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# -*- test-case-name: twisted.spread.test.test_pb -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Persistently cached objects for PB.
Maintainer: Glyph Lefkowitz
Future Plans: None known.
"""
import time
from twisted.internet import defer
from twisted.spread import banana, flavors, jelly
class Publishable(flavors.Cacheable):
"""An object whose cached state persists across sessions."""
def __init__(self, publishedID):
self.republish()
self.publishedID = publishedID
def republish(self):
"""Set the timestamp to current and (TODO) update all observers."""
self.timestamp = time.time()
def view_getStateToPublish(self, perspective):
"(internal)"
return self.getStateToPublishFor(perspective)
def getStateToPublishFor(self, perspective):
"""Implement me to special-case your state for a perspective."""
return self.getStateToPublish()
def getStateToPublish(self):
"""Implement me to return state to copy as part of the publish phase."""
raise NotImplementedError("%s.getStateToPublishFor" % self.__class__)
def getStateToCacheAndObserveFor(self, perspective, observer):
"""Get all necessary metadata to keep a clientside cache."""
if perspective:
pname = perspective.perspectiveName
sname = perspective.getService().serviceName
else:
pname = "None"
sname = "None"
return {
"remote": flavors.ViewPoint(perspective, self),
"publishedID": self.publishedID,
"perspective": pname,
"service": sname,
"timestamp": self.timestamp,
}
class RemotePublished(flavors.RemoteCache):
"""The local representation of remote Publishable object."""
isActivated = 0
_wasCleanWhenLoaded = 0
def getFileName(self, ext="pub"):
return "{}-{}-{}.{}".format(
self.service,
self.perspective,
str(self.publishedID),
ext,
)
def setCopyableState(self, state):
self.__dict__.update(state)
self._activationListeners = []
try:
with open(self.getFileName(), "rb") as dataFile:
data = dataFile.read()
except OSError:
recent = 0
else:
newself = jelly.unjelly(banana.decode(data))
recent = newself.timestamp == self.timestamp
if recent:
self._cbGotUpdate(newself.__dict__)
self._wasCleanWhenLoaded = 1
else:
self.remote.callRemote("getStateToPublish").addCallbacks(self._cbGotUpdate)
def __getstate__(self):
other = self.__dict__.copy()
# Remove PB-specific attributes
del other["broker"]
del other["remote"]
del other["luid"]
# remove my own runtime-tracking stuff
del other["_activationListeners"]
del other["isActivated"]
return other
def _cbGotUpdate(self, newState):
self.__dict__.update(newState)
self.isActivated = 1
# send out notifications
for listener in self._activationListeners:
listener(self)
self._activationListeners = []
self.activated()
with open(self.getFileName(), "wb") as dataFile:
dataFile.write(banana.encode(jelly.jelly(self)))
def activated(self):
"""Implement this method if you want to be notified when your
publishable subclass is activated.
"""
def callWhenActivated(self, callback):
"""Externally register for notification when this publishable has received all relevant data."""
if self.isActivated:
callback(self)
else:
self._activationListeners.append(callback)
def whenReady(d):
"""
Wrap a deferred returned from a pb method in another deferred that
expects a RemotePublished as a result. This will allow you to wait until
the result is really available.
Idiomatic usage would look like::
publish.whenReady(serverObject.getMeAPublishable()).addCallback(lookAtThePublishable)
"""
d2 = defer.Deferred()
d.addCallbacks(_pubReady, d2.errback, callbackArgs=(d2,))
return d2
def _pubReady(result, d2):
"(internal)"
result.callWhenActivated(d2.callback)
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