Project: OpenFeature (Observability and Analysis / Feature Flagging)
File: types.md

title: Types and Data Structures description: A description of types and data structures used within the OpenFeature specification. sidebar_position: 2 This document outlines some of the common types and data structures defined by OpenFeature and referenced elsewhere in this specification. A logical true or false, as represented idiomatically in the implementation languages. A UTF-8 encoded string. A numeric value of unspecified type or size. Implementation languages may further differentiate between integers, floating point numbers, and other specific numeric types and provide functionality as idioms dictate. Structured data, presented however is idiomatic in the implementation language, such as JSON or YAML. A language primitive for representing a date and time, optionally including timezone information. If no timezone is specified, the date and time will be treated as UTC. A structure representing the result of the , and made available in the , containing the following fields: flag key (string, required) value (boolean | string | number | structure, required) error code (, optional) error message (string, optional) reason (string, optional) variant (string, optional) flag metadata () [!NOTE] Some type systems feature useful constraints that can enhance the ergonomics of the `evaluation details` structure. For example, in the case of an unsuccessful evaluation, `error code`, `reason`, and `error message` will be set, and variant will not. If the type system of the implementation supports the expression of such constraints, consider defining them. A structure which contains a subset of the fields defined in the `evaluation details`, representing the result of the provider's , including: value (boolean | string | number | structure, required) error code (, optional) error message (string, optional) reason (string, optional) variant (string, optional) flag metadata (, optional) A set of pre-defined reasons is enumerated below: | Reason | Explanation | | | -- | | STATIC | The resolved value is static (no dynamic evaluation). | | DEFAULT | The resolved value fell back to a pre-configured value (no dynamic evaluation occurred or dynamic evaluation yielded no result). | | TARGETING_MATCH | The resolved value was the result of a dynamic evaluation, such as a rule or specific user-targeting. | | SPLIT | The resolved value was the result of pseudorandom assignment. | | CACHED | The resolved value was retrieved from cache. | | DISABLED | The resolved value was the result of the flag being disabled in the management system. | | UNKNOWN | The reason for the resolved value could not be determined. | | STALE | The resolved value is non-authoritative or possibly out of date | | ERROR | The resolved value was the result of an error. | [!NOTE] The `reason` should not be limited to the reasons enumerated above. It can be any of the pre-defined reasons, or any string value. Some type systems have features which can increase the ergonomics of `reason`, for instance a union of pre-defined types with a string, or a rust-style enumeration which allows for enumerated values to have associated content. ```rust enum Reason { Static, Default, TargetingMatch, Split, Cached, Unknown, Stale, Error, Other(String) } let myReason =

``` [!NOTE] The `resolution details` structure is not exposed to the Application Author. It defines the data which Provider Authors must return when resolving the value of flags. An enumerated error code represented idiomatically in the implementation language. | Error Code | Explanation | | | - | | PROVIDERNOTREADY | The value was resolved before the provider was initialized. | | FLAGNOTFOUND | The flag could not be found. | | PARSE_ERROR | An error was encountered parsing data, such as a flag configuration. | | TYPE_MISMATCH | The type of the flag value does not match the expected type. | | TARGETINGKEYMISSING | The provider requires a targeting key and one was not provided in the `evaluation context`. | | INVALID_CONTEXT | The `evaluation context` does not meet provider requirements. | | PROVIDER_FATAL | The provider has entered an irrecoverable error state. | | GENERAL | The error was for a reason not enumerated above. | A structure containing the following fields: hooks (one or more , optional) hook hints (, optional) A structure which supports definition of arbitrary properties, with keys of type `string`, and values of type `boolean`, `string`, or `number`. This structure is populated by a provider for use by an via the or an via . An enumeration of possible provider states. | Status | Explanation | | | -- | | NOT_READY | The provider has not been initialized. | | READY | The provider has been initialized, and is able to reliably resolve flag values. | | ERROR | The provider is initialized but is not able to reliably resolve flag values. | | STALE | The provider's cached state is no longer valid and may not be up-to-date with the source of truth. | | FATAL | The provider has entered an irrecoverable error state. | | RECONCILING* | The provider is reconciling its state with a context change. | \* only A structure defining a provider event payload, including: flags changed (string[], optional) message (string, optional) error code (, optional) event metadata () A structure defining an event payload, including: provider name (string, required) flags changed (string[], optional) message (string, optional) error code (, optional) event metadata () A structure supporting the addition of arbitrary event data. It supports definition of arbitrary properties, with keys of type `string`, and values of type `boolean`, `string`, or `number`. An enumeration of provider events. | Event | Explanation | | | - | | PROVIDER_READY | The provider is ready to perform flag evaluations. | | PROVIDER_ERROR | The provider signaled an error. | | PROVIDERCONFIGURATIONCHANGED | A change was made to the backend flag configuration. | | PROVIDER_STALE | The provider's cached state is no longer valid and may not be up-to-date with the source of truth. | | PROVIDER_RECONCILING* | The context associated with the provider has changed, and the provider has not yet reconciled its associated state. | | PROVIDERCONTEXTCHANGED* | The context associated with the provider has changed, and the provider has reconciled its associated state. | \* only A function or method which can be associated with a `provider event`, and runs when that event occurs. It declares an `event details` parameter.