Add supporting features to enable distributed tracing

This includes new internal pipeline policies and other supporting types.
See the changelog for a full description.
Added some missing doc comments.

sdk/azcore/CHANGELOG.md

@@ -3,6 +3,14 @@
 ## 1.5.0-beta.2 (Unreleased)
 
 ### Features Added
+* Added supporting features to enable distributed tracing.
+  * Added func `runtime.StartSpan()` for use by SDKs to start spans.
+  * Added method `WithContext()` to `runtime.Request` to support shallow cloning with a new context.
+  * Added field `TracingNamespace` to `runtime.PipelineOptions`.
+  * Added field `Tracer` to `runtime.NewPollerOptions` and `runtime.NewPollerFromResumeTokenOptions` types.
+  * Added field `SpanFromContext` to `tracing.TracerOptions`.
+  * Added methods `Enabled()`, `SetAttributes()`, and `SpanFromContext()` to `tracing.Tracer`.
+  * Added supporting pipeline policies to include HTTP spans when creating clients.
 
 ### Breaking Changes
 

sdk/azcore/arm/runtime/pipeline.go

@@ -13,6 +13,7 @@ import (
 	"github.com/Azure/azure-sdk-for-go/sdk/azcore"
 	armpolicy "github.com/Azure/azure-sdk-for-go/sdk/azcore/arm/policy"
 	"github.com/Azure/azure-sdk-for-go/sdk/azcore/cloud"
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore/internal/exported"
 	azpolicy "github.com/Azure/azure-sdk-for-go/sdk/azcore/policy"
 	azruntime "github.com/Azure/azure-sdk-for-go/sdk/azcore/runtime"
 )
@@ -34,7 +35,7 @@ func NewPipeline(module, version string, cred azcore.TokenCredential, plOpts azr
 	})
 	perRetry := make([]azpolicy.Policy, len(plOpts.PerRetry), len(plOpts.PerRetry)+1)
 	copy(perRetry, plOpts.PerRetry)
-	plOpts.PerRetry = append(perRetry, authPolicy)
+	plOpts.PerRetry = append(perRetry, authPolicy, exported.PolicyFunc(httpTraceNamespacePolicy))
 	if !options.DisableRPRegistration {
 		regRPOpts := armpolicy.RegistrationOptions{ClientOptions: options.ClientOptions}
 		regPolicy, err := NewRPRegistrationPolicy(cred, &regRPOpts)

sdk/azcore/arm/runtime/policy_trace_namespace.go

@@ -0,0 +1,31 @@
+//go:build go1.18
+// +build go1.18
+
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+package runtime
+
+import (
+	"net/http"
+
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore/arm/internal/resource"
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore/internal/shared"
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore/policy"
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore/tracing"
+)
+
+// httpTraceNamespacePolicy is a policy that adds the az.namespace attribute to the current Span
+func httpTraceNamespacePolicy(req *policy.Request) (resp *http.Response, err error) {
+	rawTracer := req.Raw().Context().Value(shared.CtxWithTracingTracer{})
+	if tracer, ok := rawTracer.(tracing.Tracer); ok {
+		rt, err := resource.ParseResourceType(req.Raw().URL.Path)
+		if err == nil {
+			// add the namespace attribute to the current span
+			if span, ok := tracer.SpanFromContext(req.Raw().Context()); ok {
+				span.SetAttributes(tracing.Attribute{Key: "az.namespace", Value: rt.Namespace})
+			}
+		}
+	}
+	return req.Next()
+}

