feat: Multi provider impl #168

PenguinDan · 2025-08-20T01:16:55Z

This PR

Multi Provider implementation according to the specifications outlined in https://openfeature.dev/specification/appendix-a/#multi-provider

Does not implement support for hooks for the moment

Related Issues

Fixes #149

Notes

Work that still needs to be done

Need to go through the specifications one more time to make sure the implementation aligns with it

Follow-up Tasks

Add a logging tool?
Event Type enhancements Missing OpenFeature Events types. #107
Documentation updates

How to test

Updated the sample application to utilize a multi provider

PenguinDan · 2025-08-20T01:19:52Z

kotlin-sdk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/multiprovider/FirstMatchStrategy.kt

+                    return eval
+                }
+                // Continue to next provider if error is FLAG_NOT_FOUND
+            } catch (_: OpenFeatureError.FlagNotFoundError) {


No logging tool, just swallowing for the moment

Signed-off-by: penguindan <[email protected]>

PenguinDan · 2025-08-20T18:37:24Z

kotlin-sdk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/multiprovider/MultiProvider.kt

+    // Event precedence (highest to lowest priority) - based on the specifications
+    private val eventPrecedence = mapOf(
+        OpenFeatureProviderEvents.ProviderError::class to 4, // FATAL/ERROR
+        OpenFeatureProviderEvents.ProviderNotReady::class to 3, // NOT READY, Deprecated but still supporting


Do we want to add back support for this Event?

According to the documentation https://openfeature.dev/specification/appendix-a/#status-and-event-handling

Initially the status is NOT_READY

The only way to represent the NOT_READY state is by setting the initial value of the eventFlow to an Error, where, it would probably be smarter not to represent the initial state as being in "error"?

I think we should look into this. I've thought about it recently as well and for me NOT_READY is a valid state. I don't remember why it was deprecated.

@nicklasl Not finding much details on why NOT_READY has been deprecated. I just see this PR #124 that re-introduces the ProviderNotReady object but deprecated.

I think it make sense to undeprecate this to support initializing providers with ProviderNotReady

Ah okay, was a bit confusing but Events rightfully don't have a NotReady state: https://openfeature.dev/specification/types#provider-events

The documentation makes it confusing by mentioning both Events and Statuses in the section (i.e ConfigurationChangedEvent)

Still trying to wrap my head around the specifications outlined here and what they actually mean lol: https://openfeature.dev/specification/appendix-a#multi-provider-status

Okay, so looks like what we need to do is

Listen to all events of the Providers and map those to STATUS emitted by the MultiProvider

Listen to all events of the Providers and re-emit the event from our own observe() function if that particular event updates the STATUS of our MultiProvider. (Caveat here being that we always re-emit Configuration changed..)

Okay, 4fa33eb this should now align with the specs.

Definitely need to do another round of double checking things

Signed-off-by: penguindan <[email protected]>

kotlin-sdk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/multiprovider/MultiProvider.kt

Signed-off-by: penguindan <[email protected]>

kotlin-sdk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/multiprovider/MultiProvider.kt

kotlin-sdk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/multiprovider/FirstMatchStrategy.kt

Signed-off-by: penguindan <[email protected]>

nicklasl · 2025-08-22T13:59:04Z

kotlin-sdk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/ProviderMetadata.kt

+     * See: https://openfeature.dev/specification/appendix-a/#metadata
+     */
+    val originalMetadata: Map<String, ProviderMetadata>
+        get() = emptyMap()


nice with defaults to not make it breaking 👍

Signed-off-by: penguindan <[email protected]>

bencehornak

Thanks a lot for the contributions, @PenguinDan, they look very promising! Nothing serious, only minor findings from my side!

kotlin-sdk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/multiprovider/MultiProvider.kt

...dk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/multiprovider/FirstSuccessfulStrategy.kt

kotlin-sdk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/multiprovider/Strategy.kt

...dk/src/commonTest/kotlin/dev/openfeature/kotlin/sdk/multiprovider/FirstMatchStrategyTests.kt

sampleapp/src/main/kotlin/dev/openfeature/kotlin/sdk/sampleapp/ExampleProvider.kt

…rategy into MultiProvider Signed-off-by: penguindan <[email protected]>

Signed-off-by: penguindan <[email protected]>

bencehornak

Thanks for the updates, going to the right direction!

docs/multiprovider/README.md

...dk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/multiprovider/FirstSuccessfulStrategy.kt

…ltiprovider/FirstSuccessfulStrategy.kt Co-authored-by: Bence Hornák <[email protected]> Signed-off-by: Daniel Kim <[email protected]>

Signed-off-by: penguindan <[email protected]>

PenguinDan changed the title ~~Multi provider impl~~ feat: Multi provider impl Aug 20, 2025

