temp commit

vendor/github.com/Azure/go-autorest/tracing/tracing.go

@@ -0,0 +1,195 @@
+package tracing
+
+// Copyright 2018 Microsoft Corporation
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"os"
+
+	"contrib.go.opencensus.io/exporter/ocagent"
+	"go.opencensus.io/plugin/ochttp"
+	"go.opencensus.io/plugin/ochttp/propagation/tracecontext"
+	"go.opencensus.io/stats/view"
+	"go.opencensus.io/trace"
+)
+
+var (
+	// Transport is the default tracing RoundTripper. The custom options setter will control
+	// if traces are being emitted or not.
+	Transport = NewTransport()
+
+	// enabled is the flag for marking if tracing is enabled.
+	enabled = false
+
+	// Sampler is the tracing sampler. If tracing is disabled it will never sample. Otherwise
+	// it will be using the parent sampler or the default.
+	sampler = trace.NeverSample()
+
+	// Views for metric instrumentation.
+	views = map[string]*view.View{}
+
+	// the trace exporter
+	traceExporter trace.Exporter
+)
+
+func init() {
+	enableFromEnv()
+}
+
+func enableFromEnv() {
+	_, ok := os.LookupEnv("AZURE_SDK_TRACING_ENABLED")
+	_, legacyOk := os.LookupEnv("AZURE_SDK_TRACING_ENABELD")
+	if ok || legacyOk {
+		agentEndpoint, ok := os.LookupEnv("OCAGENT_TRACE_EXPORTER_ENDPOINT")
+
+		if ok {
+			EnableWithAIForwarding(agentEndpoint)
+		} else {
+			Enable()
+		}
+	}
+}
+
+// NewTransport returns a new instance of a tracing-aware RoundTripper.
+func NewTransport() *ochttp.Transport {
+	return &ochttp.Transport{
+		Propagation:     &tracecontext.HTTPFormat{},
+		GetStartOptions: getStartOptions,
+	}
+}
+
+// IsEnabled returns true if monitoring is enabled for the sdk.
+func IsEnabled() bool {
+	return enabled
+}
+
+// Enable will start instrumentation for metrics and traces.
+func Enable() error {
+	enabled = true
+	sampler = nil
+
+	err := initStats()
+	return err
+}
+
+// Disable will disable instrumentation for metrics and traces.
+func Disable() {
+	disableStats()
+	sampler = trace.NeverSample()
+	if traceExporter != nil {
+		trace.UnregisterExporter(traceExporter)
+	}
+	enabled = false
+}
+
+// EnableWithAIForwarding will start instrumentation and will connect to app insights forwarder
+// exporter making the metrics and traces available in app insights.
+func EnableWithAIForwarding(agentEndpoint string) (err error) {
+	err = Enable()
+	if err != nil {
+		return err
+	}
+
+	traceExporter, err := ocagent.NewExporter(ocagent.WithInsecure(), ocagent.WithAddress(agentEndpoint))
+	if err != nil {
+		return err
+	}
+	trace.RegisterExporter(traceExporter)
+	return
+}
+
+// getStartOptions is the custom options setter for the ochttp package.
+func getStartOptions(*http.Request) trace.StartOptions {
+	return trace.StartOptions{
+		Sampler: sampler,
+	}
+}
+
+// initStats registers the views for the http metrics
+func initStats() (err error) {
+	clientViews := []*view.View{
+		ochttp.ClientCompletedCount,
+		ochttp.ClientRoundtripLatencyDistribution,
+		ochttp.ClientReceivedBytesDistribution,
+		ochttp.ClientSentBytesDistribution,
+	}
+	for _, cv := range clientViews {
+		vn := fmt.Sprintf("Azure/go-autorest/tracing-%s", cv.Name)
+		views[vn] = cv.WithName(vn)
+		err = view.Register(views[vn])
+		if err != nil {
+			return err
+		}
+	}
+	return
+}
+
+// disableStats will unregister the previously registered metrics
+func disableStats() {
+	for _, v := range views {
+		view.Unregister(v)
+	}
+}
+
+// StartSpan starts a trace span
+func StartSpan(ctx context.Context, name string) context.Context {
+	ctx, _ = trace.StartSpan(ctx, name, trace.WithSampler(sampler))
+	return ctx
+}
+
+// EndSpan ends a previously started span stored in the context
+func EndSpan(ctx context.Context, httpStatusCode int, err error) {
+	span := trace.FromContext(ctx)
+
+	if span == nil {
+		return
+	}
+
+	if err != nil {
+		span.SetStatus(trace.Status{Message: err.Error(), Code: toTraceStatusCode(httpStatusCode)})
+	}
+	span.End()
+}
+
+// toTraceStatusCode converts HTTP Codes to OpenCensus codes as defined
+// at https://github.com/census-instrumentation/opencensus-specs/blob/master/trace/HTTP.md#status
+func toTraceStatusCode(httpStatusCode int) int32 {
+	switch {
+	case http.StatusOK <= httpStatusCode && httpStatusCode < http.StatusBadRequest:
+		return trace.StatusCodeOK
+	case httpStatusCode == http.StatusBadRequest:
+		return trace.StatusCodeInvalidArgument
+	case httpStatusCode == http.StatusUnauthorized: // 401 is actually unauthenticated.
+		return trace.StatusCodeUnauthenticated
+	case httpStatusCode == http.StatusForbidden:
+		return trace.StatusCodePermissionDenied
+	case httpStatusCode == http.StatusNotFound:
+		return trace.StatusCodeNotFound
+	case httpStatusCode == http.StatusTooManyRequests:
+		return trace.StatusCodeResourceExhausted
+	case httpStatusCode == 499:
+		return trace.StatusCodeCancelled
+	case httpStatusCode == http.StatusNotImplemented:
+		return trace.StatusCodeUnimplemented
+	case httpStatusCode == http.StatusServiceUnavailable:
+		return trace.StatusCodeUnavailable
+	case httpStatusCode == http.StatusGatewayTimeout:
+		return trace.StatusCodeDeadlineExceeded
+	default:
+		return trace.StatusCodeUnknown
+	}
+}