supavisor VS walex

WalEx instead of pub/sub (listen/subscribe): https://github.com/cpursley/walex

Supavisor connection pooler: https://github.com/supabase/supavisor

To make use of your read replicas, copy your connection string for the read replica, update your apps to use the new read replica and you are done! A unique connection pool is also provisioned for each read replica via Supavisor.

[I'm on the supabase team]

You can find the code/docs here: https://github.com/supabase/supavisor

This release adds support for

- SQL Parsing

- Load balancing

- support for named prepared statement

- query cancellation

It's also now available on all new databases in Supabase. For some more background on scalability, we have some benchmarks available here:

https://supabase.com/blog/supavisor-1-million

PgBouncer maintainer here, so obviously biased. But I think currently PgBouncer should still be the default connection pooler that you choose. There's a few newer options: Odyssey, pgcat, and supavisor. But all focus on a solving 1 or 2 specific problems that PgBouncer did not solve well, while not solving many of the other problems that PgBouncer does solve. So if you have the exact same requirements as the authors of those tools, then switching might be good. But otherwise you should probably continue using PgBouncer.

Supavisor specifically is really immature. It's missing some really core functionality like query cancellations: https://github.com/supabase/supavisor/issues/174

I did a talk on this exact topic at PGConf NYC recently. My slides are here: https://github.com/JelteF/slides/raw/main/2023-10-05-future-...

If you are interested in exploring Supavisor's potential or want to implement its scalability in your upcoming project, check out the GitHub repository to know more.

Phoenix.PubSub is basically a noop service. It really just works. You should try it!

If discovering nodes is difficult in your env, try using a listen/notify libcluster strategy:

https://github.com/supabase/supavisor/blob/main/lib/cluster/...

[2] https://github.com/supabase/supavisor

Supavisor

The WAL CDC approach: https://github.com/cpursley/walex?tab=readme-ov-file#publica...

CREATE PUBLICATION news_item FOR TABLE news WHERE (topic IS "AAPL");

What do you mean testing with processes?

I won't suggest these are the best written tests, but I test various processes, supervisors, etc like this:

https://github.com/cpursley/walex/blob/master/test/walex/sup...

You don’t send the entire WAL, just what you subscribe to - and you can even filter via SQL: https://github.com/cpursley/walex?tab=readme-ov-file#publica...

What we do is much if the business logic in Postgres. But then there’s all the other stuff like external integrations, etc.

We handled that by having an Even system built on the Postgres WAL that we use like a callback system.

I put together a little library in Elixir (that originally started out as forked Supabase realtime) for this:

https://github.com/cpursley/walex

Recently added the ability to configure WalEx to forward events to webhooks or EventRelay (so you don’t need to know Elixir).

If you're using Elixir, check out https://github.com/cpursley/walex

I've actually been thinking about turning this idea into a product where you can just point it at your postgres database and select the tables you want to listen to (with filters, like you describe). And have that forwarded to a webhook (with possibility of other protocols).

I'd love to hear folks thoughts on that (and if it would be something people would pay for).

Neat, this is the pattern I've been thinking about for a while now. Also glad to see this is Elixir based.

I've been using https://github.com/cpursley/walex (basically a fork of cainophile via a fork for subabase) to listen to Postgres changes in Elixir.

https://github.com/cpursley/walex

Which is based on WAL logs and doesnt have the same limitations.

Great writeup, just added this to the WalEx readme:

https://github.com/cpursley/walex

(WalEx is an Elixir lib for listening to the WAL and perform callback-like actions with the data)

Very cool.

I'm using Elixir to listen to change events via https://github.com/cpursley/walex (which I basically ripped off from Supabase).