Is there any performance or concurrency difference in using a MutableSharedFlow with replay 1 buffer 1 and drop oldest over a MutableStateFlow ```MutableSharedFlow lt Something gt replay = 1 extraBufferCapacity = 1 onBufferOverflow = BufferOverflow DROP OLDEST ``` vs ```MutableStateFlow lt Something gt null ```

Is there any performance or concurrency difference in using kotlinlang #coroutines

Channels

100daysofcode

100daysofkotlin

androidgithubprojects

cincinnati-user-group

competitive-programming

event21-community-content

java-to-kotlin-refactoring

jvm-ir-backend-feedback

kotlin-multiplatform-contest

kotlinultimatechallenge

myndocs-oauth2-server

naming

navigation-architecture-component

practical-functional-programming

proguard

prozis-android-backup

refactoring-to-kotlin

russian-kotlinasfirst

skia-wasm-interop-temp

stayhungrystayfoolish

swagger-gradle-codegen

tricity-kotlin-user-group

Title

Daniele Segato

06/30/2021, 10:59 PM

Is there any performance or concurrency difference in using a MutableSharedFlow (with replay 1, buffer 1 and drop oldest) over a MutableStateFlow?

MutableSharedFlow<Something?>(
    replay = 1,
    extraBufferCapacity = 1,
    onBufferOverflow = BufferOverflow.DROP_OLDEST
)

MutableStateFlow<Something?>(null)

Dominaezzz

07/01/2021, 7:43 AM

If you mean, buffer 0, then state flow might perform ever so slightly better but I don't think it's significant enough to let that dictate your decision.

Daniele Segato

07/01/2021, 7:44 AM

I've updated my question

Dominaezzz

07/01/2021, 7:52 AM

Oh, I'm pretty sure there's a behaviour difference there. (State flow is still better)

Daniele Segato

07/01/2021, 7:52 AM

I'm trying to understand when I should use a

MutableSharedFlow

and why :)

Nick Allen

07/03/2021, 7:11 PM

To clarify:

MutableSharedFlow

maintains a buffer of size

replay + extraBufferCapacity

(it's "extra" for a reason".

MutableStateFlow

has additional behavior in that it discards duplicates. A

MutableStateFlow

is equivalent to

MutableSharedFlow(replay = 1, extraBufferCapacity = 0, onBufferOverflow = BufferOverflow.DROP_OLDEST)

, where you always read from the shared flow with

sharedFlow.distinctUntilChanged()

While

MutableStateFlow

is good for managing state that can change,

MutableSharedFlow

is better suited for broadcasting event objects, where collectors are essentially event listeners. If something happens twice, you don't necessarily want the second event to be thrown away. The "event" in this case could be a sealed class of different event types, or could just be Unit to act as a simple signal.

Daniele Segato

07/03/2021, 7:45 PM

Thanks @Nick Allen very clear.

3 Views

#coroutines Join Slack