From 5e2e1cff04d2fae4a162af5055113420bef96b99 Mon Sep 17 00:00:00 2001
From: kruskal <99559985+kruskall@users.noreply.github.com>
Date: Mon, 1 Aug 2022 06:39:34 +0200
Subject: [PATCH] fix: stop recreating http transports on each info request

http transports should be reused as per documentation. Recreating the
reverse proxy and the transport on each request is also preventing
connection resuse.
---
 apm-lambda-extension/apmproxy/receiver.go | 43 +++++++++++++----------
 1 file changed, 24 insertions(+), 19 deletions(-)

diff --git a/apm-lambda-extension/apmproxy/receiver.go b/apm-lambda-extension/apmproxy/receiver.go
index 60fb1faa..c88d14af 100644
--- a/apm-lambda-extension/apmproxy/receiver.go
+++ b/apm-lambda-extension/apmproxy/receiver.go
@@ -38,7 +38,13 @@ type AgentData struct {
 // StartHttpServer starts the server listening for APM agent data.
 func (c *Client) StartReceiver() error {
 	mux := http.NewServeMux()
-	mux.HandleFunc("/", c.handleInfoRequest())
+
+	handleInfoRequest, err := c.handleInfoRequest()
+	if err != nil {
+		return err
+	}
+
+	mux.HandleFunc("/", handleInfoRequest)
 	mux.HandleFunc("/intake/v2/events", c.handleIntakeV2Events())
 
 	c.receiver.Handler = mux
@@ -68,27 +74,26 @@ func (c *Client) Shutdown() error {
 }
 
 // URL: http://server/
-func (c *Client) handleInfoRequest() func(w http.ResponseWriter, r *http.Request) {
-	return func(w http.ResponseWriter, r *http.Request) {
-		extension.Log.Debug("Handling APM server Info Request")
+func (c *Client) handleInfoRequest() (func(w http.ResponseWriter, r *http.Request), error) {
+	// Init reverse proxy
+	parsedApmServerUrl, err := url.Parse(c.serverURL)
+	if err != nil {
+		return nil, fmt.Errorf("could not parse APM server URL: %w", err)
+	}
 
-		// Init reverse proxy
-		parsedApmServerUrl, err := url.Parse(c.serverURL)
-		if err != nil {
-			extension.Log.Errorf("could not parse APM server URL: %v", err)
-			return
-		}
+	reverseProxy := httputil.NewSingleHostReverseProxy(parsedApmServerUrl)
 
-		reverseProxy := httputil.NewSingleHostReverseProxy(parsedApmServerUrl)
+	customTransport := http.DefaultTransport.(*http.Transport).Clone()
+	customTransport.ResponseHeaderTimeout = c.dataForwarderTimeout
+	reverseProxy.Transport = customTransport
 
-		customTransport := http.DefaultTransport.(*http.Transport).Clone()
-		customTransport.ResponseHeaderTimeout = c.dataForwarderTimeout
-		reverseProxy.Transport = customTransport
+	reverseProxy.ErrorHandler = func(w http.ResponseWriter, r *http.Request, err error) {
+		c.SetApmServerTransportState(r.Context(), Failing)
+		extension.Log.Errorf("Error querying version from the APM server: %v", err)
+	}
 
-		reverseProxy.ErrorHandler = func(w http.ResponseWriter, r *http.Request, err error) {
-			c.SetApmServerTransportState(r.Context(), Failing)
-			extension.Log.Errorf("Error querying version from the APM server: %v", err)
-		}
+	return func(w http.ResponseWriter, r *http.Request) {
+		extension.Log.Debug("Handling APM server Info Request")
 
 		// Process request (the Golang doc suggests removing any pre-existing X-Forwarded-For header coming
 		// from the client or an untrusted proxy to prevent IP spoofing : https://pkg.go.dev/net/http/httputil#ReverseProxy
@@ -102,7 +107,7 @@ func (c *Client) handleInfoRequest() func(w http.ResponseWriter, r *http.Request
 
 		// Forward request to the APM server
 		reverseProxy.ServeHTTP(w, r)
-	}
+	}, nil
 }
 
 // URL: http://server/intake/v2/events