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4.2.1.2b: Using servlets in a multi application server environment

4.2.1.2b: Using servlets in a multi application server environment

The WebSphere Application Server runtime environment provides you with such workload management options for handling servlet requests as:

  • multiple servlet engines
  • OSE (Open Servlet Engine) remote
  • Servlet Redirector
View article 7: Managing workloads for more information on these options.

View articles in section 7.1.3.* for remote OSE redirector sample topology for configuration information.

Both the OSE remote and the Servlet Redirector functions distribute workload to multiple application servers.

The Servlet Redirector intercepts OSE protocol messages and forwards each servlet request to an appropriate servlet engine.

The OSE remote is a plugin to the HTTP server that sends requests to different application server machines.

With both technologies, the first time you execute a servlet instance, the first application server in the list of servers, is used to service the request. If, after completing the request, this application server has no outstanding work, it is again designated as the first available server in the list. However, if multiple requests arrive at once, the OSE plugin (or the Servlet Redirector) dispatches the requests to other application servers, depending on the amount of outstanding work in their queues.

  • The same instance of a servlet running on two application servers, one of which is a model and the other a clone, cannot use the same URI. This restriction does not apply if the two application servers are both clones, or if they are a model and clone but run on different nodes.
  • When a client prematurely ends a connection to the servlet engine, the following error occurs:
    nativeWrite operation:  Status Code: -1
    This error message does not indicate a problem. It occurs during normal operations when users close their browsers or when sessions end as a result of a network outages.

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