Part of the Scala Cats ecosystem for an IO type and associated effects.
Questions tagged [cats-effect]
191 questions
3
votes
1 answer
How to terminate FS2 stream started from SBT Shell?
If I run this program from SBT shell, then cancel it, it will keep printing "hello". I have to exit SBT to make it stop. Why is that?
import cats.effect.{ExitCode, IO, IOApp}
import fs2.Stream
import scala.concurrent.duration._
object FS2 extends…
Cpt. Senkfuss
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3
votes
2 answers
How to asynchronously interrupt an fs2 stream?
I'm trying to interrupt an fs2 stream with SignalRef. I set up and run the stream with the following. The stream should run when switch contains false and should interrupt when switch contains true
import cats.effect.IO
import fs2.Stream
…
mdornfe1
- 1,982
- 1
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3
votes
2 answers
How to configure Cats Timer on abstract effect type
Let's say I have a following method signature in a project using Cats-effect and tagless final approach:
def schedule[F[_]: Applicative : Async: Timer]
I'm trying to schedule an operation on a schedule method call using pure FP.
I tried this…
Bogdan Vakulenko
- 3,380
- 1
- 10
- 25
3
votes
1 answer
How to read from embedded-kafka with fs2-kafka
I am using fs2-kafka to read from embedded-kafka.
I create the embedded kafka using withRunningKafkaOnFoundPort, create topic and publish a few messages. However when I try to read it back with fs2-kafka I get a NullPointerException. I have isolated…
Lev Denisov
- 2,011
- 16
- 26
3
votes
1 answer
Cannot find an implicit value for ContextShift
I am trying to create webapp with http4s that is based on Http4sServlet.
The following code does not compile:
import cats.effect._
import org.http4s.servlet.BlockingServletIo
import org.http4s.servlet.Http4sServlet
import…
softshipper
- 32,463
- 51
- 192
- 400
3
votes
1 answer
fs2.Stream[IO, Something] does not return on take(1)
I have a function that returns a fs2.Stream of Measurements.
import cats.effect._
import fs2._
def apply(sds: SerialPort, interval: Int)(implicit cs: ContextShift[IO]): Stream[IO, SdsMeasurement] =
for {
blocker <-…
Jeroen Kransen
- 1,379
- 3
- 19
- 45
3
votes
1 answer
http4s Received premature EOF
I want to implement an http4s server that receives the content from another service, processes it and return the response.
The original service uses redirects so I added the Follow redirect middleware. I also added the Logger middleware to check…
Labra
- 1,412
- 1
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- 33
3
votes
1 answer
Integration tests for Http4s Client/Resource
I'm implementing a Vault client in Scala using Http4s client.
And I'm now starting to write integration tests. So far I have this:
abstract class Utils extends AsyncWordSpec with Matchers {
implicit override def executionContext =…
Simão Martins
- 1,210
- 11
- 22
3
votes
2 answers
Resolve Seq[Future[Either[A, Seq[B]]]] - Scala Cats
I am facing an issue while I am trying to resolve the result of a method. More specifically I have:
def methodA(): Future[Either[Error, Seq[A]]]
and at some point, I want to call this method for each element of a list and merge the result.…
pik4
- 1,283
- 3
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3
votes
2 answers
Stream URL to a local file with fs2
Using fs2 (ver. 1.0.4) and cats-effect IO, I can stream an URL to a local file,
import concurrent.ExecutionContext.Implicits.global
def download(spec: String, filename: String): Stream[IO, Unit] =
io.readInputStream((new…
thlim
- 2,908
- 3
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3
votes
1 answer
cats-effect: How to obtain an implicit NonEmptyParallel
I am trying to use parMapN function and I am not able to compile the code. If my type is IO then there is not problem, but when I use types on my functions, then I cannot manage to make it work.
In the snippet below, there is randomMessage which…
Zoraida
- 181
- 1
- 5
3
votes
1 answer
what is the equivalent of fs2.Scheduler in fs2 (0.10.x) in newer versions
I'm migrating fs2 0.10.x version to version 1.0.0.
Our code uses fs2.Scheduler in from fs2 version 0.10.x.
I don't know what is the equivalent in newer fs2 version 1.0.0.
I went through the migration guide here but couldn't find the migration…
user51
- 8,843
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- 79
- 158
2
votes
1 answer
How to shutdown Cats Effect Runtime
Is there a way to shutdown the cats effect runtime from within an application, similar to System.exit(0)?
There is a shutdown method on IORuntime but it is not documented and it behaves weirdly when I call it on IORuntime.global: it does not shut…
Georg Prohaska
- 23
- 2
2
votes
0 answers
Programmatically configuring logback-classic in a Typelevel Scala application
I have a program using com.monovore.decline and org.typelevel.log4cats.
app.scala
//> using scala 3
//> using resourceDir ./resources
//> using dep org.typelevel::log4cats-slf4j:2.6.0
//> using dep ch.qos.logback:logback-classic:1.4.8
//> using dep…
Zia Ur Rehman
- 103
- 6
2
votes
1 answer
Cats Effect IO - how do I ensure thrown exceptions are captured as values when using attempt / redeem "inside" a top level flatmap?
I am attempting to pass some data (an event) through a program composed out of smaller IOs. I need to run a computation (which can throw an exception) based on the event, then report out on what happened including the original event in the…
six_minute_abs
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