[dev] Re: [surf] cookie race condition for multiple instances?

On Sun, Aug 30, 2009 at 9:53 PM, Ray Kohler<ataraxia937_AT_gmail.com> wrote:
> I'm curious as to whether a race condition is created for access to
> the soup cookie jar file when multiple instances of surf are running.
> libsoup's docs don't mention any safety mechanisms for this object, so
> I'm expecting trouble is possible. Does anyone actually know for sure?

To answer my own question, after reading libsoup's source, I can say
that this race does exist. Adding a cookie opens the file for append
and writes it. Deleting one rewrites the file and filters the target
cookie while doing so. Updating a cookie is just a delete and an add.
Both kinds of writes open the file immediately before writing and
close it immediately afterward, so at least it's not as big a problem
as if it kept it open for the lifetime of the session.

The easiest way to workaround this (suckless or not) is to use
libsoup's sqlite cookie jar instead, so that's what I'm going to do.
There is still another problem not solved by this - running sessions
sharing a cookie jar trust their own memory cache of the file's
contents never to get stale. Using sqlite will make sure the cookie
jar ends up as the union of the outputs of all sessions, but it won't
allow all these sessions to take advantage of each other's changes in
real time. I don't consider this to be anywhere near as much of a
problem as corruption or loss of data from the on-disk jar, though.
Received on Fri Sep 04 2009 - 01:52:02 UTC