{"id":"d3e0efc3a1f05f3c","repo":"gofiber/fiber","slug":"failed-to-decode-session-data-w-d3e0ef","errorCode":null,"errorMessage":"failed to decode session data: %w","messagePattern":"failed to decode session data: %w","errorType":"http","errorClass":null,"httpStatus":null,"severity":"error","filePath":"middleware/session/store.go","lineNumber":179,"sourceCode":"\tsess := acquireSession()\n\n\tsess.mu.Lock()\n\n\tsess.ctx = c\n\tsess.config = s\n\tsess.id = id\n\tsess.isFresh = isFresh\n\tsess.extractor = selectedExtractor\n\n\t// Decode session data if found\n\tif rawData != nil {\n\t\tsess.data.Lock()\n\t\terr := sess.decodeSessionData(rawData)\n\t\tsess.data.Unlock()\n\t\tif err != nil {\n\t\t\tsess.mu.Unlock()\n\t\t\tsess.Release()\n\t\t\treturn nil, fmt.Errorf(\"failed to decode session data: %w\", err)\n\t\t}\n\t}\n\n\tsess.mu.Unlock()\n\n\tif isFresh && s.AbsoluteTimeout > 0 {\n\t\tsess.setAbsExpiration(time.Now().Add(s.AbsoluteTimeout))\n\t} else if sess.isAbsExpired() {\n\t\tif err := sess.Reset(); err != nil {\n\t\t\treturn nil, fmt.Errorf(\"failed to reset session: %w\", err)\n\t\t}\n\t\tsess.setAbsExpiration(time.Now().Add(s.AbsoluteTimeout))\n\t}\n\n\treturn sess, nil\n}\n\n// getSessionID returns the session ID using the configured extractor.","sourceCodeStart":161,"sourceCodeEnd":197,"githubUrl":"https://github.com/gofiber/fiber/blob/9a4c7e57fe0b080a04235d28a4b0d2b4b353d58c/middleware/session/store.go#L161-L197","documentation":"Returned by the public Store.Get(c) path: getSession pulls existing bytes from storage and decodeSessionData fails (store.go:174-179). Same root cause as the Session-level decode error but reached whenever you use the Store API directly or the middleware loads a session.","triggerScenarios":"A request arrives with a valid session ID whose stored bytes cannot gob-decode: unregistered type, schema drift, or truncated storage value, surfaced through store.Get(c)/getSession.","commonSituations":"Same as the middleware decode case: type-registration gaps across replicas, post-deploy stale sessions, storage truncation.","solutions":["Register every custom type with store.RegisterType at startup.","Clear stale sessions from the store after schema/type changes.","Check the storage backend for truncated/corrupt values and raise value-size limits if needed."],"exampleFix":null,"handlingStrategy":"try-catch","validationCode":null,"typeGuard":null,"tryCatchPattern":"sess, err := store.Get(c)\nif err != nil {\n    // Corrupt or unreadable session -> regenerate.\n    log.Warnf(\"session decode failed, resetting: %v\", err)\n    _ = sess.Destroy()\n    sess, err = store.Get(c)\n    if err != nil {\n        return fiber.ErrInternalServerError\n    }\n}","preventionTips":["Keep the RegisterType list identical across all replicas.","Version or namespace session keys when types change.","Monitor decode failures as a signal of corrupt storage."],"tags":["session","gob","serialization","store","fiber"],"analyzedSha":"9a4c7e57fe0b080a04235d28a4b0d2b4b353d58c","analyzedAt":"2026-08-04T21:44:03.395Z","schemaVersion":2}