[Koha] n-Tier deployment of Koha

[Victor Grousset/tuxayo]

Hi :)

On 22-07-28 02:49, dcook at prosentient.com.au wrote:
> Off the top of my head, technically you could have a load balancer in front of  multiple Koha application servers. You'd want to make sure that the cronjobs are only running on 1 application server though. You also would probably want to use an external Elasticsearch cluster since Zebra would be a bottleneck. In theory, you could use a multi-master MySQL/MariaDB database cluster, but I don't know if anyone has done that (and I'd be concerned about the "eventual consistency" of multi-master setups). If you wanted to a master-replica cluster, you'd need to patch Koha to allow for read-only connections (for things like the Reports module); at the moment, Koha can only use 1 read/write database connection.

Are there MariaDB front end/load balancers than could route the read 
queries to one of the multiple read only replicas? And the write queries 
to the main server. That would allow to not change apps.

So in the end the only non-horizontally-scalable thing would be DB 
writes? (unless multi-master eventual consistency works)

> In the long-term I'd love to make Koha easier to scale horizontally (and ideally deploy as a load-balanced containerized application) but there's work to do and not much demand for it from libraries, so I don't think it's a priority for devs at the moment, unfortunately.

Ideally the largest Koha installations would have contributed 
back/funded scalability improvement. Maybe they did, I don't know the 
history. So it's a matter of priority of upstreaming changes while 
having already a lot to deal with. That might show the largest 
installations are underfunded and have no margin for upstreaming :(

Cheers,

-- 
Victor Grousset/tuxayo