akka/akka-core

Convenience for attributes on Sink

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#30,199 opened on Apr 22, 2021

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 (5 comments) (0 reactions) (0 assignees)Scala (3,547 forks)batch import
1 - triagedhelp wantedt:stream

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Description

When working on https://github.com/akka/akka-persistence-cassandra/pull/888 I realized that it wasn't obvious how to set a dispatcher all the way to the Sink (and not introduce async boundary).

My first thought, when I didn't realize that the Sink is also involved, was:

.map(stuff)
.withAttributes(ActorAttributes.dispatcher(theDispatcher))
.runWith(Sink.ignore)

but it should be:

.map(stuff)
.toMat(Sink.ignore)(Keep.right)
.withAttributes(ActorAttributes.dispatcher(theDispatcher))
.run()

Contributor guide

Research direction
Examine the Akka Streams API to understand how attributes are propagated through stages. Focus on the Sink class and its existing methods. Identify the missing convenience and propose a method that allows setting attributes directly on Sink without requiring toMat and withAttributes. Consider the impact on asynchronous boundaries.
Tech stack
None
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
ScalaAkka Streams
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50