This section covers the most relevant information for performance and size tuning the Tomcat 5.5.x Servlet/JSP Container. Most of this information is available on the Apache Software Foundation Web site.
At server startup time, a Connector object creates a number of request processing threads (based on the value configured for the minSpareThreads attribute). Each incoming request requires a thread for the duration of that request. If more simultaneous requests are received than can be handled by the currently available request processing threads, additional threads are created, up to the configured maximum (the value of the maxThreads attribute). If still more simultaneous requests are received, they are stacked up inside the server socket created by the Connector, up to the configured maximum (the value of the acceptCount attribute. Any further simultaneous requests receive “connection refused” errors, until resources are available to process them.
This object and its attributes are defined in the server.xml file, located in SYBASE\tomcat\conf. The following configurable properties are available for the HTTP Connector. For simplicity only sizing relevant properties are included.
acceptCount – defines the maximum queue length for incoming connection requests when all possible request processing threads are in use. Any requests received when the queue is full are refused. The default value is 10.
bufferSize – defines the size (in bytes) of the buffer to be provided for input streams created by this connector. By default, buffers of 2048 bytes are provided.
maxKeepAliveRequests – the maximum number of HTTP requests that can be held in the pipeline until the connection is closed by the server. Setting this attribute to 1 disables HTTP/1.0 keep-alive, as well as HTTP/1.1 keep-alive and pipelining. Setting this to -1 allows an unlimited number of pipelined or keep-alive HTTP requests. If not specified, this attribute is set to 100.
maxSpareThreads – the maximum number of unused request processing threads that are allowed to exist until the thread pool starts stopping the unnecessary threads. The default value is 50.
maxThreads – the maximum number of request processing threads to be created by this Connector, which therefore determines the maximum number of simultaneous requests that can be handled. If not specified, this attribute is set to 200.
minSpareThreads – the number of request processing threads that are created when this Connector is first started. The connector will also make sure it has the specified number of idle processing threads available. This attribute should be set to a value smaller than that set for maxThreads. The default value is 4.
