{"id":"763130c48f4fdd67","repo":"gofiber/fiber","slug":"cache-failed-to-reload-key-q-after-eviction-fail","errorCode":null,"errorMessage":"cache: failed to reload key %q after eviction failure: %w","messagePattern":"cache: failed to reload key %q after eviction failure: %w","errorType":"http","errorClass":null,"httpStatus":null,"severity":"error","filePath":"middleware/cache/cache.go","lineNumber":188,"sourceCode":"\t\t\treturn\n\t\t}\n\n\t\tentry := heap.entries[indexedIdx]\n\t\tif entry.idx != heapIdx || entry.key != entryKey {\n\t\t\treturn\n\t\t}\n\n\t\t_, size := heap.remove(heapIdx)\n\t\tstoredBytes -= size\n\t}\n\n\trefreshHeapIndex := func(ctx context.Context, candidate evictionCandidate) error {\n\t\tentry, err := manager.get(ctx, candidate.key)\n\t\tif err != nil {\n\t\t\tif errors.Is(err, errCacheMiss) {\n\t\t\t\treturn nil\n\t\t\t}\n\t\t\treturn fmt.Errorf(\"cache: failed to reload key %q after eviction failure: %w\", maskKey(candidate.key), err)\n\t\t}\n\n\t\tentry.heapidx = candidate.heapIdx\n\n\t\tremainingTTL := max(secondsToTime(entry.exp).Sub(cfg.now()), 0)\n\n\t\tif err := manager.set(ctx, candidate.key, entry, remainingTTL); err != nil {\n\t\t\treturn fmt.Errorf(\"cache: failed to restore heap index for key %q: %w\", maskKey(candidate.key), err)\n\t\t}\n\n\t\treturn nil\n\t}\n\n\t// Return new handler\n\treturn func(c fiber.Ctx) error {\n\t\thasAuthorization := len(c.Request().Header.Peek(fiber.HeaderAuthorization)) > 0\n\t\treqCacheControl := c.Request().Header.Peek(fiber.HeaderCacheControl)\n\t\treqDirectives := parseRequestCacheControl(reqCacheControl)","sourceCodeStart":170,"sourceCodeEnd":206,"githubUrl":"https://github.com/gofiber/fiber/blob/9a4c7e57fe0b080a04235d28a4b0d2b4b353d58c/middleware/cache/cache.go#L170-L206","documentation":"Raised by refreshHeapIndex during the eviction-rollback path: a candidate evicted from the in-memory heap must be re-read from Storage to restore its heap index, and manager.get returned an error that is not errCacheMiss (a real backend failure). This indicates the external Storage (Redis, SQLite, etc.) is misbehaving in the middle of cache bookkeeping recovery, so the heap index for that key could not be re-established.","triggerScenarios":"cfg.Storage is a remote backend (e.g. redis, leveldb) and an eviction delete failed, triggering restore; during restore, manager.get(candidate.key) hits a connection error, timeout, or deserialization error from the storage driver. Reproducible by forcing storage errors (mock/intercept) during concurrent cache writes that cross the MaxBytes boundary.","commonSituations":"Redis briefly drops the connection mid-request; storage responses larger than the msgp limit; TLS to the storage backend expired; storage pool exhausted under load; network partition while MaxBytes eviction churn is high.","solutions":["Check the health/latency of the configured cfg.Storage backend and its connection pool sizing.","Raise cfg.MaxBytes (or set it to 0 for unbounded) to reduce eviction churn that triggers the rollback path.","Ensure the storage driver is the one Fiber expects (correct version, compatible serialization) — a stale manager encoding can cause get errors.","If errors are transient, treat as best-effort: the entry remains in storage but loses heap-based expiration tracking; consider periodic cache flush or restart under sustained failures."],"exampleFix":"// before: tiny MaxBytes + flaky redis -> eviction recovery fails on get\ncache.New(cache.Config{\n  Storage:  redisStorage,\n  MaxBytes: 1 << 16,\n})\n\n// after: larger budget + tuned redis pool\ncache.New(cache.Config{\n  Storage:  redisStorage, // pool tuned for concurrency\n  MaxBytes: 1 << 24,\n  Expiration: 10 * time.Minute,\n})","handlingStrategy":"try-catch","validationCode":"// Health-check the cache storage before serving traffic.\nfunc pingStorage(s fiber.Storage) error {\n    ctx, cancel := context.WithTimeout(context.Background(), time.Second)\n    defer cancel()\n    return s.Set(ctx, \"__ping__\", []byte(\"1\"), 5*time.Second)\n}","typeGuard":"null","tryCatchPattern":"// Cache middleware returns the error from c.Next() chain; handle at app root.\napp := fiber.New()\napp.Use(cache.New(cfg))\napp.Use(func(c fiber.Ctx) error {\n    err := c.Next()\n    if err != nil && strings.Contains(err.Error(), \"failed to reload key\") {\n        // log storage degradation but don't crash the request\n        log.Warnf(\"cache storage degraded: %v\", err)\n        return nil // or a 5xx with backoff\n    }\n    return err\n})","preventionTips":["Tune the storage driver's connection pool and timeouts for expected load.","Raise cfg.MaxBytes to reduce eviction churn that triggers the rollback path.","Monitor storage latency/errors; alert before they reach the cache hot path.","Keep the storage driver version compatible with Fiber's manager encoding."],"tags":["cache","storage","eviction","redis","bookkeeping"],"analyzedSha":"9a4c7e57fe0b080a04235d28a4b0d2b4b353d58c","analyzedAt":"2026-08-04T21:44:03.395Z","schemaVersion":2}