Add Metrics to RetryableHTTPClient

pkg/common/http.go

@@ -135,6 +135,15 @@ func (t *InstrumentedTransport) RoundTrip(req *http.Request) (*http.Response, er
 	if resp != nil {
 		// record latency and increment counter for non-200 status code
 		recordHTTPResponse(sanitizedURL, resp.StatusCode, duration.Seconds())
+
+		// wrap the response body to count bytes read
+		resp.Body = &responseSizeCounterReadCloser{
+			ReadCloser: resp.Body,
+			recordSizeFunc: func(size int) {
+				// Record response body size
+				recordResponseBodySize(sanitizedURL, size)
+			},
+		}
 	}
 
 	return resp, err
@@ -147,6 +156,35 @@ func NewInstrumentedTransport(T http.RoundTripper) *InstrumentedTransport {
 	return &InstrumentedTransport{T}
 }
 
+type responseSizeCounterReadCloser struct {
+	io.ReadCloser
+	bytesRead      *int
+	recordSizeFunc func(int)
+}
+
+func (r *responseSizeCounterReadCloser) Read(p []byte) (n int, err error) {
+	n, err = r.ReadCloser.Read(p)
+	if r.bytesRead == nil {
+		r.bytesRead = new(int)
+	}
+	*r.bytesRead += n
+	return n, err
+}
+
+func (r *responseSizeCounterReadCloser) Close() error {
+	if r.recordSizeFunc != nil {
+		if r.bytesRead == nil {
+			// this means downstream code never consumed the body, we must drain the body to get its size
+			_, err := io.Copy(io.Discard, r)
+			if err != nil {
+				return err
+			}
+		}
+		r.recordSizeFunc(*r.bytesRead)
+	}
+	return r.ReadCloser.Close()
+}
+
 func ConstantResponseHttpClient(statusCode int, body string) *http.Client {
 	return &http.Client{
 		Timeout: DefaultResponseTimeout,
@@ -198,7 +236,7 @@ func WithRetryWaitMax(wait time.Duration) ClientOption {
 func PinnedRetryableHttpClient() *http.Client {
 	httpClient := retryablehttp.NewClient()
 	httpClient.Logger = nil
-	httpClient.HTTPClient.Transport = NewCustomTransport(&http.Transport{
+	httpClient.HTTPClient.Transport = NewInstrumentedTransport(NewCustomTransport(&http.Transport{
 		TLSClientConfig: &tls.Config{
 			RootCAs: PinnedCertPool(),
 		},
@@ -212,15 +250,15 @@ func PinnedRetryableHttpClient() *http.Client {
 		IdleConnTimeout:       90 * time.Second,
 		TLSHandshakeTimeout:   10 * time.Second,
 		ExpectContinueTimeout: 1 * time.Second,
-	})
+	}))
 	return httpClient.StandardClient()
 }
 
 func RetryableHTTPClient(opts ...ClientOption) *http.Client {
 	httpClient := retryablehttp.NewClient()
 	httpClient.RetryMax = 3
 	httpClient.Logger = nil
-	httpClient.HTTPClient.Transport = NewCustomTransport(nil)
+	httpClient.HTTPClient.Transport = NewInstrumentedTransport(NewCustomTransport(nil))
 
 	for _, opt := range opts {
 		opt(httpClient)
@@ -234,7 +272,7 @@ func RetryableHTTPClientTimeout(timeOutSeconds int64, opts ...ClientOption) *htt
 	httpClient.RetryMax = 3
 	httpClient.Logger = nil
 	httpClient.HTTPClient.Timeout = time.Duration(timeOutSeconds) * time.Second
-	httpClient.HTTPClient.Transport = NewCustomTransport(nil)
+	httpClient.HTTPClient.Transport = NewInstrumentedTransport(NewCustomTransport(nil))
 
 	for _, opt := range opts {
 		opt(httpClient)

pkg/common/http_metrics.go

@@ -39,6 +39,17 @@ var (
 		},
 		[]string{"url", "status_code"},
 	)
+
+	httpResponseBodySizeBytes = promauto.NewHistogramVec(
+		prometheus.HistogramOpts{
+			Namespace: MetricsNamespace,
+			Subsystem: "http_client",
+			Name:      "response_body_size_bytes",
+			Help:      "Size of HTTP response bodies in bytes, labeled by URL.",
+			Buckets:   prometheus.ExponentialBuckets(100, 10, 5), // [100B, 1KB, 10KB, 100KB, 1MB]
+		},
+		[]string{"url"},
+	)
 )
 
