otel: include service instance id attribute to resource and move to metricutil package

Add the service instance id to the resource attributes to prevent
downstream OTEL processors and exporters from thinking that the CLI
invocations are a single process that keeps restarting. The unique id
can be removed through downstream aggregation to prevent cardinality
issues, but we need some way to tell OTEL that it shouldn't reset the
counters.

Move the check for the experimental flag to its own package and then use
that invocation to prevent creating exporters so metrics are disabled
completely. This makes it so we don't have to check for the experimental
flag in every place we add metrics until we decide to make metrics
stable in general.

This also moves the OTEL initialization to a `util/metricutil` package
to be more consistent with the existing util naming and to differentiate
it from the upstream `metric` name. Using both `metrics` and `metric` as
import names was confusing since `metric` was an upstream dependency and
`metrics` was a local utility. `metricutil` matches with the existing
utilities and makes clear that it isn't a spelling mistake.

The record version metric has been removed since we weren't planning on
keeping that metric anyway and most of the information is now included
in the instrumentation library name and version. That function is
included as a utility in the `otel/sdk/metric` package to retrieve the
appropriate meter from the meter provider.

Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com>

util/confutil/exp.go

@@ -0,0 +1,15 @@
+package confutil
+
+import (
+	"os"
+	"strconv"
+)
+
+// IsExperimental checks if the experimental flag has been configured.
+func IsExperimental() bool {
+	if v, ok := os.LookupEnv("BUILDX_EXPERIMENTAL"); ok {
+		vv, _ := strconv.ParseBool(v)
+		return vv
+	}
+	return false
+}

util/metricutil/metric.go

@@ -1,4 +1,4 @@
-package metrics
+package metricutil
 
 import (
 	"context"
@@ -7,8 +7,9 @@ import (
 	"path"
 	"time"
 
+	"github.com/docker/buildx/util/confutil"
+	"github.com/docker/buildx/version"
 	"github.com/docker/cli/cli/command"
-	"github.com/moby/buildkit/util/tracing/detect"
 	"github.com/pkg/errors"
 	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
 	"go.opentelemetry.io/otel/metric"
@@ -20,75 +21,86 @@ import (
 
 const (
 	otelConfigFieldName = "otel"
-	shutdownTimeout     = 2 * time.Second
+	reportTimeout       = 2 * time.Second
 )
 
-// ReportFunc is invoked to signal the metrics should be sent to the
-// desired endpoint. It should be invoked on application shutdown.
-type ReportFunc func()
+// MeterProvider holds a MeterProvider for metric generation and the configured
+// exporters for reporting metrics from the CLI.
+type MeterProvider struct {
+	metric.MeterProvider
+	reader    *sdkmetric.ManualReader
+	exporters []sdkmetric.Exporter
+}
 
-// MeterProvider returns a MeterProvider suitable for CLI usage.
-// The primary difference between this metric reader and a more typical
-// usage is that metric reporting only happens once when ReportFunc
-// is invoked.
-func MeterProvider(cli command.Cli) (metric.MeterProvider, ReportFunc, error) {
+// NewMeterProvider configures a MeterProvider from the CLI context.
+func NewMeterProvider(ctx context.Context, cli command.Cli) (*MeterProvider, error) {
 	var exps []sdkmetric.Exporter
 
-	if exp, err := dockerOtelExporter(cli); err != nil {
-		return nil, nil, err
-	} else if exp != nil {
-		exps = append(exps, exp)
-	}
+	// Only metric exporters if the experimental flag is set.
+	if confutil.IsExperimental() {
+		if exp, err := dockerOtelExporter(cli); err != nil {
+			return nil, err
+		} else if exp != nil {
+			exps = append(exps, exp)
+		}
 
-	if exp, err := detectOtlpExporter(context.Background()); err != nil {
-		return nil, nil, err
-	} else if exp != nil {
-		exps = append(exps, exp)
+		if exp, err := detectOtlpExporter(ctx); err != nil {
+			return nil, err
+		} else if exp != nil {
+			exps = append(exps, exp)
+		}
 	}
 
 	if len(exps) == 0 {
 		// No exporters are configured so use a noop provider.
-		return noop.NewMeterProvider(), func() {}, nil
+		return &MeterProvider{
+			MeterProvider: noop.NewMeterProvider(),
+		}, nil
 	}
 
-	// Use delta temporality because, since this is a CLI program, we can never
-	// know the cumulative value.
 	reader := sdkmetric.NewManualReader(
 		sdkmetric.WithTemporalitySelector(deltaTemporality),
 	)
 	mp := sdkmetric.NewMeterProvider(
-		sdkmetric.WithResource(detect.Resource()),
+		sdkmetric.WithResource(Resource()),
 		sdkmetric.WithReader(reader),
 	)
-	return mp, reportFunc(reader, exps), nil
+	return &MeterProvider{
+		MeterProvider: mp,
+		reader:        reader,
+		exporters:     exps,
+	}, nil
 }
 
