From e54b8c1ea91b08463317734aea96c05c5bcd262e Mon Sep 17 00:00:00 2001
From: Yunjun Mu <yunjun.mu@gmail.com>
Date: Fri, 26 Aug 2016 13:57:23 -0400
Subject: [PATCH 1/3] Change http-proxy-middleware logLevel from silent to
 error

---
 scripts/start.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/start.js b/scripts/start.js
index aa68ab40ff3..f65d8d85cb5 100644
--- a/scripts/start.js
+++ b/scripts/start.js
@@ -206,7 +206,7 @@ function addMiddleware(devServer) {
       // of both HTTP and WebSockets to work without false positives.
       httpProxyMiddleware(pathname => mayProxy.test(pathname), {
         target: proxy,
-        logLevel: 'silent',
+        logLevel: 'error',
         secure: false,
         changeOrigin: true
       })

From 4dd0d43cf05c836f8659606d73762d331aabe266 Mon Sep 17 00:00:00 2001
From: yunjun <yunjun.mu@gmail.com>
Date: Fri, 2 Sep 2016 20:54:55 -0400
Subject: [PATCH 2/3] provide onError handler for httpProxyMiddleware

---
 scripts/start.js | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/scripts/start.js b/scripts/start.js
index f33e08326cf..a0b01545b5b 100644
--- a/scripts/start.js
+++ b/scripts/start.js
@@ -170,6 +170,23 @@ function openBrowser(port, protocol) {
   opn(protocol + '://localhost:' + port + '/');
 }
 
+// We need to provide a custom onError function for httpProxyMiddleware.
+// It allows us to log custom error messages on the console.
+function onProxyError(proxy) {
+  return function(err, req, res){
+    var host = req.headers && req.headers.host;
+    console.log(
+      chalk.red('Proxy error:') + ' Could not proxy request ' + chalk.cyan(req.url) +
+      ' from ' + chalk.cyan(host) + ' to ' + chalk.cyan(proxy) + '.'
+    );
+    console.log(
+      'See https://nodejs.org/api/errors.html#errors_common_system_errors for more information (' + 
+      chalk.cyan(err.code) + ').'
+    );
+    console.log();
+  }
+}
+
 function addMiddleware(devServer) {
   // `proxy` lets you to specify a fallback server during development.
   // Every unrecognized request will be forwarded to it.
@@ -208,7 +225,8 @@ function addMiddleware(devServer) {
       // of both HTTP and WebSockets to work without false positives.
       httpProxyMiddleware(pathname => mayProxy.test(pathname), {
         target: proxy,
-        logLevel: 'error',
+        logLevel: 'silent',
+        onError: onProxyError(proxy),
         secure: false,
         changeOrigin: true
       })

From 1079a6ef7c41af8dae783b92563a70f441ae2f79 Mon Sep 17 00:00:00 2001
From: yunjun <yunjun.mu@gmail.com>
Date: Mon, 5 Sep 2016 12:30:25 -0400
Subject: [PATCH 3/3] Send proper error reponse upon proxy error.

---
 scripts/start.js | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/scripts/start.js b/scripts/start.js
index a0b01545b5b..667a4b8f440 100644
--- a/scripts/start.js
+++ b/scripts/start.js
@@ -175,6 +175,8 @@ function openBrowser(port, protocol) {
 function onProxyError(proxy) {
   return function(err, req, res){
     var host = req.headers && req.headers.host;
+
+    // Log the error to the deveopment console.
     console.log(
       chalk.red('Proxy error:') + ' Could not proxy request ' + chalk.cyan(req.url) +
       ' from ' + chalk.cyan(host) + ' to ' + chalk.cyan(proxy) + '.'
@@ -184,6 +186,15 @@ function onProxyError(proxy) {
       chalk.cyan(err.code) + ').'
     );
     console.log();
+
+    // And immediately send the proper error response to the client.
+    // Otherwise, the request will eventually timeout with ERR_EMPTY_RESPONSE on the client side.
+    if (res.writeHead && !res.headersSent) {
+        res.writeHead(500);
+    }
+    res.end('Proxy error: Could not proxy request ' + req.url + ' from ' + 
+      host + ' to ' + proxy + ' (' + err.code + ').'
+    );
   }
 }