From: Brian Warner Date: Fri, 18 Apr 2008 02:12:42 +0000 (-0700) Subject: mutable: implement MutableFileNode.modify, plus tests X-Git-Tag: allmydata-tahoe-1.1.0~230 X-Git-Url: https://git.rkrishnan.org/specifications/something?a=commitdiff_plain;h=004d3c14bf83cf6fd6fd73c3df335a5421bfef8a;p=tahoe-lafs%2Ftahoe-lafs.git mutable: implement MutableFileNode.modify, plus tests --- diff --git a/src/allmydata/mutable/node.py b/src/allmydata/mutable/node.py index 0c1ffc25..ae9a54a3 100644 --- a/src/allmydata/mutable/node.py +++ b/src/allmydata/mutable/node.py @@ -1,11 +1,12 @@ -import weakref +import weakref, random from twisted.application import service from zope.interface import implements -from twisted.internet import defer +from twisted.internet import defer, reactor from allmydata.interfaces import IMutableFileNode, IMutableFileURI from allmydata.util import hashutil +from allmydata.util.assertutil import precondition from allmydata.uri import WriteableSSKFileURI from allmydata.encode import NotEnoughSharesError from pycryptopp.publickey import rsa @@ -13,11 +14,33 @@ from pycryptopp.cipher.aes import AES from publish import Publish from common import MODE_READ, MODE_WRITE, UnrecoverableFileError, \ - ResponseCache + ResponseCache, UncoordinatedWriteError from servermap import ServerMap, ServermapUpdater from retrieve import Retrieve +class BackoffAgent: + # these parameters are copied from foolscap.reconnector, which gets them + # from twisted.internet.protocol.ReconnectingClientFactory + initialDelay = 1.0 + factor = 2.7182818284590451 # (math.e) + jitter = 0.11962656492 # molar Planck constant times c, Joule meter/mole + maxRetries = 4 + + def __init__(self): + self._delay = self.initialDelay + self._count = 0 + def delay(self, node, f): + self._count += 1 + if self._count == 4: + return f + self._delay = self._delay * self.factor + self._delay = random.normalvariate(self._delay, + self._delay * self.jitter) + d = defer.Deferred() + reactor.callLater(self._delay, d.callback, None) + return d + # use client.create_mutable_file() to make one of these class MutableFileNode: @@ -253,14 +276,13 @@ class MutableFileNode: return d def _try_once_to_download_best_version(self, servermap, mode): d = self._update_servermap(servermap, mode) - def _updated(ignored): - goal = servermap.best_recoverable_version() - if not goal: - raise UnrecoverableFileError("no recoverable versions") - return self._try_once_to_download_version(servermap, goal) - d.addCallback(_updated) + d.addCallback(self._once_updated_download_best_version, servermap) return d - + def _once_updated_download_best_version(self, ignored, servermap): + goal = servermap.best_recoverable_version() + if not goal: + raise UnrecoverableFileError("no recoverable versions") + return self._try_once_to_download_version(servermap, goal) def overwrite(self, new_contents): return self._do_serialized(self._overwrite, new_contents) @@ -271,7 +293,7 @@ class MutableFileNode: return d - def modify(self, modifier, *args, **kwargs): + def modify(self, modifier, backoffer=None): """I use a modifier callback to apply a change to the mutable file. I implement the following pseudocode:: @@ -283,7 +305,8 @@ class MutableFileNode: if new == old: break try: publish(new) - except UncoordinatedWriteError: + except UncoordinatedWriteError, e: + backoffer(e) continue break release_mutable_filenode_lock() @@ -295,8 +318,49 @@ class MutableFileNode: Note that the modifier is required to run synchronously, and must not invoke any methods on this MutableFileNode instance. + + The backoff-er is a callable that is responsible for inserting a + random delay between subsequent attempts, to help competing updates + from colliding forever. It is also allowed to give up after a while. + The backoffer is given two arguments: this MutableFileNode, and the + Failure object that contains the UncoordinatedWriteError. It should + return a Deferred that will fire when the next attempt should be + made, or return the Failure if the loop should give up. If + backoffer=None, a