[#DWR-81] ErrorHandler is not always called - DWR

Details

Type: Bug
Status: Closed
Priority: Major
Resolution: Fixed
Affects Version/s: 2.0.1
Fix Version/s: 2.0.2
Component/s: Engine

Description:

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Let's say I have DWR script running in some web browser and then web server it is connected to is suddenly disappear. What I am observing is that errorHandler hook is not being called reliable (it works sometimes on FireFox but almost never works on MS IE 6). I've tried DWR 1.1.3 and 2.0m3 (haven't got chance to try latest releases).

To work around that I came up with the following code:

<script type='text/javascript' src='/coordination/dwr/engine.js'></script>
<script type='text/javascript' src='/coordination/dwr/interface/Counter.js'></script>
<script type='text/javascript' src='/coordination/dwr/util.js'></script>
<script type='text/javascript'>
   timestamp = new Date().getTime();
   isServerDown = "Cannot connect to the server, it is running?";

   function checkCounter() {
     setTimeout('checkCounter()', 1000)
     setTimeout('checkTimeout()', 4000)
     try {
       Counter.getStatus(
       {
         timeout:4000,
         callback:function(counter) {
           DWRUtil.setValue("counter", counter);
           timestamp = new Date().getTime();
         },
         errorHandler:function(message) {
           DWRUtil.setValue("counter", isServerDown);
         }
       });
     } catch(e) {
       DWRUtil.setValue("counter", isServerDown);
     }
   }

   function checkTimeout() {
     if((timestamp + 10000) < new Date().getTime()) {
       DWRUtil.setValue("counter", isServerDown);
     }
   }

   function startDemo() {
      document.getElementById("errmsg0").style.display = 'none';
      checkCounter();
   }
</script>
</head>
<body onload="startDemo()">
...

Complete code is included into the Terracotta kit in Spring demo called Coordination, which shows clustered Spring runtime working with DWR. Currently this demo is polling server every so often, which is not efficient and I would appreciate your thoughts how it can be improved

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Let's say I have DWR script running in some web browser and then web server it is connected to is suddenly disappear. What I am observing is that errorHandler hook is not being called reliable (it works sometimes on FireFox but almost never works on MS IE 6). I've tried DWR 1.1.3 and 2.0m3 (haven't got chance to try latest releases). To work around that I came up with the following code: <script type='text/javascript' src='/coordination/dwr/engine.js'></script> <script type='text/javascript' src='/coordination/dwr/interface/Counter.js'></script> <script type='text/javascript' src='/coordination/dwr/util.js'></script> <script type='text/javascript'>    timestamp = new Date().getTime();    isServerDown = "Cannot connect to the server, it is running?";    function checkCounter() {      setTimeout('checkCounter()', 1000)      setTimeout('checkTimeout()', 4000)      try {        Counter.getStatus(        {          timeout:4000,          callback:function(counter) {            DWRUtil.setValue("counter", counter);            timestamp = new Date().getTime();          },          errorHandler:function(message) {            DWRUtil.setValue("counter", isServerDown);          }        });      } catch(e) {        DWRUtil.setValue("counter", isServerDown);      }    }    function checkTimeout() {      if((timestamp + 10000) < new Date().getTime()) {        DWRUtil.setValue("counter", isServerDown);      }    }    function startDemo() {       document.getElementById("errmsg0").style.display = 'none';       checkCounter();    } </script> </head> <body onload="startDemo()"> ... Complete code is included into the Terracotta kit in Spring demo called Coordination, which shows clustered Spring runtime working with DWR. Currently this demo is polling server every so often, which is not efficient and I would appreciate your thoughts how it can be improved

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dwr-error-recovery.patch

(3 kB)

Ilya Perminov

27/Apr/07 9:01 PM

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Ilya Perminov added a comment - 27/Apr/07 9:00 PM

When a batch response is received completely, the engine can check that for every call in the batch either its callback handler or its error handler was invoked.
Any call without a result indicates a communication error.
I have a patch which improves IO error handling in FireFox and IE 6, I did not test it with any other browsers.

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Ilya Perminov added a comment - 27/Apr/07 9:00 PM When a batch response is received completely, the engine can check that for every call in the batch either its callback handler or its error handler was invoked. Any call without a result indicates a communication error. I have a patch which improves IO error handling in FireFox and IE 6, I did not test it with any other browsers.

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Ilya Perminov added a comment - 27/Apr/07 9:01 PM

A patch to improve detection of IO-errors.
Function validateBatch checks that there is a result for every call.
It is invoked from the "onload" event hander for iframe-s, and form the _stateChange for XMLHttpRequest-s.

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Ilya Perminov added a comment - 27/Apr/07 9:01 PM A patch to improve detection of IO-errors. Function validateBatch checks that there is a result for every call. It is invoked from the "onload" event hander for iframe-s, and form the _stateChange for XMLHttpRequest-s.

DWR

ErrorHandler is not always called

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