PenguinDan commented Aug 20, 2025

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PenguinDan added 4 commits August 20, 2025 11:06

Multi provider impl draft

af65a59

Signed-off-by: penguindan <[email protected]>

Ktlint

79f59ba

Signed-off-by: penguindan <[email protected]>

Try emit initial state for Multi provider

6127d68

Signed-off-by: penguindan <[email protected]>

Shared flow should always have content

2142879

Signed-off-by: penguindan <[email protected]>

PenguinDan force-pushed the MultiProvider-Impl branch from 79a2d9a to 2142879 Compare August 20, 2025 18:06

PenguinDan commented Aug 20, 2025

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PenguinDan added 2 commits August 20, 2025 12:05

Add tests

c6f3a8f

Signed-off-by: penguindan <[email protected]>

Update multi provider strategy to better align with Open Feature specs

f2f415a

Signed-off-by: penguindan <[email protected]>

PenguinDan commented Aug 20, 2025

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kotlin-sdk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/multiprovider/MultiProvider.kt Outdated Show resolved Hide resolved

Add original metadata and allow all providers to shutdown

199236c

Signed-off-by: penguindan <[email protected]>

nicklasl reviewed Aug 21, 2025

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kotlin-sdk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/multiprovider/MultiProvider.kt Outdated Show resolved Hide resolved

PenguinDan commented Aug 21, 2025

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kotlin-sdk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/multiprovider/MultiProvider.kt Outdated Show resolved Hide resolved

PenguinDan commented Aug 21, 2025

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kotlin-sdk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/multiprovider/FirstMatchStrategy.kt Outdated Show resolved Hide resolved

PenguinDan added 4 commits August 21, 2025 13:06

Add default reason to default value in First Match Strategy

38fac8c

Signed-off-by: penguindan <[email protected]>

Remove json dependency and update ProviderMetadata

48033c5

Signed-off-by: penguindan <[email protected]>

Align to Event spec

4fa33eb

Signed-off-by: penguindan <[email protected]>

Ktlint

d5f5546

Signed-off-by: penguindan <[email protected]>

nicklasl reviewed Aug 22, 2025

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PenguinDan marked this pull request as ready for review August 22, 2025 17:11

PenguinDan added 2 commits August 22, 2025 10:55

Update API dumps for multiprovider and ProviderMetadata changes

8d8cbec

Signed-off-by: penguindan <[email protected]>

Use Lazy and ktlint

3818a11

Signed-off-by: penguindan <[email protected]>

beeme1mr requested review from jonathannorris, thomaspoignant, toddbaert, lukas-reining and bencehornak August 25, 2025 15:46

jescriba mentioned this pull request Aug 25, 2025

feat: add multiprovider open-feature/swift-sdk#78

Open

Add TODO once EventDetails have been added

f834a43

Signed-off-by: penguindan <[email protected]>

bencehornak requested changes Aug 26, 2025

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PenguinDan added 6 commits August 26, 2025 09:58

PR comments; remove redundant comments, fix test definitions, move st…

c299717

…rategy into MultiProvider Signed-off-by: penguindan <[email protected]>

Return an error result for FirstSuccessfulStrategy rather than throwing

2305056

Signed-off-by: penguindan <[email protected]>

Revert sample app changes

70a892d

Signed-off-by: penguindan <[email protected]>

Add README documentation for Multiprovider

6fe18eb

Signed-off-by: penguindan <[email protected]>

Lets favor not throwing in the FirstMatchStrategy also

870ae07

Signed-off-by: penguindan <[email protected]>

Update tests to represent to non-throwing pattern and api dump

5472c08

Signed-off-by: penguindan <[email protected]>

PenguinDan requested a review from bencehornak August 26, 2025 17:50

Kotlin Format

7df6772

Signed-off-by: penguindan <[email protected]>

bencehornak reviewed Aug 30, 2025

View reviewed changes

PenguinDan and others added 2 commits August 30, 2025 16:05

Update kotlin-sdk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/mu…

2cc75c5

…ltiprovider/FirstSuccessfulStrategy.kt Co-authored-by: Bence Hornák <[email protected]> Signed-off-by: Daniel Kim <[email protected]>

Update multi provider readme

e71d448

Signed-off-by: penguindan <[email protected]>

PenguinDan requested a review from bencehornak August 30, 2025 23:26

bencehornak approved these changes Aug 31, 2025

View reviewed changes

PenguinDan added 2 commits September 1, 2025 07:46

Merge branch 'main' into MultiProvider-Impl

c4c49db

API dump

f540783

Signed-off-by: penguindan <[email protected]>

feat: Multi provider impl #168

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Related Issues

Notes

Follow-up Tasks

How to test

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PenguinDan commented Aug 20, 2025 •

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