Guido van Rossum wrote:
I just noticed in the development docs that when a timeout on a socket occurs, socket.error is raised. I rather liked the idea that a different exception was raised for timeouts (I used Tim O'Malley's timeout_socket module). Making a TimeoutError exception a subclass of socket.error would be fine so you can catch it with existing code, but I could see recovering differently for a timeout as opposed to other possible errors:
sock.settimeout(5.0) try: data = sock.recv(8192) except socket.TimeoutError: # maybe requeue the request ... except socket.error, codes: # some more drastic solution is needed ...
+1 on your suggestion. Anyway, under windows, the current implementation returns incorrect socket.error code for timeout. I am working on the test suite as well as a fix for problem found. Once the code is bug free maybe we can put the TimeoutError in.
I will leave it to Guido for the approval of the change. When he comes back from his holiday.
The way I restructured the code it is impossible to distinguish a timeout error from other errors; you simply get the "no data available" error from the socket operation. This is the same error you'd get in non-blocking mode.
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)
Before I recomplicate the code so that it can raise a separate error when the select fails, I'd like to understand the use case better. Why would you want to make this distinction? Requeueing the request (as in Skip's example) doesn't make sense IMO: you set the timeout for a reason, and that reason is that you want to give up if it takes too long. If you really intend to retry you're better of disabling the timeout!
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.
If you really want to, you can already distinguish the timeout case, because you get an EAGAIN error then (maybe something else on Windows -- Bernard, if you have a fix for that, please send it to me).
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.
Please bear with me a bit longer for a patch :.(
So a -0 unless more evidence is brought forward.
--Guido van Rossum (home page: http://www.python.org/%7Eguido/)