 // sanitizeURL sanitizes a URL to avoid high cardinality metrics.
@@ -106,3 +117,8 @@ func recordHTTPResponse(sanitizedURL string, statusCode int, durationSeconds flo
 func recordNetworkError(sanitizedURL string) {
 	httpNon200ResponsesTotal.WithLabelValues(sanitizedURL, "network_error").Inc()
 }
+
+// recordResponseBodySize records metrics for the size of an HTTP response body.
+func recordResponseBodySize(sanitizedURL string, sizeBytes int) {
+	httpResponseBodySizeBytes.WithLabelValues(sanitizedURL).Observe(float64(sizeBytes))
+}

pkg/common/http_test.go

@@ -2,6 +2,7 @@ package common
 
 import (
 	"context"
+	"io"
 	"math"
 	"net/http"
 	"net/http/httptest"
@@ -405,6 +406,76 @@ func TestSaneHttpClientMetrics(t *testing.T) {
 	}
 }
 
+func TestRetryableHttpClientMetrics(t *testing.T) {
+	// Create a test server that returns different status codes
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.URL.Path {
+		case "/success":
+			w.WriteHeader(http.StatusOK)
+			_, _ = w.Write([]byte("success"))
+		case "/error":
+			w.WriteHeader(http.StatusInternalServerError)
+			_, _ = w.Write([]byte("error"))
+		case "/notfound":
+			w.WriteHeader(http.StatusNotFound)
+			_, _ = w.Write([]byte("not found"))
+		default:
+			w.WriteHeader(http.StatusOK)
+			_, _ = w.Write([]byte("default"))
+		}
+	}))
+	defer server.Close()
+
+	// Create a RetryableHttpClient
+	client := RetryableHTTPClient()
+
+	testCases := []struct {
+		name               string
+		path               string
+		expectedStatusCode int
+		expectsNon200      bool
+	}{
+		{
+			name:               "successful request",
+			path:               "/success",
+			expectedStatusCode: 200,
+			expectsNon200:      false,
+		},
+		{
+			name:               "not found request",
+			path:               "/notfound",
+			expectedStatusCode: 404,
+			expectsNon200:      true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			var requestURL string
+			if strings.HasPrefix(tc.path, "http") {
+				requestURL = tc.path
+			} else {
+				requestURL = server.URL + tc.path
+			}
+
+			// Get initial metric values
+			sanitizedURL := sanitizeURL(requestURL)
+			initialRequestsTotal := testutil.ToFloat64(httpRequestsTotal.WithLabelValues(sanitizedURL))
+
+			// Make the request
+			resp, err := client.Get(requestURL)
+
+			require.NoError(t, err)
+			defer resp.Body.Close()
+			assert.Equal(t, tc.expectedStatusCode, resp.StatusCode)
+
+			// Check that request counter was incremented
+			requestsTotal := testutil.ToFloat64(httpRequestsTotal.WithLabelValues(sanitizedURL))
+			assert.Equal(t, initialRequestsTotal+1, requestsTotal)
+		})
+	}
+}
+
 func TestInstrumentedTransport(t *testing.T) {
 	// Create a mock transport that we can control
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -439,3 +510,51 @@ func TestInstrumentedTransport(t *testing.T) {
 	// Note: Testing histogram metrics is complex due to the way Prometheus handles them
 	// The main thing is that the request completed successfully and counters were incremented
 }
+
+func TestResponseSizeCounterReadCloser(t *testing.T) {
+	bodyContent := "This is a test response body."
+	expectedSize := len(bodyContent)
+	resp := &http.Response{
+		Body: io.NopCloser(strings.NewReader(bodyContent)),
+	}
+
+	var recordedSize int
+	readCloser := &responseSizeCounterReadCloser{
+		ReadCloser: resp.Body,
+		recordSizeFunc: func(size int) {
+			recordedSize = size
+		},
+	}
+	// Read the entire body
+	_, err := io.ReadAll(readCloser)
+	require.NoError(t, err)
+
+	// Close the ReadCloser to trigger size recording
+	err = readCloser.Close()
+	require.NoError(t, err)
+
+	assert.Equal(t, expectedSize, recordedSize, "Response body size does not match expected")
+}
+
+func TestResponseSizeCounterReadCloser_UnreadBody(t *testing.T) {
+	bodyContent := "This is a test response body."
+	expectedSize := len(bodyContent)
+	resp := &http.Response{
+		Body: io.NopCloser(strings.NewReader(bodyContent)),
+	}
+
+	var recordedSize int
+	readCloser := &responseSizeCounterReadCloser{
+		ReadCloser: resp.Body,
+		recordSizeFunc: func(size int) {
+			recordedSize = size
+		},
+	}
+	// Do not read the body
+
+	// Close the ReadCloser to trigger size recording
+	err := readCloser.Close()
+	require.NoError(t, err)
+
+	assert.Equal(t, expectedSize, recordedSize, "Response body size does not match expected for unread body")
+}