txmsgpackrpc

For the latest source code, see http://github.com/jakm/txmsgpackrpc

txmsgpackrpc is a library for writing asynchronous msgpack-rpc servers and clients in Python, using Twisted framework. Library is based on txMsgpack, but some improvements and fixes were made.

Features

user friendly API
modular object model
working timeouts and reconnecting
connection pool support
TCP, SSL, UDP and UNIX sockets

Python 3 note

To use UNIX sockets with Python 3 please use Twisted framework 15.3.0 and above.

Dependencies

msgpack-python https://pypi.python.org/pypi/msgpack-python/
Twisted http://twistedmatrix.com/trac/

Installation

% pip install txmsgpackrpc

Debian packages are available on project's Releases page.

TCP example

Computation of PI using Chudnovsky algorithm in subprocess. For details, see http://www.craig-wood.com/nick/articles/pi-chudnovsky/.

Results

Computation of PI with 5 places finished in 0.022390 seconds

Computation of PI with 100 places finished in 0.037856 seconds

Computation of PI with 1000 places finished in 0.038070 seconds

Computation of PI with 10000 places finished in 0.073907 seconds

Computation of PI with 100000 places finished in 6.741683 seconds

Computation of PI with 5 places finished in 0.001142 seconds

Computation of PI with 100 places finished in 0.001182 seconds

Computation of PI with 1000 places finished in 0.001206 seconds

Computation of PI with 10000 places finished in 0.001230 seconds

Computation of PI with 100000 places finished in 0.001255 seconds

Computation of PI with 1000000 places finished in 432.574457 seconds

Computation of PI with 1000000 places finished in 402.551226 seconds

DONE

Server

from __future__ import print_function

from collections import defaultdict
from twisted.internet import defer, reactor, utils
from twisted.python import failure
from txmsgpackrpc.server import MsgpackRPCServer


pi_chudovsky_bs = '''
"""
Python3 program to calculate Pi using python long integers, binary
splitting and the Chudnovsky algorithm

See: http://www.craig-wood.com/nick/articles/pi-chudnovsky/ for more
info

Nick Craig-Wood <nick@craig-wood.com>
"""

import math
from time import time

def sqrt(n, one):
    """
    Return the square root of n as a fixed point number with the one
    passed in.  It uses a second order Newton-Raphson convgence.  This
    doubles the number of significant figures on each iteration.
    """
    # Use floating point arithmetic to make an initial guess
    floating_point_precision = 10**16
    n_float = float((n * floating_point_precision) // one) / floating_point_precision
    x = (int(floating_point_precision * math.sqrt(n_float)) * one) // floating_point_precision
    n_one = n * one
    while 1:
        x_old = x
        x = (x + n_one // x) // 2
        if x == x_old:
            break
    return x

def pi_chudnovsky_bs(digits):
    """
    Compute int(pi * 10**digits)

    This is done using Chudnovsky's series with binary splitting
    """
    C = 640320
    C3_OVER_24 = C**3 // 24
    def bs(a, b):
        """
        Computes the terms for binary splitting the Chudnovsky infinite series

        a(a) = +/- (13591409 + 545140134*a)
        p(a) = (6*a-5)*(2*a-1)*(6*a-1)
        b(a) = 1
        q(a) = a*a*a*C3_OVER_24

        returns P(a,b), Q(a,b) and T(a,b)
        """
        if b - a == 1:
            # Directly compute P(a,a+1), Q(a,a+1) and T(a,a+1)
            if a == 0:
                Pab = Qab = 1
            else:
                Pab = (6*a-5)*(2*a-1)*(6*a-1)
                Qab = a*a*a*C3_OVER_24
            Tab = Pab * (13591409 + 545140134*a) # a(a) * p(a)
            if a & 1:
                Tab = -Tab
        else:
            # Recursively compute P(a,b), Q(a,b) and T(a,b)
            # m is the midpoint of a and b
            m = (a + b) // 2
            # Recursively calculate P(a,m), Q(a,m) and T(a,m)
            Pam, Qam, Tam = bs(a, m)
            # Recursively calculate P(m,b), Q(m,b) and T(m,b)
            Pmb, Qmb, Tmb = bs(m, b)
            # Now combine
            Pab = Pam * Pmb
            Qab = Qam * Qmb
            Tab = Qmb * Tam + Pam * Tmb
        return Pab, Qab, Tab
    # how many terms to compute
    DIGITS_PER_TERM = math.log10(C3_OVER_24/6/2/6)
    N = int(digits/DIGITS_PER_TERM + 1)
    # Calclate P(0,N) and Q(0,N)
    P, Q, T = bs(0, N)
    one = 10**digits
    sqrtC = sqrt(10005*one, one)
    return (Q*426880*sqrtC) // T

if __name__ == "__main__":
    import sys
    digits = int(sys.argv[1])
    pi = pi_chudnovsky_bs(digits)
    print(pi)
'''


def set_timeout(deferred, timeout=30):
    def callback(value):
        if not watchdog.called:
            watchdog.cancel()
        return value

    deferred.addBoth(callback)

    watchdog = reactor.callLater(timeout, defer.timeout, deferred)


class ComputePI(MsgpackRPCServer):

    def __init__(self):
        self.waiting = defaultdict(list)
        self.results = {}

    def remote_PI(self, digits, timeout=None):
        if digits in self.results:
            return defer.succeed(self.results[digits])

        d = defer.Deferred()

