limits the number of simultaneous dhtget requests to the daemon to less than max browser connections per domain.

should improve the responsiveness of user searching.

twister_following.js

@@ -12,6 +12,7 @@ var _followingSeqNum = 0;
 var _followSuggestions = [];
 var _searchingPartialUsers = "";
 var _searchKeypressTimer = undefined;
+var _lastSearchUsersResults = [];
 var _lastLoadFromDhtTime = 0;
 
 // load followingUsers from localStorage
@@ -326,6 +327,8 @@ function closeSearchDialog()
 {
     var $this = $(".userMenu-search-field");//$( this );
     $( this ).siblings().slideUp( "fast" );
+    removeUsersFromDhtgetQueue( _lastSearchUsersResults );
+    _lastSearchUsersResults = [];
 }
 
 function userSearchKeypress(item) {
@@ -367,6 +370,9 @@ function processDropdownUserResults(partialName, results){
         return;
     }
 
+    removeUsersFromDhtgetQueue( _lastSearchUsersResults );
+    _lastSearchUsersResults = results;
+
     var typeaheadAccounts = $(".userMenu-search-profiles");
     var template = $("#search-profile-template").detach();
 

twister_io.js

@@ -15,11 +15,23 @@ function twisterRpc(method, params, resultFunc, resultArg, errorFunc, errorArg)
     );
 }
 
-// private variables for cache or pending and already known values returned by dhtget
+// join multiple dhtgets to the same resources in this map
 var _dhtgetPendingMap = {};
+
+// memory cache for profile and avatar
 var _profileMap = {};
 var _avatarMap = {};
 
+// number of dhtgets in progress (requests to the daemon)
+var _dhtgetsInProgress = 0;
+
+// keep _maxDhtgets smaller than the number of daemon/browser sockets
+// most browsers limit to 6 per domain (see http://www.browserscope.org/?category=network)
+var _maxDhtgets = 5;
+
+// requests not yet sent to the daemon due to _maxDhtgets limit
+var _queuedDhtgets = [];
+
 // private function to define a key in _dhtgetPendingMap
 function _dhtgetLocator(username, resource, multi) {
     return username+";"+resource+";"+multi;
@@ -83,16 +95,59 @@ function dhtget( username, resource, multi, cbFunc, cbArg ) {
         _dhtgetAddPending(locator, cbFunc, cbArg);
     } else {
         _dhtgetAddPending(locator, cbFunc, cbArg);
+        // limit the number of simultaneous dhtgets.
+        // this should leave some sockets for other non-blocking daemon requests.
+        if( _dhtgetsInProgress < _maxDhtgets ) {
+            _dhtgetInternal( username, resource, multi );
+        } else {
+            // just queue the locator. it will be unqueue when some dhtget completes.
+            _queuedDhtgets.push(locator);
+        }
+    }
+}
 
+function _dhtgetInternal( username, resource, multi ) {
+    var locator = _dhtgetLocator(username, resource, multi);
+    _dhtgetsInProgress++;
     twisterRpc("dhtget", [username,resource,multi],
                function(args, ret) {
+                   _dhtgetsInProgress--;
                    _dhtgetProcessPending(args.locator, args.multi, ret);
+                   _dhtgetDequeue();
                }, {locator:locator,multi:multi},
                function(cbArg, ret) {
                    console.log("ajax error:" + ret);
+                   _dhtgetsInProgress--;
                    _dhtgetAbortPending(locator);
+                   _dhtgetDequeue();
                }, locator);
 }
+
+function _dhtgetDequeue() {
+    if( _queuedDhtgets.length ) {
+        var locatorSplit = _queuedDhtgets.pop().split(";");
+        _dhtgetInternal(locatorSplit[0], locatorSplit[1], locatorSplit[2]);
+    }
+}
+
+// removes queued dhtgets (requests that have not been made to the daemon)
+// this is used by user search dropdown to discard old users we are not interested anymore
+function removeUserFromDhtgetQueue(username) {
+    var resources = ["profile","avatar"]
+    for (var i = 0; i < resources.length; i++) {
+        var locator = _dhtgetLocator(username,resources[i],"s");
+        var locatorIndex = _queuedDhtgets.indexOf(locator);
+        if( locatorIndex > -1 ) {
+            _queuedDhtgets.splice(locatorIndex,1);
+            delete _dhtgetPendingMap[locator];
+        }
+    }
+}
+
+function removeUsersFromDhtgetQueue(users) {
+    for (var i = 0; i < users.length; i++ ) {
+        removeUserFromDhtgetQueue( users[i] );
+    }
 }
 
 // store value at the dht resource