Re: Recommendations on Locking/SharedMem/IPC modules

Stephen Adkins wrote:
> I am looking for recommendations for modules which handle
> cooperative resource locking across processes (similar to
> semaphores in Unix).

The kind of locking you're talking about may not be implemented 
conveniently in the same modules that do data sharing well.  For 
example, Cache::Cache has no separate locking interface since it uses 
atomic renaming instead.

> "Cooperative" is in contrast to something like "flock"
> where the operating system knows about the resource being
> locked and can actually enforce the locking.

Hmmm.  I thought flock was strictly voluntary.  The OS knows about it, 
but does nothing to enforce it.  You have to write your code to ask for 
permission to change a file by attempting to flock it yourself.

I'm working on an article that will cover the best options for data 
sharing, but I don't have hard data yet.  There was a thread about this 
on the mod_perl list with some basic benchmark numbers.  It starts here:
http://groups.yahoo.com/group/modperl/message/39954

The best performers were IPC::MM and Cache::Mmap.

If you decide to go with Cache::Cache, you may want to use the internal 
modules Cache::FileBackend or Cache::SharedMemoryBackend, because they 
give better performance when you just need shared data and don't need 
the cache interface.

- Perrin