import random from zope.interface import implements from twisted.internet import defer, reactor from foolscap.api import eventually from allmydata.interfaces import IMutableFileNode, \ ICheckable, ICheckResults, NotEnoughSharesError from allmydata.util import hashutil, log from allmydata.util.assertutil import precondition from allmydata.uri import WriteableSSKFileURI, ReadonlySSKFileURI from allmydata.monitor import Monitor from pycryptopp.cipher.aes import AES from publish import Publish from common import MODE_READ, MODE_WRITE, UnrecoverableFileError, \ ResponseCache, UncoordinatedWriteError from servermap import ServerMap, ServermapUpdater from retrieve import Retrieve from checker import MutableChecker, MutableCheckAndRepairer from repairer import Repairer 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 nodemaker.create_mutable_file() to make one of these class MutableFileNode: implements(IMutableFileNode, ICheckable) def __init__(self, storage_broker, secret_holder, default_encoding_parameters, history): self._storage_broker = storage_broker self._secret_holder = secret_holder self._default_encoding_parameters = default_encoding_parameters self._history = history self._pubkey = None # filled in upon first read self._privkey = None # filled in if we're mutable # we keep track of the last encoding parameters that we use. These # are updated upon retrieve, and used by publish. If we publish # without ever reading (i.e. overwrite()), then we use these values. self._required_shares = default_encoding_parameters["k"] self._total_shares = default_encoding_parameters["n"] self._sharemap = {} # known shares, shnum-to-[nodeids] self._cache = ResponseCache() # all users of this MutableFileNode go through the serializer. This # takes advantage of the fact that Deferreds discard the callbacks # that they're done with, so we can keep using the same Deferred # forever without consuming more and more memory. self._serializer = defer.succeed(None) def __repr__(self): if hasattr(self, '_uri'): return "<%s %x %s %s>" % (self.__class__.__name__, id(self), self.is_readonly() and 'RO' or 'RW', self._uri.abbrev()) else: return "<%s %x %s %s>" % (self.__class__.__name__, id(self), None, None) def init_from_cap(self, filecap): # we have the URI, but we have not yet retrieved the public # verification key, nor things like 'k' or 'N'. If and when someone # wants to get our contents, we'll pull from shares and fill those # in. assert isinstance(filecap, (ReadonlySSKFileURI, WriteableSSKFileURI)) self._uri = filecap self._writekey = None if isinstance(filecap, WriteableSSKFileURI): self._writekey = self._uri.writekey self._readkey = self._uri.readkey self._storage_index = self._uri.storage_index self._fingerprint = self._uri.fingerprint # the following values are learned during Retrieval # self._pubkey # self._required_shares # self._total_shares # and these are needed for Publish. They are filled in by Retrieval # if possible, otherwise by the first peer that Publish talks to. self._privkey = None self._encprivkey = None return self def create_with_keys(self, (pubkey, privkey), contents): """Call this to create a brand-new mutable file. It will create the shares, find homes for them, and upload the initial contents (created with the same rules as IClient.create_mutable_file() ). Returns a Deferred that fires (with the MutableFileNode instance you should use) when it completes. """ self._pubkey, self._privkey = pubkey, privkey pubkey_s = self._pubkey.serialize() privkey_s = self._privkey.serialize() self._writekey = hashutil.ssk_writekey_hash(privkey_s) self._encprivkey = self._encrypt_privkey(self._writekey, privkey_s) self._fingerprint = hashutil.ssk_pubkey_fingerprint_hash(pubkey_s) self._uri = WriteableSSKFileURI(self._writekey, self._fingerprint) self._readkey = self._uri.readkey self._storage_index = self._uri.storage_index initial_contents = self._get_initial_contents(contents) return self._upload(initial_contents, None) def _get_initial_contents(self, contents): if isinstance(contents, str): return contents if contents is None: return "" assert callable(contents), "%s should be callable, not %s" % \ (contents, type(contents)) return contents(self) def _encrypt_privkey(self, writekey, privkey): enc = AES(writekey) crypttext = enc.process(privkey) return crypttext def _decrypt_privkey(self, enc_privkey): enc = AES(self._writekey) privkey = enc.process(enc_privkey) return privkey def _populate_pubkey(self, pubkey): self._pubkey = pubkey def _populate_required_shares(self, required_shares): self._required_shares = required_shares def _populate_total_shares(self, total_shares): self._total_shares = total_shares def _populate_privkey(self, privkey): self._privkey = privkey def _populate_encprivkey(self, encprivkey): self._encprivkey = encprivkey def get_write_enabler(self, peerid): assert len(peerid) == 20 return hashutil.ssk_write_enabler_hash(self._writekey, peerid) def get_renewal_secret(self, peerid): assert len(peerid) == 20 crs = self._secret_holder.get_renewal_secret() frs = hashutil.file_renewal_secret_hash(crs, self._storage_index) return hashutil.bucket_renewal_secret_hash(frs, peerid) def get_cancel_secret(self, peerid): assert len(peerid) == 20 ccs = self._secret_holder.get_cancel_secret() fcs = hashutil.file_cancel_secret_hash(ccs, self._storage_index) return hashutil.bucket_cancel_secret_hash(fcs, peerid) def get_writekey(self): return self._writekey def get_readkey(self): return self._readkey def get_storage_index(self): return self._storage_index def get_privkey(self): return self._privkey def get_encprivkey(self): return self._encprivkey def get_pubkey(self): return self._pubkey def get_required_shares(self): return self._required_shares def get_total_shares(self): return self._total_shares #################################### # IFilesystemNode def get_size(self): return "?" # TODO: this is likely to cause problems, not being an int def get_cap(self): return self._uri def get_readcap(self): return self._uri.get_readonly() def get_verify_cap(self): return self._uri.get_verify_cap() def get_repair_cap(self): if self._uri.is_readonly(): return None return self._uri def get_uri(self): return self._uri.to_string() def get_readonly_uri(self): return self._uri.get_readonly().to_string() def get_readonly(self): if self.is_readonly(): return self ro = MutableFileNode(self._storage_broker, self._secret_holder, self._default_encoding_parameters, self._history) ro.init_from_cap(self._uri.get_readonly()) return ro def is_mutable(self): return self._uri.is_mutable() def is_readonly(self): return self._uri.is_readonly() def __hash__(self): return hash((self.__class__, self._uri)) def __cmp__(self, them): if cmp(type(self), type(them)): return cmp(type(self), type(them)) if cmp(self.__class__, them.__class__): return cmp(self.__class__, them.__class__) return cmp(self._uri, them._uri) def _do_serialized(self, cb, *args, **kwargs): # note: to avoid deadlock, this callable is *not* allowed to invoke # other serialized methods within this (or any other) # MutableFileNode. The callable should be a bound method of this same # MFN instance. d = defer.Deferred() self._serializer.addCallback(lambda ignore: cb(*args, **kwargs)) # we need to put off d.callback until this Deferred is finished being # processed. Otherwise the caller's subsequent activities (like, # doing other things with this node) can cause reentrancy problems in # the Deferred code itself self._serializer.addBoth(lambda res: eventually(d.callback, res)) # add a log.err just in case something really weird happens, because # self._serializer stays around forever, therefore we won't see the # usual Unhandled Error in Deferred that would give us a hint. self._serializer.addErrback(log.err) return d ################################# # ICheckable def check(self, monitor, verify=False, add_lease=False): checker = MutableChecker(self, self._storage_broker, self._history, monitor) return checker.check(verify, add_lease) def check_and_repair(self, monitor, verify=False, add_lease=False): checker = MutableCheckAndRepairer(self, self._storage_broker, self._history, monitor) return checker.check(verify, add_lease) ################################# # IRepairable def repair(self, check_results, force=False): assert ICheckResults(check_results) r = Repairer(self, check_results) d = r.start(force) return d ################################# # IMutableFileNode # allow the use of IDownloadTarget def download(self, target): # fake it. TODO: make this cleaner. d = self.download_best_version() def _done(data): target.open(len(data)) target.write(data) target.close() return target.finish() d.addCallback(_done) return d # new API def download_best_version(self): return self._do_serialized(self._download_best_version) def _download_best_version(self): servermap = ServerMap() d = self._try_once_to_download_best_version(servermap, MODE_READ) def _maybe_retry(f): f.trap(NotEnoughSharesError) # the download is worth retrying once. Make sure to use the # old servermap, since it is what remembers the bad shares, # but use MODE_WRITE to make it look for even more shares. # TODO: consider allowing this to retry multiple times.. this # approach will let us tolerate about 8 bad shares, I think. return self._try_once_to_download_best_version(servermap, MODE_WRITE) d.addErrback(_maybe_retry) return d def _try_once_to_download_best_version(self, servermap, mode): d = self._update_servermap(servermap, mode) 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 get_size_of_best_version(self): d = self.get_servermap(MODE_READ) def _got_servermap(smap): ver = smap.best_recoverable_version() if not ver: raise UnrecoverableFileError("no recoverable version") return smap.size_of_version(ver) d.addCallback(_got_servermap) return d def overwrite(self, new_contents): return self._do_serialized(self._overwrite, new_contents) def _overwrite(self, new_contents): servermap = ServerMap() d = self._update_servermap(servermap, mode=MODE_WRITE) d.addCallback(lambda ignored: self._upload(new_contents, servermap)) return d def modify(self, modifier, backoffer=None): """I use a modifier callback to apply a change to the mutable file. I implement the following pseudocode:: obtain_mutable_filenode_lock() first_time = True while True: update_servermap(MODE_WRITE) old = retrieve_best_version() new = modifier(old, servermap, first_time) first_time = False if new == old: break try: publish(new) except UncoordinatedWriteError, e: backoffer(e) continue break release_mutable_filenode_lock() The idea is that your modifier function can apply a delta of some sort, and it will be re-run as necessary until it succeeds. The modifier must inspect the old version to see whether its delta has already been applied: if so it should return the contents unmodified. 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. """ 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, True) def _modify_and_retry(self, servermap, modifier, backoffer, first_time): d = self._modify_once(servermap, modifier, first_time) def _retry(f): f.trap(UncoordinatedWriteError) d2 = defer.maybeDeferred(backoffer, self, f) d2.addCallback(lambda ignored: self._modify_and_retry(servermap, modifier, backoffer, False)) return d2 d.addErrback(_retry) return d def _modify_once(self, servermap, modifier, first_time): 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, servermap, first_time) if new_contents is None or new_contents == old_contents: # no changes need to be made if first_time: return # However, since Publish is not automatically doing a # recovery when it observes UCWE, we need to do a second # publish. See #551 for details. We'll basically loop until # we managed an uncontested publish. new_contents = old_contents 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) def _get_servermap(self, mode): servermap = ServerMap() return self._update_servermap(servermap, mode) def _update_servermap(self, servermap, mode): u = ServermapUpdater(self, self._storage_broker, Monitor(), servermap, mode) if self._history: self._history.notify_mapupdate(u.get_status()) return u.update() def download_version(self, servermap, version, fetch_privkey=False): return self._do_serialized(self._try_once_to_download_version, servermap, version, fetch_privkey) def _try_once_to_download_version(self, servermap, version, fetch_privkey=False): r = Retrieve(self, servermap, version, fetch_privkey) if self._history: self._history.notify_retrieve(r.get_status()) return r.download() def upload(self, new_contents, servermap): return self._do_serialized(self._upload, new_contents, servermap) def _upload(self, new_contents, servermap): assert self._pubkey, "update_servermap must be called before publish" p = Publish(self, self._storage_broker, servermap) if self._history: self._history.notify_publish(p.get_status(), len(new_contents)) return p.publish(new_contents)