Re: Recommendations on Locking/SharedMem/IPC modules

FYI.

I have added Resource Locking and Shared Storage to my components list.

   http://www.officevision.com/pub/p5ee/components.html#locking

Resource Locking

IPC::Locker - uses a lock daemon (lockerd, included) to 
              do network-wide unique resource locking
IPC::Semaphore (IPC::SysV) - uses System V Unix semaphores

Shared Storage

IPC::MM - interface to Ralf Engelschall's libmm library (cross-platform 
          shared mem), can "tie" multiple scalars and hashes into the 
          shared mem segment, locking available for the entire segment
DBI - can store a multi-level hash in a table if you serialize first
MLDBM (MLDBM+BerkeleyDB, MLDBM+GDBM) - store multi-level hash in a DBM 
          using Storable
MLDBM::Sync - same as MLDBM but with locking
IPC::Shareable - allows a tied var in shared mem, 1 var per shared mem 
          segment!, some locking, depends in SysV IPC
IPC::ShareLite - store()/fetch in shared mem, 1 var per shared mem 
          segment!, some locking, depends in SysV IPC
Cache::Mmap
Cache::Cache (Cache::FileCache, Cache::SharedMemoryCache)

If any others of you have additional suggestions, send them in and I'll
add them.

Stephen

At 03:38 PM 3/12/2002 -0500, Perrin Harkins wrote:
>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
>
>
>