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#
# Copyright (c) 2011-2014 Red Hat, Inc. <http://www.redhat.com>
# This file is part of GlusterFS.
# This file is licensed to you under your choice of the GNU Lesser
# General Public License, version 3 or any later version (LGPLv3 or
# later), or the GNU General Public License, version 2 (GPLv2), in all
# cases as published by the Free Software Foundation.
#
import os
import sys
import time
import logging
from threading import Condition
import thread
from Queue import Queue
import cPickle as pickle
from syncdutils import Thread, select, lf
pickle_proto = -1
repce_version = 1.0
def ioparse(i, o):
if isinstance(i, int):
i = os.fdopen(i)
# rely on duck typing for recognizing
# streams as that works uniformly
# in py2 and py3
if hasattr(o, 'fileno'):
o = o.fileno()
return (i, o)
def send(out, *args):
"""pickle args and write out wholly in one syscall
ie. not use the ability of pickle to dump directly to
a stream, as that would potentially mess up messages
by interleaving them
"""
os.write(out, pickle.dumps(args, pickle_proto))
def recv(inf):
"""load an object from input stream"""
return pickle.load(inf)
class RepceServer(object):
"""RePCe is Hungarian for canola, http://hu.wikipedia.org/wiki/Repce
... also our homebrewed RPC backend where the transport layer is
reduced to a pair of filehandles.
This is the server component.
"""
def __init__(self, obj, i, o, wnum=6):
"""register a backend object .obj to which incoming messages
are dispatched, also incoming/outcoming streams
"""
self.obj = obj
self.inf, self.out = ioparse(i, o)
self.wnum = wnum
self.q = Queue()
def service_loop(self):
"""fire up worker threads, get messages and dispatch among them"""
for i in range(self.wnum):
t = Thread(target=self.worker)
t.start()
try:
while True:
self.q.put(recv(self.inf))
except EOFError:
logging.info("terminating on reaching EOF.")
def worker(self):
"""life of a worker
Get message, extract its id, method name and arguments
(kwargs not supported), call method on .obj.
Send back message id + return value.
If method call throws an exception, rescue it, and send
back the exception as result (with flag marking it as
exception).
"""
while True:
in_data = self.q.get(True)
rid = in_data[0]
rmeth = in_data[1]
exc = False
if rmeth == '__repce_version__':
res = repce_version
else:
try:
res = getattr(self.obj, rmeth)(*in_data[2:])
except:
res = sys.exc_info()[1]
exc = True
logging.exception("call failed: ")
send(self.out, rid, exc, res)
class RepceJob(object):
"""class representing message status we can use
for waiting on reply"""
def __init__(self, cbk):
"""
- .rid: (process-wise) unique id
- .cbk: what we do upon receiving reply
"""
self.rid = (os.getpid(), thread.get_ident(), time.time())
self.cbk = cbk
self.lever = Condition()
self.done = False
def __repr__(self):
return ':'.join([str(x) for x in self.rid])
def wait(self):
self.lever.acquire()
if not self.done:
self.lever.wait()
self.lever.release()
return self.result
def wakeup(self, data):
self.result = data
self.lever.acquire()
self.done = True
self.lever.notify()
self.lever.release()
class RepceClient(object):
"""RePCe is Hungarian for canola, http://hu.wikipedia.org/wiki/Repce
... also our homebrewed RPC backend where the transport layer is
reduced to a pair of filehandles.
This is the client component.
"""
def __init__(self, i, o):
self.inf, self.out = ioparse(i, o)
self.jtab = {}
t = Thread(target=self.listen)
t.start()
def listen(self):
while True:
select((self.inf,), (), ())
rid, exc, res = recv(self.inf)
rjob = self.jtab.pop(rid)
if rjob.cbk:
rjob.cbk(rjob, [exc, res])
def push(self, meth, *args, **kw):
"""wrap arguments in a RepceJob, send them to server
and return the RepceJob
@cbk to pass on RepceJob can be given as kwarg.
"""
cbk = kw.get('cbk')
if not cbk:
def cbk(rj, res):
if res[0]:
raise res[1]
rjob = RepceJob(cbk)
self.jtab[rjob.rid] = rjob
logging.debug("call %s %s%s ..." % (repr(rjob), meth, repr(args)))
send(self.out, rjob.rid, meth, *args)
return rjob
def __call__(self, meth, *args):
"""RePCe client is callabe, calling it implements a synchronous
remote call.
We do a .push with a cbk which does a wakeup upon receiving anwser,
then wait on the RepceJob.
"""
rjob = self.push(
meth, *args, **{'cbk': lambda rj, res: rj.wakeup(res)})
exc, res = rjob.wait()
if exc:
logging.error(lf('call failed',
call=repr(rjob),
method=meth,
error=str(type(res).__name__)))
raise res
logging.debug("call %s %s -> %s" % (repr(rjob), meth, repr(res)))
return res
class mprx(object):
"""method proxy, standard trick to implement rubyesque
method_missing in Python
A class is a closure factory, you know what I mean, or go read
some SICP.
"""
def __init__(self, ins, meth):
self.ins = ins
self.meth = meth
def __call__(self, *a):
return self.ins(self.meth, *a)
def __getattr__(self, meth):
"""this implements transparent method dispatch to remote object,
so that you don't need to call the RepceClient instance like
rclient('how_old_are_you_if_born_in', 1979)
but you can make it into an ordinary method call like
rclient.how_old_are_you_if_born_in(1979)
"""
return self.mprx(self, meth)
def __version__(self):
"""used in handshake to verify compatibility"""
d = {'proto': self('__repce_version__')}
try:
d['object'] = self('version')
except AttributeError:
pass
return d
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