问题
Here is the scenario:
- We have 3 web servers A, B, C.
- We want to release a new version of the application without taking the application down
(e.g. not using the "Down for maintenance page"). - Server A goes live with latest code.
- Server B gets taken off-line. Users on Server B get routed to A and C.
- Page1.aspx was updated with new control. Anyone that came from Server B to Server A while
on this page will get a viewstate error when they perform an action on this page. This is what we want to prevent.
How do some of you resolve this issue?
Here are some thoughts we had (whether it's possible or not using our load balancer, I don't know... I am not familiar with load balancer configuration [it's an F5]):
The more naive approach:
Take down servers A and B and update. C retains the old code. All traffic will be directed to C, and that's ok since it's the old code. When A and B go live with the update, if possible tell the load balancer to only keep people with active sessions on C and all new sessions get initiated on A and B. The problem with this approach is that in theory sessions can stick around for a long time if the user keeps using the application.
The less naive approach:
Similar to the naive approach, except (if possible) we tell the load balancer about "safe" pages, which are pages that were not changed. When the user eventually ends up on a "safe" page, he or she gets routed to server A or B. In theory the user may never land on one of these pages, but this approach is a little less risky (but requires more work).
回答1:
I assume that your load balancer is directing individual users back to the same server in the web farm during normal operations, which is why you do not normally experience this issue, but only when you start redirecting users between servers.
If that assumption is correct then it is likely the issue is a inconsistent machinekey across the server farm.
ViewState is hashed against the machine key of the server to prevent tampering by the user on the client side. The machine key is generated automatically by IIS, and will change every time the server restarts or is reset, as well as being unique to each server.
In order to ensure that you don't hit viewstate validation issues when users move between servers there are two possible courses of action.
Disable the anti-tampering protection on the individual page or globally in the pages element of the web.config file using the enableViewStateMac attribute with a false value. I mention this purely for the sake of completeness - you should never do this on a production website.
Manually generate a machine key and share that same value across each application (you could use the same key for all your applications, but it is sensible to use one key per application to maximise security), on each of your servers. To do this you need to generate keys (do not use any you may see in demos on the internet, this defeats the purpose of the unique machine key), this can be done programatically or in IIS manager (see http://www.codeproject.com/Articles/221889/How-to-Generate-Machine-Key-in-IIS7). Use the same machine key when deploying the website to all of your servers.
I can't answer on the best practice for upgrading applications that require 100% uptime.
来源：https://stackoverflow.com/questions/12863166/avoiding-invalid-viewstate-when-deploying-on-a-load-balanced-website-without-dow