move instrumentation from request executor to client factory

Author: dhontecillas

http/client/client.go

@@ -44,7 +44,7 @@ import (
 // Check the [TransportOptions] struct for details..
 func InstrumentedHTTPClient(c *http.Client, t *TransportOptions, clientName string,
 	getState state.GetterFn,
-) (*http.Client, error) {
+) *http.Client {
 	// the default options is to have everything activated
 	// TODO: we might want to return the provided client if no transport options are provided ?
 	// TODO: we might want to return an error if no transport options are provided ?
@@ -77,5 +77,5 @@ func InstrumentedHTTPClient(c *http.Client, t *TransportOptions, clientName stri
 		Jar:           c.Jar,
 		Timeout:       c.Timeout,
 	}
-	return wc, nil
+	return wc
 }

lura/backend.go

@@ -38,17 +38,25 @@ func HTTPRequestExecutorFromConfig(clientFactory transport.HTTPClientFactory,
 	cfg *config.Backend, opts *otelconfig.BackendOpts, skipPaths []string,
 	getState otelstate.GetterFn,
 ) transport.HTTPRequestExecutor {
+
+	cf := InstrumentedHTTPClientFactory(clientFactory, cfg, opts, skipPaths, getState)
+	return transport.DefaultHTTPRequestExecutor(cf)
+}
+
+func InstrumentedHTTPClientFactory(clientFactory transport.HTTPClientFactory,
+	cfg *config.Backend, opts *otelconfig.BackendOpts, skipPaths []string,
+	getState otelstate.GetterFn,
+) transport.HTTPClientFactory {
+
 	for _, sp := range skipPaths {
 		if cfg.ParentEndpoint == sp {
-			// TODO: check if there might be some othe executor that is
-			// not the default one ?
-			return transport.DefaultHTTPRequestExecutor(clientFactory)
+			return clientFactory
 		}
 	}
 
 	if !opts.Enabled() {
 		// no configuration for the backend, then .. no metrics nor tracing:
-		return transport.DefaultHTTPRequestExecutor(clientFactory)
+		return clientFactory
 	}
 
 	if opts == nil {
@@ -106,11 +114,9 @@ func HTTPRequestExecutorFromConfig(clientFactory transport.HTTPClientFactory,
 		},
 	}
 
-	return func(ctx context.Context, req *http.Request) (*http.Response, error) {
-		c, err := clienthttp.InstrumentedHTTPClient(clientFactory(ctx), &t, clientName, getState)
-		if err != nil {
-			return nil, err
-		}
-		return c.Do(req.WithContext(ctx))
+	return func(ctx context.Context) *http.Client {
+		// TODO: this can be optimized, because inside InstrumentedHTTPClient we
+		// are creating a RoundTripper that could be "prebuilt" and reused
+		return clienthttp.InstrumentedHTTPClient(clientFactory(ctx), &t, clientName, getState)
 	}
 }