@metajack's post saved from codexon Category: Internet, Programming, Python The recent server benchmark posted here comparing Erlang, Haskell, and Python understandably upset many people. Today we will move away from polarizing benchmarks and more about features. Even though Erlang may not be the fastest language, it still has at least one grea…

gistfile1.txt

import os
import time
import socket
import sys
import fcntl
import _multiprocessing
from multiprocessing import Pipe
 
# global pipe variable
pipe       = None
spare_pipe = None
 
def PipeFromFD(fd):
    return _multiprocessing.Connection(fd)
 
def recordPipe(p1, p2):
    with open('fd.txt', 'w') as f:
        f.write('%s,%s' % (p1.fileno(), p2.fileno()))
 
def upgrade():
    os.spawnlp(os.P_NOWAIT, 'python', 'python', sys.argv[0], '-upgrade')
 
def upgradeBootstrap():
    global pipe, spare_pipe
    with open('fd.txt', 'r') as f:
        p1, p2 = (int(fd) for fd in f.read().split(','))
        pipe = PipeFromFD(p1)
        spare_pipe = PipeFromFD(p2)
 
    recordPipe(spare_pipe, pipe)
    pipe.send("I am upgraded!")
 
if __name__ == '__main__':    
 
    if '-upgrade' in sys.argv:
        upgradeBootstrap()
    else:
        pipe, spare_pipe = Pipe()
        recordPipe(spare_pipe, pipe)
 
    pid = os.getpid()
    print '%i: Version 1. Upgrade in 5 seconds.' % pid
    time.sleep(5)
    print '%i: Upgrading' % pid
    upgrade()
    print '%i: Message from new process: %s' % (pid, pipe.recv())
    print '%i: Upgrade Complete. Exiting' % pid

Example Output

user@test:/mnt/shared$ python upgrade.py
22930: Version 1. Upgrade in 10 seconds.
22930: Upgrading
22971: Version 2. Upgrade in 10 seconds.
22930: Message from new process: I am upgraded!
22930: Upgrade Complete. Exiting
user@test:/mnt/shared$ 22971: Upgrading
23025: Version 3. Upgrade in 10 seconds.
22971: Message from new process: I am upgraded!
22971: Upgrade Complete. Exiting
killall python