chore: backend config response size metric (#4309)

Author: fracasula

backend-config/backend_config_test.go

@@ -113,16 +113,18 @@ func TestBadResponse(t *testing.T) {
 
 	configs := map[string]workspaceConfig{
 		"namespace": &namespaceConfig{
-			configBackendURL: parsedURL,
-			namespace:        "some-namespace",
-			client:           http.DefaultClient,
-			logger:           logger.NOP,
-			httpCallsStat:    stats.NOP.NewStat("backend_config_http_calls", stats.CountType),
+			configBackendURL:     parsedURL,
+			namespace:            "some-namespace",
+			client:               http.DefaultClient,
+			logger:               logger.NOP,
+			httpCallsStat:        stats.NOP.NewStat("backend_config_http_calls", stats.CountType),
+			httpResponseSizeStat: stats.NOP.NewStat("backend_config_http_response_size", stats.HistogramType),
 		},
 		"single-workspace": &singleWorkspaceConfig{
-			configBackendURL: parsedURL,
-			logger:           logger.NOP,
-			httpCallsStat:    stats.NOP.NewStat("backend_config_http_calls", stats.CountType),
+			configBackendURL:     parsedURL,
+			logger:               logger.NOP,
+			httpCallsStat:        stats.NOP.NewStat("backend_config_http_calls", stats.CountType),
+			httpResponseSizeStat: stats.NOP.NewStat("backend_config_http_response_size", stats.HistogramType),
 		},
 	}
 	disableCache()

backend-config/namespace_config.go

@@ -44,7 +44,8 @@ type namespaceConfig struct {
 	lastUpdatedAt            time.Time
 	workspacesConfig         map[string]ConfigT
 
-	httpCallsStat stats.Counter
+	httpCallsStat        stats.Counter
+	httpResponseSizeStat stats.Histogram
 }
 
 func (nc *namespaceConfig) SetUp() (err error) {
@@ -77,6 +78,7 @@ func (nc *namespaceConfig) SetUp() (err error) {
 	}
 	nc.workspacesConfig = make(map[string]ConfigT)
 	nc.httpCallsStat = stats.Default.NewStat("backend_config_http_calls", stats.CountType)
+	nc.httpResponseSizeStat = stats.Default.NewStat("backend_config_http_response_size", stats.HistogramType)
 
 	if nc.logger == nil {
 		nc.logger = logger.NewLogger().Child("backend-config").Withn(obskit.Namespace(nc.namespace))
@@ -210,6 +212,8 @@ func (nc *namespaceConfig) makeHTTPRequest(req *http.Request) ([]byte, error) {
 		return nil, err
 	}
 
+	nc.httpResponseSizeStat.Observe(float64(len(respBody)))
+
 	if resp.StatusCode >= 300 {
 		return nil, getNotOKError(respBody, resp.StatusCode)
 	}

backend-config/single_workspace.go

@@ -31,12 +31,14 @@ type singleWorkspaceConfig struct {
 	workspaceIDOnce sync.Once
 	workspaceID     string
 
-	logger        logger.Logger
-	httpCallsStat stats.Counter
+	logger               logger.Logger
+	httpCallsStat        stats.Counter
+	httpResponseSizeStat stats.Histogram
 }
 
 func (wc *singleWorkspaceConfig) SetUp() error {
 	wc.httpCallsStat = stats.Default.NewStat("backend_config_http_calls", stats.CountType)
+	wc.httpResponseSizeStat = stats.Default.NewStat("backend_config_http_response_size", stats.HistogramType)
 
 	if wc.logger == nil {
 		wc.logger = logger.NewLogger().Child("backend-config").Withn(obskit.WorkspaceID(wc.workspaceID))
@@ -182,6 +184,8 @@ func (wc *singleWorkspaceConfig) makeHTTPRequest(ctx context.Context, url string
 		return nil, err
 	}
 
+	wc.httpResponseSizeStat.Observe(float64(len(respBody)))
+
 	if resp.StatusCode >= 300 {
 		return nil, getNotOKError(respBody, resp.StatusCode)
 	}