profiler: record Orchestrion, activation information (#2814)

For tracking adoption of SSI for profiling, record whether the profiler
was added using Orchestrion and how the profiler was activated,
following the internal "Adding SSI information to profiles" RFC.

profiler/profiler_test.go

@@ -30,6 +30,7 @@ import (
 	"gopkg.in/DataDog/dd-trace-go.v1/internal/globalconfig"
 	"gopkg.in/DataDog/dd-trace-go.v1/internal/httpmem"
 	"gopkg.in/DataDog/dd-trace-go.v1/internal/log"
+	"gopkg.in/DataDog/dd-trace-go.v1/internal/orchestrion"
 	"gopkg.in/DataDog/dd-trace-go.v1/internal/traceprof"
 	"gopkg.in/DataDog/dd-trace-go.v1/internal/version"
 
@@ -748,3 +749,33 @@ func TestUDSDefault(t *testing.T) {
 
 	<-profiles
 }
+
+func TestOrchestrionProfileInfo(t *testing.T) {
+	testCases := []struct {
+		env  string
+		want string
+	}{
+		{want: "manual"},
+		{env: "1", want: "manual"},
+		{env: "true", want: "manual"},
+		{env: "auto", want: "auto"},
+	}
+	for _, tc := range testCases {
+		t.Run(fmt.Sprintf("env=\"%s\"", tc.env), func(t *testing.T) {
+			t.Setenv("DD_PROFILING_ENABLED", tc.env)
+			p := doOneShortProfileUpload(t)
+			info := p.event.Info.Profiler
+			t.Logf("%+v", info)
+			if got := info.Activation; got != tc.want {
+				t.Errorf("wanted profiler activation \"%s\", got %s", tc.want, got)
+			}
+			want := "none"
+			if orchestrion.Enabled() {
+				want = "orchestrion"
+			}
+			if got := info.SSI.Mechanism; got != want {
+				t.Errorf("wanted profiler injected = %v, got %v", want, got)
+			}
+		})
+	}
+}

profiler/upload.go

@@ -16,10 +16,12 @@ import (
 	"mime/multipart"
 	"net/http"
 	"net/textproto"
+	"os"
 	"strings"
 	"time"
 
 	"gopkg.in/DataDog/dd-trace-go.v1/internal/log"
+	"gopkg.in/DataDog/dd-trace-go.v1/internal/orchestrion"
 )
 
 // maxRetries specifies the maximum number of retries to have when an error occurs.
@@ -144,6 +146,20 @@ type uploadEvent struct {
 	Version          string            `json:"version"`
 	EndpointCounts   map[string]uint64 `json:"endpoint_counts,omitempty"`
 	CustomAttributes []string          `json:"custom_attributes,omitempty"`
+	Info             struct {
+		Profiler profilerInfo `json:"profiler"`
+	} `json:"info"`
+}
+
+// profilerInfo holds profiler-specific information which should be attached to
+// the event for backend consumption
+type profilerInfo struct {
+	SSI struct {
+		Mechanism string `json:"mechanism,omitempty"`
+	} `json:"ssi"`
+	// Activation distinguishes how the profiler was enabled, either "auto"
+	// (env var set via admission controller) or "manual"
+	Activation string `json:"activation"`
 }
 
 // encode encodes the profile as a multipart mime request.
@@ -167,6 +183,22 @@ func encode(bat batch, tags []string) (contentType string, body io.Reader, err e
 		CustomAttributes: bat.customAttributes,
 	}
 
+	// DD_PROFILING_ENABLED is only used to enable profiling when added with
+	// Orchestrion. The "auto" value comes from the Datadog Kubernetes
+	// admission controller. Otherwise, the client library doesn't care
+	// about the value and assumes it was something "truthy", or this code
+	// wouldn't run. We just track it to be consistent with other languages
+	if os.Getenv("DD_PROFILING_ENABLED") == "auto" {
+		event.Info.Profiler.Activation = "auto"
+	} else {
+		event.Info.Profiler.Activation = "manual"
+	}
+	if orchestrion.Enabled() {
+		event.Info.Profiler.SSI.Mechanism = "orchestrion"
+	} else {
+		event.Info.Profiler.SSI.Mechanism = "none"
+	}
+
 	for _, p := range bat.profiles {
 		event.Attachments = append(event.Attachments, p.name)
 		f, err := mw.CreateFormFile(p.name, p.name)