BizTalk enables users to configure WCF host to limit the maximum connections to a particular address. Through some painful trial an error I was able to get this setting to do what the documentation so easily described. To help save others from facing similar issues that i had i decided to help a brother out.
<system.net>
<connectionManagement>
<add address = “*“ maxconnection = “2“ />
</connectionManagement>
</system.net>
The connectionManagement element in the btsntsvc.config file is designed to specify the number of connections to a given address. By default BizTalk allows for 2 connections for any given WCF host. If you are calling http://someiishost/MyService.svc and http://someiishost/MyOtherService.svc BizTalk would only allow 2 simultaneous calls to the someiishost address. As a result as soon as the request hits the send port, even if a connection is not available, BizTalk starts a send timeout and if a response is not returned in the allotted Send Time Out it cancels the request and starts a retry.
What I originally found was that this setting was particularly useful when trying to increase throughput. I went from only having 2 services instances running at a time, to 10 (because of WCF service throttling). I increased the wild card * from 2 to 125. This worked great, but I ran into major issues when trying to use anything besides a wild card. The documentation states that the address attribute can be any dns or ip address. For my environment I found this to be false. I finally came to the conclusion that the address needed to be prefixed with ‘http://.’ I then found a difference between a computer hosted service, and a service hosted through a header.
Computer Hosted Service
For accessing a service on a network that is hosted on a computer I found that the computer name was case sensitive, and could not be fully qualified. So http://MYCOMPUTERNAME , http://MYCOMPUTERNAME.FullyQualifiied.DomainName.com did not work. I even ping’ed COMPUTERNAME, computername, computername.fullyqualified.com all of which resolved to the same address. So my conclusion was whenever a computer is hosting the service the format is “http://computername” (My blowing I know, wait till you see the next issue). Example computername setting:
<system.net>
<connectionManagement>
<add address = “*“ maxconnection = “125″ />
<add address = “http://mycomputername” maxconnection = “2“ />
<add address = “http://myheader.domain.com” maxconnection = “4“ />
</connectionManagement>
</system.net>
Host Header/Load Balanced Service
Ready for your headache? So I found the solution in our dev environment it was now time to deploy to production. The main difference between DEV and PROD environment was that the services were hosted behind a load balancer. As a result we had configured a host header (myheader) for our web site. I restart the host instances and tested the connectionManagement setting and to my surprise… the throttling setting is not working yet again. After some more agony I came to find out that the host header had to be fully qualified. This time the correct address was http://myheader .domain.com . I do some old school analysis and run ping on myheader and myheader.domain.com get the same IP yet again.
I still can’t explain why/how the setting was resolving address, but if you are seeing a similar issue, throw all logic aside and try the above.
