[Koha] n-Tier deployment of Koha

[Coehoorn, Joel]

In my experience, you're usually MUCH better off adding more resources to
your single database server.

For any given server purchase, there is a cost per performance breaking
point where it starts to make more sense to buy two (or more) smaller
servers for the same performance vs one large server. It's been a couple
years, but the last time I checked the breaking point was something like
64GB RAM and 2 16-core CPUs. You can serve a lot of books to a lot of
patrons on a machine like that.

Joel Coehoorn
Director of Information Technology
York University of Nebraska


On Wed, Jul 27, 2022 at 7:49 PM <dcook at prosentient.com.au> wrote:

> Hi Admire,
>
> You'll probably have more luck asking on the dev listserv:
> koha-devel at lists.koha-community.org. However, I'll try to offer some
> insight here. I'm also CCing in Mengu who has probably the biggest
> horizontally scaled out Koha in the world.
>
> 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.
> You'd also need to move your RabbitMQ server to an external server which is
> problematic with the koha-common package at the moment (but there are
> ways). (Note: I may be missing another horizontal scaling issue, but these
> are what come to mind at the moment. You might need to use a network share
> for some file system resources in /var/koha/* but I can't recall off the
> top of my head.)
>
> It would be much easier to scale vertically. I'd suggest you do some
> analysis to see where your key pain points are.
> - Out of the box, Koha only uses 2 Starman/Plack workers, so if it's a
> case where your Koha is overwhelmed by legitimate traffic, I'd recommend
> adding more Starman/Plack workers via koha-conf.xml (if you have the CPU
> and RAM to spare).
> - If your Koha is slow, you might want to look at your database's I/O
> performance as well. Using quality SSDs can make a huge difference for
> database driven applications. (Note also that having MySQL/MariaDB on an
> external server is a common practice but technically speaking it does add
> some latency to database transactions which you wouldn't have if you ran
> MySQL/MariaDB on the same server and used Unix sockets. For very large Koha
> databases, we've noticed that having an external DB server adds too much
> latency.)
> - If you're getting a lot of traffic, you should check to see how much
> traffic is from bots. You might need to implement something like fail2ban
> to block bots that put too much load on your system. Typically, I find when
> Koha is overwhelmed, it's due to bots. (You can experiment with a
> robots.txt file to help with this but it's not a completely effective
> solution.)
>
> There's lots of things to explore.
>
> 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.
>
> Anyway, I hope that helps!
>
> David Cook
> Senior Software Engineer
> Prosentient Systems
> Suite 7.03
> 6a Glen St
> Milsons Point NSW 2061
> Australia
>
> Office: 02 9212 0899
> Online: 02 8005 0595
>
> -----Original Message-----
> Message: 10
> Date: Wed, 27 Jul 2022 16:28:12 +0100
> From: Admire Mutsikiwa <amutsikiwa at uzlib.uz.ac.zw>
> To: koha at lists.katipo.co.nz
> Subject: [Koha] n-Tier deployment of Koha
> Message-ID:
>         <CAD4nctbymX-UfziZr67h-4p4O0GBPapecRCXfc=
> obHtmiFt0VQ at mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> My Koha implementation is sometimes overwhelmed  as it is a two-tier
> implementation with a database on one server and a Koha application on
> another server.  I am wondering if it is possible to have a 3 or 4 tier
> deployment architecture, with for instance, having a load balancer, koha
> application server and a clustered MySQL/Mariadb implementation.
>
> Kind Regards,
>
> --
>
>
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