[Python-Dev] Minor socket timeout quibble - timeout raises
Fri, 12 Jul 2002 14:56:11 -0600
Guido van Rossum wrote:
> > To distinguish a timeout error, the caller can check s->sock_timeout
> > when a non-blocking mode error occured, or just return an error code
> > from internal_select() (I guess you must have your reason to taken it
> > out in the first place)
> I don't understand your first suggestion. Not all errors mean that
> the timeout triggered!
For example, when accept() fail with error code EAGAIN and
s->sock_timeout = 5.0, it indicates timeout. Same for connect() fail
with EINPROGRESS. Anyway, on second thought, it is messy.
> > How about the following (assume we have socket.setDefaultTimeout()):
> > import socket
> > import urllib
> > socket.setDefaultTimeout(5.0)
> > retry = 0
> > url = 'some url'
> > while retry < 3:
> > try:
> > file = urllib.urlretrieve(url)
> > except socket.TimeoutError:
> > if retry == 2:
> > print "Server too busy, given up!"
> > raise
> > else:
> > print "Server busy, retry!"
> > retry += 1
> > else:
> > break
> > MS IIS behave strangely to http request. When the server is very busy,
> > it will randomly drop some requests without disconnecting the client.
> > So the best approach for the client is to timeout and retry. I guess
> > that might be the reason why people needed timeoutsocket in the first
> > place.
> One of the reasons (there are lots of reasons why a connect or receive
> attempt may be very slow to time out, or even never time out).
> Of course, this stll doesn't distinguish between a timeout from
> connect() and one from recv().
I think you are right on the point. Client might not care if the call
is timeouted on connect() or recv(). In this case a timeout error comes
> Have you ever written code like this?
Yes I did.
> > I am struggling with the test case for the new socket code. The timeout
> > test case I've send you works with the old socketmodule.c (attached),
> > but not with the lastest version (on linux or windows). It's strange,
> > your new implementation looks much cleaner.
> No need to attach copies of old versions -- just give me the CVS
> revision number. :-)
socketmodule.c version 1.225
socketmodule.h version 1.7
> > Please bear with me a bit longer for a patch :.(
> Anyway, I have no time to play with this right now, so I'm glad you
> aren't giving up just yet. :-)
It is very painful indeed (Tim was so right).
> --Guido van Rossum (home page: http://www.python.org/~guido/)