        if digits not in self.waiting:
            subprocessDeferred = self.computePI(digits, timeout)

            def callWaiting(res):
                waiting = self.waiting[digits]
                del self.waiting[digits]

                if isinstance(res, failure.Failure):
                    func = lambda d: d.errback(res)
                else:
                    func = lambda d: d.callback(res)

                for d in waiting:
                    func(d)

            subprocessDeferred.addBoth(callWaiting)

        self.waiting[digits].append(d)

        return d

    def computePI(self, digits, timeout):
        d = utils.getProcessOutputAndValue('/usr/bin/python', args=('-c', pi_chudovsky_bs, str(digits)))

        def callback((out, err, code)):
            if code == 0:
                pi = int(out)
                self.results[digits] = pi
                return pi
            else:
                return failure.Failure(RuntimeError('Computation failed: ' + err))

        if timeout is not None:
            set_timeout(d, timeout)

        d.addCallback(callback)

        return d


def main():
    server = ComputePI()
    reactor.listenTCP(8000, server.getStreamFactory())

if __name__ == '__main__':
    reactor.callWhenRunning(main)
    reactor.run()

Client

from __future__ import print_function

import sys
import time
from twisted.internet import defer, reactor, task
from twisted.python import failure

@defer.inlineCallbacks
def main():
    try:

        from txmsgpackrpc.client import connect

        c = yield connect('localhost', 8000, waitTimeout=900)

        def callback(res, digits, start_time):
            if isinstance(res, failure.Failure):
                print('Computation of PI with %d places failed: %s' %
                      (digits, res.getErrorMessage()), end='\n\n')
            else:
                print('Computation of PI with %d places finished in %f seconds' %
                      (digits, time.time() - start_time), end='\n\n')
            sys.stdout.flush()

        defers = []
        for _ in range(2):
            for digits in (5, 100, 1000, 10000, 100000, 1000000):
                d = c.createRequest('PI', digits, 600)
                d.addBoth(callback, digits, time.time())
                defers.append(d)
            # wait for 30 seconds
            yield task.deferLater(reactor, 30, lambda: None)

        yield defer.DeferredList(defers)

        print('DONE')

    except Exception:
        import traceback
        traceback.print_exc()
    finally:
        reactor.stop()

if __name__ == '__main__':
    reactor.callWhenRunning(main)
    reactor.run()

Multicast UDP example

Example servers join to group 224.0.0.5 and listen on port 8000. Their only method echo returns its parameter.

Client joins group to 224.0.0.5, sends multicast request to group on port 8000 and waits for 5 seconds for responses. If some responses are received, protocol callbacks with tuple of results and individual parts are checked for errors. If no responses are received, protocol errbacks with TimeoutError.

Because there is no common way to determine number of peers in group, MsgpackMulticastDatagramProtocol always wait for responses until waitTimeout expires.

$ # setup multicast routing
$ ip route add 224.0.0.0/4 dev eth0
$ echo 1 > /proc/sys/net/ipv4/ip_forward
$
$ # start servers listening on port 8000
$ python examples/tx_rpc_server_udp_multicast.py &
[1] 3584
$ python examples/tx_rpc_server_udp_multicast.py &
[2] 3585
$ python examples/tx_rpc_server_udp_multicast.py &
[3] 3586
$ python examples/tx_rpc_server_udp_multicast.py &
[4] 3587
$ python examples/tx_rpc_server_udp_multicast.py &
[5] 3588
$
$ # execute client
$ python examples/tx_rpc_client_udp_multicast.py
Received results from 5 peers
$

Server

from twisted.internet import defer, reactor, task
from txmsgpackrpc.server import MsgpackRPCServer


class EchoRPC(MsgpackRPCServer):

    @defer.inlineCallbacks
    def remote_echo(self, value, delay=None, msgid=None):
        if delay is not None:
            yield task.deferLater(reactor, delay, lambda: None)
        defer.returnValue(value)


def main():
    server = EchoRPC()
    reactor.listenMulticast(8000, server.getMulticastProtocol('228.0.0.5', ttl=5),
                            listenMultiple=True)

if __name__ == '__main__':
    reactor.callWhenRunning(main)
    reactor.run()

Client

from __future__ import print_function

from twisted.internet import defer, reactor

@defer.inlineCallbacks
def main():
    try:

        from txmsgpackrpc.client import connect_multicast

        c = yield connect_multicast('228.0.0.5', 8000, ttl=5, waitTimeout=5)

        data = {
                    'firstName': 'John',
                    'lastName': 'Smith',
                    'isAlive': True,
                    'age': 25,
                    'height_cm': 167.6,
                    'address': {
                      'streetAddress': "21 2nd Street",
                      "city": 'New York',
                      "state": 'NY',
                      'postalCode': '10021-3100'
                    },
                    'phoneNumbers': [
                      {
                        'type': 'home',
                        'number': '212 555-1234'
                      },
                      {
                        'type': 'office',
                        'number': '646 555-4567'
                      }
                    ],
                    'children': [],
                    'spouse': None
                  }

        results = yield c.createRequest('echo', data)

        assert isinstance(results, tuple)

        print('Received results from %d peers' % len(results))

        for i, result in enumerate(results):
            if result != data:
                print('Result %d mismatch' % i)
                print(result)

    except Exception:
        import traceback
        traceback.print_exc()
    finally:
        reactor.stop()

if __name__ == '__main__':
    reactor.callWhenRunning(main)
    reactor.run()