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Replace SpanBuilder#wrapResource API #273

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merged 3 commits into from
Jul 24, 2023

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NthPortal
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@NthPortal NthPortal commented Jul 7, 2023

Replace SpanBuilder#wrapResource with
SpanOps#resource:Resource[F,F~>F], which no longer automatically
provides 'acquire', 'use' and 'release' spans.

This API change allows further simplification of the API in future commits.

This PR is a follow-up to the discussion on #261.

  • rebase -i --autosquash before merge

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cc: @iRevive @rossabaker @armanbilge

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NthPortal commented Jul 7, 2023

there is an argument that the entirety of SpanOps can now be discarded, with the new SpanOps#resource method moving to SpanBuilder and replacing build (name can be bikeshedded)

@NthPortal NthPortal force-pushed the Tracer-spanResource/PR branch 2 times, most recently from ec21382 to e8b6044 Compare July 7, 2023 16:28
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Looking at this some more, the only way to directly access the Span anymore is startUnmanaged. is that still needed? should it be moved? should SpanOps be kept just for that and resource?

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iRevive commented Jul 7, 2023

I'm firmly against removing SpanOps. SpanOps provides the only option to modify the span somewhere downstream.

For example, I can do the following:

tracer.span("my-span").use { span =>
  for {
    isSuccess <- someLogic
    _ <- span.addAttribute(Attribute("success", isSuccess))
  } yield ()
}

With F ~> F we cannot do such a thing.

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iRevive commented Jul 7, 2023

I like the direction. The moment we limited tracing to Local semantics, wrapResource does not offer much benefit.

If someone needs it, a similar tracing (acquire, use, release) can be achieved with a few lines utility method.

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NthPortal commented Jul 7, 2023

pushed a commit where resource now returns Resource[F, (Span[F], F ~> F)].

If someone needs it, a similar tracing (acquire, use, release) can be achieved with a few lines utility method.

TracerSuite currently defines such a method, so that I didn't have to mess with the test outputs.

I think I agree that it's still worth keeping SpanOps even with this change, however, as it allows a user to not have to faff about with the natural transformation. however, we can probably make the other methods final defs that delegate to resource (other than startUnmanaged).

edit: they cannot be final defs as things are because they require MonadCancelThrow. unless we're okay with requiring MonadCancelThrow as an implicit parameter for those? I definitely am

Comment on lines 136 to 150
.spanResource("Start up")
.use { case (_, nt /* natural transformation */ ) =>
for {
_ <- nt(tracer.span("acquire").surround(IO.sleep(50.millis)))
_ <- nt {
tracer.span("use").surround {
userIdAlg
.getAllUsersForInstitution(
"9902181e-1d8d-4e00-913d-51532b493f1b"
)
.flatMap(IO.println)
}
}
_ <- nt(tracer.span("release").surround(IO.sleep(100.millis)))
} yield ()
}
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I'm concerned that my original commit implemented this incorrectly (before I'd quite understood things), but nothing caught it. is there a way we can run the examples and make sure they're correct?

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Hmm. sbt-doctest can make unit tests out of scaladoc comments, but I don't know of anything that tests the output of examples.

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I've pretty much done the simplification (you can see it at https://github.com/NthPortal/otel4s/tree/Tracer-simplify/R1), but I'm holding off on PRing it until everything is hashed out in this PR

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I'm firmly against removing SpanOps. SpanOps provides the only option to modify the span somewhere downstream.

In Natchez, there's a near 1:1 relationship between things you can do on a span and things you can do on a Tracer without a reference to the Span. To check my understanding, is that the basic tradeoff we've made here: we have to carry around a SpanOps but not mirror all the span operations?

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Nice work!

Comment on lines 136 to 150
.spanResource("Start up")
.use { case (_, nt /* natural transformation */ ) =>
for {
_ <- nt(tracer.span("acquire").surround(IO.sleep(50.millis)))
_ <- nt {
tracer.span("use").surround {
userIdAlg
.getAllUsersForInstitution(
"9902181e-1d8d-4e00-913d-51532b493f1b"
)
.flatMap(IO.println)
}
}
_ <- nt(tracer.span("release").surround(IO.sleep(100.millis)))
} yield ()
}
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Hmm. sbt-doctest can make unit tests out of scaladoc comments, but I don't know of anything that tests the output of examples.

examples/src/main/scala/TraceExample.scala Outdated Show resolved Hide resolved
examples/src/main/scala/TraceExample.scala Outdated Show resolved Hide resolved
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iRevive commented Jul 8, 2023

In Natchez, there's a near 1:1 relationship between things you can do on a span and things you can do on a Tracer without a reference to the Span. To check my understanding, is that the basic tradeoff we've made here: we have to carry around a SpanOps but not mirror all the span operations?

Hm, it's a nice question. We can keep some conversation here #89, to make things easier

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I like the current changes, thanks for the contribution!

There are a few leftovers (e.g. remove Result type member, etc) I can take care of.

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There are a few leftovers (e.g. remove Result type member, etc) I can take care of.

too late ;)

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Looks good. Only one change is up for discussion.

examples/src/main/scala/TracingExample.scala Outdated Show resolved Hide resolved
@NthPortal NthPortal requested a review from iRevive July 17, 2023 17:08
@@ -105,9 +136,3 @@ trait SpanOps[F[_]] {
*/
def surround[A](fa: F[A]): F[A]
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this can still be final ... = use(_ => fa), will change momentarily

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It's not final on Resource itself. I wonder whether that implies possible optimizations. But I can't imagine any offhand.

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technically you can optimise the no-op implementation slightly by not creating a wrapper Function1 around the F[A] to pass to use, but honestly I still feel it's cleaner to have it be final. it can be made not final in a minor release if minds are changed later. or someone can make a PR after this is merged. or if others also want it non-final, I can add another fixup commit to this PR

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if no one else has any objections within a couple days, I'll autosquash so this can be ready to merge

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This is tremendous, both the code and review discussion. I should take vacations more often!

Replace `SpanBuilder#wrapResource` with
`SpanOps#resource:Resource[F,F~>F]`, which no longer automatically
provides 'acquire', 'use' and 'release' spans.

This API change allows further simplification of the API in future
commits.
Add `SpanOps.Res` type for the return type of `SpanOps#resource`,
for clearer, more evolvable and more documentable API.
@iRevive iRevive merged commit 5a90aac into typelevel:main Jul 24, 2023
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iRevive commented Jul 24, 2023

Thanks for the contribution @NthPortal!

@NthPortal NthPortal deleted the Tracer-spanResource/PR branch July 24, 2023 15:38
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NthPortal commented Jul 24, 2023

@iRevive thank you for reviewing this PR and collaborating with me!

@NthPortal NthPortal mentioned this pull request Jul 24, 2023
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3 participants