HTTP Request routing

WebSphere Application Server can use HTTP to route requests from a Web server to Application Servers on remote machines.

HTTP transport

In the diagram, Machine B hosts the Web server and the WebSphere Web server plug-in, and receives HTTP requests from clients. The Web server plug-in forwards the requests to an HTTP transport in the Application Server on Machine C, using HTTP or HTTPS protocol.

Variations on this configuration include vertical scaling of the application servers by creating new application servers on the same machine. Alternatively, for a horizontal scaling scenario, add machines (D, E, ....N) running application servers to the environment.

The Web server plug-in supports Network Address Translation (NAT) firewalls. See Port number settings in WebSphere Application Server versions for a list of default ports that WebSphere Application Server uses. See Default coexistence settings for port numbers for a list of default port settings in the coexistence panel. The installer program for the Application Server displays the coexistence panel when it detects another installation of Application Server.

Load balancing support

The Web server plug-in is fully integrated with WebSphere Application Server workload management and the clustering facility. HTTP transport balances loads within a cluster.

If you are using a third party load balancer in between the plug-in and the Application Server for HTTP requests that are not subject to an existing affinity, you can override the round robin algorithm that determines where to route a request. To override this algorithm, specify the IP address of your third party load balancer on the ClusterAddress element within the ServerCluster tag in plugin-cfg.xml file. Specifying this IP address delegates load balancing for the servers within this cluster to the third party load balancer.

Failover support

The Web server plug-in automatically handles failover and changes in the number of available cluster members.

Typical use

The Web server plug-in has the following advantages:

The Web server plug-in has the disadvantage of requiring at least one firewall port, more if multiple Application Server cluster members are configured, or WebSphere Application Server security is used on the machine hosting the Web server.

A variation of the Web server plug-in topology occurs when an instance of the Application Server runs on the same machine as the Web server. Such a configuration is illustrated in the following figure.

Web server on the same machine

Such configurations can direct client requests to additional application server cluster members on other machines. This example redirects client requests to both the Application Server instance running on Machine A and the cluster members running on Machine B. You can administer all Application Server instances from the deployment manager node, which can exist on Machine A, Machine B, or another machine. The deployment manager communicates with the node agent server process on each machine, to coordinate configuration changes.

Typical use

This topology is recommended only in situations where hardware limitations prevent you from hosting the Web server on a dedicated machine.

In many production environments, one set of servers is configured to run Web servers and another set of servers is configured to run Application Servers. This configuration lets you add capacity in a production environment. You might also use this topology to more fully replicate a production configuration in a test environment. This topology provides a means of load distribution between a machine hosting both the Web server and Application Server, and machines hosting just the Application Server.

You can also use this topology to distribute the workload in situations where there are a limited number of machines.


Related concepts
Web server separation
Related reference
Port number settings in WebSphere Application Server versions
Default coexistence settings for port numbers
plugin-cfg.xml file



Searchable topic ID:   cins_httptrans
Last updated: Jun 21, 2007 8:07:48 PM CDT    WebSphere Business Integration Server Foundation, Version 5.0.2
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