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7.3: Redirecting servlets
7.3: Redirecting servlets
Servlet redirectors are used to direct requests from a Web server to one or more clones
of a servlet engine in an application server. WebSphere Application Server supports
two mechanisms for redirecting HTTP requests to servlets:
- Open Servlet Engine (OSE). OSE is a proprietary mechanism for
transporting data. It can be used to direct client requests from the Web server to
servlets on the same machine (local OSE) or on a remote machine (remote OSE). OSE is
fully integrated with WebSphere's modeling and cloning facility.
- Servlet redirector. A servlet redirector is a dedicated
application server that is specifically designed to forward client requests to remote
servlet engines. The servlet redirector receives requests locally through OSE.
However, instead of processing them itself, it redirects them to other application
servers. The servlet redirector can be run in three different configurations:
- The thick servlet redirector is configured on a machine that is a full
WebSphere Application Server node with an administrative server. It can be
administered like any other application server.
- The thick servlet redirector can also run with a simplified version of the
administrative server known as an administrative agent. The administrative agent
manages the servlet redirector, but it is controlled by a master administrative server on
another node.
- The thin servlet redirector runs without the administrative server. Special
scripts are provided to manually start it and generate its configuration files.
Servlet redirection is generally used to scale up configurations
that use a single servlet engine on a single machine to configurations
that use multiple servlet engines on multiple machines. Both
servlet redirection mechanisms provide load balancing, failover
support, and availability management for servlet engines.
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