move out tracers

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

tracer/noop.go

@@ -0,0 +1,25 @@
+package tracer
+
+import "context"
+
+type noop struct{}
+
+func (n *noop) Init(...Option) error {
+	return nil
+}
+
+func (n *noop) Start(ctx context.Context, name string) (context.Context, *Span) {
+	return nil, nil
+}
+
+func (n *noop) Finish(*Span) error {
+	return nil
+}
+
+func (n *noop) Read(...ReadOption) ([]*Span, error) {
+	return nil, nil
+}
+
+func newTracer(opts ...Option) Tracer {
+	return &noop{}
+}

tracer/options.go

@@ -0,0 +1,34 @@
+package tracer
+
+type Options struct {
+	// Size is the size of ring buffer
+	Size int
+}
+
+type Option func(o *Options)
+
+type ReadOptions struct {
+	// Trace id
+	Trace string
+}
+
+type ReadOption func(o *ReadOptions)
+
+// Read the given trace
+func ReadTrace(t string) ReadOption {
+	return func(o *ReadOptions) {
+		o.Trace = t
+	}
+}
+
+const (
+	// DefaultSize of the buffer
+	DefaultSize = 64
+)
+
+// DefaultOptions returns default options
+func DefaultOptions() Options {
+	return Options{
+		Size: DefaultSize,
+	}
+}

tracer/trace.go

@@ -0,0 +1,81 @@
+// Package trace provides an interface for distributed tracing
+package tracer
+
+import (
+	"context"
+	"time"
+
+	"github.com/unistack-org/micro/v3/metadata"
+)
+
+var (
+	DefaultTracer Tracer = newTracer()
+)
+
+// Tracer is an interface for distributed tracing
+type Tracer interface {
+	// Start a trace
+	Start(ctx context.Context, name string) (context.Context, *Span)
+	// Finish the trace
+	Finish(*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 map[string]string
+	// Type
+	Type SpanType
+}
+
+const (
+	traceIDKey = "Micro-Trace-Id"
+	spanIDKey  = "Micro-Span-Id"
+)
+
+// FromContext returns a span from context
+func FromContext(ctx context.Context) (traceID string, parentSpanID string, isFound bool) {
+	traceID, traceOk := metadata.Get(ctx, traceIDKey)
+	microID, microOk := metadata.Get(ctx, "Micro-Id")
+	if !traceOk && !microOk {
+		isFound = false
+		return
+	}
+	if !traceOk {
+		traceID = microID
+	}
+	parentSpanID, ok := metadata.Get(ctx, spanIDKey)
+	return traceID, parentSpanID, ok
+}
+
+// ToContext saves the trace and span ids in the context
+func ToContext(ctx context.Context, traceID, parentSpanID string) context.Context {
+	return metadata.MergeContext(ctx, map[string]string{
+		traceIDKey: traceID,
+		spanIDKey:  parentSpanID,
+	}, true)
+}