[Zope] Re: Running more than one instance on windows often block each other

[Sune B. Woeller]

Tim Peters wrote:
> The attached hasn't failed on my box (Win XP Pro SP2, Python 2.3.5)
> for about two hours, running it in 3 processes.  Was using 2 processes
> before; discovered it was much easier to provoke problems using 3; but
> the # of ephemeral ports in use increases too, typically hovering
> between 7-8 thousand after reaching steady state.
> 
> I'll let it run the rest of today, and start changing ZODB code if it
> still looks good.  I hope someone(s) else will then volunteer to port
> the Windows changes to all the copies of Medusa code in the various
> active Zope trunks and branches.

I have been running 8 simultaneous processes with socktest29() for
12 hours, on my xp box. No problems except for an occasional "Address already in 
use".



> 
> This suffers from what I still believe to be bugs in the Windows
> socket implementation, but there is only one symptom I see with this,
> and the code uses try/except to implement what appears to be a
> reliable workaround.
> 
> import socket, errno
> import time, random
> 
> class BindError(Exception):
>     pass
> 
> def socktest29():
>     w = socket.socket()
> 
>     # Disable buffering -- pulling the trigger sends 1 byte,
>     # and we want that sent immediately, to wake up asyncore's
>     # select() ASAP.
>     w.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
> 
>     count = 0
>     while 1:
>         count += 1
>         # Bind to a local port; for efficiency, let the OS pick
>         # a free port for us.
>         # Unfortunately, stress tests showed that we may not
>         # be able to connect to that port ("Address already in
>         # use") despite that the OS picked it.  This appears
>         # to be a race bug in the Windows socket implementation.
>         # So we loop until a connect() succeeds (almost always
>         # on the first try).
>         a = socket.socket()
>         a.bind(("127.0.0.1", 0))
>         print 'b',
>         connect_address = a.getsockname()  # assigned (host, port) pair
>         a.listen(1)
>         try:
>             w.connect(connect_address)
>             print 'c',
>             break
>         except socket.error, detail:
>             if detail[0] != errno.WSAEADDRINUSE:
>                 # "Address already in use" is the only error
>                 # I've seen on two WinXP Pro SP2 boxes, under
>                 # Pythons 2.3.5 and 2.4.1.
>                 raise
>             # (10048, 'Address already in use')
>             # assert count <= 2 # never triggered in Tim's tests
>             if count >= 10:  # I've never seen it go above 2
>                 a.close()
>                 w.close()
>                 raise BindError("Cannot bind trigger!")
>             # Close `a` and try again.  Note:  I originally put a short
>             # sleep() here, but it didn't appear to help or hurt.
>             print
>             print detail, a.getsockname()
>             a.close()
>     
>     r, addr = a.accept()  # r becomes asyncore's (self.)socket
>     print 'a',
>     a.close()
>     print 'c',
> 
>     return (r, w)
> 
> sofar = []
> try:
>    while 1:
>        print '.',
>        stuff = socktest29()
>        sofar.append(stuff)
>        time.sleep(random.random()/10)
>        if len(sofar) == 50:
>            tup = sofar.pop(0)
>            r, w = tup
>            msg = str(random.randrange(1000000))
>            w.send(msg)
>            msg2 = r.recv(100)
>            assert msg == msg2, (msg, msg2, r.getsockname(), w.getsockname())
>            r.close()
>            w.close()
> except KeyboardInterrupt:
>    for tup in sofar:
>        for s in tup:
>            s.close()
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