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Issues running behind a hardware load-balancer?

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  • Issues running behind a hardware load-balancer?


    We're going to be running vB on a site that is already set up to have two web server machines behind a hardware load-balancer. My plan is to install vB on both web machines, both sharing a single MySQL instance on a third machine, and I want to make sure to minimize any issues vB might have with this.

    (Note, first, that the site is load-balanced for redundancy, not for high volume traffic. So for us a lot of issues discussed recently about MySQL being a bottleneck are not a concern. Yet.)

    The two potential problems I see (as a vB newbie) are user sessions, and file-based configuration.

    How does vB handle user sessions? I come from the servlet world, where (usually) the user's session is tied to a particular machine, and so load-balancers have to make sure a user is always pointed to the same machine. Do we have the same issue with vB?

    As for configuration, a lot of the vB config is in the database, so both vB servers can share that. But how much of the config is in the file system? Are there any approaches to making sure changes are applied to both servers?

    I'm sure there are other concerns I haven't thought of.

    Any and all suggestions greatly appreciated! Thanks.


  • #2
    It can run entirely from the database with no configuration being held on the file system. The problem is mainly that IPADDRESS will show as the balancers IP for every request you need to alter the definition in init.php to match the IP address that the request is from. The load balancer just adds this to the request header usually.
    Scott MacVicar

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