Friday, 29 July 2011

Load Balancing in MS Dynamics CRM

In its infinite wisdom Microsoft decided to make my life harder by making it MS Dynamics CRM not work out of the box with a load balancer and I'm not talking about Microsoft software based network load balancing although it would apply too, if memory servers right, but a proper hardware based solution, which if again, memory serves me right, it's a Cisco 11506, but that is by the by.

In a normal load balancing situation, you would want a DNS entry for your load balancer's VIP and you would direct your clients to that VIP, so far so good. The problem is that there is a few pesky rows in the DeploymentProperties table in the MSCRM_CONFIG database
The NvarCharColumn for these rows is, by default, set to the first server in a deployment, which is all well and good if you have a single server in your deployment, but the minute you add another server you are creating a single point of failure, because if the first server goes down, down goes your application. In actual fact it won't come down until the app pool gets recycled if I remember correctly. It will also refuse to start if the first server is down.

In the three+ years since we encountered this problem, it seems that this is all now clearly documented, I should've done a search in google before I wrote all this, oh well.

Note that some people have reported that this setting also needs changing, I guess it depends on whether or not you are using asynchronous plugins, which we don't.

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