Protecting reserved roles with PostgreSQL Hooks

Supabase gives you free Postgres instances with full access iirc

I use to swear on RDS being an AWS certified person. AWS taugh us managed is the best and always put warning when you want to self hosted.

Then recently at my small company(an email forwarding app that process 500K email daily https://hanami.run) I want to cut cost and go with dedicated server for our Postgres database.

At that moment, so many cool thing appear. You suddenly give super power to tune yoru database however you like.

On the other hand, RDS and multi-az deployment is just DNS failure at the end of day. You still have to handle stuff like restarting the app to make sure it got the right DNS after RDS failover.

So at the end of day, pick a hosting provider with reliable uptime(look at their history status page about outage in term of network/power). Tune postgres use tool like https://www.pgconfig.org/#/?max_connections=100&pg_version=1...

Add 2 read replicas(it takes like 10 commands to do that in modern postgres) for streaming replication.

Practice failover(promote read replica to master) once per month.

Then you will be good.

Speaking for myself, I tried managed solutions at the major cloud providers. Way overpriced and not that performant.

I then decided to go back to running my own database but this time in a docker container on k3s on bare metal. A few hours fiddling with the config upon launch and that's it. Rock solid, way more performant because I can tweak the config to my specific needs.

In the 2 years I have been running a MySQL server on k3s, I have about 60-90 seconds of down time. Caused by 3 separate instances where the db became unresponsive and k3s rebooted it. Most likely just some tweaks i need to make with the health check timeouts.

It has been more set it and forget than a managed solution and about 20% the cost.

You mean event triggers[1] right?

For the problem mentioned in the blog post — protecting roles — it's not possible to use event triggers because PostgreSQL doesn't fire[2] a DDL event for `CREATE/ALTER/DROP ROLE`.

If an event for role modification was added, then maybe the same could be accomplished with event triggers(perhaps in pure SQL). Though hooks will always be more strict, since you can enforce conditions by preloading the extension in C code, without custom SQL. Also, hooks can enforce a condition even in presence of superusers[3], something that event triggers can't because a superuser can drop them.

[1]: https://www.postgresql.org/docs/current/sql-createeventtrigg...

[2]: https://www.postgresql.org/docs/current/event-trigger-matrix... (full list of events fired)

[3]: https://paquier.xyz/postgresql-2/hooks-in-postgres-super-sup... (example hook that does this)

Not a 100% technically correct answer most likely but first look suggests they hook into the statement preprocessing pipeline. In the example, they’re hooking into the ALTER ROLE statement and deny execution if the role is a protected one. I don’t think this can be done with triggers without creating triggers on system tables and knowing the exact places where postgres would try to make changes. This seems to be an ott solution and probably a pretty bulletproof one.

Very timely article, I wonder if this works with yugabyte...