Re: Sharing read/WRITE data between threads?

Or you can also consider using IPC::Shareable
<https://metacpan.org/pod/IPC::Shareable> if your system supports IPC.

Jacques Deguest

On 2021/08/25 17:11, Brad Van Sickle wrote:
> I've shared read-only data across threads many times a cheap and easy
> caching mechanims, but as I'm sure you've found in your research, the
> "copy-on-write" methodology employed by mod_perl prevents you from
> doing that for mutable data and I'm not aware of a way around that
> without fundamental changes to mod_perl itself.
>
> There are some very good reasons that mod_perl is architected that
> way.  You may very well have a specific use case that makes sharing
> mutable data in memory for a threaded application desirable, but I
> know that oftentimes when I've  tried to find ways to workaround a
> fundamental architectural element in a toolset, the best solution for
> me has ultimately been to rethink my approach rather than to wrestle
> the toolset into submission.
>
> In short, and although this isn't what you asked and I know next to
> nothing about your project, constraints or requirements... it sounds
> like you might want to consider a cache server
> (Redis/Varnish/Elasticache/etc...) and then solve the problem and
> proactively notify subscribed threads of changes if you need to.
>
>
>
>
> On 8/24/2021 7:50 PM, David Booth wrote:
>> I am using Apache/2.4.41 (Ubuntu), with mod_perl.  Apache uses
>> multiple threads, and I want to share read/WRITE data between
>> threads. (I.e., I want to be able to modify some shared data in one
>> thread, such that other threads can see those changes.)  In
>> "Practical mod_perl" Stas Bekman describes how to share read-only
>> data between threads, but says nothing about how to share WRITABLE
>> data between threads.
>>
>> Any clues about how this can be done?  I've searched high and low and
>> found nothing.  I will also want to know what mechanisms are
>> available to coordinate access to that shared data, such as locks or
>> semaphores.
>>
>> I also posted this message to StackOverflow, but got no response so far:
>> https://stackoverflow.com/questions/68901260/how-to-share-read-write-data-in-mod-perl-apache2
>>
>>
>> Any help would be appreciated!
>>
>> Thanks,
>> David Booth