OpenFeature.Providers.Flagd.Core 1.0.0

flagd .NET Core

The in-process flagd flag evaluation engine for .NET.

This package contains only the evaluation logic: parsing a flagd flag configuration and resolving flags against it, including targeting rules and the custom flagd operators (fractional, sem_ver, starts_with, ends_with) and shared $evaluators. It performs no I/O. Fetching, syncing and watching flag configurations is left to the concrete provider.

If you want to evaluate flags from a flagd service or a file, use OpenFeature.Providers.Flagd instead. Use this package when you are building your own flagd-compatible provider and want to reuse the evaluation engine.

Requirements

• open-feature/dotnet-sdk v2.9.0 or later, below v3.0.0

Install

dotnet add package OpenFeature.Providers.Flagd.Core

Usage

using OpenFeature.Model;
using OpenFeature.Providers.Flagd.Core;

var core = new FlagdCore();

// Load a flagd flag configuration. Returns the keys of the flags that were added, removed or changed.
IReadOnlyList<string> changedKeys = core.SetConfigurations(flagConfigurationJson);

// Flag-set metadata, e.g. a "version" supplied by the flag source
var metadata = core.GetFlagSetMetadata();

// All currently loaded flag keys
IReadOnlyList<string> allKeys = core.GetFlagKeys();

// Resolve flags synchronously
var context = EvaluationContext.Builder().SetTargetingKey("user-1").Set("email", "me@example.com").Build();
ResolutionDetails<bool> details = core.ResolveBoolean("my-flag", false, context);

ResolveBoolean, ResolveString, ResolveInteger, ResolveDouble and ResolveStructure return ResolutionDetails<T> and throw the OpenFeature FeatureProviderException subtypes (for example flag not found or type mismatch) that a provider is expected to surface to the SDK.

Thread safety

A FlagdCore instance is safe for concurrent use. Flags can be resolved from any number of threads while another thread calls SetConfigurations; each resolution sees either the previous or the new configuration in full, never a mix of both.

Invalid configurations

SetConfigurations throws a ParseErrorException when the configuration cannot be parsed. The previously loaded flags and metadata are left untouched, so a failed update never leaves the engine empty.

Schema validation

Flag configurations can additionally be checked against the flagd flags and targeting JSON schemas. Validation only logs warnings, it never rejects a configuration. It is off until the schemas are loaded, which is asynchronous:

var core = new FlagdCore(new FlagdCoreOptions { Logger = logger });
await core.InitializeAsync();

Logger is the only option. FlagdCore itself performs no I/O, so constructing and using it without calling InitializeAsync never touches the network or the file system.