feature_flags.go

package config

import "context"

var (
	flagsCtxKey         = struct{}{}
	defaultFeatureFlags = noFeatureFlags{}
)

// AwsSdkV2 is a feature flag used to enable the use of aws sdk v2 which is expected to come with performance benefits
const AwsSdkV2 = "aws-sdk-v2"

// AlwaysReturnInfoMetrics is a feature flag used to enable the return of info metrics even when there are no corresponding CloudWatch metrics
const AlwaysReturnInfoMetrics = "always-return-info-metrics"

// FeatureFlags is an interface all objects that can tell wether or not a feature flag is enabled can implement.
type FeatureFlags interface {
	// IsFeatureEnabled tells if the feature flag identified by flag is enabled.
	IsFeatureEnabled(flag string) bool
}

// CtxWithFlags injects a FeatureFlags inside a given context.Context, so that they are easily communicated through layers.
func CtxWithFlags(ctx context.Context, ctrl FeatureFlags) context.Context {
	return context.WithValue(ctx, flagsCtxKey, ctrl)
}

// FlagsFromCtx retrieves a FeatureFlags from a given context.Context, defaulting to one with all feature flags disabled if none is found.
func FlagsFromCtx(ctx context.Context) FeatureFlags {
	if ctrl := ctx.Value(flagsCtxKey); ctrl != nil {
		return ctrl.(FeatureFlags)
	}
	return defaultFeatureFlags
}

// noFeatureFlags implements a no-op FeatureFlags
type noFeatureFlags struct{}

func (nff noFeatureFlags) IsFeatureEnabled(_ string) bool {
	return false
}