tpolecat/natchez

Timothy Bess

@tdbgamer

right I could do like state.set(child) *> k <* state.set(span), but the puts and stuff will all be attached to the wrong spans since the last child process to write state will have the current span

Timothy Bess

@tdbgamer

I'll give the Kleisli way another go, tried to look through the chat history for people solving the ConcurrentEffect problem, but a lot of the examples were a little hard for me to follow

Adam Rosien

@arosien

i understood the general idea of those examples, but got lost in the impl. basically it was lifting IO => Kleisli[IO, Span[IO], ?], to get a Trace, then running the thing with a root to get back an IO for the next layer

(i think)

Rob Norris

@tpolecat

You can always pass the span explicitly, it works fine.

Burying it it Kleisli is a convenience.

Timothy Bess

@tdbgamer

So the problem is I'm using the finally tagless MTL style where you pass the Client[F] all the way down to some Repositories that do the HTTP requests, so when I'm creating the program, I have to instantiate them with F[_], which means the F has to be Kleisli[F, Span[F], *], but the main body of my code executes within the BlazeClientBuilder resource, so the Client[F]'s F[_] has to have ConcurrentEffect

I'm sure there's something simple I'm not getting or maybe I'm just not structuring it right

I essentially structured my app similarly to this:
https://http4s-tracer.profunktor.dev/guide.html

Christopher Davenport

@ChristopherDavenport

Ember support that or you can translate a prebuilt client into a client in kleisli

Rob Norris

@tpolecat

Yeah you can use the ember client. It seems to work fine.

The ConcurrentEffect constraint is a big issue in general. Maybe CE3 will help somehow, I don’t know.

Timothy Bess

@tdbgamer

Ok I'll try that out and report back, thanks!

To verify when you say "client in kleisli" do you mean as a second argument or translating Client[F] to Client[Kleisli...]?

Tristan Lohman

@gatorcse

I’m actually running into http4s natchez Kleisli concurrent effect things right now as well. I was using Ember, but is is broken for me right now (hangs on all requests, 0.21.4 and 0.21.6). I was going to use Blaze and try to do “translate” or something. Does anyone have some good def wrapExistingClient[F[_], G[_]: Trace](underlyingClient: Client[F]): Client[G] code laying around?

Christopher Davenport

@ChristopherDavenport

0.21.6? Would love an example

That is broken.

Tristan Lohman

@gatorcse

you mean Ember is broken for 0.21.6?

(on jdk 8, if it matters)

or really, if anyone has that code for any version, I’ll upgrade if it helps

Christopher Davenport

@ChristopherDavenport

It shouldn't be. I just fixed chunked which is the last bug I knew of.

Tristan Lohman

@gatorcse

k, I’ll see if I can reproduce it in a minimal example tonight

I literally just switched from blaze to ember in my app harness, app hung on all outgoing requests, and switched back, I have no other info than that.

Christopher Davenport

@ChristopherDavenport

As far as the client. It requires the span and then you translate to kleisli. Then you apply the base span for the stream transformation. I have this in an example but I need to rip out the proprietary stuff tomorrow.

Christopher Davenport

@ChristopherDavenport

Alright, I threw it together again

def liftKleisli[F[_]: Bracket[*[_], Throwable]: cats.Defer, A](
  client: Client[F], 
  a: A
): Client[Kleisli[F, A, *]] = Client{
  req: Request[Kleisli[F, A, *]] => 
    val newReq = req.mapK(Kleisli.applyK(a))
    client.run(newReq)
      .mapK(Kleisli.liftK[F, A])
      .map(_.mapK(Kleisli.liftK))
  }

So you can get it there via extracting the span and then using that function
liftKleisli(blazeClient, baseSpan)

You can also just extract it using the algebra

Scratch that, use this

Christopher Davenport

@ChristopherDavenport

def liftKleisli[F[_]: Bracket[*[_], Throwable]: cats.Defer, A](client: Client[F]): Client[Kleisli[F, A, *]] = 
    Client{ req: Request[Kleisli[F, A, *]] => 
      Resource.liftF(Kleisli.ask[F, A]).flatMap{ a =>
        val newReq = req.mapK(Kleisli.applyK(a))
        client.run(newReq)
        .mapK(Kleisli.liftK[F, A])
        .map(_.mapK(Kleisli.liftK))
      }
    }

Timothy Bess

@tdbgamer

Wow that's gonna take me a second to digest, thanks for whipping it up so fast, really appreciate it. I'll test it out

Christopher Davenport

@ChristopherDavenport

http4s/http4s#3552 - I also created a PR to http4s to hopefully get this easier out of the box.

Timothy Bess

@tdbgamer

Dude! you're the greatest, thanks so much.

wow talk about going above and beyond

this also solved my issue with having the root created at the wrong level

Christopher Davenport

@ChristopherDavenport

This is what OSS is all about. :+1:

Tristan Lohman

@gatorcse

@ChristopherDavenport oh, that looks like exactly what I needed. I was getting too crazy trying to translate straight from F to G, your way just using all the mapK’s and liftK’s looks way better

~~just~~

Tristan Lohman

@gatorcse

@ChristopherDavenport Hey, finally got a minimal example. Normally the ember client is fine, the problem actually only crops up when using with the natchez Kleisli.

Example incoming

Sorry, it hangs when using the natchez kleisli and the response is more than one chunk.

here’s the gist: https://gist.github.com/gatorcse/b39cfa6ae70551ccd197fea1d581cdb5

Scala 2.13, http4s 0.21.6, natchez 0.0.11

Tristan Lohman

@gatorcse

Thanks, any help would be greatly appreciated!

Actually should this be a bug report? And in http4s or in natchez?

Christopher Davenport

@ChristopherDavenport

Http4s is probably the appropriate place for that bug report please. I just fixed chunked so I find that suprising but perhaps I can figure it out from that.

Stephen Bly

@sbly

Hello @tpolecat! Thank you for this project, it's very helpful. Is there any chance you could review my PR tpolecat/natchez#145 when you get the chance? I also have a few more I'm planning to make.

Rob Norris

@tpolecat

Yep, I have it in a tab. I'll try to get to it tomorrow.

Stephen Bly

@sbly

Thank you!

Ryan Zeigler

@rzeigler

Question about the trait Fields. Is this meant to be automatically handled by natchez? I thought it seemed like it might be something that was, however, I went reading and couldn't find anything in the source code that consumes it.

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