Oracle Application Server 10g Essentials [Electronic resources] نسخه متنی

5.1 Apache Architecture

Before
examining how Oracle
has extended the Apache server for use in Oracle Application Server,
you need to take some time to learn about Apache's
basic architecture. The Apache architecture (prefork model) consists
of a parent process that starts one or more child processes (Unix) or
threads (Windows). The child processes each serve a single
request at a time. When a child process
finishes serving a request, it once again becomes available to serve
another request.

A child process manages a request through its life cycle. The request
life cycle can be broken down into phases. Each request is taken
through the life cycle phases until the request is completed, or
until an error occurs. Figure 5-1 shows the Apache
request life cycle. Apache functionality is provided by modules that
are plugged into an appropriate phase of the request life cycle.

Figure 5-1. The Apache request life cycle

Modules are typically plugged in using an
AddHandler or SetHandler
directive within a URL mapping directive in the Apache
configuration file httpd.conf. A module has
hooks in the form of callback methods that are implemented
for the desired phase of the life cycle. The URL directive activates
the handler based on a particular characteristic of a
request's URI.

At the end of each request, Apache logs
the request URI to an access log file. A different access log can be
created for each URL mapping directive you specify in the
configuration file. In addition, you can customize the format with
directives or replace the logging
mechanism altogether with the appropriate directive. If an error
occurs, the error is logged to its own error log file.

Tools exist that allow an Apache server administrator to analyze
these logs for bad URLs, traffic patterns, and so on. Using these
tools, an administrator can eliminate bad links, plan server
capacity, or identify malicious activityto name only a few
possibilities.

To learn more about Apache, check out the Apache documentation available
online at http://httpd.apache.org. You may also want to
consult the book Apache: The Definitive Guide
(O'Reilly)