Support writing traces to a directory, wire it up in kubetest2

If given a directory, we can construct a reasonable name based on the
executable name, pid and timestamp.  Then this is relatively easy to
wire up from kubetest2, if we have an artifacts directory.

cmd/kops/otel.go

@@ -19,8 +19,11 @@ package main
 import (
 	"context"
 	"errors"
+	"fmt"
 	"net/http"
 	"os"
+	"path/filepath"
+	"strings"
 	"time"
 
 	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
@@ -88,15 +91,46 @@ func newResource(serviceName, serviceVersion string) (*resource.Resource, error)
 }
 
 func newTraceProvider(ctx context.Context, res *resource.Resource) (*trace.TracerProvider, error) {
-	s := os.Getenv("OTEL_EXPORTER_OTLP_TRACES_FILE")
-	if s == "" {
-		s = os.Getenv("OTEL_EXPORTER_OTLP_FILE")
+	destIsDirectory := false
+
+	dest := os.Getenv("OTEL_EXPORTER_OTLP_TRACES_FILE")
+	if dest == "" {
+		dest = os.Getenv("OTEL_EXPORTER_OTLP_FILE")
 	}
-	if s == "" {
+	if dest == "" {
+		dest = os.Getenv("OTEL_EXPORTER_OTLP_TRACES_DIR")
+		if dest != "" {
+			destIsDirectory = true
+		}
+	}
+	if dest == "" {
+		dest = os.Getenv("OTEL_EXPORTER_OTLP_DIR")
+		if dest != "" {
+			destIsDirectory = true
+		}
+	}
+	if dest == "" {
 		return nil, nil
 	}
 
-	traceExporter, err := otlptracefile.New(ctx, otlptracefile.WithPath(s))
+	// If we are writing to a directory, construct a (likely) unique name
+	if destIsDirectory {
+		if err := os.MkdirAll(dest, 0755); err != nil {
+			return nil, fmt.Errorf("creating directories %q: %w", dest, err)
+		}
+		processName, err := os.Executable()
+		if err != nil {
+			return nil, fmt.Errorf("getting process name: %w", err)
+		}
+		processName = filepath.Base(processName)
+		processName = strings.TrimSuffix(processName, ".exe")
+		pid := os.Getpid()
+		timestamp := time.Now().UTC().Format(time.RFC3339)
+		filename := fmt.Sprintf("%s-%d-%s.otel", processName, pid, timestamp)
+		dest = filepath.Join(dest, filename)
+	}
+
+	traceExporter, err := otlptracefile.New(ctx, otlptracefile.WithPath(dest))
 	if err != nil {
 		return nil, err
 	}

tests/e2e/kubetest2-kops/deployer/common.go

@@ -222,6 +222,29 @@ func (d *deployer) env() []string {
 	} else if baseURL := os.Getenv("KOPS_BASE_URL"); baseURL != "" {
 		vars = append(vars, fmt.Sprintf("KOPS_BASE_URL=%v", os.Getenv("KOPS_BASE_URL")))
 	}
+
+	// Pass through OpenTelemetry flags
+	{
+		foundOTEL := false
+		for _, k := range []string{
+			"OTEL_EXPORTER_OTLP_TRACES_FILE", "OTEL_EXPORTER_OTLP_FILE",
+			"OTEL_EXPORTER_OTLP_TRACES_DIR", "OTEL_EXPORTER_OTLP_DIR",
+		} {
+			v := os.Getenv(k)
+			if v != "" {
+				foundOTEL = true
+				vars = append(vars, k+"="+v)
+			}
+		}
+
+		// If no otel flags were explicitly specified, and we have artifacts, log under the artifacts directory
+		if !foundOTEL {
+			artifacts := d.ArtifactsDir
+			if artifacts != "" {
+				vars = append(vars, "OTEL_EXPORTER_OTLP_TRACES_DIR="+filepath.Join(artifacts, "otlp"))
+			}
+		}
+	}
 	return vars
 }