _assert +from allmydata.codec import CRSEncoder +from allmydata.interfaces import IEncoder + +""" + +The goal of the encoder is to turn the original file into a series of +'shares'. Each share is going to a 'shareholder' (nominally each shareholder +is a different host, but for small meshes there may be overlap). The number +of shares is chosen to hit our reliability goals (more shares on more +machines means more reliability), and is limited by overhead (proportional to +numshares or log(numshares)) and the encoding technology in use (Reed-Solomon +only permits 256 shares total). It is also constrained by the amount of data +we want to send to each host. For estimating purposes, think of 100 shares +out of which we need 25 to reconstruct the file. + +The encoder starts by cutting the original file into segments. All segments +except the last are of equal size. The segment size is chosen to constrain +the memory footprint (which will probably vary between 1x and 4x segment +size) and to constrain the overhead (which will be proportional to either the +number of segments or log(number of segments)). + + +Each segment (A,B,C) is read into memory, encrypted, and encoded into +blocks. The 'share' (say, share #1) that makes it out to a host is a +collection of these blocks (block A1, B1, C1), plus some hash-tree +information necessary to validate the data upon retrieval. Only one segment +is handled at a time: all blocks for segment A are delivered before any +work is begun on segment B. + +As blocks are created, we retain the hash of each one. The list of +block hashes for a single share (say, hash(A1), hash(B1), hash(C1)) is +used to form the base of a Merkle hash tree for that share (hashtrees[1]). +This hash tree has one terminal leaf per block. The complete block hash +tree is sent to the shareholder after all the data has been sent. At +retrieval time, the decoder will ask for specific pieces of this tree before +asking for blocks, whichever it needs to validate those blocks. + +(Note: we don't really need to generate this whole block hash tree +ourselves. It would be sufficient to have the shareholder generate it and +just tell us the root. This gives us an extra level of validation on the +transfer, though, and it is relatively cheap to compute.) + +Each of these block hash trees has a root hash. The collection of these +root hashes for all shares are collected into the 'share hash tree', which +has one terminal leaf per share. After sending the blocks and the complete +block hash tree to each shareholder, we send them the portion of the share +hash tree that is necessary to validate their share. The root of the share +hash tree is put into the URI. + +""" + +def pad(s, l, c='\x00'): + """ + Return string s with enough chars c appended to it to make its length be + an even multiple of l bytes. + + @param s the original string + @param l the length of the resulting padded string in bytes + @param c the pad char + """ + return s + c * mathutil.pad_size(len(s), l) + +KiB=1024 +MiB=1024*KiB +GiB=1024*MiB +TiB=1024*GiB +PiB=1024*TiB + +class Encoder(object): + implements(IEncoder) + NEEDED_SHARES = 25 + TOTAL_SHARES = 100 + + def setup(self, infile): + self.infile = infile + infile.seek(0, 2) + self.file_size = infile.tell() + infile.seek(0, 0) + + self.num_shares = self.TOTAL_SHARES + self.required_shares = self.NEEDED_SHARES + + self.segment_size = min(2*MiB, self.file_size) + # this must be a multiple of self.required_shares + self.segment_size = mathutil.next_multiple(self.segment_size, + self.required_shares) + self.setup_codec() + + def setup_codec(self): + assert self.segment_size % self.required_shares == 0 + self._codec = CRSEncoder() + self._codec.set_params(self.segment_size, + self.required_shares, self.num_shares) + + # the "tail" is the last segment. This segment may or may not be + # shorter than all other segments. We use the "tail codec" to handle + # it. If the tail is