Shibboleth Developers

[André Cruz <>]

On May 4, 2007, at 4:22 PM, Scott Cantor wrote:

> > You could store the version number separately and increment it with
> > the memcache methods but i think eliminating race conditions without
> > locks is next to impossible.
>
> Yes, I think you're quite right.

I think we missed something. The add function, since it returns an  
error if the key is already set, can be used to create locks:

while ( ! memcache->add("LOCK:ID", 1) {
        sleep();
}

# lock obtained
# fetch value and store new one

memcache->del("LOCK:ID");
# lock released


There... Locks. :)

André