import logging
import treq
from random import choice
from twisted.internet import defer, task
from twisted.internet.error import ConnectingCancelledError
from twisted.web._newclient import ResponseNeverReceived
from lbrynet.utils import DeferredDict
from lbrynet.p2p.Error import DownloadCanceledError
log = logging.getLogger(__name__)
class HTTPBlobDownloader:
'''
A downloader that is able to get blobs from HTTP mirrors.
Note that when a blob gets downloaded from a mirror or from a peer, BlobManager will mark it as completed
and cause any other type of downloader to progress to the next missing blob. Also, BlobFile is naturally able
to cancel other writers when a writer finishes first. That's why there is no call to cancel/resume/stop between
different types of downloaders.
'''
def __init__(self, blob_manager, blob_hashes=None, servers=None, client=None, sd_hashes=None, retry=True,
clock=None):
if not clock:
from twisted.internet import reactor
self.clock = reactor
else:
self.clock = clock
self.blob_manager = blob_manager
self.servers = servers or []
self.client = client or treq
self.blob_hashes = blob_hashes or []
self.missing_blob_hashes = []
self.downloaded_blob_hashes = []
self.sd_hashes = sd_hashes or []
self.head_blob_hashes = []
self.max_failures = 3
self.semaphore = defer.DeferredSemaphore(2)
self.deferreds = []
self.writers = []
self.retry = retry
self.looping_call = task.LoopingCall(self._download_lc)
self.looping_call.clock = self.clock
self.finished_deferred = defer.Deferred()
self.finished_deferred.addErrback(lambda err: err.trap(defer.CancelledError))
self.short_delay = 30
self.long_delay = 600
self.delay = self.short_delay
self.last_missing = 10000000
self.lc_deferred = None
@defer.inlineCallbacks
def start(self):
if not self.looping_call.running:
self.lc_deferred = self.looping_call.start(self.short_delay, now=True)
self.lc_deferred.addErrback(lambda err: err.trap(defer.CancelledError))
yield self.finished_deferred
def stop(self):
for d in reversed(self.deferreds):
d.cancel()
while self.writers:
writer = self.writers.pop()
writer.close(DownloadCanceledError())
self.blob_hashes = []
if self.looping_call.running:
self.looping_call.stop()
if self.lc_deferred and not self.lc_deferred.called:
self.lc_deferred.cancel()
if not self.finished_deferred.called:
self.finished_deferred.cancel()
@defer.inlineCallbacks
def _download_lc(self):
delay = yield self._download_and_get_retry_delay()
log.debug("delay: %s, missing: %i, downloaded from mirror: %i", delay, len(self.missing_blob_hashes),
len(self.downloaded_blob_hashes))
while self.missing_blob_hashes:
self.blob_hashes.append(self.missing_blob_hashes.pop())
if not delay:
if self.looping_call.running:
self.looping_call.stop()
if not self.finished_deferred.called:
log.debug("mirror finished")
self.finished_deferred.callback(None)
elif delay and delay != self.delay:
if delay == self.long_delay:
log.debug("mirror not making progress, trying less frequently")
elif delay == self.short_delay:
log.debug("queueing retry of %i blobs", len(self.missing_blob_hashes))
if self.looping_call.running:
self.looping_call.stop()
self.delay = delay
self.looping_call = task.LoopingCall(self._download_lc)
self.looping_call.clock = self.clock
self.lc_deferred = self.looping_call.start(self.delay, now=False)
self.lc_deferred.addErrback(lambda err: err.trap(defer.CancelledError))
yield self.finished_deferred
@defer.inlineCallbacks
def _download_and_get_retry_delay(self):
if self.blob_hashes and self.servers:
if self.sd_hashes:
log.debug("trying to download stream from mirror (sd %s)", self.sd_hashes[0][:8])
else:
log.debug("trying to download %i blobs from mirror", len(self.blob_hashes))
blobs = yield DeferredDict(
{blob_hash: self.blob_manager.get_blob(blob_hash) for blob_hash in self.blob_hashes}
)
self.deferreds = [self.download_blob(blobs[blob_hash]) for blob_hash in self.blob_hashes]
yield defer.DeferredList(self.deferreds)
if self.retry and self.missing_blob_hashes:
if not self.downloaded_blob_hashes:
defer.returnValue(self.long_delay)
if len(self.missing_blob_hashes) < self.last_missing:
self.last_missing = len(self.missing_blob_hashes)
defer.returnValue(self.short_delay)
if self.retry and self.last_missing and len(self.missing_blob_hashes) == self.last_missing:
defer.returnValue(self.long_delay)
defer.returnValue(None)
@defer.inlineCallbacks
def _download_blob(self, blob):
for _ in range(self.max_failures):
writer, finished_deferred = blob.open_for_writing('mirror')
self.writers.append(writer)
try:
downloaded = yield self._write_blob(writer, blob)
if downloaded:
yield finished_deferred # yield for verification errors, so we log them
if blob.verified:
log.info('Mirror completed download for %s', blob.blob_hash)
should_announce = blob.blob_hash in self.sd_hashes or blob.blob_hash in self.head_blob_hashes
yield self.blob_manager.blob_completed(blob, should_announce=should_announce)
self.downloaded_blob_hashes.append(blob.blob_hash)
break
except (IOError, Exception, defer.CancelledError, ConnectingCancelledError, ResponseNeverReceived) as e:
if isinstance(
e, (DownloadCanceledError, defer.CancelledError, ConnectingCancelledError,
ResponseNeverReceived)
) or 'closed file' in str(e):
# some other downloader finished first or it was simply cancelled
log.info("Mirror download cancelled: %s", blob.blob_hash)
break
else:
log.exception('Mirror failed downloading')
finally:
finished_deferred.addBoth(lambda _: None) # suppress echoed errors
if 'mirror' in blob.writers:
writer.close()
self.writers.remove(writer)
def download_blob(self, blob):
if not blob.verified:
d = self.semaphore.run(self._download_blob, blob)
d.addErrback(lambda err: err.trap(defer.TimeoutError, defer.CancelledError))
return d
return defer.succeed(None)
@defer.inlineCallbacks
def _write_blob(self, writer, blob):
response = yield self.client.get(url_for(choice(self.servers), blob.blob_hash))
if response.code != 200:
log.debug('Missing a blob: %s', blob.blob_hash)
if blob.blob_hash in self.blob_hashes:
self.blob_hashes.remove(blob.blob_hash)
if blob.blob_hash not in self.missing_blob_hashes:
self.missing_blob_hashes.append(blob.blob_hash)
defer.returnValue(False)
log.debug('Download started: %s', blob.blob_hash)
blob.set_length(response.length)
yield self.client.collect(response, writer.write)
defer.returnValue(True)
@defer.inlineCallbacks
def download_stream(self, stream_hash, sd_hash):
stream_crypt_blobs = yield self.blob_manager.storage.get_blobs_for_stream(stream_hash)
self.blob_hashes.extend([
b.blob_hash for b in stream_crypt_blobs
if b.blob_hash and b.blob_hash not in self.blob_hashes
])
if sd_hash not in self.sd_hashes:
self.sd_hashes.append(sd_hash)
head_blob_hash = stream_crypt_blobs[0].blob_hash
if head_blob_hash not in self.head_blob_hashes:
self.head_blob_hashes.append(head_blob_hash)
yield self.start()
def url_for(server, blob_hash=''):
return f'http://{server}/{blob_hash}'