default one is provided which will perform + exponential backoff, and give up after 4 tries. Note that the + backoffer should not invoke any methods on this MutableFileNode + instance, and it needs to be highly conscious of deadlock issues. """ - NotImplementedError + return self._do_serialized(self._modify, modifier, backoffer) + def _modify(self, modifier, backoffer): + servermap = ServerMap() + if backoffer is None: + backoffer = BackoffAgent().delay + return self._modify_and_retry(servermap, modifier, backoffer) + def _modify_and_retry(self, servermap, modifier, backoffer): + d = self._modify_once(servermap, modifier) + def _retry(f): + f.trap(UncoordinatedWriteError) + d2 = defer.maybeDeferred(backoffer, self, f) + d2.addCallback(lambda ignored: + self._modify_and_retry(servermap, modifier, + backoffer)) + return d2 + d.addErrback(_retry) + return d + def _modify_once(self, servermap, modifier): + d = self._update_servermap(servermap, MODE_WRITE) + d.addCallback(self._once_updated_download_best_version, servermap) + def _apply(old_contents): + new_contents = modifier(old_contents) + if new_contents is None or new_contents == old_contents: + # no changes need to be made + return + precondition(isinstance(new_contents, str), + "Modifier function must return a string or None") + return self._upload(new_contents, servermap) + d.addCallback(_apply) + return d def get_servermap(self, mode): return self._do_serialized(self._get_servermap, mode) diff --git a/src/allmydata/test/test_mutable.py b/src/allmydata/test/test_mutable.py index 7b5626c5..a3623bf8 100644 --- a/src/allmydata/test/test_mutable.py +++ b/src/allmydata/test/test_mutable.py @@ -14,9 +14,10 @@ from foolscap.eventual import eventually, fireEventually from foolscap.logging import log import sha -from allmydata.mutable.node import MutableFileNode +from allmydata.mutable.node import MutableFileNode, BackoffAgent from allmydata.mutable.common import DictOfSets, ResponseCache, \ - MODE_CHECK, MODE_ANYTHING, MODE_WRITE, MODE_READ, UnrecoverableFileError + MODE_CHECK, MODE_ANYTHING, MODE_WRITE, MODE_READ, \ + UnrecoverableFileError, UncoordinatedWriteError from allmydata.mutable.retrieve import Retrieve from allmydata.mutable.publish import Publish from allmydata.mutable.servermap import ServerMap, ServermapUpdater @@ -254,6 +255,27 @@ class Filenode(unittest.TestCase): d.addCallback(_created) return d + def test_serialize(self): + n = MutableFileNode(self.client) + calls = [] + def _callback(*args, **kwargs): + self.failUnlessEqual(args, (4,) ) + self.failUnlessEqual(kwargs, {"foo": 5}) + calls.append(1) + return 6 + d = n._do_serialized(_callback, 4, foo=5) + def _check_callback(res): + self.failUnlessEqual(res, 6) + self.failUnlessEqual(calls, [1]) + d.addCallback(_check_callback) + + def _errback(): + raise ValueError("heya") + d.addCallback(lambda res: + self.shouldFail(ValueError, "_check_errback", "heya", + n._do_serialized, _errback)) + return d + def test_upload_and_download(self): d = self.client.create_mutable_file() def _created(n): @@ -296,6 +318,147 @@ class Filenode(unittest.TestCase): d.addCallback(_created) return d + def failUnlessCurrentSeqnumIs(self, n, expected_seqnum): + d = n.get_servermap(MODE_READ) + d.addCallback(lambda servermap: servermap.best_recoverable_version()) + d.addCallback(lambda verinfo: + self.failUnlessEqual(verinfo[0], expected_seqnum)) + return d + + def shouldFail(self, expected_failure, which, substring, + callable, *args, **kwargs): + assert substring is None or isinstance(substring, str) + d = defer.maybeDeferred(callable, *args, **kwargs) + def done(res): + if isinstance(res, failure.Failure): + res.trap(expected_failure) + if substring: + self.failUnless(substring in str(res), + "substring '%s' not in '%s'" + % (substring, str(res))) + else: + self.fail("%s was supposed to raise %s, not get '%s'" % + (which, expected_failure, res)) + d.addBoth(done) + return d + + def test_modify(self): + def _modifier(old_contents): + return old_contents + "line2" + def _non_modifier(old_contents): + return