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# Error

## Error Attributes

This document defines the shared attributes used to report an error.

| Attribute    | Type   | Description                                              | Examples                                                                        | Stability                                                  |
| ------------ | ------ | -------------------------------------------------------- | ------------------------------------------------------------------------------- | ---------------------------------------------------------- |
| `error.type` | string | Describes a class of error the operation ended with. [1] | `timeout`; `java.net.UnknownHostException`; `server_certificate_invalid`; `500` | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |

**[1]:** The `error.type` SHOULD be predictable, and SHOULD have low cardinality.

When `error.type` is set to a type (e.g., an exception type), its
canonical class name identifying the type within the artifact SHOULD be used.

Instrumentations SHOULD document the list of errors they report.

The cardinality of `error.type` within one instrumentation library SHOULD be low.
Telemetry consumers that aggregate data from multiple instrumentation libraries and applications
should be prepared for `error.type` to have high cardinality at query time when no
additional filters are applied.

If the operation has completed successfully, instrumentations SHOULD NOT set `error.type`.

If a specific domain defines its own set of error identifiers (such as HTTP or gRPC status codes),
it's RECOMMENDED to:

- Use a domain-specific attribute
- Set `error.type` to capture all errors, regardless of whether they are defined within the domain-specific set or not.

`error.type` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

| Value    | Description                                                                               | Stability                                                  |
| -------- | ----------------------------------------------------------------------------------------- | ---------------------------------------------------------- |
| `_OTHER` | A fallback error value to be used when the instrumentation doesn't define a custom value. | ![Stable](https://img.shields.io/badge/-stable-lightgreen) |