short, we use a different codec instance. In + # addition, the tail codec must be fed data which has been padded out + # to the right size. + self.tail_size = self.file_size % self.segment_size + if not self.tail_size: + self.tail_size = self.segment_size + + # the tail codec is responsible for encoding tail_size bytes + padded_tail_size = mathutil.next_multiple(self.tail_size, + self.required_shares) + self._tail_codec = CRSEncoder() + self._tail_codec.set_params(padded_tail_size, + self.required_shares, self.num_shares) + + def get_share_size(self): + share_size = mathutil.div_ceil(self.file_size, self.required_shares) + overhead = self.compute_overhead() + return share_size + overhead + def compute_overhead(self): + return 0 + def get_block_size(self): + return self._codec.get_block_size() + + def set_shareholders(self, landlords): + assert isinstance(landlords, dict) + for k in landlords: + # it would be nice to: + #assert RIBucketWriter.providedBy(landlords[k]) + pass + self.landlords = landlords.copy() + + def start(self): + #paddedsize = self._size + mathutil.pad_size(self._size, self.needed_shares) + self.num_segments = mathutil.div_ceil(self.file_size, + self.segment_size) + self.share_size = mathutil.div_ceil(self.file_size, + self.required_shares) + self.setup_encryption() + self.setup_codec() + d = defer.succeed(None) + + for i in range(self.num_segments-1): + d.addCallback(lambda res: self.do_segment(i)) + d.addCallback(lambda res: self.do_tail_segment(self.num_segments-1)) + + d.addCallback(lambda res: self.send_all_subshare_hash_trees()) + d.addCallback(lambda res: self.send_all_share_hash_trees()) + d.addCallback(lambda res: self.close_all_shareholders()) + d.addCallback(lambda res: self.done()) + return d + + def setup_encryption(self): + self.key = "\x00"*16 + self.cryptor = AES.new(key=self.key, mode=AES.MODE_CTR, + counterstart="\x00"*16) + self.segment_num = 0 + self.subshare_hashes = [[] for x in range(self.num_shares)] + # subshare_hashes[i] is a list that will be accumulated and then send + # to landlord[i]. This list contains a hash of each segment_share + # that we sent to that landlord. + self.share_root_hashes = [None] * self.num_shares + + def do_segment(self, segnum): + chunks = [] + codec = self._codec + # the ICodecEncoder API wants to receive a total of self.segment_size + # bytes on each encode() call, broken up into a number of + # identically-sized pieces. Due to the way the codec algorithm works, + # these pieces need to be the same size as the share which the codec + # will generate. Therefore we must feed it with input_piece_size that + # equals the output share size. + input_piece_size = codec.get_block_size() + + # as a result, the number of input pieces per encode() call will be + # equal to the number of required shares with which the codec was + # constructed. You can think of the codec as chopping up a + # 'segment_size' of data into 'required_shares' shares (not doing any + # fancy math at all, just doing a split), then creating some number + # of additional shares which can be substituted if the primary ones + # are unavailable + + for i in range(self.required_shares): + input_piece = self.infile.read(input_piece_size) + # non-tail segments should be the full segment size + assert len(input_piece) == input_piece_size + encrypted_piece = self.cryptor.encrypt(input_piece) + chunks.append(encrypted_piece) + d = codec.encode(chunks) + d.addCallback(self._encoded_segment, segnum) + return d + + def do_tail_segment(self, segnum): + chunks = [] + codec = self._tail_codec + input_piece_size = codec.get_block_size() + + for i in range(self.required_shares): + input_piece = self.infile.read(input_piece_size) + if len(input_piece) < input_piece_size: + # padding + input_piece += ('\x00' * (input_piece_size - len(input_piece))) + encrypted_piece = self.cryptor.encrypt(input_piece) + chunks.append(encrypted_piece) + d = codec.encode(chunks) + d.addCallback(self._encoded_segment, segnum) + return d + + def _encoded_segment(self, (shares, shareids), segnum): + _assert(set(shareids) == set(self.landlords.keys()), + shareids=shareids, landlords=self.landlords) + dl = [] + for i in range(len(shares)): + subshare = shares[i] + shareid = shareids[i] + d = self.send_subshare(shareid, segnum, subshare) + dl.append(d) + subshare_hash = hashutil.tagged_hash("encoded subshare", subshare) + self.subshare_hashes[shareid].append(subshare_hash) + dl = defer.DeferredList(dl) + def _logit(res): + log.msg("%s uploaded %s / %s bytes of your file." % (self, self.segment_size*(segnum+1), self.segment_size*self.num_segments)) + return res + dl.addCallback(_logit) + return dl + + def send_subshare(self, shareid, segment_num, subshare): + return self.send(shareid, "put_block", segment_num, subshare) + + def send(self, shareid, methname, *args, **kwargs): + ll = self.landlords[shareid] + return ll.callRemote(methname, *args, **kwargs) + + def send_all_subshare_hash_trees(self): + dl = [] + for shareid,hashes in enumerate(self.subshare_hashes): + # hashes is a list of the hashes of all subshares that were sent + # to shareholder[shareid]. + dl.append(self.send_one_subshare_hash_tree(shareid, hashes)) + return defer.DeferredList(dl) + + def send_one_subshare_hash_tree(self, shareid, subshare_hashes): + t = HashTree(subshare_hashes) + all_hashes = list(t) + # all_hashes[0] is the root hash, == hash(ah[1]+ah[2]) + # all_hashes[1] is the left child, == hash(ah[3]+ah[4]) + # all_hashes[n] == hash(all_hashes[2*n+1] + all_hashes[2*n+2]) + self.share_root_hashes[shareid] = t[0] + return self.send(shareid, "put_block_hashes", all_hashes) + + def send_all_share_hash_trees(self): + dl = [] + for h in self.share_root_hashes: + assert h + # create the share hash tree + t = HashTree(self.share_root_hashes) + # the root of this hash tree goes into our URI + self.root_hash = t[0] + # now send just the necessary pieces out to each shareholder + for i in range(self.num_shares): + # the HashTree is given a list of leaves: 0,1,2,3..n . + # These become nodes A+0,A+1,A+2.. of the tree, where A=n-1 + tree_width = roundup_pow2(self.num_shares) + base_index = i + tree_width - 1 + needed_hash_indices = t.needed_for(base_index) + hashes = [(hi, t[hi]) for hi in needed_hash_indices] + dl.append(self.send_one_share_hash_tree(i, hashes)) + return defer.DeferredList(dl) + + def send_one_share_hash_tree(self, shareid, needed_hashes): + return self.send(shareid, "put_share_hashes", needed_hashes) + + def close_all_shareholders(self): + dl = [] + for shareid in range(self.num_shares): + dl.append(self.send(shareid, "close")) + return defer.DeferredList(dl) + + def done(self): + return self.root_hash diff --git a/src/allmydata/encode_new.py b/src/allmydata/encode_new.py deleted file mode 100644 index a0e92922..00000000 --- a/src/allmydata/encode_new.py +++ /dev/null @@ -1,284 +0,0 @@ -# -*- test-case-name: allmydata.test.test_encode -*- - -from zope.interface import implements -from twisted.internet import defer -from twisted.python import log -from allmydata.chunk import HashTree, roundup_pow2 -from allmydata.Crypto.Cipher import AES -from allmydata.util import mathutil, hashutil -from allmydata.util.assertutil import _assert -from allmydata.codec import CRSEncoder -from allmydata.interfaces import IEncoder - -""" - -The goal of the encoder is to turn the original file into a series of -'shares'. Each share is going to a 'shareholder' (nominally each shareholder -is a different host, but for small meshes there may be overlap). The number -of shares is chosen to hit our reliability goals (more shares on more -machines means more reliability), and is limited by overhead (proportional to -numshares or log(numshares)) and the encoding technology in use (Reed-Solomon -only permits 256 shares total). It is also constrained by the amount of data -we want to send to each host. For estimating purposes, think