# Semantic Conventions for Connect RPC **Status**: [Experimental][DocumentStatus] The Semantic Conventions for [Connect](http://connect.build) extend and override the [RPC spans](rpc-spans.md) and [RPC metrics](rpc-metrics.md) Semantic Conventions that describe common RPC operations attributes in addition to the Semantic Conventions described on this page. ## Connect RPC Attributes `rpc.system` MUST be set to `"connect_rpc"`. Below is a table of attributes that SHOULD be included on client and server Connect RPC measurements. | Attribute | Type | Description | Examples | [Requirement Level](https://opentelemetry.io/docs/specs/semconv/general/attribute-requirement-level/) | Stability | |---|---|---|---|---|---| | [`rpc.connect_rpc.error_code`](/docs/attributes-registry/rpc.md) | string | The [error codes](https://connect.build/docs/protocol/#error-codes) of the Connect request. Error codes are always string values. | `cancelled`; `unknown`; `invalid_argument` | `Conditionally Required` [1] |  | | [`rpc.connect_rpc.request.metadata.`](/docs/attributes-registry/rpc.md) | string[] | Connect request metadata, `` being the normalized Connect Metadata key (lowercase), the value being the metadata values. [2] | `rpc.request.metadata.my-custom-metadata-attribute=["1.2.3.4", "1.2.3.5"]` | `Opt-In` |  | | [`rpc.connect_rpc.response.metadata.`](/docs/attributes-registry/rpc.md) | string[] | Connect response metadata, `` being the normalized Connect Metadata key (lowercase), the value being the metadata values. [3] | `rpc.response.metadata.my-custom-metadata-attribute=["attribute_value"]` | `Opt-In` |  | **[1]:** If response is not successful and if error code available. **[2]:** Instrumentations SHOULD require an explicit configuration of which metadata values are to be captured. Including all request metadata values can be a security risk - explicit configuration helps avoid leaking sensitive information. **[3]:** Instrumentations SHOULD require an explicit configuration of which metadata values are to be captured. Including all response metadata values can be a security risk - explicit configuration helps avoid leaking sensitive information. `rpc.connect_rpc.error_code` 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 | |---|---|---| | `aborted` | aborted |  | | `already_exists` | already_exists |  | | `cancelled` | cancelled |  | | `data_loss` | data_loss |  | | `deadline_exceeded` | deadline_exceeded |  | | `failed_precondition` | failed_precondition |  | | `internal` | internal |  | | `invalid_argument` | invalid_argument |  | | `not_found` | not_found |  | | `out_of_range` | out_of_range |  | | `permission_denied` | permission_denied |  | | `resource_exhausted` | resource_exhausted |  | | `unauthenticated` | unauthenticated |  | | `unavailable` | unavailable |  | | `unimplemented` | unimplemented |  | | `unknown` | unknown |  | ## Connect RPC Status If `rpc.connect_rpc.error_code` is set, [Span Status](https://github.com/open-telemetry/opentelemetry-specification/tree/v1.33.0/specification/trace/api.md#set-status) MUST be set to `Error` and left unset in all other cases. [DocumentStatus]: https://opentelemetry.io/docs/specs/otel/document-status