From: Brian Warner Date: Wed, 19 Sep 2007 07:34:47 +0000 (-0700) Subject: download.py: use producer/consumer to reduce memory usage, closes #129. X-Git-Tag: allmydata-tahoe-0.6.0~67 X-Git-Url: https://git.rkrishnan.org/components/%22news.html/...?a=commitdiff_plain;h=1340c484c6c60c524096e98ee78243c8c00a12b7;p=tahoe-lafs%2Ftahoe-lafs.git download.py: use producer/consumer to reduce memory usage, closes #129. If the DownloadTarget is also an IConsumer, give it control of the brakes by offering ourselves to target.registerProducer(). When they tell us to pause, set a flag, which is checked between segment downloads and decodes. webish.py: make WebDownloadTarget an IConsumer and pass control along to the http.Request, which already knows how to be an IConsumer. This reduces the memory footprint of stalled HTTP GETs to a bare minimum, and thus closes #129. --- diff --git a/src/allmydata/download.py b/src/allmydata/download.py index 12acd64f..8e5cd05e 100644 --- a/src/allmydata/download.py +++ b/src/allmydata/download.py @@ -3,7 +3,9 @@ import os, random from zope.interface import implements from twisted.python import log from twisted.internet import defer +from twisted.internet.interfaces import IPushProducer, IConsumer from twisted.application import service +from foolscap.eventual import eventually from allmydata.util import idlib, mathutil, hashutil from allmydata.util.assertutil import _assert @@ -23,6 +25,9 @@ class BadPlaintextHashValue(Exception): class BadCrypttextHashValue(Exception): pass +class DownloadStopped(Exception): + pass + class Output: def __init__(self, downloadable, key, total_length): self.downloadable = downloadable @@ -282,6 +287,7 @@ class SegmentDownloader: self.parent.bucket_failed(vbucket) class FileDownloader: + implements(IPushProducer) check_crypttext_hash = True check_plaintext_hash = True @@ -295,7 +301,12 @@ class FileDownloader: self._size = u.size self._num_needed_shares = u.needed_shares + if IConsumer.providedBy(downloadable): + downloadable.registerProducer(self, True) + self._downloadable = downloadable self._output = Output(downloadable, u.key, self._size) + self._paused = False + self._stopped = False self.active_buckets = {} # k: shnum, v: bucket self._share_buckets = [] # list of (sharenum, bucket) tuples @@ -311,8 +322,23 @@ class FileDownloader: "crypttext_hashtree": 0, } + def pauseProducing(self): + if self._paused: + return + self._paused = defer.Deferred() + + def resumeProducing(self): + if self._paused: + p = self._paused + self._paused = None + eventually(p.callback, None) + + def stopProducing(self): + log.msg("Download.stopProducing") + self._stopped = True + def start(self): - log.msg("starting download [%s]" % idlib.b2a(self._storage_index)) + log.msg("starting download [%s]" % idlib.b2a(self._storage_index)[:6]) # first step: who should we download from? d = defer.maybeDeferred(self._get_all_shareholders) @@ -324,6 +350,11 @@ class FileDownloader: d.addCallback(self._create_validated_buckets) # once we know that, we can download blocks from everybody d.addCallback(self._download_all_segments) + def _finished(res): + if IConsumer.providedBy(self._downloadable): + self._downloadable.unregisterProducer() + return res + d.addBoth(_finished) def _failed(why): self._output.fail(why) return why @@ -541,20 +572,40 @@ class FileDownloader: d = defer.succeed(None) for segnum in range(self._total_segments-1): d.addCallback(self._download_segment, segnum) + # this pause, at the end of write, prevents pre-fetch from + # happening until the consumer is ready for more data. + d.addCallback(self._check_for_pause) d.addCallback(self._download_tail_segment, self._total_segments-1) return d + def _check_for_pause(self, res): + if self._paused: + d = defer.Deferred() + self._paused.addCallback(lambda ignored: d.callback(res)) + return d + if self._stopped: + raise DownloadStopped("our Consumer called stopProducing()") + return res + def _download_segment(self, res, segnum): + log.msg("downloading seg#%d of %d (%d%%)" + % (segnum, self._total_segments, + 100.0 * segnum / self._total_segments)) # memory footprint: when the SegmentDownloader finishes pulling down # all shares, we have 1*segment_size of usage. segmentdler = SegmentDownloader(self, segnum, self._num_needed_shares) d = segmentdler.start() + # pause before using more memory + d.addCallback(self._check_for_pause) # while the codec does its job, we hit 2*segment_size d.addCallback(lambda (shares, shareids): self._codec.decode(shares, shareids)) # once the codec is done, we drop back to 1*segment_size, because # 'shares' goes out of scope. The memory usage is all in the # plaintext now, spread out into a bunch of tiny buffers. + + # pause/check-for-stop just before writing, to honor stopProducing + d.addCallback(self._check_for_pause) def _done(buffers): # we start by joining all these buffers together into a single # string. This makes Output.write easier, since it wants to hash @@ -571,10 +622,17 @@ class FileDownloader: return d def _download_tail_segment(self, res, segnum): + log.msg("downloading seg#%d of %d (%d%%)" + % (segnum, self._total_segments, + 100.0 * segnum / self._total_segments)) segmentdler = SegmentDownloader(self, segnum, self._num_needed_shares) d = segmentdler.start() + # pause before using more memory + d.addCallback(self._check_for_pause) d.addCallback(lambda (shares, shareids): self._tail_codec.decode(shares, shareids)) + # pause/check-for-stop just before writing, to honor stopProducing + d.addCallback(self._check_for_pause) def _done(buffers): # trim off any padding added by the upload side segment = "".join(buffers) @@ -589,11 +647,8 @@ class FileDownloader: return d def _done(self, res): + log.msg("download done [%s]" % idlib.b2a(self._storage_index)[:6]) self._output.close() - log.msg("computed CRYPTTEXT_HASH: %s" % - idlib.b2a(self._output.crypttext_hash)) - log.msg("computed PLAINTEXT_HASH: %s" % - idlib.b2a(self._output.plaintext_hash)) if self.check_crypttext_hash: _assert(self._crypttext_hash == self._output.crypttext_hash, "bad crypttext_hash: computed=%s, expected=%s" % diff --git a/src/allmydata/webish.py b/src/allmydata/webish.py index a1e99338..3cc6c83c 100644 --- a/src/allmydata/webish.py +++ b/src/allmydata/webish.py @@ -5,6 +5,7 @@ from twisted.application import service, strports, internet from twisted.web import static, resource, server, html, http from twisted.python import util, log from twisted.internet import defer +from twisted.internet.interfaces import IConsumer from nevow import inevow, rend, loaders, appserver, url, tags as T from nevow.static import File as nevow_File # TODO: merge with static.File? from allmydata.util import fileutil @@ -271,12 +272,18 @@ class Directory(rend.Page): return "" class WebDownloadTarget: - implements(IDownloadTarget) + implements(IDownloadTarget, IConsumer) def __init__(self, req, content_type, content_encoding): self._req = req self._content_type = content_type self._content_encoding = content_encoding self._opened = False + self._producer = None + + def registerProducer(self, producer, streaming): + self._req.registerProducer(producer, streaming) + def unregisterProducer(self): + self._req.unregisterProducer() def open(self, size): self._opened = True