forked from LBRYCommunity/lbry-sdk
209 lines
7.7 KiB
Python
209 lines
7.7 KiB
Python
import logging
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import os
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from twisted.internet import defer, threads
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from twisted.web.client import FileBodyProducer
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from twisted.python.failure import Failure
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from lbrynet.core.Error import DownloadCanceledError, InvalidDataError, InvalidBlobHashError
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from lbrynet.core.utils import is_valid_blobhash
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from lbrynet.blob.writer import HashBlobWriter
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from lbrynet.blob.reader import HashBlobReader
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log = logging.getLogger(__name__)
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MAX_BLOB_SIZE = 2 * 2 ** 20
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class BlobFile:
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"""
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A chunk of data available on the network which is specified by a hashsum
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This class is used to create blobs on the local filesystem
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when we already know the blob hash before hand (i.e., when downloading blobs)
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Also can be used for reading from blobs on the local filesystem
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"""
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def __str__(self):
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return self.blob_hash[:16]
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def __repr__(self):
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return '<{}({})>'.format(self.__class__.__name__, str(self))
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def __init__(self, blob_dir, blob_hash, length=None):
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if not is_valid_blobhash(blob_hash):
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raise InvalidBlobHashError(blob_hash)
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self.blob_hash = blob_hash
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self.length = length
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self.writers = {} # {Peer: writer, finished_deferred}
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self._verified = False
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self.readers = 0
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self.blob_dir = blob_dir
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self.file_path = os.path.join(blob_dir, self.blob_hash)
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self.blob_write_lock = defer.DeferredLock()
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self.saved_verified_blob = False
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if os.path.isfile(self.file_path):
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self.set_length(os.path.getsize(self.file_path))
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# This assumes that the hash of the blob has already been
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# checked as part of the blob creation process. It might
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# be worth having a function that checks the actual hash;
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# its probably too expensive to have that check be part of
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# this call.
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self._verified = True
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def open_for_writing(self, peer):
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"""
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open a blob file to be written by peer, supports concurrent
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writers, as long as they are from differnt peers.
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returns tuple of (writer, finished_deferred)
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writer - a file like object with a write() function, close() when finished
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finished_deferred - deferred that is fired when write is finished and returns
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a instance of itself as HashBlob
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"""
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if not peer in self.writers:
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log.debug("Opening %s to be written by %s", str(self), str(peer))
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finished_deferred = defer.Deferred()
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writer = HashBlobWriter(self.get_length, self.writer_finished)
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self.writers[peer] = (writer, finished_deferred)
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return (writer, finished_deferred)
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log.warning("Tried to download the same file twice simultaneously from the same peer")
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return None, None
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def open_for_reading(self):
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"""
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open blob for reading
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returns a file like object that can be read() from, and closed() when
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finished
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"""
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if self._verified is True:
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f = open(self.file_path, 'rb')
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reader = HashBlobReader(f, self.reader_finished)
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self.readers += 1
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return reader
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return None
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def delete(self):
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"""
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delete blob file from file system, prevent deletion
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if a blob is being read from or written to
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returns a deferred that firesback when delete is completed
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"""
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if not self.writers and not self.readers:
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self._verified = False
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self.saved_verified_blob = False
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def delete_from_file_system():
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if os.path.isfile(self.file_path):
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os.remove(self.file_path)
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d = threads.deferToThread(delete_from_file_system)
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def log_error(err):
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log.warning("An error occurred deleting %s: %s",
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str(self.file_path), err.getErrorMessage())
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return err
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d.addErrback(log_error)
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return d
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else:
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return defer.fail(Failure(
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ValueError("File is currently being read or written and cannot be deleted")))
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@property
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def verified(self):
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"""
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Protect verified from being modified by other classes.
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verified is True if a write to a blob has completed succesfully,
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or a blob has been read to have the same length as specified
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in init
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"""
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return self._verified
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def set_length(self, length):
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if self.length is not None and length == self.length:
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return True
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if self.length is None and 0 <= length <= MAX_BLOB_SIZE:
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self.length = length
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return True
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log.warning("Got an invalid length. Previous length: %s, Invalid length: %s",
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self.length, length)
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return False
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def get_length(self):
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return self.length
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def get_is_verified(self):
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return self.verified
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def is_downloading(self):
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if self.writers:
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return True
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return False
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def reader_finished(self, reader):
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self.readers -= 1
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return defer.succeed(True)
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def writer_finished(self, writer, err=None):
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def fire_finished_deferred():
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self._verified = True
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for p, (w, finished_deferred) in self.writers.items():
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if w == writer:
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del self.writers[p]
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finished_deferred.callback(self)
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return True
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log.warning(
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"Somehow, the writer that was accepted as being valid was already removed: %s",
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writer)
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return False
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def errback_finished_deferred(err):
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for p, (w, finished_deferred) in self.writers.items():
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if w == writer:
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del self.writers[p]
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finished_deferred.errback(err)
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def cancel_other_downloads():
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for p, (w, finished_deferred) in self.writers.items():
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w.close()
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if err is None:
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if writer.len_so_far == self.length and writer.blob_hash == self.blob_hash:
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if self._verified is False:
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d = self.save_verified_blob(writer)
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d.addCallbacks(lambda _: fire_finished_deferred(), errback_finished_deferred)
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d.addCallback(lambda _: cancel_other_downloads())
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else:
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d = defer.succeed(None)
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fire_finished_deferred()
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else:
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if writer.len_so_far != self.length:
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err_string = "blob length is %i vs expected %i" % (writer.len_so_far, self.length)
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else:
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err_string = "blob hash is %s vs expected %s" % (writer.blob_hash, self.blob_hash)
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errback_finished_deferred(Failure(InvalidDataError(err_string)))
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d = defer.succeed(None)
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else:
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errback_finished_deferred(err)
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d = defer.succeed(None)
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d.addBoth(lambda _: writer.close_handle())
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return d
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def save_verified_blob(self, writer):
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# we cannot have multiple _save_verified_blob interrupting
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# each other, can happen since startProducing is a deferred
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return self.blob_write_lock.run(self._save_verified_blob, writer)
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@defer.inlineCallbacks
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def _save_verified_blob(self, writer):
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if self.saved_verified_blob is False:
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writer.write_handle.seek(0)
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out_path = os.path.join(self.blob_dir, self.blob_hash)
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producer = FileBodyProducer(writer.write_handle)
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yield producer.startProducing(open(out_path, 'wb'))
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self.saved_verified_blob = True
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defer.returnValue(True)
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else:
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raise DownloadCanceledError()
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