How to Build a SaaS Application Block by Block | Hacker News Reader

How to Build a SaaS Application Block by Block

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93 pointsjoeyespo13 comments

> A monolith is an organism-like distributed set of services with predictable behavior. That predictability makes it an ideal foundation for SaaS architecture. With your monolith in place...

Wat? Title should be: "How to do tenant isolation and audit logs"; this is in no way a sketch of how to build a SaaS application.

Totally agree with your point, this is an attention grabber title for a poor article.

Cool, seems about right and that is similar to how I did multitenancy in Django years ago. If anyone reads this and has a good answer, I’m still curious on one question that I was never able to answer (due to my limited knowledge of Postgres and other databases).

Is there a good solution for automatically scoping a query to a tenant at the database-level (perhaps using a custom extension or PL/PgSQL to rewrite the queries), assuming the tenant_id is in the SQL request?

I guess I'm asking if it's possible to move this functionality to the database layer with something like PL/pgSQL or the Postgres rule system... both of which I know very little about.

    @db.event.listens_for(TenantQuery, 'before_compile', retval=True)
    def ensure_tenant_constrained(query):
        for desc in query.column_descriptions:
            if hasattr(desc['type'], 'tenant') and \
                query.current_tenant_constrained:
                  query = query.filter_by(tenant=get_current_tenant())
        return query

Of course the only point in asking such a question is if there's a good reason to do it, and I can't remember why I looked into this in the first place (it's been more than a couple of years).

Maybe something like https://schinckel.net/2017/12/20/django-multitenancy-using-p...

Ahhh nice, I will check this and the other guy's links out!

That was a good read, I am going to take a look at his Github now and see where he got with it. Thanks

You can use postgres' row level security to do this: https://www.postgresql.org/docs/9.5/ddl-rowsecurity.html

I've used RLS and it works great for this. Make sure you have your tenant_id on all tables, which makes it easy to partition later. I think you can even do per-tenant backups/archives like this with pgdump, by using a specific user.

Here's an up-to-date example using Rails and Postgres row level security: https://github.com/kuroda/multi_tenancy

Oracle has Virtual Private Database https://docs.oracle.com/cd/B28359_01/network.111/b28531/vpd....

If you have a way of 'presetting' in advance the number of tenants.

You could use Postgres's partial indexes. (basically an index scoped per tenant).

Your 'WHERE' clauses would need to include the field indexed by those partial indexes.

https://devcenter.heroku.com/articles/postgresql-indexes#par...

I have not thought more though this, but may be combining that with the PG 11s partitioning, would get me even closer to tenant-specific archiving/backup and other admin tasks beyond query.

Its super simple to do this In Spring Boot using AOP

If those are all blocks required to build a SaaS app I would be a happy man.

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