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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
29 lines
675 B
Haskell
29 lines
675 B
Haskell
module Hasura.Tracing.Reporter
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( Reporter (..),
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noReporter,
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)
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where
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import Control.Monad.Trans.Control
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import Hasura.Prelude
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import Hasura.Tracing.Context
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newtype Reporter = Reporter
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{ runReporter ::
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forall m a.
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(MonadIO m, MonadBaseControl IO m) =>
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-- \| Current trace context, providing the trace id and span info.
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TraceContext ->
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-- \| Human readable name of this span.
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Text ->
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-- \| IO action that retrieves the metadata associated with the
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-- current span.
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IO TraceMetadata ->
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-- \| The monadic action to report
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m a ->
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m a
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}
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noReporter :: Reporter
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noReporter = Reporter \_ _ _ -> id
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