load balancing with multiprocessor servers

Discussion in 'ASP .Net' started by Jon, Feb 19, 2004.

  1. Jon

    Jon Guest

    Ok, so say you have 4 servers, each with 4 processors.
    Each processor has its own application domain for your
    web application, and therefore has its own cache, right?

    If so, is there a load balancer that handles processor
    affinity for requests - so that requests are sent to the
    same server, same processor, for a given user? If not,
    then you are limited to single processor server, right?
    Will a load balance handle server affinity so that
    requests are sent each time to the same server during a
    session?

    Can anyone offer any expertise on this? We do not
    necessarily need to handle a web farm with multiple
    processors and multiple servers, but it would be nice to
    understand the technical limits of the caching technology
    with ASP.NET.

    Thanks,

    Jon
     
    Jon, Feb 19, 2004
    #1
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  2. You should consider the fact that you can use other cross request caching methods like a State Server or SQL Server to contain the session variables

    Application variables are indeed bound to the server the were started on

    Check out StateServer and SQLServer session state management for more information

    Kind Regards
    Bjorn
     
    =?Utf-8?B?Qmpvcm4gQg==?=, Feb 19, 2004
    #2
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  3. Jon

    Jon Guest

    Ok, so how do I put put my page fragments into session
    variables? Enlighten me.

    Jon
     
    Jon, Feb 19, 2004
    #3
  4. Ok

    Runnig on a web farm rules out the use of Application data caching because the Application object is unique to each Web server. Since each Web server has its own copy of the data cached in memory, data will become out of sync when data on one of the Web servers is updated independently of the others. Since you have no control over which server in a Web farm receives a request, the Web Service consumer might receive different results from two consecutive Web Service calls hitting two different Web servers.

    More info here: http://msdn.microsoft.com/msdnmag/issues/02/12/WebFarms/default.aspx
     
    =?Utf-8?B?Qmpvcm4gQg==?=, Feb 20, 2004
    #4
  5. Jon

    Jon Paugh Guest

    Ok, this was an interesting read, and I appreciate it.

    Responses:
    1) Is there really no way to send all requests for a
    single user session to a single web server?
    Look:
    http://www.winnetmag.com/SQLServer/Article/ArticleID/7637/
    7637.html. Why would we not want to do this? I know there
    would be some performance degradation compared to the
    perfect web farm situation where any server can processor
    and request. But maybe there are some performance
    benefits as far as caching goes? At least it would be
    simpler I would think.
    2) Again, if 1) is possible, then is there a way to send
    all requests for a single user session to a single
    server, to a single processor? Do any of the MS servers
    support this?
    3) In the article you reference, the technique the author
    describes is interesting, but how will locking work?
    Isn't it possible that between the time that the user
    changes the database and the web service calls to other
    servers execute, another web request comes in to another
    server and uses the wrong data?
    4) In the article you reference, when application data
    changes on one server handling the web service, requests
    are sent to all the other servers in the web farm that
    handle the web service. OK. But what if the other web
    servers in the web farm have multiple processors. Since
    each processor has its own cache, don't we need to send
    one message to each web server, per processor (i.e. 3
    servers, with 4 processors = 12 messages?)?
    5) If 4) is correct, is there a way to send messages to
    each processor on a server?

    Thanks,

    Jon Paugh
     
    Jon Paugh, Feb 20, 2004
    #5
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