Question

I got the above error message running Heroku Postgres Basic (as per this question) and have been trying to diagnose the problem.

One of the suggestions is to use connection pooling but it seems Rails has this built in. Another suggestion is that the app is configured improperly and opens too many connections.

My app manages all it’s connections through Active Record, and I had one direct connection to the database from Navicat (or at least I thought I had).

How would I debug this?

RESOLUTION

Turns out it was an Heroku issue. From Heroku support:

We’ve detected an issue on the server running your Basic database.
While we pinpoint this and address it, we would recommend you
provision a new Basic database and migrate over with PGBackups as
detailed here:
https://devcenter.heroku.com/articles/upgrade-heroku-postgres-with-pgbackups
. That should put your database on a new server. I apologize for this
disruption – we’re working to fix this issue and prevent it from
occurring in the future.

Answer 1

You might be able to find why you have so many connections by inspecting view pg_stat_activity:

SELECT * FROM pg_stat_activity

Most likely, you have some stray loop that opens new connection(s) without closing it.