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  • IJ 6 posts 26 karma points
    Jan 30, 2013 @ 11:50
    IJ
    0

    Odd performance / slow requests randomly

    Hi,

     

    We are using umbraco v 4.9.0 on a site.  The site using imagegen, which is version 2.5.7 (2.5.7.27945).  We are experiencing issues where randeomly imagegen is taking extended periods of time to generate responses to requests.

    Here is a IIS log entry showing one such entry

    2013-01-30 11:40:27 xx.xx.xx.xx GET / - 80 - xx.xx.xx.xx Mozilla/5.0+(compatible;+PRTG+Network+Monitor+(www.paessler.com);+Windows) 200 0 0 242

    2013-01-30 11:40:30 xx.xx.xx.xx GET /imagegen.ashx width=459&height=198&image=/media/221256/rc_people_mix_home_page.jpg 80 - xx.xx.xx.xx Mozilla/5.0+(compatible;+PRTG+Network+Monitor+(www.paessler.com);+Windows) 200 0 0 93

    2013-01-30 11:40:30 xx.xx.xx.xx POST /umbraco/webservices/legacyajaxcalls.asmx/GetSecondsBeforeUserLogout - 80 - xx.xx.xx.xx Mozilla/5.0+(Windows+NT+6.1;+WOW64)+AppleWebKit/537.17+(KHTML,+like+Gecko)+Chrome/24.0.1312.56+Safari/537.17 200 0 0 213

    2013-01-30 11:40:31 31.222.169.10 GET /imagegen.ashx width=459&height=198&image=/media/221256/rc_people_mix_home_page.jpg 80 - 217.155.170.6 Mozilla/5.0+(Windows+NT+6.1;+WOW64)+AppleWebKit/535.19+(KHTML,+like+Gecko)+Chrome/18.0.1025.166+Safari/535.19 200 0 0 11917

    2013-01-30 11:40:31 xx.xx.xx.xx GET /css/groupCompanies/Main/images/arrow1.gif - 80 - xx.xx.xx.xx Mozilla/5.0+(Windows+NT+6.1;+WOW64)+AppleWebKit/535.19+(KHTML,+like+Gecko)+Chrome/18.0.1025.166+Safari/535.19 200 0 0 12534

    This IIS log is real time, no records have been between these requests.

    As you can see this took 12534 milliseconds to make the call to imagegen the second time for the same image, all within a time frame of 1 second.

    The original image in question is a jpg of 118 KB with a dimention of 459x198

    What we are seeing is that the cached folder and associated index file is not being created, presumably as the original size matches what is requested.

    During these slow requests the app pool running the site maxes its CPU duration of the request

    Any thoughts would be most appreciated.

    Ian

     

  • IJ 6 posts 26 karma points
    Jan 30, 2013 @ 11:56
    IJ
    0

    Wanted to edit this to say the image request is taking 11917 ms not 12534 but the edit feature is not working. :)

     

    Ian

  • Douglas Robar 3570 posts 4670 karma points MVP 6x admin c-trib
    Jan 30, 2013 @ 15:59
    Douglas Robar
    0

    Very odd.

    How many files do you have in the /media/221256 folder? A few, hundreds, thousands, more?

    How many files do you have in the /media/221256/cached folder? A few, hundreds, thousands, more?

    Delete the /media/221256/cached folder. ImageGen will re-create the folder and make new cached images for subsequent requests. Does this help?

    cheers,
    doug. 

  • IJ 6 posts 26 karma points
    Jan 30, 2013 @ 16:51
    IJ
    0

    Hi Douglas,

    There are only 10 files in the  /media/221256 folder  and as the requested image dimentions is equal to the source image dimentions, no /media/221256/cached  folder is created at all.

    Hope this helps

    Ian

  • Douglas Robar 3570 posts 4670 karma points MVP 6x admin c-trib
    Jan 30, 2013 @ 17:02
    Douglas Robar
    0

    Thanks, Ian. That's all very normal and no problem at all. 