-// reportFunc returns a ReportFunc for collecting ResourceMetrics and then
-// exporting them to the configured Exporter.
-func reportFunc(reader sdkmetric.Reader, exps []sdkmetric.Exporter) ReportFunc {
-	return func() {
-		ctx, cancel := context.WithTimeout(context.Background(), shutdownTimeout)
-		defer cancel()
-
-		var rm metricdata.ResourceMetrics
-		if err := reader.Collect(ctx, &rm); err != nil {
-			// Error when collecting metrics. Do not send any.
-			return
-		}
-
-		var eg errgroup.Group
-		for _, exp := range exps {
-			exp := exp
-			eg.Go(func() error {
-				_ = exp.Export(ctx, &rm)
-				_ = exp.Shutdown(ctx)
-				return nil
-			})
-		}
-
-		// Can't report an error because we don't allow it to.
-		_ = eg.Wait()
+// Report exports metrics to the configured exporter. This should be done before the CLI
+// exits.
+func (m *MeterProvider) Report(ctx context.Context) {
+	if m.reader == nil {
+		// Not configured.
+		return
 	}
+
+	ctx, cancel := context.WithTimeout(ctx, reportTimeout)
+	defer cancel()
+
+	var rm metricdata.ResourceMetrics
+	if err := m.reader.Collect(ctx, &rm); err != nil {
+		// Error when collecting metrics. Do not send any.
+		return
+	}
+
+	var eg errgroup.Group
+	for _, exp := range m.exporters {
+		exp := exp
+		eg.Go(func() error {
+			_ = exp.Export(ctx, &rm)
+			_ = exp.Shutdown(ctx)
+			return nil
+		})
+	}
+
+	// Can't report an error because we don't allow it to.
+	_ = eg.Wait()
 }
 
 // dockerOtelExporter reads the CLI metadata to determine an OTLP exporter
@@ -184,6 +196,20 @@ func otelExporterOtlpEndpoint(cli command.Cli) (string, error) {
 }
 
 // deltaTemporality sets the Temporality of every instrument to delta.
+//
+// This isn't really needed since we create a unique resource on each invocation,
+// but it can help with cardinality concerns for downstream processors since they can
+// perform aggregation for a time interval and then discard the data once that time
+// period has passed. Cumulative temporality would imply to the downstream processor
+// that they might receive a successive point and they may unnecessarily keep state
+// they really shouldn't.
 func deltaTemporality(_ sdkmetric.InstrumentKind) metricdata.Temporality {
 	return metricdata.DeltaTemporality
 }
+
+// Meter returns a Meter from the MetricProvider that indicates the measurement
+// comes from buildx with the appropriate version.
+func Meter(mp metric.MeterProvider) metric.Meter {
+	return mp.Meter(version.Package,
+		metric.WithInstrumentationVersion(version.Version))
+}

util/metricutil/otlp.go

@@ -1,4 +1,4 @@
-package metrics
+package metricutil
 
 import (
 	"context"
@@ -35,13 +35,9 @@ func detectOtlpExporter(ctx context.Context) (sdkmetric.Exporter, error) {
 
 	switch proto {
 	case "grpc":
-		return otlpmetricgrpc.New(ctx,
-			otlpmetricgrpc.WithTemporalitySelector(deltaTemporality),
-		)
+		return otlpmetricgrpc.New(ctx)
 	case "http/protobuf":
-		return otlpmetrichttp.New(ctx,
-			otlpmetrichttp.WithTemporalitySelector(deltaTemporality),
-		)
+		return otlpmetrichttp.New(ctx)
 	// case "http/json": // unsupported by library
 	default:
 		return nil, errors.Errorf("unsupported otlp protocol %v", proto)

util/metricutil/resource.go

@@ -0,0 +1,53 @@
+package metricutil
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"sync"
+
+	"github.com/google/uuid"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/sdk/resource"
+	semconv "go.opentelemetry.io/otel/semconv/v1.21.0"
+)
+
+var (
+	res     *resource.Resource
+	resOnce sync.Once
+)
+
+// Resource retrieves the OTEL resource for the buildx CLI.
+func Resource() *resource.Resource {
+	resOnce.Do(func() {
+		var err error
+		res, err = resource.New(context.Background(),
+			resource.WithDetectors(serviceNameDetector{}),
+			resource.WithAttributes(
+				// Use a unique instance id so OTEL knows that each invocation
+				// of the CLI is its own instance. Without this, downstream
+				// OTEL processors may think the same process is restarting
+				// continuously and reset the metric counters.
+				semconv.ServiceInstanceID(uuid.New().String()),
+			),
+			resource.WithFromEnv(),
+			resource.WithTelemetrySDK(),
+		)
+		if err != nil {
+			otel.Handle(err)
+		}
+	})
+	return res
+}
+
+type serviceNameDetector struct{}
+
+func (serviceNameDetector) Detect(ctx context.Context) (*resource.Resource, error) {
+	return resource.StringDetector(
+		semconv.SchemaURL,
+		semconv.ServiceNameKey,
+		func() (string, error) {
+			return filepath.Base(os.Args[0]), nil
+		},
+	).Detect(ctx)
+}