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[GrowthBook provider] Auto refresh flags with a stale-while-revalidate strategy #148

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[GrowthBook provider] Auto refresh flags with a stale-while-revalidate strategy #148

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c4b64f7
Auto refresh features with a stale-while-revalidate strategy
jdorn Jun 17, 2025
048ce3f
Update default cache TTL for a better developer experience
jdorn Jun 17, 2025
c485efb
Reduce latency for edge config
jdorn Jun 17, 2025
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43 changes: 41 additions & 2 deletions packages/adapter-growthbook/src/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ import type { Adapter } from 'flags';
import { createClient } from '@vercel/edge-config';
import {
GrowthBookClient,
configureCache,
type Attributes,
type ClientOptions,
type InitOptions,
Expand Down Expand Up @@ -36,6 +37,7 @@ type EdgeConfig = {
type AdapterResponse = {
feature: <T>() => Adapter<T, Attributes>;
initialize: () => Promise<GrowthBookClient>;
refresh: () => Promise<void>;
setTrackingCallback: (cb: TrackingCallback) => void;
setStickyBucketService: (stickyBucketService: StickyBucketService) => void;
stickyBucketService?: StickyBucketService;
Expand All @@ -62,6 +64,8 @@ export function createGrowthbookAdapter(options: {
stickyBucketService?: StickyBucketService;
/** Provide Edge Config details to use the optional Edge Config adapter */
edgeConfig?: EdgeConfig;
/** How long to cache feature definitions (in milliseconds). Default to 1s in dev and 30s in prod */
cacheTTLms?: number;
}): AdapterResponse {
let trackingCallback = options.trackingCallback;
let stickyBucketService = options.stickyBucketService;
Expand All @@ -72,9 +76,14 @@ export function createGrowthbookAdapter(options: {
...(options.clientOptions || {}),
});

let _initializePromise: Promise<void> | undefined;
const cacheTTLms =
options.cacheTTLms ??
(process.env.NODE_ENV === 'development' ? 1_000 : 30_000);
configureCache({
staleTTL: cacheTTLms,
});

const initializeGrowthBook = async (): Promise<void> => {
const getEdgePayload = async (): Promise<FeatureApiResponse | undefined> => {
let payload: FeatureApiResponse | undefined;
if (options.edgeConfig) {
try {
Expand All @@ -91,14 +100,21 @@ export function createGrowthbookAdapter(options: {
console.error('Error fetching edge config', e);
}
}
return payload;
};

let _initializePromise: Promise<void> | undefined;
const initializeGrowthBook = async (): Promise<void> => {
const payload = await getEdgePayload();
await growthbook.init({
streaming: false,
payload,
...(options.initOptions || {}),
});
};

let _lastRefreshTimestamp = 0;

/**
* Initialize the GrowthBook SDK.
*
Expand All @@ -109,12 +125,32 @@ export function createGrowthbookAdapter(options: {
*/
const initialize = async (): Promise<GrowthBookClient> => {
if (!_initializePromise) {
_lastRefreshTimestamp = Date.now();
_initializePromise = initializeGrowthBook();
}
await _initializePromise;
return growthbook;
};

const refresh = async (): Promise<void> => {
const isStale = _lastRefreshTimestamp + cacheTTLms < Date.now();
if (!isStale) return;
_lastRefreshTimestamp = Date.now();

if (options.edgeConfig) {
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@dferber90 dferber90 Aug 1, 2025 •
edited
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As a next step: When Edge Config is active you should be able to always read Edge Config without any caching on your ned. The Edge Config client returns the same reference if the Edge Config has not changed, so you can skip any re-initialization then.

Our goal with Edge Config is to eliminate any need for TTL or time based caching. Doesn't need to happen in this pull request but would be nice as a north star for this adapter.

// Await does not block on the network here. Edge Config returns immediately and kicks off a background refresh
const payload = await getEdgePayload();
if (payload) {
await growthbook.setPayload(payload);
}
} else {
// Await would block on the network here, so we use a promise to kick off the refresh in the background
growthbook.refreshFeatures().catch((e) => {
console.error('Failed to refresh features', e);
});
}
};

function origin(prefix: string) {
return (key: string) => {
const appOrigin = options.appOrigin || 'https://app.growthbook.io';
Expand All @@ -139,6 +175,7 @@ export function createGrowthbookAdapter(options: {
origin: origin('features'),
decide: async ({ key, entities, defaultValue }) => {
await initialize();
await refresh();
const userContext: UserContext = {
attributes: entities as Attributes,
trackingCallback: opts.exposureLogging ? trackingCallback : undefined,
Expand Down Expand Up @@ -172,6 +209,7 @@ export function createGrowthbookAdapter(options: {
return {
feature,
initialize,
refresh,
setTrackingCallback,
setStickyBucketService,
stickyBucketService,
Expand Down Expand Up @@ -255,6 +293,7 @@ export function getOrCreateDefaultGrowthbookAdapter(): AdapterResponse {
export const growthbookAdapter: AdapterResponse = {
feature: (...args) => getOrCreateDefaultGrowthbookAdapter().feature(...args),
initialize: () => getOrCreateDefaultGrowthbookAdapter().initialize(),
refresh: () => getOrCreateDefaultGrowthbookAdapter().refresh(),
setTrackingCallback: (...args) =>
getOrCreateDefaultGrowthbookAdapter().setTrackingCallback(...args),
setStickyBucketService: (...args) =>
Expand Down