From 9600d92ca7ebecdf05577d692c1e4fe6effc2fb5 Mon Sep 17 00:00:00 2001
From: Slava Kim <slava@meteor.com>
Date: Fri, 26 Sep 2014 17:21:48 -0700
Subject: [PATCH] Limit the number of concurrent downloads

Doesn't actually help!
---
 packages/autoupdate/autoupdate_cordova.js | 46 +++++++++++++++--------
 1 file changed, 31 insertions(+), 15 deletions(-)

diff --git a/packages/autoupdate/autoupdate_cordova.js b/packages/autoupdate/autoupdate_cordova.js
index 9ae7359fc6..3af120e6b0 100644
--- a/packages/autoupdate/autoupdate_cordova.js
+++ b/packages/autoupdate/autoupdate_cordova.js
@@ -1,4 +1,12 @@
 var DEBUG_TAG = 'METEOR CORDOVA DEBUG ';
+
+// This constant was picked by testing on iOS 7.1
+// We limit the number of concurrent downloads because iOS gets angry on the
+// application when a certain limit is exceeded and starts timing-out the
+// connections in 1-2 minutes which makes the whole HCP really slow.
+var MAX_NUM_CONCURRENT_DOWNLOADS = 15;
+var MAX_RETRY_COUNT = 5;
+
 var autoupdateVersionCordova = __meteor_runtime_config__.autoupdateVersionCordova || "unknown";
 
 // The collection of acceptable client versions.
@@ -81,14 +89,19 @@ var onNewVersion = function () {
 
     manifest.push({ url: '/index.html?' + Random.id() });
 
-    var downloads = 0;
-    _.each(manifest, function (item) {
-      if (item.url) downloads++;
-    });
-
     var versionPrefix = localPathPrefix + version;
 
-    var afterAllFilesDownloaded = _.after(downloads, function () {
+    var queue = [];
+    _.each(manifest, function (item) {
+      if (! item.url) return;
+
+      var url = item.url;
+      url = url.replace(/\?.+$/, '');
+
+      queue.push(url);
+    });
+
+    var afterAllFilesDownloaded = _.after(queue.length, function () {
       writeFile(versionPrefix, 'manifest.json',
           JSON.stringify(program, undefined, 2),
           function (err) {
@@ -118,12 +131,8 @@ var onNewVersion = function () {
       });
     });
 
-    _.each(manifest, function (item) {
-      if (! item.url) return;
-
-      var url = item.url;
-      url = url.replace(/\?.+$/, '');
-
+    var dowloadUrl = function (url) {
+      console.log(DEBUG_TAG + "start dowloading " + url);
       // Add a cache buster to ensure that we don't cache an old asset.
       var uri = encodeURI(urlPrefix + url + '?' + Random.id());
 
@@ -132,20 +141,27 @@ var onNewVersion = function () {
       var tryDownload = function () {
         ft.download(uri, versionPrefix + url, function (entry) {
           if (entry) {
+            console.log(DEBUG_TAG + "done dowloading " + url);
+            // start downloading next queued url
+            if (queue.length)
+              dowloadUrl(queue.shift());
             afterAllFilesDownloaded();
           }
         }, function (err) {
           // It failed, try again if we have tried less than 5 times.
-          if (tries++ < 5) {
+          if (tries++ < MAX_RETRY_COUNT) {
             tryDownload();
           } else {
-            console.log(DEBUG_TAG + 'fail source: ', error.source);
-            console.log(DEBUG_TAG + 'fail target: ', error.target);
+            console.log(DEBUG_TAG + "failed dowloading " + url);
           }
         });
       };
 
       tryDownload();
+    };
+
+    _.times(Math.min(MAX_NUM_CONCURRENT_DOWNLOADS, queue.length), function () {
+      dowloadUrl(queue.shift());
     });
   });
 };