CODEWITHSUNDEEP
azureasp.net-mvc-5load-balancing
CalumMcCall
CalumMcCall

Reputation: 1687

Load balancing stateful web application

I am trying to scale a web app on Azure from a single web instance to multiple instances. The web app does a fair amount of processing of per-user state, it's also fairly interactive so latency is important. We currently have a single database, testing has shown it is not the bottleneck so for this question let's assume we don't have to worry about scaling it, all instances will hit the same database. In this case, I think per-user load balancing is the best option, as per-request will result in per-user state being duplicated in lots of web instances. Apart from the issue of maintaining consistency, I am concerned this would result in unacceptable latency for end users.

This link says that ARR does per-user load balancing by default on Azure. However, the Traffic Manager, which from what I can gather is automatically enabled when you spin up multiple web instances on Azure, does per-request load balancing.

So my question is, which of these two load balancing schemes will I be using if I add a few more instances to my Web Hosting Plan? If I need to manually disable the Traffic Manager, what is the best way to do this?

Upvotes: 3

Views: 1429

Answers (1)

Simon W
Simon W

Reputation: 5496

Calum - you can leverage the standard SQL Session State Provider in Azure or you could look at the Azure Redis Cache provider as well for backing stores for user session state.

When deploying to Cloud Service Web Roles you automatically get a load balancer instance in front of your hosts. It's relatively transparent other than configuration of Endpoints. Each newly added/removed auto-scaled instance gets added to the Cloud Service and is automatically added/removed to the load balancer.

As others have said, Azure Traffic Manager provides a higher level service which can direct traffic to multiple Azure Regions (data centers) and even on-premises endpoints.

A good overview of Load Balancing can be found here: http://azure.microsoft.com/blog/2014/04/08/microsoft-azure-load-balancing-services/

Upvotes: 3

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