stateLogDebouncePoolTimeout is an MVar initialized on the first logging of PoolAcqTimeoutObs. The code in logWithDebounce has race condition that could lead to creation of multiple debouncers.
This change simplifies logic by getting rid of lazy initialization of debouncer.
PoolAcqTimeoutObs is always created with SQL.AcquisitionTimeoutUsageError so the parameter does not provide any useful information.
On the other hand, it complicates debouncing logic in Logger as logWithDebounce has to lazily create the debouncer (which is error prone and hence the logic has a race condition).
This change removes the parameter from PoolAcqTimeoutObs. It is a prerequisite to simplifying logWithDebounce.
Closes https://github.com/PostgREST/postgrest/issues/4226.
This requires moving query generation to the top App.hs module.
At this point is also simple to log the transaction variables + the
pre-request function call but this is not done here to reduce scope.
Changes:
1. Refactoring and some cleanup of JWT handling code:
* Instead of caching AuthResult cache decoded claims (which signature was verified). Validating claims and determining role is done after cache lookup
* Cleaned up API so that usage of it is simplified: lookupJwtCache cache key >>= parseClaims configJwtAud time
* Handling of JwtCacheState initialization and updates of configuration is encapsulated in Auth.JwtCache module
2. Generic high performance (hopefully) scalable, dynamically resizeable cache implementation based on stm, stm-hamt and sieve algorithm. It also integrates with PostgREST measurements infrastructure providing usage stats (ie. hit ratio, evictions count)
It used to be that this was only enabled with log-level=debug.
But the default log-level is misleading, for example:
```
$ PGRST_DB_SCHEMAS="apflora" postgrest-with-postgresql-16 -f test/io/big_schema.sql postgrest-run
...
13/Nov/2024:22:08:20 -0500: Config reloaded
13/Nov/2024:22:08:20 -0500: Schema cache queried in 36.3 milliseconds
13/Nov/2024:22:08:20 -0500: Schema cache loaded 326 Relations, 305 Relationships, 7 Functions, 0 Domain Representations, 4 Media Type Handlers, 1194 Timezones
```
The "Schema cache loaded" can take a while to appear, yet the 22:08:20
time is the same. If we reveal the load time this is clarified:
```
13/Nov/2024:22:08:37 -0500: Schema cache loaded in 16770.1 milliseconds
```
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).
