Fixing socket hang up error on node side for slow response. (#1752)

* Fixing socket hang up error on node side for slow response.

* eslint check

lib/adapters/http.js

@@ -19,13 +19,10 @@ var isHttps = /https:?/;
 /*eslint consistent-return:0*/
 module.exports = function httpAdapter(config) {
   return new Promise(function dispatchHttpRequest(resolvePromise, rejectPromise) {
-    var timer;
     var resolve = function resolve(value) {
-      clearTimeout(timer);
       resolvePromise(value);
     };
     var reject = function reject(value) {
-      clearTimeout(timer);
       rejectPromise(value);
     };
     var data = config.data;
@@ -249,10 +246,15 @@ module.exports = function httpAdapter(config) {
 
     // Handle request timeout
     if (config.timeout) {
-      timer = setTimeout(function handleRequestTimeout() {
+      // Sometime, the response will be very slow, and does not respond, the connect event will be block by event loop system.
+      // And timer callback will be fired, and abort() will be invoked before connection, then get "socket hang up" and code ECONNRESET.
+      // At this time, if we have a large number of request, nodejs will hang up some socket on background. and the number will up and up.
+      // And then these socket which be hang up will devoring CPU little by little.
+      // ClientRequest.setTimeout will be fired on the specify milliseconds, and can make sure that abort() will be fired after connect.
+      req.setTimeout(config.timeout, function handleRequestTimeout() {
         req.abort();
         reject(createError('timeout of ' + config.timeout + 'ms exceeded', config, 'ECONNABORTED', req));
-      }, config.timeout);
+      });
     }
 
     if (config.cancelToken) {