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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
50 lines
1.9 KiB
Haskell
50 lines
1.9 KiB
Haskell
-- | This module contains a collection of utility functions we use with tracing
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-- throughout the codebase, but that are not a core part of the library. If we
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-- were to move tracing to a separate library, those functions should be kept
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-- here in the core engine code.
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module Hasura.Tracing.Utils
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( traceHTTPRequest,
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)
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where
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import Control.Lens
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import Data.String
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import Hasura.Prelude
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import Hasura.Tracing.Class
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import Hasura.Tracing.Context
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import Hasura.Tracing.Sampling
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import Hasura.Tracing.TraceId
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import Network.HTTP.Client.Transformable qualified as HTTP
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-- | Wrap the execution of an HTTP request in a span in the current
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-- trace. Despite its name, this function does not start a new trace, and the
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-- span will therefore not be recorded if the surrounding context isn't traced
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-- (see 'spanWith').
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--
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-- Additionally, this function adds metadata regarding the request to the
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-- created span, and injects the trace context into the HTTP header.
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traceHTTPRequest ::
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(MonadIO m, MonadTrace m) =>
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-- | http request that needs to be made
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HTTP.Request ->
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-- | a function that takes the traced request and executes it
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(HTTP.Request -> m a) ->
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m a
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traceHTTPRequest req f = do
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let method = bsToTxt (view HTTP.method req)
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uri = view HTTP.url req
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newSpan (method <> " " <> uri) do
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let reqBytes = HTTP.getReqSize req
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attachMetadata [("request_body_bytes", fromString (show reqBytes))]
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headers <- fmap (maybe [] toHeaders) currentContext
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f $ over HTTP.headers (headers <>) req
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where
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toHeaders :: TraceContext -> [HTTP.Header]
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toHeaders TraceContext {..} =
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catMaybes
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[ Just ("X-B3-TraceId", traceIdToHex tcCurrentTrace),
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Just ("X-B3-SpanId", spanIdToHex tcCurrentSpan),
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("X-B3-ParentSpanId",) . spanIdToHex <$> tcCurrentParent,
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("X-B3-Sampled",) <$> samplingStateToHeader tcSamplingState
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]
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