sdk/azcore/arm/runtime/policy_trace_namespace_test.go

@@ -0,0 +1,97 @@
+//go:build go1.18
+// +build go1.18
+
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+package runtime
+
+import (
+	"context"
+	"net/http"
+	"testing"
+
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore/internal/exported"
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore/internal/shared"
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore/tracing"
+	"github.com/Azure/azure-sdk-for-go/sdk/internal/mock"
+	"github.com/stretchr/testify/require"
+)
+
+func TestHTTPTraceNamespacePolicy(t *testing.T) {
+	srv, close := mock.NewServer()
+	defer close()
+
+	pl := exported.NewPipeline(srv, exported.PolicyFunc(httpTraceNamespacePolicy))
+
+	// no tracer
+	req, err := exported.NewRequest(context.Background(), http.MethodGet, srv.URL())
+	require.NoError(t, err)
+	srv.AppendResponse()
+	_, err = pl.Do(req)
+	require.NoError(t, err)
+
+	// wrong tracer type
+	req, err = exported.NewRequest(context.WithValue(context.Background(), shared.CtxWithTracingTracer{}, 0), http.MethodGet, srv.URL())
+	require.NoError(t, err)
+	srv.AppendResponse()
+	_, err = pl.Do(req)
+	require.NoError(t, err)
+
+	// no SpanFromContext impl
+	tr := tracing.NewTracer(func(ctx context.Context, spanName string, options *tracing.SpanOptions) (context.Context, tracing.Span) {
+		return ctx, tracing.Span{}
+	}, nil)
+	req, err = exported.NewRequest(context.WithValue(context.Background(), shared.CtxWithTracingTracer{}, tr), http.MethodGet, srv.URL())
+	require.NoError(t, err)
+	srv.AppendResponse()
+	_, err = pl.Do(req)
+	require.NoError(t, err)
+
+	// failed to parse resource ID, shouldn't call SetAttributes
+	var attrString string
+	tr = tracing.NewTracer(func(ctx context.Context, spanName string, options *tracing.SpanOptions) (context.Context, tracing.Span) {
+		return ctx, tracing.Span{}
+	}, &tracing.TracerOptions{
+		SpanFromContext: func(ctx context.Context) (tracing.Span, bool) {
+			spanImpl := tracing.SpanImpl{
+				SetAttributes: func(a ...tracing.Attribute) {
+					require.Len(t, a, 1)
+					v, ok := a[0].Value.(string)
+					require.True(t, ok)
+					attrString = a[0].Key + ":" + v
+				},
+			}
+			return tracing.NewSpan(spanImpl), true
+		},
+	})
+	req, err = exported.NewRequest(context.WithValue(context.Background(), shared.CtxWithTracingTracer{}, tr), http.MethodGet, srv.URL())
+	require.NoError(t, err)
+	srv.AppendResponse()
+	_, err = pl.Do(req)
+	require.NoError(t, err)
+	require.Empty(t, attrString)
+
+	// success
+	tr = tracing.NewTracer(func(ctx context.Context, spanName string, options *tracing.SpanOptions) (context.Context, tracing.Span) {
+		return ctx, tracing.Span{}
+	}, &tracing.TracerOptions{
+		SpanFromContext: func(ctx context.Context) (tracing.Span, bool) {
+			spanImpl := tracing.SpanImpl{
+				SetAttributes: func(a ...tracing.Attribute) {
+					require.Len(t, a, 1)
+					v, ok := a[0].Value.(string)
+					require.True(t, ok)
+					attrString = a[0].Key + ":" + v
+				},
+			}
+			return tracing.NewSpan(spanImpl), true
+		},
+	})
+	req, err = exported.NewRequest(context.WithValue(context.Background(), shared.CtxWithTracingTracer{}, tr), http.MethodGet, srv.URL()+requestEndpoint)
+	require.NoError(t, err)
+	srv.AppendResponse()
+	_, err = pl.Do(req)
+	require.NoError(t, err)
+	require.EqualValues(t, "az.namespace:Microsoft.Storage", attrString)
+}

sdk/azcore/core.go

@@ -99,6 +99,9 @@ func NewClient(clientName, moduleVersion string, plOpts runtime.PipelineOptions,
 	pl := runtime.NewPipeline(pkg, moduleVersion, plOpts, options)
 
 	tr := options.TracingProvider.NewTracer(clientName, moduleVersion)
+	if tr.Enabled() && plOpts.TracingNamespace != "" {
+		tr.SetAttributes(tracing.Attribute{Key: "az.namespace", Value: plOpts.TracingNamespace})
+	}
 	return &Client{pl: pl, tr: tr}, nil
 }
 

sdk/azcore/core_test.go

@@ -7,11 +7,17 @@
 package azcore
 
 import (
+	"context"
+	"net/http"
 	"reflect"
 	"testing"
 
