Funny you should mention this Christopher, I just had to do the same thing for a client. It seems the normal configuration is to point all ARS clients (user tool, mid-tier, API, etc) to the load balancer alias name, which is also the name of the server group. The load balancer then does its job and spreads the load among the group member servers. Since each member of the group knows the load balancer alias as itself, it doesn't really matter which server handles any given transaction (speaking generally, in practice there are "sticky" session matters to deal with). So what to do if you're not using a load balancer?
We followed the instructions in the AR System guide for managing server groups and then added one additional step of our own -- for each host that will run an ARS client, we manually updated the hosts file to resolve the server group name to one of the group member server's IP address. We estimated the load each client would generate, and tried to balance that load across the member servers. Of course if a client is running on a member server, then it's efficient to have the server group name resolve to 127.0.0.1 (or the equivalent). It's important to note that all clients are configured with server name = group name except for admin class clients, who always have server name = admin server name. HTH, --Phil -----Original Message----- From: Action Request System discussion list(ARSList) [mailto:arsl...@arslist.org] On Behalf Of strauss Sent: Thursday, October 28, 2010 16:20 To: arslist@ARSLIST.ORG Subject: DNS entry for Server Group I am experimenting with a server group for 7.6.03, but had not planned to use a load balancer for a variety of reasons. This is driven in part by the need to run multiple mid-tiers with different settings for different groups, as we may be forced to make mid-tier primary in 7.6.03 because so many parts of the applications no longer work at all in the User Tool (RKM in particular). We need an admin mid-tier on the admin server (only one allowing the forms list), helpdesk mid-tier on a support staff server (longer timeouts - all use fixed licenses), and a general mid-tier for other support staff with mostly floating licenses (shorter timeouts), and possibly for customer access to RKM. Some day we may need another mid-tier optimized for SRM if/when we implement it; today the Kinetic Request application has its own web server. My current 7.6.03 installs place the mid-tier on the AR Server - currently using IIS since the distributed tomcat 6.0.18 installs refuse to do SSL via OpenSSL/PKCS, and the 7.6.03 mid-tier refuses to work properly with the current 6.0.29 tomcat distribution (which does support SSL). These still aren't entirely stable - on two of them the tomcat dies overnight, leaving the Jakarta Isapi redirector down - killing the mid-tier. These are 2 cpu/8 core/16 thread machines with 12 to 24 gb of RAM, so horsepower isn't an issue. I still need to define a common server name alias for the server group in DNS. All of the member servers (Windows Server 2003 Ent x64, 2003 R2 Ent x64, or 2008 R2 Ent x64) are registered in both my AD Forest/DNS and the campus DNS under the FQDN. They are only resolvable by short name within my forest, although I know that our campus DNS can have an alias to a short name if I need it. Mid-tiers within the forest have no problem resolving an AR Server on another machine by the short name since they are all in the same forest/domain DNS. Since I am not using a load balancer, I think that the server alias name for all of the server group members can be a short name registered only in my AD DNS; nothing will ever refer to it from outside my forest (will it?). What I am not sure of (not a DNS jockey at all...) is what has to be in the record. Is the alias supposed to point to all of the IP addresses for all of the server group member servers? Does anything ever actually USE the alias to connect to one or more of the servers? I guess that I might bring up a common mid-tier that points at it (that _should_ work since the mid-tier will be able to resolve it in my DNS, and the mid-tier will be in campus DNS by FQDN), but for now we will be directing the different clienteles to separate mid-tiers co-located on the appropriate functional servers for their purposes. Every bit of this is radically different from our current ARS 7.1 setup with a single AR Server, a single mid-tier server, and a separate RKM 7.2 server, so I really need some insight from anyone who has already fought the battle of implementing server groups (and won, I hope). The server group alias name has me stuck for now, since it does not exist and isn't in any DNS yet. The docs and the BMC knowledgebase don't get me to an answer on how to set it up. Christopher Strauss, Ph.D. Call Tracking Administration Manager University of North Texas Computing & IT Center http://itsm.unt.edu/ _______________________________________________________________________________ UNSUBSCRIBE or access ARSlist Archives at www.arslist.org attend wwrug11 www.wwrug.com ARSList: "Where the Answers Are" _______________________________________________________________________________ UNSUBSCRIBE or access ARSlist Archives at www.arslist.org attend wwrug11 www.wwrug.com ARSList: "Where the Answers Are"
