Resource finalization out of order when using with concurrent stream.
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bug
- Dominant language
- Scala
- Stars
- 2.5k
- Forks
- 636
- Avg merge
- 2d 4h
- Merged PRs (30d)
- 7
Description
It appears that resource finalizer is not being called correctly in order. In this simple example, almost all runs I did, the finalizer gets called before the last .use statement
Version: 3.2.8
import cats.effect.syntax.all.*
import cats.syntax.all.*
import cats.effect.*
import fs2.Stream
object Main extends IOApp.Simple:
val run = Stream
.resource(
Resource.make(IO.println("hello").as(100))(n =>
IO.println(s"goodbye: $n")
)
)
.concurrently(Stream.emits[IO, Int](1 to 10).evalMap(IO.println))
.compile
.resource
.lastOrError
.use(x => IO.println(s"From use: $x"))
Output:
1
hello
2
goodbye: 100
3
4
From use: 100
5
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by running the Scala reproducer from the issue and tracing the interaction between Stream.concurrently, compile.resource, and use. Investigate the resource-finalization ordering around concurrent streams; done means the finalizer runs only after the stream and the outer use callback have completed.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- scala
- Domain
- stream-processing
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100