ImgRequest issue

[nick]

We are testing a project that hosts a dynamic diagram.

Although things work well, diagram hangs randomly due to ImgRequest failures.

More specifically at random times, diagram does not show the nodes images (Pallette images work well). And from that moment it will not work unless we recycle the whole application pool.

We found that the problem is caused by the call to imgrequest.ashx timing out. For example when the problem occurs, the call to "ImgRequest.ashx?dID=bb36892e-6871-4e98-a948-a5fff1342c9c&nName=psg&recLeft=0&recTop=0&recRight=684&recBottom=584&DrawPorts=true&t=Mon%2C%2021%20Jan%202013%2012%3A17%3A33%20GMT"

will not fetch the image and from that moment no other requests to ImgRequest will work until restarting the whole application pool.

We also noticed that incidents occur more often when editing the diagram.

Any ideas?

[Amsath Ali M]

Hi Nick,

 

Thanks for using Syncfusion products.

 

We are afraid that we are unable to reproduce the issue reported by you. Could you please share us more information probably a simple sample or the code which you been used in your application or modify the below sample to reproduce the reported issue, this will help us to reproduce the reported issue effectively at our end and to provide a better solution to you?

 

Here is the sample:

http://www.syncfusion.com/downloads/Support/DirectTrac/102644/F106668704196531.zip

 

Please let us know if you have any queries.

 

Regards,

Amsath Ali. M

[nick]

Thank you for your reply.

After a LOT of research we found out that some random times, requests are being made to imgrequest without providing parameter nName (within querystring). These calls cause "object reference not set to an instance of an object" but from then on, imgrequest hangs and the whole application pool must be restarted. We have not found out why nName is not provided. 

The solution we applied, is developing a new managed handler, that checks whether nName is provided. If nName is provided, it redirects (server.transfer) request to imgrequest. If not, it renders back another image.

If you want to check this error, make a call to imgrequest without nName. The call will cause an error. But from then on imgrequest will hang.

[Amsath Ali M]

Hi Nick,

 

Thanks for your update.

 

We suspect that the requests (callbacks) are overlapping at your end while editing connectors/nodes or doing any actions on diagram. Please note that the issue may be due to the simultaneous request are send to the diagram for two different actions on the same node. The node which has been updated based on the previous requests, may be not available for current because the node is no longer the same one before it has been requested, and it is a usability issue.

We suggest you to initiate a new action on a diagram once the previous request (callback/action) is fully completed.  

 

Please let us know if you have any queries.

 

Regards,

Amsath Ali. M

[nick]

Thank you for your reply

Searching for solutions we think we have come up with a possible explanation.

We think that the problem is happening when session has timed out after long period of inactivity.

Whereas the whole application is checking for active session, calls to ImgRequest don't. And apart from that there is no meaningful explanation why the handler stops and application pool needs to be restarted...We think that the rational approach would be to fetch empty image and work up again when sesison restarts. Moreover, it would be rational to work for other users.

Please provide me with some feedback because we will have to switch to another software solution to solve this.

Thanx in advance

[Amsath Ali M]

Hi Nick,

 

Thanks for your update.

 

We are afraid that we are unable to reproduce the issue reported by you after made the sample (DiagramBuilder) inactive for some amount of time.  Could you please share us more information probably a video or a simple sample or the steps to reproduce the reported issue, this will help us to reproduce the issue effectively at our end, and to provide a better solution to you?

 

Please let us know if you have any queries.

 

Regards,

Amsath Ali. M

[Len Ford]

I too am seeing exactly the same problem as Nick when I try to edit a complex diagram. The imgRequest handler locks requiring a restart of the Web Server. I think that I have reproduced this problem by uploading the attached file to your demo server and editing it. I can't tell you which operation actually failed but I was dragging the most complex symbol around and selecting multiple symbols by dragging around them.

 

This diagram also demonstrates an additional problem I am seeing which is that ports do not stay on the periphery of the symbol when the symbol is resized.

 

Without a fix to stop the imgRequest handler locking up I am afraid that I cannot release this version to my customers.

 

Len Ford.

 

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[Amsath Ali M]

Hi Len,

 

Thanks for your interest in Syncfusion products.

 

As you have reported the same issue “The DiagramWebControl hung while moving symbols or resizing the complex symbol?” in your Direct-Trac incident #105146, we have updated our response in that incident. Please refer that incident for further follow up.

 

Please let us know if you have any queries.

 

Regards,

Amsath Ali. M