p2pool/util/deferral.py

   1 from __future__ import division
   2
   3 import itertools
   4 import random
   5 import sys
   6
   7 from twisted.internet import defer, reactor
   8 from twisted.python import failure, log
   9
  10 def sleep(t):
  11     d = defer.Deferred(canceller=lambda d_: dc.cancel())
  12     dc = reactor.callLater(t, d.callback, None)
  13     return d
  14
  15 def run_repeatedly(f, *args, **kwargs):
  16     current_dc = [None]
  17     def step():
  18         delay = f(*args, **kwargs)
  19         current_dc[0] = reactor.callLater(delay, step)
  20     step()
  21     def stop():
  22         current_dc[0].cancel()
  23     return stop
  24
  25 class RetrySilentlyException(Exception):
  26     pass
  27
  28 def retry(message='Error:', delay=3, max_retries=None, traceback=True):
  29     '''
  30     @retry('Error getting block:', 1)
  31     @defer.inlineCallbacks
  32     def get_block(hash):
  33         ...
  34     '''
  35
  36     def retry2(func):
  37         @defer.inlineCallbacks
  38         def f(*args, **kwargs):
  39             for i in itertools.count():
  40                 try:
  41                     result = yield func(*args, **kwargs)
  42                 except Exception, e:
  43                     if i == max_retries:
  44                         raise
  45                     if not isinstance(e, RetrySilentlyException):
  46                         if traceback:
  47                             log.err(None, message)
  48                         else:
  49                             print >>sys.stderr, message, e
  50                     yield sleep(delay)
  51                 else:
  52                     defer.returnValue(result)
  53         return f
  54     return retry2
  55
  56 class ReplyMatcher(object):
  57     '''
  58     Converts request/got response interface to deferred interface
  59     '''
  60
  61     def __init__(self, func, timeout=5):
  62         self.func = func
  63         self.timeout = timeout
  64         self.map = {}
  65
  66     def __call__(self, id):
  67         if id not in self.map:
  68             self.func(id)
  69         df = defer.Deferred()
  70         def timeout():
  71             self.map[id].remove((df, timer))
  72             if not self.map[id]:
  73                 del self.map[id]
  74             df.errback(failure.Failure(defer.TimeoutError('in ReplyMatcher')))
  75         timer = reactor.callLater(self.timeout, timeout)
  76         self.map.setdefault(id, set()).add((df, timer))
  77         return df
  78
  79     def got_response(self, id, resp):
  80         if id not in self.map:
  81             return
  82         for df, timer in self.map.pop(id):
  83             df.callback(resp)
  84             timer.cancel()
  85
  86 class GenericDeferrer(object):
  87     '''
  88     Converts query with identifier/got response interface to deferred interface
  89     '''
  90
  91     def __init__(self, max_id, func, timeout=5, on_timeout=lambda: None):
  92         self.max_id = max_id
  93         self.func = func
  94         self.timeout = timeout
  95         self.on_timeout = on_timeout
  96         self.map = {}
  97
  98     def __call__(self, *args, **kwargs):
  99         while True:
 100             id = random.randrange(self.max_id)
 101             if id not in self.map:
 102                 break
 103         def cancel(df):
 104             df, timer = self.map.pop(id)
 105             timer.cancel()
 106         try:
 107             df = defer.Deferred(cancel)
 108         except TypeError:
 109             df = defer.Deferred() # handle older versions of Twisted
 110         def timeout():
 111             self.map.pop(id)
 112             df.errback(failure.Failure(defer.TimeoutError('in GenericDeferrer')))
 113             self.on_timeout()
 114         timer = reactor.callLater(self.timeout, timeout)
 115         self.map[id] = df, timer
 116         self.func(id, *args, **kwargs)
 117         return df
 118
 119     def got_response(self, id, resp):
 120         if id not in self.map:
 121             return
 122         df, timer = self.map.pop(id)
 123         timer.cancel()
 124         df.callback(resp)
 125
 126     def respond_all(self, resp):
 127         while self.map:
 128             id, (df, timer) = self.map.popitem()
 129             timer.cancel()
 130             df.errback(resp)
 131
 132 class NotNowError(Exception):
 133     pass
 134
 135 class DeferredCacher(object):
 136     '''
 137     like memoize, but for functions that return Deferreds
 138
 139     @DeferredCacher
 140     def f(x):
 141         ...
 142         return df
 143
 144     @DeferredCacher.with_backing(bsddb.hashopen(...))
 145     def f(x):
 146         ...
 147         return df
 148     '''
 149
 150     @classmethod
 151     def with_backing(cls, backing):
 152         return lambda func: cls(func, backing)
 153
 154     def __init__(self, func, backing=None):
 155         if backing is None:
 156             backing = {}
 157
 158         self.func = func
 159         self.backing = backing
 160         self.waiting = {}
 161
 162     @defer.inlineCallbacks
 163     def __call__(self, key):
 164         if key in self.waiting:
 165             yield self.waiting[key]
 166
 167         if key in self.backing:
 168             defer.returnValue(self.backing[key])
 169         else:
 170             self.waiting[key] = defer.Deferred()
 171             try:
 172                 value = yield self.func(key)
 173             finally:
 174                 self.waiting.pop(key).callback(None)
 175
 176         self.backing[key] = value
 177         defer.returnValue(value)
 178
 179     _nothing = object()
 180     def call_now(self, key, default=_nothing):
 181         if key in self.backing:
 182             return self.backing[key]
 183         if key not in self.waiting:
 184             self.waiting[key] = defer.Deferred()
 185             def cb(value):
 186                 self.backing[key] = value
 187                 self.waiting.pop(key).callback(None)
 188             def eb(fail):
 189                 self.waiting.pop(key).callback(None)
 190                 if fail.check(RetrySilentlyException):
 191                     return
 192                 print
 193                 print 'Error when requesting noncached value:'
 194                 fail.printTraceback()
 195                 print
 196             self.func(key).addCallback(cb).addErrback(eb)
 197         if default is not self._nothing:
 198             return default
 199         raise NotNowError(key)