HTTP Receive location failing to in BizTalk

Question

Hi All,
BizTalk application receives request from external vendor using HTTP Receive location which uses HTTPReceive.dll
2 servers A and B in the production performing well, but it fails from yesterday. Could see request coming through the IIS in the IIS log, but it is not reaching to biztalk application.
I have tried these steps in both A and B machines
1. restart the biztalk app
2. restart the application pool of the website that connects this app
3. reset iis in the machines 
How a request from IIS is routed to machines, I can't understand which machine handles the request, currently it reaches machine B, I could see previous IIS log where it processed successfully in machine A IIS log.
I could see error 500 in machine B IIS log for each request that comes in but cannot make it to BizTalk app
No error log in the event viewer of A and B BizTalk servers.
Can anyone guide me how to resolve it?
Regards
Vivek

Answer 1

Hi Vivek,
If you get HTTP-500 error you will have eventlog entries, not just in IIS logs.
"How a request from IIS is routed to machines, I can't understand which machine handles the request, currently it
reaches machine B, I could see previous IIS log where it processed successfully in machine A IIS log." -
IIS would route to BizTalk machines, only if you have separate servers as webserver(IIS) and BizTalk. If IIS is host in the same servers as BizTalk, then when the IIS receive the message,
it would route to its standalone internal BizTalk server. The routing to different machines is due to the loadbalancer. Your statement is bit contradictory. I assume your IIS is local to the BizTalk servers. So when the client send the message to HTTPReceive.dll,
the url is bound to loadbalacer, which based on its load balancer logic route the message to anyone of the BizTalk server's IIS (machine A and machine B) hence you see two different IIS logs in machine A and machine B.
Many Load-balancers, I have seen work with a unique logic where they send the requests primary to one server always and only if that primary server is busy (or not available) then it would
send it to other server. May be load-balancer have been sending its request to mahicne-A until recently and may be due to some reasons its sending the request to machine-B now. The reason machine-B may not be working now, could be because it was never configured
properly before and when machine-B start to receive the message, it gives error(as load-balancer request are always handled by machine-A before). To prove this, stop IIS in machine-B and see machine-A receive the message.
For this HTTP-500 error, check the HTTPReceive.dll is configured correctly. Check the following articles for configuration:
Configuring BTSHTTPReceive.dll to work on IIS 7
http://www.biztalkbill.com/Home/tabid/40/EntryId/66/Configuring-BTSHTTPReceive-dll-to-work-on-IIS-7.aspx
http://social.msdn.microsoft.com/Forums/en-US/20ea5954-4ca8-40ca-b043-2e6c3d3ae105/btshttpreceivedll-remote-server-returned-an-error-500
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