Need irule to disable node if http service goes down for any node in pool.

Why not just use a standard HTTP monitor? Seems like it would fit your need and you wouldn't have to mess with an iRule.

Thanks Cory! , Currently i have standard http health monitor configured for my both sharepoint nodes , but i need to configure something so if 1 node http service goes down in server itself, then F5 automatically disable that node so users cannot connect or send request to that node ..

Do you mean that if any single pool member is marked down then mark all the other pool members down?

Thanks again ! I have Application Pool X with two nodes - A and B ( both nodes are configured with SharePoint application) i have http health monitor configured below -

Send String : GET /Pages/default.aspx HTTP/1.1\r\nHost: www.X.com\r\nConnection: Close\r\n\r\n Receive String : http|401

Now recently node A had some local http issue and its Http/application pool service goes down, but node A still was online with F5 LTM - now if it happens again ( http service goes down) i want to disable node A -

My concern is that you are expecting a 401 response from the server in order to mark it as 'up' Ideally this should be a 200 OK or similar status. Is there a reason your Sharepoint resources return a 401 instead of a 200 level response?

I agree you should try to use a standard HTTP monitor which checks a page that is only successful when the web daemon and the server instance is up.

You can monitor a Windows service though it's more work for BIG-IP to do so.

https://devcentral.f5.com/articles/monitoring-windows-services-from-big-ip

Aaron