ChartImage in Webfarm

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  1. Amir Mohammad
    Amir Mohammad avatar
    2 posts
    Member since:
    Sep 2012

    Posted 06 Sep 2012 Link to this post

    Hi, Im having problem while using the chart image in the webfarm,
    We r using the sqlsession state in our webfarm,
    I read some threads in this blog , and for webfarm the telerik customer service said:
    The solution for web farm environment would be to implement State server or SQL server session state mode or sticky sessions, ensuring that all the request from one user will be handled by the same server.  
    [ ]

    Now my question is why only one machine has to serve the requests for the page i have my charts on that when we are storing our session item in the database?
    If the picture stored in the session the picture has to be in the sqlserver , and all of the requests are requesting the same session collection.
    Im not that expert about how the exactly sql session mode works but im really interested find the solution or atleast know the reason of this situation.

    Thank u very much.
  2. Giuseppe
    Giuseppe avatar
    2363 posts

    Posted 11 Sep 2012 Link to this post

    Hello Amir,

    Since generally chart images are stored in the session state there are two recommendations when using webfarm scenarios:

    1. Use sticky sessions -- sticky session refers to the feature of many commercial load balancing solutions for web-farms to route the requests for a particular session to the same physical machine that serviced the first request for that session. This is mainly used to ensure that a in-proc session is not lost as a result of requests for a session being routed to different servers.
    2. Configure a shared session with SQL server ot session state server.

    Kind regards,
    the Telerik team
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  4. Amir Mohammad
    Amir Mohammad avatar
    2 posts
    Member since:
    Sep 2012

    Posted 18 Sep 2012 Link to this post

    Thanks for your answer.
    It was not the any issue or bug in or anything related to your product it was my problem lol.
    I want to share the problem i had. In session database there is small thing we have to care to dont get in to the same problem i have...when i have 2 chart on the same page one of the use the one of the webservers to get generated but when the page goes on the client browser the incoming image requests for those charts come back to the different server. All of the webservers must use the same session because they are pointing to the same session datasource. In the scenario of two webserver in webfarm only one of the charts showed up. Then i went to the session table in sql, i delete all the rows, and i started over , when i loaded the page i saw the the web application created two different session for each chart(or incoming requests). then i took a look at this table [ASPStateTempApplications] and i saw two row for one my application with the different application id. i knew i have two webserver in our staging webfarm... lol Cause of this problem was when u create the web sites in the iis server, each website get the WebSiteID in the order of creation. This web site id is part of the application name in this table [ASPStateTempApplications]  
    like this [/lm/w3svc/1/root].(number 1 was my website id).
    The problem started since we were implementing the web farm. we had like 14 web sites, we copied the iis config file to create the web sites, but for some reason we created this website later on some other webservers without config file. So we got separate website id for the same website. It means on webserver1 the website had the id of 1 but in other webserver which was webserver2 or second webserver the same website had website id of 14 ... and i had the /lm/w3svc/1/root and /lm/w3svc/14/root. so they had to have 2 different session id because they had different website id. in iis7 we can just change the website id from the iis website settings but i think in iis 6 there is some commands for that.
    Thank u very much.
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