Web server

In order to utilize WAS resources on request processing instead of request queuing, the client requests that arrive at the Web server when the WAS is saturated should be queued in the network. All Web servers have settings for configuring the maximum number of concurrent requests accepted. For information about how to configure this setting, refer to 19.4.8, The Web server. For details the new features of IBM HTTP Server 2.0 and how to use them, refer to IBM HTTP Server 2.0.

 

Limiting connections from plug-in to Web container

In WAS V5.1, the plug-in has been enhanced with the MaxConnections attribute. The MaxConnections value specifies the maximum number of connections permitted concurrently to each appserver. When this number of connections is reached, the plug-in automatically skips that application server on establishing new connections, and tries the next available one (see also MaxConnections setting).

The MaxConnections attribute works best with Web servers that follow the threading model instead of the process model, and where only one process is started (also called single process-multiple threads model). This is true for IBM HTTP Server version 2, which is the recommended Web server for WAS V5.1.

Important: IBM HTTP Server v1.3.x follows the process model (in contrary to IBM HTTP Server v2.0.x). With the process model, a new process is created to handle each connection from the appserver, and typically, one process handles only one connection to the application server. Therefore, the MaxConnections attribute does not have much of an impact in restricting the number of concurrent requests to the application server.

 

Determining the Web server maximum concurrency threads setting

A Web server monitor (see 16.8, Monitoring the IBM HTTP Server) can help tune the maximum concurrent thread processing setting for the Web server. Use a standard workload that represents a typical number of incoming client requests, use a fixed number of iterations, and use a standard set of configuration settings. Watch the number of Web server threads going to the Web container and the number of threads accessing static content locally on the Web server. Set the concurrent requests setting to the sum of the Web container thread pool size and the number of static content requests processed by the Web server. If no static content is served from the Web server, the number of requests should be about equal to the Web container thread pool size (depending on how many clients and Web servers are concurrently accessing the same Web container).

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