From 058fd8adbf69fa88e2d2ac07075d9d222bafd209 Mon Sep 17 00:00:00 2001
From: Asim Aslam <asim@aslam.me>
Date: Sat, 18 Jan 2020 10:20:46 +0000
Subject: [PATCH] trace 1

---
 debug/trace/default.go | 71 ++++++++++++++++++++++++++++++++++++++++++
 debug/trace/options.go | 12 +++++++
 debug/trace/trace.go   | 48 ++++++++++++++++++++++++++++
 3 files changed, 131 insertions(+)
 create mode 100644 debug/trace/default.go
 create mode 100644 debug/trace/options.go
 create mode 100644 debug/trace/trace.go

diff --git a/debug/trace/default.go b/debug/trace/default.go
new file mode 100644
index 00000000..abbf1c15
--- /dev/null
+++ b/debug/trace/default.go
@@ -0,0 +1,71 @@
+package trace
+
+import (
+	"context"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/micro/go-micro/util/ring"
+)
+
+type trace struct {
+	opts Options
+
+	// ring buffer of traces
+	buffer *ring.Buffer
+}
+
+func (t *trace) Read(opts ...ReadOption) ([]*Span, error) {
+	return []*Span{}, nil
+}
+
+func (t *trace) Start(ctx context.Context, name string) *Span {
+	span := &Span{
+		Name:     name,
+		Trace:    uuid.New().String(),
+		Id:       uuid.New().String(),
+		Started:  time.Now(),
+		Metadata: make(map[string]string),
+	}
+
+	// return span if no context
+	if ctx == nil {
+		return span
+	}
+
+	s, ok := FromContext(ctx)
+	if !ok {
+		return span
+	}
+
+	// set trace id
+	span.Trace = s.Trace
+	// set parent
+	span.Parent = s.Id
+
+	// return the sapn
+	return span
+}
+
+func (t *trace) Finish(s *Span) error {
+	// set finished time
+	s.Finished = time.Now()
+
+	// save the span
+	t.buffer.Put(s)
+
+	return nil
+}
+
+func NewTrace(opts ...Option) Trace {
+	var options Options
+	for _, o := range opts {
+		o(&options)
+	}
+
+	return &trace{
+		opts: options,
+		// the last 64 requests
+		buffer: ring.New(64),
+	}
+}
diff --git a/debug/trace/options.go b/debug/trace/options.go
new file mode 100644
index 00000000..d92abad9
--- /dev/null
+++ b/debug/trace/options.go
@@ -0,0 +1,12 @@
+package trace
+
+type Options struct{}
+
+type Option func(o *Options)
+
+type ReadOptions struct {
+	// Trace id
+	Trace string
+}
+
+type ReadOption func(o *ReadOptions)
diff --git a/debug/trace/trace.go b/debug/trace/trace.go
new file mode 100644
index 00000000..4a4471c3
--- /dev/null
+++ b/debug/trace/trace.go
@@ -0,0 +1,48 @@
+// Package trace provides an interface for distributed tracing
+package trace
+
+import (
+	"context"
+	"time"
+)
+
+// Trace is an interface for distributed tracing
+type Trace interface {
+	// Start a trace
+	Start(ctx context.Context, name string) *Span
+	// Finish the trace
+	Finish(*Span) error
+	// Read the traces
+	Read(...ReadOption) ([]*Span, error)
+}
+
+// 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
+	// Finish time
+	Finished time.Time
+	// associated data
+	Metadata map[string]string
+}
+
+type spanKey struct{}
+
+// FromContext returns a span from context
+func FromContext(ctx context.Context) (*Span, bool) {
+	s, ok := ctx.Value(spanKey{}).(*Span)
+	return s, ok
+}
+
+// NewContext creates a new context with the span
+func NewContext(ctx context.Context, s *Span) context.Context {
+	return context.WithValue(ctx, spanKey{}, s)
+}