It's important for observability to have an historic trace of the pool
size. Currently we expose it on the metrics endpoint, but not all
deployments use it.
This logs the pool size after the successful connection log to make it
more visible:
<timestamp>: Connection Pool initialized with a maximum size of 4 connections
It's not immediately clear on which port the API server is listening.
Also it's not clear that the "pgrst" channel is for database
notifications.
Goes from:
<timestamp>: Admin server listening on 0.0.0.0:3001
<timestamp>: Listening on 0.0.0.0:3000
<timestamp>: Listening for notifications on the "pgrst" channel
To:
<timestamp>: Admin server listening on 0.0.0.0:3001
<timestamp>: API server listening on 0.0.0.0:3000
<timestamp>: Listening for database notifications on the "pgrst" channel
Fixes https://github.com/PostgREST/postgrest/issues/3523.
Now if there's a failure when obtaining the pg version OR schema cache,
we do the same retrying process. This way we don't add two retries.
Refactors and renames the "connectionWorker" to "schemaCacheLoader".
This makes more sense since what we really want is the schema cache,
the version is the pre-requisite for ensuring our
schema cache queries work.
Additionally, we no longer log ` Attempting to connect to the database...`
at startup unnecessarily. This is only logged whenever there's a retry attempt.
Update hasql-notifications to include the fix on
https://github.com/diogob/hasql-notifications/issues/24.
Which now reveals the following error:
```
$ postgrest-with-postgresql-16 --replica -f test/spec/fixtures/load.sql postgrest-run
17/May/2024:18:35:38 -0500: Successfully connected to PostgreSQL 16.2 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 13.2.0, 64-bit
17/May/2024:18:35:38 -0500: Could not listen for notifications on the "pgrst" channel. ERROR: cannot execute LISTEN during recovery
17/May/2024:18:35:38 -0500: Retrying listening for notifications...
```
This is still not good because the LISTEN channel will be retried
forever without a backoff.
The fatal logic is now inside `usePool`. It centralizes the
logic which is better for Locality of Behavior.
Removes:
- The need to do checkIsFatal on other parts of the code
- SCFatalFail/ConnFatalFail states which are no longer needed.
With this:
- Is no longer necessary to pass observer as an argument
to every function that needs observations.
- We can invoke the observer on every function that uses AppConfig.
However it'd be better to just call the observer in the upper modules
(like on App.hs).