    Just to be sure... what happens if you request a different size... does the 'cached' folder get created properly?

    And is this problem only when the requested size is the same as the original size?

    cheers,
    doug. 

  • IJ 6 posts 26 karma points
    Jan 30, 2013 @ 17:06
    IJ
    0

    Hi Douglas,

    I tested the 1st part of your question earlier and yes it did create the cached folder (deleted it again afterwards as its not required here).  

    I will trawl the logs now and see if we are getting slow response on resized images too.  As soon as I have done this I will update you.

    Thanks

    Ian

  • IJ 6 posts 26 karma points
    Jan 30, 2013 @ 17:19
    IJ
    0

    Douglas,

    We have this entry too:

    2013-01-30 00:09:15 xx.xx.xx.xx GET /imagegen.ashx width=504&height=284&image=/media/223449/gfonne-pr-8445.jpg 80 -  xx.xx.xx.xx Mozilla/5.0+(Windows+NT+6.1;+WOW64)+AppleWebKit/535.19+(KHTML,+like+Gecko)+Chrome/18.0.1025.166+Safari/535.19 200 0 0 13622

    This source image is 2123x1414 in size (2.48MB)

    So no, it does not look as though the issue is isolated to matching sized images.

    What is also strange, like the example I highlighted earlier its it followed by the following entry

    2013-01-30 00:09:15 xx.xx.xx.xx GET /css/main.css - 80 - xx.xx.xx.xx Mozilla/5.0+(Windows+NT+6.1;+WOW64)+AppleWebKit/535.19+(KHTML,+like+Gecko)+Chrome/18.0.1025.166+Safari/535.19 200 0 0 13990

    Why would the getting of a static file be effected and which is the cause and which is the symtom?  To this end I had another look and these lines show a case where imagegen alone is showing signed of performance issues
    2013-01-30 00:13:15 xx.xx.xx.xx GET /css/groupCompanies/Main/images/line-left.jpg - 80 - xx.xx.xx.xx Mozilla/5.0+(Windows+NT+6.1;+WOW64)+AppleWebKit/535.19+(KHTML,+like+Gecko)+Chrome/18.0.1025.166+Safari/535.19 200 0 0 33
    2013-01-30 00:13:15 xx.xx.xx.xx GET /imagegen.ashx width=459&height=198&image=/media/221256/rc_people_mix_home_page.jpg 80 - xx.xx.xx.xx Mozilla/5.0+(Windows+NT+6.1;+WOW64)+AppleWebKit/535.19+(KHTML,+like+Gecko)+Chrome/18.0.1025.166+Safari/535.19 200 0 0 14030
    2013-01-30 00:13:15 xx.xx.xx.xx GET /css/groupCompanies/Main/images/line-right.jpg - 80 - xx.xx.xx.xx Mozilla/5.0+(Windows+NT+6.1;+WOW64)+AppleWebKit/535.19+(KHTML,+like+Gecko)+Chrome/18.0.1025.166+Safari/535.19 200 0 0 41
    The other thing I have noticed is that most of the slow requests are all in the same ball park in terms of time 10-14 seconds, we dont seem to get any 6-7 second requests.
    But this does have me wondering if there is somthing environmental going on here.
    Any thoughts would be most appreciated
    Ian

     

  • Douglas Robar 3570 posts 4670 karma points MVP 6x admin c-trib
    Feb 01, 2013 @ 08:24
    Douglas Robar
    0

    There goes my hopes of a common scenario we might look to reproduce. Oh well. We'll keep looking.

    At a guess, how long does it take for your application pool to recycle? Any chance it is 10-14 seconds? If so, it would seem that the slow requests (imagegen or static resources) are because of a recycle prior to/during the request. What do you think? Plausible?

    Also, does this site have a lot of activity/hits?

    cheers,
    doug. 

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