old_contents + def _none_modifier(old_contents): + return None + def _error_modifier(old_contents): + raise ValueError + calls = [] + def _ucw_error_modifier(old_contents): + # simulate an UncoordinatedWriteError once + calls.append(1) + if len(calls) <= 1: + raise UncoordinatedWriteError("simulated") + return old_contents + "line3" + + d = self.client.create_mutable_file("line1") + def _created(n): + d = n.modify(_modifier) + d.addCallback(lambda res: n.download_best_version()) + d.addCallback(lambda res: self.failUnlessEqual(res, "line1line2")) + d.addCallback(lambda res: self.failUnlessCurrentSeqnumIs(n, 2)) + + d.addCallback(lambda res: n.modify(_non_modifier)) + d.addCallback(lambda res: n.download_best_version()) + d.addCallback(lambda res: self.failUnlessEqual(res, "line1line2")) + d.addCallback(lambda res: self.failUnlessCurrentSeqnumIs(n, 2)) + + d.addCallback(lambda res: n.modify(_none_modifier)) + d.addCallback(lambda res: n.download_best_version()) + d.addCallback(lambda res: self.failUnlessEqual(res, "line1line2")) + d.addCallback(lambda res: self.failUnlessCurrentSeqnumIs(n, 2)) + + d.addCallback(lambda res: + self.shouldFail(ValueError, "error_modifier", None, + n.modify, _error_modifier)) + d.addCallback(lambda res: n.download_best_version()) + d.addCallback(lambda res: self.failUnlessEqual(res, "line1line2")) + d.addCallback(lambda res: self.failUnlessCurrentSeqnumIs(n, 2)) + + d.addCallback(lambda res: n.modify(_ucw_error_modifier)) + d.addCallback(lambda res: self.failUnlessEqual(len(calls), 2)) + d.addCallback(lambda res: n.download_best_version()) + d.addCallback(lambda res: self.failUnlessEqual(res, + "line1line2line3")) + d.addCallback(lambda res: self.failUnlessCurrentSeqnumIs(n, 3)) + + return d + d.addCallback(_created) + return d + + def test_modify_backoffer(self): + def _modifier(old_contents): + return old_contents + "line2" + calls = [] + def _ucw_error_modifier(old_contents): + # simulate an UncoordinatedWriteError once + calls.append(1) + if len(calls) <= 1: + raise UncoordinatedWriteError("simulated") + return old_contents + "line3" + def _always_ucw_error_modifier(old_contents): + raise UncoordinatedWriteError("simulated") + def _backoff_stopper(node, f): + return f + def _backoff_pauser(node, f): + d = defer.Deferred() + reactor.callLater(0.5, d.callback, None) + return d + + # the give-up-er will hit its maximum retry count quickly + giveuper = BackoffAgent() + giveuper._delay = 0.1 + giveuper.factor = 1 + + d = self.client.create_mutable_file("line1") + def _created(n): + d = n.modify(_modifier) + d.addCallback(lambda res: n.download_best_version()) + d.addCallback(lambda res: self.failUnlessEqual(res, "line1line2")) + d.addCallback(lambda res: self.failUnlessCurrentSeqnumIs(n, 2)) + + d.addCallback(lambda res: + self.shouldFail(UncoordinatedWriteError, + "_backoff_stopper", None, + n.modify, _ucw_error_modifier, + _backoff_stopper)) + d.addCallback(lambda res: n.download_best_version()) + d.addCallback(lambda res: self.failUnlessEqual(res, "line1line2")) + d.addCallback(lambda res: self.failUnlessCurrentSeqnumIs(n, 2)) + + def _reset_ucw_error_modifier(res): + calls[:] = [] + return res + d.addCallback(_reset_ucw_error_modifier) + d.addCallback(lambda res: n.modify(_ucw_error_modifier, + _backoff_pauser)) + d.addCallback(lambda res: n.download_best_version()) + d.addCallback(lambda res: self.failUnlessEqual(res, + "line1line2line3")) + d.addCallback(lambda res: self.failUnlessCurrentSeqnumIs(n, 3)) + + d.addCallback(lambda res: + self.shouldFail(UncoordinatedWriteError, + "giveuper", None, + n.modify, _always_ucw_error_modifier, + giveuper.delay)) + d.addCallback(lambda res: n.download_best_version()) + d.addCallback(lambda res: self.failUnlessEqual(res, + "line1line2line3")) + d.addCallback(lambda res: self.failUnlessCurrentSeqnumIs(n, 3)) + + return d + d.addCallback(_created) + return d + def test_upload_and_download_full_size_keys(self): self.client.mutable_file_node_class = MutableFileNode d = self.client.create_mutable_file()