@e-volv/openfeature-node

OpenFeature provider for e-volv Launch feature flags, on the Node.js reference SDK (@e-volv/logs). Flags are evaluated locally — streaming delivery, polling fallback, a last-known cache and exposure tracking all live in the underlying client; this package only adapts it to the OpenFeature server API.

Install

npm install @e-volv/openfeature-node @openfeature/server-sdk @e-volv/logs

Use

import { OpenFeature } from '@openfeature/server-sdk';
import { init } from '@e-volv/logs';
import { EvolveProvider } from '@e-volv/openfeature-node';

const evolve = init({ key: process.env.EVOLVE_KEY });
await OpenFeature.setProviderAndWait(new EvolveProvider(evolve.flags));

const flags = OpenFeature.getClient();
const checkout = await flags.getBooleanDetails('checkout.new', false, {
  targetingKey: user.id,
  plan: user.plan,
});

Every evaluation resolves synchronously against the held ruleset (the provider's initialize() waits up to 5 s for the first delivery), so reads never block on the network. The native API remains available on evolve.flags when OpenFeature is not wanted.

Reason mapping

| e-volv reason (flagMetadata.evolveReason) | OpenFeature reason | | ------------------------------------------- | -------------------------- | | RULE:*, TARGET_MATCH | TARGETING_MATCH | | ROLLOUT | SPLIT | | OFF, KILLED | DISABLED | | DEFAULT, PREREQUISITE_FAILED | DEFAULT | | FLAG_NOT_FOUND | ERROR (FLAG_NOT_FOUND) | | TYPE_MISMATCH | ERROR (TYPE_MISMATCH) | | ERROR | ERROR (GENERAL) |

The full e-volv reason is always present on flagMetadata.evolveReason.

Per the OpenFeature contract, when a resolution carries an errorCode the client substitutes the caller's default value and drops the variant — so an errored evaluation returns your default, while flagMetadata.evolveReason still names the native e-volv reason.

Lifecycle and exposures

The LogsClient owns delivery and telemetry: closing the OpenFeature client (OpenFeature.close()) does not stop the underlying client, and exposures are recorded by @e-volv/logs on each evaluation of a flag that is present in the ruleset. Shut the client down with evolve.close() (also flushable via evolve.flush()).

Conformance

The provider is tested against the whole @e-volv/flags-kernel fixture: every case must resolve to the same value, variant and reason as the native flags.detail API (__tests__/provider.spec.ts).