select() call and filedescriptor out of range in select error
steve-REMOVE-THIS at cybersource.com.au
Thu Sep 16 07:00:50 CEST 2010
On Wed, 15 Sep 2010 21:05:49 -0700, k3xji wrote:
> Hi all,
> We have a select-based server written in Python. Occasionally, maybe
> twice a month there occurs a weird problem, select() returns with
> filedescriptor out of range in select() error. This is of course a
> normal error and handled gracefully. Our policy is to take down few
> users for select() to handle the next cycle. However, once this error
> occurs, this also fails too:
> self.__Socket's is the very basic list of sockets we use in our IO loop.
> The call fails with:
> remove(x): x not in list
Please show the *exact* error message, including the traceback, by
copying and pasting it. Do not retype it by hand, or summarize it, or put
it into your own words.
> First of all, in our entire application there is no line of code like
> remove(x), meaning there is no x variable.
Look at this example:
>>> sockets = 
>>> sockets.remove("Hello world")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: list.remove(x): x not in list
"x" is just a placeholder. It doesn't refer to an actual variable x.
> Second, the Exception shows
> the line number containing above code. So self.__Sockets.remove(socket)
> this fails with remove(x): x not in list....
> I cannot understand the problem. It happens in sporadic manner and it
> feels that the ValueError of select() call somehow corrupts the List
> structure itself in Python? Not sure if something like that is possible.
Anything is possible, but it's not likely. What's far more likely is that
you have a bug in your code, and that somehow, under rare circumstances,
it tries to remove something from a list that was never inserted into the
list. Or it tries to remove it twice.
My guess is something like this:
socket = get_socket()
# later on
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