micro: rewrite options to support multiple building blocks

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

tracer/tracer.go

@@ -0,0 +1,58 @@
+// Package tracer provides an interface for distributed tracing
+package tracer
+
+import (
+	"context"
+	"time"
+
+	"github.com/unistack-org/micro/v3/metadata"
+)
+
+var (
+	// DefaultTracer is the global default tracer
+	DefaultTracer Tracer = NewTracer()
+)
+
+// Tracer is an interface for distributed tracing
+type Tracer interface {
+	Name() string
+	Init(...Option) error
+	// Start a trace
+	Start(ctx context.Context, name string) (context.Context, *Span)
+	// Finish the trace
+	Finish(*Span) error
+	// Lookup get span from context
+	Lookup(ctx context.Context) (*Span, error)
+	// Read the traces
+	Read(...ReadOption) ([]*Span, error)
+}
+
+// SpanType describe the nature of the trace span
+type SpanType int
+
+const (
+	// SpanTypeRequestInbound is a span created when serving a request
+	SpanTypeRequestInbound SpanType = iota
+	// SpanTypeRequestOutbound is a span created when making a service call
+	SpanTypeRequestOutbound
+)
+
+// Span is used to record an entry
+type Span struct {
+	// Id of the trace
+	Trace string
+	// name of the span
+	Name string
+	// id of the span
+	Id string
+	// parent span id
+	Parent string
+	// Start time
+	Started time.Time
+	// Duration in nano seconds
+	Duration time.Duration
+	// associated data
+	Metadata metadata.Metadata
+	// Type
+	Type SpanType
+}