[Ur] Multitenancy

[Simon Van Casteren]

I considered it briefly as I was doing some research on the topic. It's the
first time I'll be running and deploying a SaaS app myself (I've so far
always been on the programming side only) so it felt more natural to me to
keep everything inside a single application. Running the application right
now consists of me ssh'ing into a Linode and running the exe by hand. If I
want to split this into one application per database (which does guarantee
data security better, that's really nice) then deployment seems to become
much more complicated.

But let's say I do go that route. Is using one of the new deployment tools
a good idea for a just-started scenario? I appreciate how ur/web uses very
basic and simple tools, eg: Using curl in the Worldffi project to do HTTP
requests, not having editor tooling but having the compiler use standard
error formatting so emacs picks it up automatically. This is in strong
contrast to the javascript community where I normally reside, which likes
to re-implement things a lot. So I'd like to know what advice the community
has on the right tools for setting up a new application and database
automatically (probably via the C FFI?) and then running and updating them
together. I would like to note that adding and running new clients without
any manual work is strongly preferred.

Because I don't have any idea of how I would handle this adding and
deploying of clients, I can't weigh the two alternatives: Complicating the
app with tenantIds, or complicating the deployment with seperate apps.

2018-05-13 15:31 GMT+02:00 Adam Chlipala <adamc at csail.mit.edu>:

> Can you explain why you don't want to run separate applications with
> separate databases?
>
>
> On 05/13/2018 05:50 AM, Simon Van Casteren wrote:
>
> Hi,
>
> I'm in the process of making a new application for music schools, using
> ur/web for front and backend. I'm at the point where I have two customers
> and am starting to implement support for multiple clients/tenants in one DB
> (postgres). I've been planning to implement multitenancy from the start,
> but haven't had the time yet.
>
> Has anyone implemented a form of multitenancy in ur/web before?
>
> I see two areas that need consideration.
>
> 1. Deciding which user belongs to which tenant. Ideally I'd have a
> seperate url for each tenant that I can give out to my clients (=the
> schools), do some dns magic to send them all to the same exe, extract the
> tenantname from the url and save the tenantId in a cookie. Also ideally,
> the user's url would not change, ie. All urls should go to
> myschool.coolschools.be during a session, not getting redirected at all.
> This is all in an ideal situation of course.
>
> 2. Database access: I'll have tenantId columns in all tables + foreign
> keys and indexes on these columns. I'm a bit afraid I'll forget adding
> tenantId = cookie.tenantid somewhere, so I was thinking I could make a
> function that takes a sql_exp and a tenantId and adds these clauses to all
> tables involved. Not 100% sure that will work but I think it's possible, I
> haven't had to dive into the internals of sql_exp yet. Secondly, I wonder
> if I can somehow declare my endpoints to be tenantdepandent (all but the
> most general will be) maybe via newtyping the transaction datatype and then
> allowing the execute only sql queries that have the above function applied.
> Just dreaming out loud here.
>
> I'd be very interested in any ideas or examples!
>
> Simon
>
>
>
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