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore/internal/exported"
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore/internal/shared"
 	"github.com/Azure/azure-sdk-for-go/sdk/azcore/policy"
 	"github.com/Azure/azure-sdk-for-go/sdk/azcore/runtime"
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore/tracing"
+	"github.com/Azure/azure-sdk-for-go/sdk/internal/mock"
 	"github.com/stretchr/testify/require"
 )
 
@@ -131,3 +137,37 @@ func TestNewClientError(t *testing.T) {
 	require.Error(t, err)
 	require.Nil(t, client)
 }
+
+func TestNewClientTracingEnabled(t *testing.T) {
+	srv, close := mock.NewServer()
+	defer close()
+
+	var attrString string
+	client, err := NewClient("package.Client", "v1.0.0", runtime.PipelineOptions{TracingNamespace: "Widget.Factory"}, &policy.ClientOptions{
+		TracingProvider: tracing.NewProvider(func(name, version string) tracing.Tracer {
+			return tracing.NewTracer(func(ctx context.Context, spanName string, options *tracing.SpanOptions) (context.Context, tracing.Span) {
+				require.NotNil(t, options)
+				for _, attr := range options.Attributes {
+					if attr.Key == "az.namespace" {
+						v, ok := attr.Value.(string)
+						require.True(t, ok)
+						attrString = attr.Key + ":" + v
+					}
+				}
+				return ctx, tracing.Span{}
+			}, nil)
+		}, nil),
+		Transport: srv,
+	})
+	require.NoError(t, err)
+	require.NotNil(t, client)
+	require.NotZero(t, client.Pipeline())
+	require.NotZero(t, client.Tracer())
+
+	const requestEndpoint = "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/fakeResourceGroupo/providers/Microsoft.Storage/storageAccounts/fakeAccountName"
+	req, err := exported.NewRequest(context.WithValue(context.Background(), shared.CtxWithTracingTracer{}, client.Tracer()), http.MethodGet, srv.URL()+requestEndpoint)
+	require.NoError(t, err)
+	srv.AppendResponse()
+	client.Pipeline().Do(req)
+	require.EqualValues(t, "az.namespace:Widget.Factory", attrString)
+}

sdk/azcore/internal/exported/request.go

@@ -170,6 +170,14 @@ func (req *Request) Clone(ctx context.Context) *Request {
 	return &r2
 }
 
+// WithContext returns a shallow copy of the request with its context changed to ctx.
+func (req *Request) WithContext(ctx context.Context) *Request {
+	r2 := new(Request)
+	*r2 = *req
+	r2.req = r2.req.WithContext(ctx)
+	return r2
+}
+
 // not exported but dependent on Request
 
 // PolicyFunc is a type that implements the Policy interface.

sdk/azcore/internal/exported/request_test.go

@@ -194,3 +194,20 @@ func TestNewRequestFail(t *testing.T) {
 		t.Fatal("unexpected request")
 	}
 }
+
+func TestRequestWithContext(t *testing.T) {
+	type ctxKey1 struct{}
+	type ctxKey2 struct{}
+
+	req1, err := NewRequest(context.WithValue(context.Background(), ctxKey1{}, 1), http.MethodPost, testURL)
+	require.NoError(t, err)
+	require.NotNil(t, req1.Raw().Context().Value(ctxKey1{}))
+
+	req2 := req1.WithContext(context.WithValue(context.Background(), ctxKey2{}, 1))
+	require.Nil(t, req2.Raw().Context().Value(ctxKey1{}))
+	require.NotNil(t, req2.Raw().Context().Value(ctxKey2{}))
+
+	// shallow copy, so changing req2 affects req1
+	req2.Raw().Header.Add("added-req2", "value")
+	require.EqualValues(t, "value", req1.Raw().Header.Get("added-req2"))
+}

