MESSAGE
| DATE | 2021-08-25 |
| FROM | Brad Van Sickle
|
| SUBJECT | Re: [Hangout - NYLXS] Sharing read/WRITE data between threads?
|
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
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