measure and pickup external http dependencies

http/transport/default_transport.go

@@ -7,6 +7,22 @@ package transport
 // If not explicitly finalized via `Final` it uses `http.DefaultTransport` as finalizer.
 func NewDefaultTransportChain() *RoundTripperChain {
 	return Chain(
+		&ExternalDependencyRoundTripper{},
+		NewDefaultRetryRoundTripper(),
+		&JaegerRoundTripper{},
+		NewDumpRoundTripperEnv(),
+		&LoggingRoundTripper{},
+		&LocaleRoundTripper{},
+		&RequestIDRoundTripper{},
+	)
+}
+
+// NewDefaultTransportChain returns a transport chain with retry, jaeger and logging support.
+// If not explicitly finalized via `Final` it uses `http.DefaultTransport` as finalizer.
+// The passed name is recorded as external dependency
+func NewDefaultTransportChainWithExternalName(name string) *RoundTripperChain {
+	return Chain(
+		&ExternalDependencyRoundTripper{name: name},
 		NewDefaultRetryRoundTripper(),
 		&JaegerRoundTripper{},
 		NewDumpRoundTripperEnv(),

http/transport/external_dependency_round_tripper.go

@@ -0,0 +1,51 @@
+// Copyright © 2020 by PACE Telematics GmbH. All rights reserved.
+// Created at 2020/12/14 by Vincent Landgraf
+
+package transport
+
+import (
+	"net/http"
+	"time"
+
+	"github.com/pace/bricks/http/middleware"
+)
+
+// ExternalDependencyRoundTripper greps external dependency headers and
+// attach them to the currect context
+type ExternalDependencyRoundTripper struct {
+	name      string
+	transport http.RoundTripper
+}
+
+// Transport returns the RoundTripper to make HTTP requests
+func (l *ExternalDependencyRoundTripper) Transport() http.RoundTripper {
+	return l.transport
+}
+
+// SetTransport sets the RoundTripper to make HTTP requests
+func (l *ExternalDependencyRoundTripper) SetTransport(rt http.RoundTripper) {
+	l.transport = rt
+}
+
+// RoundTrip executes a single HTTP transaction via Transport()
+func (l *ExternalDependencyRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
+	start := time.Now()
+	resp, err := l.Transport().RoundTrip(req)
+	elapsed := time.Since(start)
+
+	ec := middleware.ExternalDependencyContextFromContext(req.Context())
+	if ec != nil {
+		if l.name != "" {
+			ec.AddDependency(l.name, elapsed)
+		}
+
+		if resp != nil {
+			header := resp.Header.Get(middleware.ExternalDependencyHeaderName)
+			if header != "" {
+				ec.Parse(header)
+			}
+		}
+	}
+
+	return resp, err
+}

http/transport/external_dependency_round_tripper_test.go

@@ -0,0 +1,68 @@
+// Copyright © 2020 by PACE Telematics GmbH. All rights reserved.
+// Created at 2020/12/15 by Vincent Landgraf
+
+package transport
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/pace/bricks/http/middleware"
+	"github.com/stretchr/testify/assert"
+)
+
+type edRoundTripperMock struct {
+	req  *http.Request
+	resp *http.Response
+}
+
+func (m *edRoundTripperMock) RoundTrip(req *http.Request) (*http.Response, error) {
+	m.req = req
+	return m.resp, nil
+}
+
+func TestExternalDependencyRoundTripper(t *testing.T) {
+	var edc middleware.ExternalDependencyContext
+	ctx := middleware.ContextWithExternalDependency(context.Background(), &edc)
+
+	r := httptest.NewRequest("GET", "http://example.com/test", nil)
+	r = r.WithContext(ctx)
+
+	mock := &edRoundTripperMock{
+		resp: &http.Response{
+			Header: http.Header{
+				middleware.ExternalDependencyHeaderName: []string{"test1:123,test2:53"},
+			},
+		},
+	}
+	lrt := &ExternalDependencyRoundTripper{transport: mock}
+
+	_, err := lrt.RoundTrip(r)
+	assert.NoError(t, err)
+
+	assert.EqualValues(t, "test1:123,test2:53", edc.String())
+}
+
+func TestExternalDependencyRoundTripperWithName(t *testing.T) {
+	var edc middleware.ExternalDependencyContext
+	ctx := middleware.ContextWithExternalDependency(context.Background(), &edc)
+
+	r := httptest.NewRequest("GET", "http://example.com/test", nil)
+	r = r.WithContext(ctx)
+
+	mock := &edRoundTripperMock{
+		resp: &http.Response{
+			Header: http.Header{
+				middleware.ExternalDependencyHeaderName: []string{"test1:123,test2:53"},
+			},
+		},
+	}
+	lrt := &ExternalDependencyRoundTripper{name: "ext", transport: mock}
+
+	_, err := lrt.RoundTrip(r)
+	assert.NoError(t, err)
+
+	assert.EqualValues(t, "ext:0,test1:123,test2:53", edc.String())
+}