of 100 shares -out of which we need 25 to reconstruct the file. - -The encoder starts by cutting the original file into segments. All segments -except the last are of equal size. The segment size is chosen to constrain -the memory footprint (which will probably vary between 1x and 4x segment -size) and to constrain the overhead (which will be proportional to either the -number of segments or log(number of segments)). - - -Each segment (A,B,C) is read into memory, encrypted, and encoded into -blocks. The 'share' (say, share #1) that makes it out to a host is a -collection of these blocks (block A1, B1, C1), plus some hash-tree -information necessary to validate the data upon retrieval. Only one segment -is handled at a time: all blocks for segment A are delivered before any -work is begun on segment B. - -As blocks are created, we retain the hash of each one. The list of -block hashes for a single share (say, hash(A1), hash(B1), hash(C1)) is -used to form the base of a Merkle hash tree for that share (hashtrees[1]). -This hash tree has one terminal leaf per block. The complete block hash -tree is sent to the shareholder after all the data has been sent. At -retrieval time, the decoder will ask for specific pieces of this tree before -asking for blocks, whichever it needs to validate those blocks. - -(Note: we don't really need to generate this whole block hash tree -ourselves. It would be sufficient to have the shareholder generate it and -just tell us the root. This gives us an extra level of validation on the -transfer, though, and it is relatively cheap to compute.) - -Each of these block hash trees has a root hash. The collection of these -root hashes for all shares are collected into the 'share hash tree', which -has one terminal leaf per share. After sending the blocks and the complete -block hash tree to each shareholder, we send them the portion of the share -hash tree that is necessary to validate their share. The root of the share -hash tree is put into the URI. - -""" - -def pad(s, l, c='\x00'): - """ - Return string s with enough chars c appended to it to make its length be - an even multiple of l bytes. - - @param s the original string - @param l the length of the resulting padded string in bytes - @param c the pad char - """ - return s + c * mathutil.pad_size(len(s), l) - -KiB=1024 -MiB=1024*KiB -GiB=1024*MiB -TiB=1024*GiB -PiB=1024*TiB - -class Encoder(object): - implements(IEncoder) - NEEDED_SHARES = 25 - TOTAL_SHARES = 100 - - def setup(self, infile): - self.infile = infile - infile.seek(0, 2) - self.file_size = infile.tell() - infile.seek(0, 0) - - self.num_shares = self.TOTAL_SHARES - self.required_shares = self.NEEDED_SHARES - - self.segment_size = min(2*MiB, self.file_size) - # this must be a multiple of self.required_shares - self.segment_size = mathutil.next_multiple(self.segment_size, - self.required_shares) - self.setup_codec() - - def setup_codec(self): - assert self.segment_size % self.required_shares == 0 - self._codec = CRSEncoder() - self._codec.set_params(self.segment_size, - self.required_shares, self.num_shares) - - # the "tail" is the last segment. This segment may or may not be - # shorter than all other segments. We use the "tail codec" to handle - # it. If the tail is short, we use a different codec instance. In - # addition, the tail codec must be fed data which has been padded out - # to the right size. - self.tail_size = self.file_size % self.segment_size - if not self.tail_size: - self.tail_size = self.segment_size - - # the tail codec is responsible for encoding tail_size bytes - padded_tail_size = mathutil.next_multiple(self.tail_size, - self.required_shares) - self._tail_codec = CRSEncoder() - self._tail_codec.set_params(padded_tail_size, - self.required_shares, self.num_shares) - - def get_share_size(self): - share_size = mathutil.div_ceil(self.file_size, self.required_shares) - overhead = self.compute_overhead() - return share_size + overhead - def compute_overhead(self): - return 0 - def get_block_size(self): - return self._codec.get_block_size() - - def set_shareholders(self, landlords): - assert isinstance(landlords, dict) - for k in landlords: - # it would be nice to: - #assert RIBucketWriter.providedBy(landlords[k]) - pass - self.landlords = landlords.copy() - - def start(self): - #paddedsize = self._size + mathutil.pad_size(self._size, self.needed_shares) - self.num_segments = mathutil.div_ceil(self.file_size, - self.segment_size) - self.share_size = mathutil.div_ceil(self.file_size, - self.required_shares) - self.setup_encryption() - self.setup_codec() - d = defer.succeed(None) - - for i in range(self.num_segments-1): - d.addCallback(lambda res: self.do_segment(i)) - d.addCallback(lambda res: self.do_tail_segment(self.num_segments-1)) - - d.addCallback(lambda res: self.send_all_subshare_hash_trees()) - d.addCallback(lambda res: self.send_all_share_hash_trees()) - d.addCallback(lambda res: self.close_all_shareholders()) - d.addCallback(lambda res: self.done()) - return d - - def setup_encryption(self): - self.key = "\x00"*16 - self.cryptor = AES.new(key=self.key, mode=AES.MODE_CTR, - counterstart="\x00"*16) - self.segment_num = 0 - self.subshare_hashes = [[] for x in range(self.num_shares)] - # subshare_hashes[i] is a list that will be accumulated and then send - # to landlord[i]. This list contains a hash of each segment_share - # that we sent to that landlord. - self.share_root_hashes = [None] * self.num_shares - - def do_segment(self, segnum): - chunks = [] - codec = self._codec - # the ICodecEncoder API wants to receive a total of self.segment_size - # bytes on each encode() call, broken up into a number of - # identically-sized pieces. Due to the way the codec algorithm works, - # these pieces need to be the same size as the share which the codec - # will generate. Therefore we must feed it with input_piece_size that - # equals the output share size. - input_piece_size = codec.get_block_size() - - # as a result, the number of input pieces per encode() call will be - # equal to the number of required shares with which the codec was - # constructed. You can think of the codec as chopping up a - # 'segment_size' of data into 'required_shares' shares (not doing any - # fancy math at all, just doing a split), then creating some number - # of additional shares which can be substituted if the primary ones - # are unavailable - - for i in range(self.required_shares): - input_piece = self.infile.read(input_piece_size) - # non-tail segments should be the full segment size - assert len(input_piece) == input_piece_size - encrypted_piece = self.cryptor.encrypt(input_piece) - chunks.append(encrypted_piece) - d = codec.encode(chunks) - d.addCallback(self._encoded_segment, segnum) - return d - - def do_tail_segment(self, segnum): - chunks = [] - codec = self._tail_codec - input_piece_size = codec.get_block_size() - - for i in range(self.required_shares): - input_piece = self.infile.read(input_piece_size) - if len(input_piece) < input_piece_size: - # padding - input_piece += ('\x00' * (input_piece_size - len(input_piece))) - encrypted_piece = self.cryptor.encrypt(input_piece) - chunks.append(encrypted_piece) - d = codec.encode(chunks) - d.addCallback(self._encoded_segment, segnum) - return d - - def _encoded_segment(self, (shares, shareids), segnum): - _assert(set(shareids) == set(self.landlords.keys()), - shareids=shareids, landlords=self.landlords) - dl = [] - for i in range(len(shares)): - subshare = shares[i] - shareid = shareids[i] - d = self.send_subshare(shareid, segnum, subshare) - dl.append(d) - subshare_hash = hashutil.tagged_hash("encoded subshare", subshare) - self.subshare_hashes[shareid].append(subshare_hash) - dl = defer.DeferredList(dl) - def _logit(res): - log.msg("%s uploaded %s / %s bytes of your file." % (self, self.segment_size*(segnum+1), self.segment_size*self.num_segments)) - return res - dl.addCallback(_logit) - return dl - - def send_subshare(self, shareid, segment_num, subshare): - return self.send(shareid, "put_block", segment_num, subshare) - - def send(self, shareid, methname, *args, **kwargs): - ll = self.landlords[shareid] - return ll.callRemote(methname, *args, **kwargs) - - def send_all_subshare_hash_trees(self): - dl = [] - for shareid,hashes in enumerate(self.subshare_hashes): - # hashes is a list of the hashes of all subshares that were sent - # to shareholder[shareid]. - dl.append(self.send_one_subshare_hash_tree(shareid, hashes)) - return defer.DeferredList(dl) - - def send_one_subshare_hash_tree(self, shareid, subshare_hashes): - t = HashTree(subshare_hashes) - all_hashes = list(t) - # all_hashes[0] is the root hash, == hash(ah[1]+ah[2]) - # all_hashes[1] is the left child, == hash(ah[3]+ah[4]) - # all_hashes[n] == hash(all_hashes[2*n+1] + all_hashes[2*n+2]) - self.share_root_hashes[shareid] = t[0] - return self.send(shareid, "put_block_hashes", all_hashes) - - def send_all_share_hash_trees(self): - dl = [] - for h in self.share_root_hashes: - assert h - # create the share hash tree - t = HashTree(self.share_root_hashes) - # the root of this hash tree goes into our URI - self.root_hash = t[0] - # now send just the necessary pieces out to each shareholder - for i in range(self.num_shares): - # the HashTree is given a list of leaves: 0,1,2,3..n . - # These become nodes A+0,A+1,A+2.. of the tree, where A=n-1 - tree_width = roundup_pow2(self.num_shares) - base_index = i + tree_width - 1 - needed_hash_indices = t.needed_for(base_index) - hashes = [(hi, t[hi]) for hi in needed_hash_indices] - dl.append(self.send_one_share_hash_tree(i, hashes)) - return defer.DeferredList(dl) - - def send_one_share_hash_tree(self, shareid, needed_hashes): - return self.send(shareid, "put_share_hashes", needed_hashes) - - def close_all_shareholders(self): - dl = [] - for shareid in range(self.num_shares): - dl.append(self.send(shareid, "close")) - return defer.DeferredList(dl) - - def done(self): - return self.root_hash diff --git a/src/allmydata/test/test_encode.py b/src/allmydata/test/test_encode.py index e0383759..71a91d7e 100644 --- a/src/allmydata/test/test_encode.py +++ b/src/allmydata/test/test_encode.py @@ -3,11 +3,11 @@ from twisted.trial import unittest from twisted.internet import defer from foolscap import eventual -from allmydata import encode_new, download +from allmydata import encode, download from allmydata.uri import pack_uri from cStringIO import StringIO -class MyEncoder(encode_new.Encoder): +class MyEncoder(encode.Encoder): def send(self, share_num, methname, *args, **kwargs): if False and share_num < 10: print "send[%d].%s()" % (share_num, methname) @@ -92,7 +92,7 @@ class FakeBucketWriter: class Encode(unittest.TestCase): def test_send(self): - e = encode_new.Encoder() + e = encode.Encoder() data = "happy happy joy joy" * 4 e.setup(StringIO(data)) NUM_SHARES = 100 @@ -131,7 +131,7 @@ class Encode(unittest.TestCase): class Roundtrip(unittest.TestCase): def send_and_recover(self, NUM_SHARES, NUM_PEERS, NUM_SEGMENTS=4): - e = encode_new.Encoder() + e = encode.Encoder() data = "happy happy joy joy" * 4 e.setup(StringIO(data)) diff --git a/src/allmydata/upload.py b/src/allmydata/upload.py index e77cec5e..bb8b8329 100644 --- a/src/allmydata/upload.py +++ b/src/allmydata/upload.py @@ -5,7 +5,7 @@ from twisted.application import service from foolscap import Referenceable from allmydata.util import idlib -from allmydata import encode_new +from allmydata import encode from allmydata.uri import pack_uri from allmydata.interfaces import IUploadable, IUploader @@ -92,7 +92,7 @@ class FileUploader: assert self.needed_shares # create the encoder, so we can know how large the shares will be - self._encoder = encode_new.Encoder() + self._encoder = encode.Encoder() self._encoder.setup(self._filehandle) share_size = self._encoder.get_share_size() block_size = self._encoder.get_block_size()