sdk/azcore/internal/shared/constants.go

@@ -23,6 +23,7 @@ const (
 	HeaderUserAgent              = "User-Agent"
 	HeaderWWWAuthenticate        = "WWW-Authenticate"
 	HeaderXMSClientRequestID     = "x-ms-client-request-id"
+	HeaderXMSRequestID           = "x-ms-request-id"
 )
 
 const BearerTokenPrefix = "Bearer "

sdk/azcore/internal/shared/shared.go

@@ -28,6 +28,9 @@ type CtxWithRetryOptionsKey struct{}
 // CtxIncludeResponseKey is used as a context key for retrieving the raw response.
 type CtxIncludeResponseKey struct{}
 
+// CtxWithTracingTracer is used as a context key for adding/retrieving tracing.Tracer.
+type CtxWithTracingTracer struct{}
+
 // Delay waits for the duration to elapse or the context to be cancelled.
 func Delay(ctx context.Context, delay time.Duration) error {
 	select {

sdk/azcore/policy/policy.go

@@ -29,7 +29,8 @@ type Request = exported.Request
 // ClientOptions contains optional settings for a client's pipeline.
 // All zero-value fields will be initialized with default values.
 type ClientOptions struct {
-	// APIVersion overrides the default version requested of the service. Set with caution as this package version has not been tested with arbitrary service versions.
+	// APIVersion overrides the default version requested of the service.
+	// Set with caution as this package version has not been tested with arbitrary service versions.
 	APIVersion string
 
 	// Cloud specifies a cloud for the client. The default is Azure Public Cloud.

sdk/azcore/runtime/pipeline.go

@@ -13,9 +13,29 @@ import (
 
 // PipelineOptions contains Pipeline options for SDK developers
 type PipelineOptions struct {
-	AllowedHeaders, AllowedQueryParameters []string
-	APIVersion                             APIVersionOptions
-	PerCall, PerRetry                      []policy.Policy
+	// AllowedHeaders is the slice of headers to log with their values intact.
+	// All headers not in the slice will have their values REDACTED.
+	// Applies to request and response headers.
+	AllowedHeaders []string
+
+	// AllowedQueryParameters is the slice of query parameters to log with their values intact.
+	// All query parameters not in the slice will have their values REDACTED.
+	AllowedQueryParameters []string
+
+	// APIVersion overrides the default version requested of the service.
+	// Set with caution as this package version has not been tested with arbitrary service versions.
+	APIVersion APIVersionOptions
+
+	// PerCall contains custom policies to inject into the pipeline.
+	// Each policy is executed once per request.
+	PerCall []policy.Policy
+
+	// PerRetry contains custom policies to inject into the pipeline.
+	// Each policy is executed once per request, and for each retry of that request.
+	PerRetry []policy.Policy
+
+	// TracingNamespace contains the value to use for the az.namespace span attribute.
+	TracingNamespace string
 }
 
 // Pipeline represents a primitive for sending HTTP requests and receiving responses.
@@ -58,6 +78,7 @@ func NewPipeline(module, version string, plOpts PipelineOptions, options *policy
 	policies = append(policies, cp.PerRetryPolicies...)
 	policies = append(policies, NewLogPolicy(&cp.Logging))
 	policies = append(policies, exported.PolicyFunc(httpHeaderPolicy), exported.PolicyFunc(bodyDownloadPolicy))
+	policies = append(policies, newHTTPTracePolicy(cp.Logging.AllowedQueryParams))
 	transport := cp.Transport
 	if transport == nil {
 		transport = defaultHTTPClient