tracer: finalize tracer implementation

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

tracer/noop.go

@@ -0,0 +1,69 @@
+package tracer
+
+import (
+	"context"
+)
+
+type noopTracer struct {
+	opts Options
+}
+
+func (t *noopTracer) Start(ctx context.Context, name string, opts ...SpanOption) (context.Context, Span) {
+	span := &noopSpan{
+		name:   name,
+		ctx:    ctx,
+		tracer: t,
+	}
+	if span.ctx == nil {
+		span.ctx = context.Background()
+	}
+	return NewSpanContext(ctx, span), span
+}
+
+func (t *noopTracer) Init(opts ...Option) error {
+	for _, o := range opts {
+		o(&t.opts)
+	}
+	return nil
+}
+
+func (t *noopTracer) Name() string {
+	return t.opts.Name
+}
+
+type noopSpan struct {
+	name   string
+	ctx    context.Context
+	tracer Tracer
+}
+
+func (s *noopSpan) Finish(opts ...SpanOption) {
+
+}
+
+func (s *noopSpan) Context() context.Context {
+	return s.ctx
+}
+
+func (s *noopSpan) Tracer() Tracer {
+	return s.tracer
+}
+
+func (s *noopSpan) AddEvent(name string, opts ...EventOption) {
+
+}
+
+func (s *noopSpan) SetName(name string) {
+	s.name = name
+}
+
+func (s *noopSpan) SetLabels(labels ...Label) {
+
+}
+
+// NewTracer returns new memory tracer
+func NewTracer(opts ...Option) Tracer {
+	return &noopTracer{
+		opts: NewOptions(opts...),
+	}
+}