feat: allow multiple attempts to fail before caching a negative result

bucketco · Jun 19, 2024 · 751211a · 751211a
1 parent 79ee9bd
commit 751211a
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Showing 2 changed files with 30 additions and 6 deletions.
diff --git a/packages/tracking-sdk/src/flags-cache.ts b/packages/tracking-sdk/src/flags-cache.ts
@@ -11,6 +11,7 @@ interface cacheEntry {
   staleAt: number;
   success: boolean; // we also want to cache failures to avoid the UI waiting and spamming the API
   flags: Flags | undefined;
+  attemptCount: number;
 }
 
 export function validateFlags(flagsInput: any): Flags | undefined {
@@ -35,6 +36,7 @@ export interface CacheResult {
   flags: Flags | undefined;
   stale: boolean;
   success: boolean;
+  attemptCount: number;
 }
 
 export class FlagCache {
@@ -48,7 +50,14 @@ export class FlagCache {
     this.expireTimeMs = expireTimeMs;
   }
 
-  set(key: string, success: boolean, flags?: Flags) {
+  set(
+    key: string,
+    {
+      success,
+      flags,
+      attemptCount,
+    }: { success: boolean; flags?: Flags; attemptCount: number },
+  ) {
     let cacheData: CacheData = {};
 
     try {
@@ -65,6 +74,7 @@ export class FlagCache {
       staleAt: Date.now() + this.staleTimeMs,
       flags,
       success,
+      attemptCount,
     } satisfies cacheEntry;
 
     cacheData = Object.fromEntries(
@@ -90,6 +100,7 @@ export class FlagCache {
             flags: cachedResponse[key].flags,
             success: cachedResponse[key].success,
             stale: cachedResponse[key].staleAt < Date.now(),
+            attemptCount: cachedResponse[key].attemptCount,
           };
         }
       }
@@ -119,6 +130,7 @@ function validateCacheData(cacheDataInput: any) {
       typeof cacheEntry.expireAt !== "number" ||
       typeof cacheEntry.staleAt !== "number" ||
       typeof cacheEntry.success !== "boolean" ||
+      typeof cacheEntry.attemptCount !== "number" ||
       (cacheEntry.flags && !validateFlags(cacheEntry.flags))
     ) {
       return;
@@ -129,6 +141,7 @@ function validateCacheData(cacheDataInput: any) {
       staleAt: cacheEntry.staleAt,
       success: cacheEntry.success,
       flags: cacheEntry.flags,
+      attemptCount: cacheEntry.attemptCount,
     };
   }
   return cacheData;

diff --git a/packages/tracking-sdk/src/flags-fetch.ts b/packages/tracking-sdk/src/flags-fetch.ts
@@ -98,16 +98,20 @@ export async function fetchFlags(url: string, timeoutMs: number) {
       console.error("[Bucket] error fetching flags: ", e);
     } finally {
       if (success) {
-        cache.set(url, success, flags);
+        cache.set(url, { success, flags, attemptCount: 0 });
       } else {
         const current = cache.get(url);
         if (current) {
-          // if there is a previous version, extend it's expireAt time
-          cache.set(url, current.success, current.flags);
+          // if there is a previous failure cached, increase the attempt count
+          cache.set(url, {
+            success: current.success,
+            flags: current.flags,
+            attemptCount: current.attemptCount + 1,
+          });
         } else {
           // otherwise cache if the request failed and there is no previous version to extend
           // to avoid having the UI wait and spam the API
-          cache.set(url, false, flags);
+          cache.set(url, { success: false, flags, attemptCount: 1 });
         }
       }
 
@@ -123,6 +127,7 @@ export async function fetchFlags(url: string, timeoutMs: number) {
 const FLAG_FETCH_DEFAULT_TIMEOUT_MS = 5000;
 export const FLAGS_STALE_MS = 60000; // turn stale after 60 seconds, optionally reevaluate in the background
 export const FLAGS_EXPIRE_MS = 7 * 24 * 60 * 60 * 1000; // expire entirely after 7 days
+const FAILURE_RETRY_ATTEMPTS = 3;
 const localStorageCacheKey = `__bucket_flags`;
 
 const cache = new FlagCache(
@@ -160,10 +165,16 @@ export async function getFlags({
   const url = `${apiBaseUrl}/flags/evaluate?` + params.toString();
   const cachedItem = cache.get(url);
 
-  if (!cachedItem) {
+  // if there's no cached item OR the cached item is a failure and we haven't retried
+  // too many times yet - fetch now
+  if (
+    !cachedItem ||
+    (!cachedItem.success && cachedItem.attemptCount <= FAILURE_RETRY_ATTEMPTS)
+  ) {
     return fetchFlags(url, timeoutMs);
   }
 
+  // cachedItem is a success or a failed attempt that we've retried too many times
   if (cachedItem.stale) {
     // serve successful stale cache if `staleWhileRevalidate` is enabled
     if (staleWhileRevalidate && cachedItem.success) {