graphql-engine/server/src-lib/Hasura/Backends/MySQL/Instances
Antoine Leblanc cf531b05cb Rewrite Tracing to allow for only one TraceT in the entire stack.
This PR is on top of #7789.

### Description

This PR entirely rewrites the API of the Tracing library, to make `interpTraceT` a thing of the past. Before this change, we ran traces by sticking a `TraceT` on top of whatever we were doing. This had several major drawbacks:
- we were carrying a bunch of `TraceT` across the codebase, and the entire codebase had to know about it
- we needed to carry a second class constraint around (`HasReporterM`) to be able to run all of those traces
- we kept having to do stack rewriting with `interpTraceT`, which went from inconvenient to horrible
- we had to declare several behavioral instances on `TraceT m`

This PR rewrite all of `Tracing` using a more conventional model: there is ONE `TraceT` at the bottom of the stack, and there is an associated class constraint `MonadTrace`: any part of the code that happens to satisfy `MonadTrace` is able to create new traces. We NEVER have to do stack rewriting, `interpTraceT` is gone, and `TraceT` and `Reporter` become  implementation details that 99% of the code is blissfully unaware of: code that needs to do tracing only needs to declare that the monad in which it operates implements `MonadTrace`.

In doing so, this PR revealed **several bugs in the codebase**: places where we were expecting to trace something, but due to the default instance of `HasReporterM IO` we would actually not do anything. This PR also splits the code of `Tracing` in more byte-sized modules, with the goal of potentially moving to `server/lib` down the line.

### Remaining work

This PR is a draft; what's left to do is:
- [x] make Pro compile; i haven't updated `HasuraPro/Main` yet
- [x] document Tracing by writing a note that explains how to use the library, and the meaning of "reporter", "trace" and "span", as well as the pitfalls
- [x] discuss some of the trade-offs in the implementation, which is why i'm opening this PR already despite it not fully building yet
- [x] it depends on #7789 being merged first

PR-URL: https://github.com/hasura/graphql-engine-mono/pull/7791
GitOrigin-RevId: cadd32d039134c93ddbf364599a2f4dd988adea8
2023-03-13 17:38:39 +00:00
..
API.hs server: add explicit export lists in OSS server and enforce with warning 2021-11-04 16:09:38 +00:00
Execute.hs Allow backend execution to happen on the base app monad. 2023-02-09 14:40:04 +00:00
Metadata.hs Block adding remote relationships where they are not supported by the Data Connector agent 2023-03-08 06:01:04 +00:00
Schema.hs Refactor Update IR to generalize Update vs Update Many across backends - compositional approach [GDC-687] 2023-01-10 01:56:14 +00:00
SchemaCache.hs Define IR types for AggregationPredicates. 2022-08-19 15:41:47 +00:00
Transport.hs Rewrite Tracing to allow for only one TraceT in the entire stack. 2023-03-13 17:38:39 +00:00
Types.hs Remove NativeQueryMetadata 2023-02-15 16:27:47 +00:00