internal: capture user-agent in metrics (#2644)

Author: lucix-aws

.changelog/33f766393bb344b9b26b55846650e8a0.json

@@ -0,0 +1,8 @@
+{
+    "id": "33f76639-3bb3-44b9-b26b-55846650e8a0",
+    "type": "feature",
+    "description": "Capture user agent in internal metrics.",
+    "modules": [
+        "."
+    ]
+}

aws/middleware/private/metrics/metrics.go

@@ -124,6 +124,7 @@ type MetricData struct {
 	OperationName              string
 	PartitionID                string
 	Region                     string
+	UserAgent                  string
 	RequestContentLength       int64
 	Stream                     StreamMetrics
 	Attempts                   []AttemptMetrics

aws/middleware/private/metrics/middleware/configuration.go

@@ -54,6 +54,9 @@ func WithMetricMiddlewares(
 		if err := timeSigning(stack); err != nil {
 			return err
 		}
+		if err := stack.Build.Add(&captureUserAgent{}, middleware.After); err != nil {
+			return err
+		}
 		return nil
 	}
 }

aws/middleware/private/metrics/middleware/user_agent.go

@@ -0,0 +1,29 @@
+package middleware
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/aws/aws-sdk-go-v2/aws/middleware/private/metrics"
+	"github.com/aws/smithy-go/middleware"
+	smithyhttp "github.com/aws/smithy-go/transport/http"
+)
+
+type captureUserAgent struct{}
+
+func (*captureUserAgent) ID() string { return "captureUserAgent" }
+
+func (*captureUserAgent) HandleBuild(
+	ctx context.Context, in middleware.BuildInput, next middleware.BuildHandler,
+) (
+	out middleware.BuildOutput, md middleware.Metadata, err error,
+) {
+	r, ok := in.Request.(*smithyhttp.Request)
+	if !ok {
+		return out, md, fmt.Errorf("unexpected transport type %T", in.Request)
+	}
+
+	mctx := metrics.Context(ctx)
+	mctx.Data().UserAgent = r.Header.Get("User-Agent")
+	return next.HandleBuild(ctx, in)
+}