{"record":{"id":"39dd9e66225d6624","repo":"nautechsystems/nautilus_trader","slug":"failed-to-convert-value-to-target-type-e","errorCode":null,"errorMessage":"Failed to convert value to target type: {e}","messagePattern":"Failed to convert value to target type: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"crates/infrastructure/src/redis/queries.rs","lineNumber":129,"sourceCode":"        payload: &[u8],\n    ) -> anyhow::Result<T> {\n        let mut value = match encoding {\n            SerializationEncoding::MsgPack => rmp_serde::from_slice(payload)\n                .map_err(|e| anyhow::anyhow!(\"Failed to deserialize msgpack `payload`: {e}\"))?,\n            SerializationEncoding::Json => serde_json::from_slice(payload)\n                .map_err(|e| anyhow::anyhow!(\"Failed to deserialize json `payload`: {e}\"))?,\n            SerializationEncoding::Sbe => {\n                anyhow::bail!(\"SBE encoding is not supported for Redis cache payloads\")\n            }\n            SerializationEncoding::Capnp => {\n                anyhow::bail!(\"Cap'n Proto encoding is not supported for Redis cache payloads\")\n            }\n        };\n\n        convert_timestamp_strings(&mut value);\n\n        serde_json::from_value(value)\n            .map_err(|e| anyhow::anyhow!(\"Failed to convert value to target type: {e}\"))\n    }\n\n    /// Scans Redis for keys matching the given `pattern`.\n    ///\n    /// # Errors\n    ///\n    /// Returns an error if the Redis scan operation fails.\n    pub async fn scan_keys(\n        con: &mut ConnectionManager,\n        pattern: String,\n    ) -> anyhow::Result<Vec<String>> {\n        let mut result = Vec::new();\n        let mut cursor = 0u64;\n\n        loop {\n            let scan_result: (u64, Vec<String>) = redis::cmd(\"SCAN\")\n                .arg(cursor)\n                .arg(\"MATCH\")","sourceCodeStart":111,"sourceCodeEnd":147,"githubUrl":"https://github.com/nautechsystems/nautilus_trader/blob/18893faf8b356be3320add8de2f861b0b647cf06/crates/infrastructure/src/redis/queries.rs#L111-L147","documentation":"After the raw JSON bytes parse successfully and timestamp strings are normalized, serde_json::from_value converts the intermediate serde_json::Value into the concrete type T. This error is thrown when the JSON structure is valid JSON but its shape/field types do not match T (missing fields, wrong types, unexpected nulls).","triggerScenarios":"Calling deserialize_payload with data whose JSON fields do not match struct T: e.g. a numeric field stored as string (not corrected by convert_timestamp_strings), a missing required field, or a changed field name between writer and reader versions.","commonSituations":"Schema drift between write and read versions of NautilusTrader; hand-edited Redis values; data written by a different component with slightly different field naming; an Optional field made required in a newer version while old data lacks it.","solutions":["Read the serde error detail in {e}: it names the missing/invalid field path — fix the data at that path in Redis.","Align reader/writer versions or re-write the cache with the current schema version.","Migrate old payloads (e.g. script to re-serialize stored JSON into the new struct shape).","If a field type changed (string vs number), normalize the stored values."],"exampleFix":"// before: old payload has ts_init as RFC3339 string, struct expects integer nanos\n{\"ts_init\": \"2024-01-01T00:00:00Z\"}\n// after: normalize to integer nanoseconds expected by the struct\n{\"ts_init\": 1704067200000000000}","handlingStrategy":"validation","validationCode":"// Pre-check: payload fits target type\nfn fits<T: serde::de::DeserializeOwned>(bytes: &[u8]) -> bool {\n    serde_json::from_slice::<T>(bytes).is_ok()\n}","typeGuard":"fn is_complete_object(v: &serde_json::Value) -> bool {\n    v.as_object().map(|o| !o.is_empty()).unwrap_or(false)\n}","tryCatchPattern":"match deserialize_payload::<MyData>(encoding, &value) {\n    Ok(data) => data,\n    Err(e) if e.to_string().contains(\"convert value to target type\") => {\n        tracing::warn!(\"schema drift for stored payload: {e}\");\n        Default::default() // or migrate/skip the record\n    }\n    Err(e) => return Err(e),\n}","preventionTips":["Keep writer and reader struct versions in lockstep; add serde defaults for new fields.","Test deserialization of old cache snapshots in CI after any schema change.","Never hand-edit Redis payloads; regenerate them via the library."],"tags":["redis","deserialization","schema","json"],"backgroundTag":"schema-validation-failed","analyzedSha":"18893faf8b356be3320add8de2f861b0b647cf06","analyzedAt":"2026-09-08T20:49:34.690Z","contentChangedAt":"2026-09-08T20:49:34.690Z","schemaVersion":2},"datasetVersion":"2026-09-14T00:17:10.932Z"}