feat(openfeature): emit provider events from the DevCycle config lifecycle

[jonathannorris]

Summary

• DevCycleProvider now extends EventProvider and emits PROVIDER_CONFIGURATION_CHANGED, PROVIDER_STALE, PROVIDER_ERROR, and PROVIDER_READY
• Adds a ConfigUpdateListener to EnvironmentConfigManager so config fetch outcomes are no longer swallowed into the logger
• Replaces the 2 second busy-wait in initialize() with a latch released by the first config load, and fails fast with FatalError when the SDK key is unauthorized
• 124 tests pass (117 before)

Without these events, nothing downstream could tell a config refreshing normally from one that had been failing for hours.

Event	When it is emitted
PROVIDER_READY	A config has been loaded, or fetching recovered after a failure.
PROVIDER_CONFIGURATION_CHANGED	A newly fetched config has a different ETag than the one in use.
PROVIDER_STALE	A fetch failed while a previously fetched config is still being served.
PROVIDER_ERROR	A fetch failed and no config was ever loaded. PROVIDER_FATAL when the SDK key is unauthorized.

Implementation

EnvironmentConfigManager calls onConfigLoaded(etag, firstLoad, changed) on every successful fetch and onConfigError(error, fatal) from the polling catch block. changed is derived from the ETag, so a 304 or an out-of-order config doesn't report a change. DevCycleLocalClient forwards to the provider once one exists, and replays a fatal error to a provider created after the failure.

Worth calling out for review:

1. initialize() never emits PROVIDER_READY/PROVIDER_ERROR itself. FeatureProviderStateManager already sets those states from the initialize() outcome, and EventProvider's javadoc says the same.
2. A successful fetch after a failed initialize() emits PROVIDER_READY explicitly. The SDK doesn't call initialize() again, so otherwise the provider stays in ERROR forever after the config arrives.
3. shutdown() calls super.shutdown(). EventProvider.shutdown() is concrete, so an override that forgets it compiles fine and leaks the emitter thread pool. Regression test included.
4. flagsChanged is intentionally unset. DevCycle resolves variables per-user at evaluation time, so the changed key set isn't knowable at fetch time. The ETag goes in eventMetadata instead.

DevCycleCloudClient is unaffected: no config to change, isInitialized() always true. Docs added to OpenFeature.md.

[Copilot]

Pull request overview

This PR enhances the Java Server SDK’s OpenFeature Local Bucketing integration by emitting standard OpenFeature provider lifecycle events driven by the DevCycle config polling/SSE lifecycle, allowing downstream consumers to distinguish healthy config refresh from prolonged failure.

Changes:

• Make DevCycleProvider an EventProvider and emit PROVIDER_READY, PROVIDER_CONFIGURATION_CHANGED, PROVIDER_STALE, and PROVIDER_ERROR based on config fetch outcomes.
• Add a ConfigUpdateListener hook to EnvironmentConfigManager and forward those callbacks through DevCycleLocalClient to the provider (including replay of fatal errors).
• Replace the initialize() busy-wait with a latch-based first-config signal and fail fast for unauthorized SDK keys; add integration/unit tests and documentation.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/main/java/com/devcycle/sdk/server/openfeature/DevCycleProvider.java	Converts provider to EventProvider, tracks degraded/failed init state, and emits provider events from config lifecycle callbacks.
src/main/java/com/devcycle/sdk/server/local/managers/EnvironmentConfigManager.java	Adds ConfigUpdateListener wiring and notifies on config load/error instead of only logging failures.
src/main/java/com/devcycle/sdk/server/local/managers/ConfigUpdateListener.java	Introduces an interface for config lifecycle callbacks (success + failure, with fatal flag).
src/main/java/com/devcycle/sdk/server/local/api/DevCycleLocalClient.java	Forwards config lifecycle callbacks to the OpenFeature provider and replays fatal errors if provider is created late.
src/test/java/com/devcycle/sdk/server/openfeature/DevCycleProviderTest.java	Adds unit coverage for provider shutdown behavior and init-time failure when the client never initializes.
src/test/java/com/devcycle/sdk/server/openfeature/DevCycleProviderEventsTest.java	Adds integration tests validating emitted OpenFeature provider events across config updates, failures, recovery, and unauthorized keys.
src/test/java/com/devcycle/sdk/server/helpers/LocalConfigServer.java	Extends the test config server to support ETag changes and controllable HTTP error responses.
OpenFeature.md	Documents emitted provider events and their meaning for Local vs Cloud bucketing.

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[JamieSinn]

Do we really need to mark this volatile? This seems like a quick and dirty method instead of properly accessing the various callbacks safely. I'm worried about potential side effects in the actual regular use of the provider from this.