Why have a webtier?

I recently saw a post on a mail list which basically asked if in a Weblogic Server installation , if it worth having a Webtier when you have a load balancer front ending everything.

Now, me personally, I always recommend putting a webtier in front of Weblogic Server, in my case this is almost always Apache HTTP Server and the main reason is to harden the inbuilt Weblogic http server.. however someone else responded with a great list of reasons why you should *always* have a webtier even if you have a load balancer.. namely.

• Allows the WLS cluster membership to be reconfigured (new servers added, others removed) without having to change the web server configuration (so long as at least some of the servers in the configured list remain). The plug-in will learn about the cluster membership and direct work accordingly.
• More parallelism. You can have as many web servers as you like, and spray inbound traffic across the web server "farm" using stateless load balancers. The plug-in will ensure the requests are directed to the correct server. In contrast, with connection-aware load balancers, you may be limited to using a single LB, or chaining it to a single peer LB.
• Faster fail-over in the event of a WLS instance failing. The plug-in actively learn about the failed WLS instance using information supplied by its peers, and avoid it until the peers notify the plug-in that it is again available.
• Somewhere to terminate SSL which isn't the server.
• Static content hosting.
• HTTP redirection and munging capability over and above what WLS provides. You can also use the web server tier to front off against many different WLS clusters, and perhaps do content based routing.
• Provides a sacrificial lamb for the DMZ. This is often fits in well with existing infrastructure and is sufficient to satisfy customer security teams.


Thanks Phil for the response.. nicely done

Angelo

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