make applyCommands asynchronous

services/sync/modules/engines.js

@@ -337,10 +337,12 @@ Engine.prototype = {
       // Note that we need to need to apply client changes to the
       // current tree, not the saved snapshot
 
-      localJson.applyCommands(clientChanges);
+      localJson.applyCommands.async(localJson, self.cb, clientChanges);
+      yield;
       this._snapshot.data = localJson.data;
       this._snapshot.version = server.maxVersion;
-      this._store.applyCommands(clientChanges);
+      this._store.applyCommands.async(this._store, self.cb, clientChanges);
+      yield;
       newSnapshot = this._store.wrap();
 
       this._core.detectUpdates(self.cb, this._snapshot.data, newSnapshot);
@@ -570,7 +572,8 @@ Engine.prototype = {
       }
 
       for (var i = 0; i < deltas.length; i++) {
-        snap.applyCommands(deltas[i]);
+        snap.applyCommands.async(snap, self.cb, deltas[i]);
+        yield;
       }
 
       ret.status = 0;

services/sync/modules/stores.js

@@ -57,6 +57,7 @@ function Store() {
 }
 Store.prototype = {
   _logName: "Store",
+  _yieldDuringApply: true,
 
   __json: null,
   get _json() {
@@ -71,7 +72,16 @@ Store.prototype = {
   },
 
   applyCommands: function Store_applyCommands(commandList) {
+    let self = yield;
+
+    if (this._yieldDuringApply)
+      let timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+
     for (var i = 0; i < commandList.length; i++) {
+      if (this._yieldDuringApply) {
+        timer.initWithCallback(listener, 0, timer.TYPE_ONE_SHOT);
+        yield; // Yield to main loop
+      }
       var command = commandList[i];
       this._log.debug("Processing command: " + this._json.encode(command));
       switch (command["action"]) {
@@ -89,6 +99,7 @@ Store.prototype = {
         break;
       }
     }
+    self.done();
   },
 
   // override these in derived objects