tracer: Refactor TracerProviderConfig

sdk/trace/provider.go

@@ -31,11 +31,13 @@ const (
 	defaultTracerName = "go.opentelemetry.io/otel/sdk/tracer"
 )
 
-// TODO (MrAlias): unify this API option design:
-// https://github.com/open-telemetry/opentelemetry-go/issues/536
-
-// TracerProviderConfig
-type TracerProviderConfig struct {
+// tracerProviderConfig
+type tracerProviderConfig struct {
+	// processors contains collection of SpanProcessors that are processing pipeline
+	// for spans in the trace signal.
+	// SpanProcessors registered with a TracerProvider and are called at the start
+	// and end of a Span's lifecycle, and are called in the order they are
+	// registered.
 	processors []SpanProcessor
 
 	// sampler is the default sampler used when creating new spans.
@@ -51,8 +53,6 @@ type TracerProviderConfig struct {
 	resource *resource.Resource
 }
 
-type TracerProviderOption func(*TracerProviderConfig)
-
 type TracerProvider struct {
 	mu             sync.Mutex
 	namedTracer    map[instrumentation.Library]*tracer
@@ -76,10 +76,10 @@ var _ trace.TracerProvider = &TracerProvider{}
 // The passed opts are used to override these default values and configure the
 // returned TracerProvider appropriately.
 func NewTracerProvider(opts ...TracerProviderOption) *TracerProvider {
-	o := &TracerProviderConfig{}
+	o := &tracerProviderConfig{}
 
 	for _, opt := range opts {
-		opt(o)
+		opt.apply(o)
 	}
 
 	ensureValidTracerProviderConfig(o)
@@ -234,6 +234,16 @@ func (p *TracerProvider) Shutdown(ctx context.Context) error {
 	return nil
 }
 
+type TracerProviderOption interface {
+	apply(*tracerProviderConfig)
+}
+
+type traceProviderOptionFunc func(*tracerProviderConfig)
+
+func (fn traceProviderOptionFunc) apply(cfg *tracerProviderConfig) {
+	fn(cfg)
+}
+
 // WithSyncer registers the exporter with the TracerProvider using a
 // SimpleSpanProcessor.
 //
@@ -254,9 +264,9 @@ func WithBatcher(e SpanExporter, opts ...BatchSpanProcessorOption) TracerProvide
 
 // WithSpanProcessor registers the SpanProcessor with a TracerProvider.
 func WithSpanProcessor(sp SpanProcessor) TracerProviderOption {
-	return func(opts *TracerProviderConfig) {
+	return traceProviderOptionFunc(func(opts *tracerProviderConfig) {
 		opts.processors = append(opts.processors, sp)
-	}
+	})
 }
 
 // WithResource returns a TracerProviderOption that will configure the
@@ -267,9 +277,9 @@ func WithSpanProcessor(sp SpanProcessor) TracerProviderOption {
 // If this option is not used, the TracerProvider will use the
 // resource.Default() Resource by default.
 func WithResource(r *resource.Resource) TracerProviderOption {
-	return func(opts *TracerProviderConfig) {
+	return traceProviderOptionFunc(func(opts *tracerProviderConfig) {
 		opts.resource = resource.Merge(resource.Environment(), r)
-	}
+	})
 }
 
 // WithIDGenerator returns a TracerProviderOption that will configure the
@@ -280,11 +290,11 @@ func WithResource(r *resource.Resource) TracerProviderOption {
 // If this option is not used, the TracerProvider will use a random number
 // IDGenerator by default.
 func WithIDGenerator(g IDGenerator) TracerProviderOption {
-	return func(opts *TracerProviderConfig) {
+	return traceProviderOptionFunc(func(opts *tracerProviderConfig) {
 		if g != nil {
 			opts.idGenerator = g
 		}
-	}
+	})
 }
 
 // WithSampler returns a TracerProviderOption that will configure the Sampler
@@ -295,11 +305,11 @@ func WithIDGenerator(g IDGenerator) TracerProviderOption {
 // If this option is not used, the TracerProvider will use a
 // ParentBased(AlwaysSample) Sampler by default.
 func WithSampler(s Sampler) TracerProviderOption {
-	return func(opts *TracerProviderConfig) {
+	return traceProviderOptionFunc(func(opts *tracerProviderConfig) {
 		if s != nil {
 			opts.sampler = s
 		}
-	}
+	})
 }
 
 // WithSpanLimits returns a TracerProviderOption that will configure the
@@ -310,13 +320,13 @@ func WithSampler(s Sampler) TracerProviderOption {
 // If this option is not used, the TracerProvider will use the default
 // SpanLimits.
 func WithSpanLimits(sl SpanLimits) TracerProviderOption {
-	return func(opts *TracerProviderConfig) {
+	return traceProviderOptionFunc(func(opts *tracerProviderConfig) {
 		opts.spanLimits = sl
-	}
+	})
 }
 
 // ensureValidTracerProviderConfig ensures that given TracerProviderConfig is valid.
-func ensureValidTracerProviderConfig(cfg *TracerProviderConfig) {
+func ensureValidTracerProviderConfig(cfg *tracerProviderConfig) {
 	if cfg.sampler == nil {
 		cfg.sampler = ParentBased(AlwaysSample())
 	}