Oracle9iAS HTTP Server  

Oracle HTTP Server (OHS) provides a web server and also the necessary infrastructure to create dynamic applications. In Release 2, it has also been enhanced to provide the clustering infrastructure for Oracle9iAS Core. 

Based on the proven Apache Infrastructure, Oracle HTTP Server adds significant punch by allowing developers to program their site in a variety of languages and technologies - Perl (via mod_perl, cgi), C (via CGI, and FastCGI), C++ (FastCGI), and of course the popular Oracle language - PLSQL. It can also be a proxy server - both forward and reverse. Oracle HTTP Server also provides several libraries and frameworks (Business Components for Java, XML Developer's Kit, JNDI, JDBC libraries etc.). In addition the new features of single sign on, clustered deployment and high availability, make the operations using OHS that much easier. 

OHS: The Web Server

Based on Apache - HTTP v1.1 Support
Oracle HTTP Server code is based on Apache Web Server (http://www.apache.org). According to NetCraft survey (http://www.netcraft.com), as of November 2001, Apache Web Server powers twice as many sites as Microsoft's IIS, and over thirty times as many as iPlanet! With such a proven code base, Oracle HTTP Server, provides Oracle9iAS customers with the stability, flexibility, and scalability required of a web server.

Security - Encryption with SSL
Secure Sockets Layer is required to run any web-site securely. Oracle HTTP Server supports it, and also pre-configured with a demo certificate, to ease development and testing in https mode. The SSL encryption is based on the industry standard, patented, algorithms from RSA. The SSL works seamlessly with both IE and Netscape browsers. In the new release (Release 2), the infrastructure has been upgraded to share the same wallet information as the database uses.

Security - Single Sign On
Oracle HTTP Server supports the standard basic authentication feature of web servers. The source for the username and password used in this scenario is a flat file (with encrypted passwords). In addition, a new module - mod_osso - has been included in Release 2 to support single sign on across sites and across applications. This provides for a much better end user experience (they have to login only once), and a much easier development cycle (most of the security is declarative).

Virtual Hosts
A virtual host, as the name suggests, is a web site that may share its web server with other similar sites. Oracle HTTP Server provides a 'container' environment for a virtual host, thus providing a virtual host with its own set of security and other configuration directives, in addition to locations from which the files are served. This allows an ISP to save on hardware and administrative costs, by enabling hundreds to thousands of sites to be served from a single runtime instance of Oracle HTTP Server. Due to technology limitations - and not due to restrictions within the product - only one virtual host can enable SSL.

Distributed Authoring and Versioning Support
WebDAV, an IETF standard, is an HTTP based protocol that lets DAV enabled clients (such as MS Office, Windows Explorer) edit files on a server. Apache organization provides a module that enables this for file based storage on the server - in addition to productizing that, OHS enables people to let the server side store be a database or other repository. 

Proxy Server and URL Rewriting
Any web site that is "alive" changes often. Along with that, the directory structures and the urls change. Oracle HTTP Server makes it easy to accommodate these changes by including an engine to support URL rewriting (so that the end users do not have to change their bookmarks). It also supports forward and reverse proxy capabilities, thus making it easier to make content served by different servers to appear from one single server. This feature is also extensively used to segregate modem connections which may otherwise tie up processes from the application server.

Proxy Plugin
A new component has been added in OHS Release 2 - which now enables IIS and NES (iPlanet) to route requests to Oracle9iAS - i.e. you can benefit from all of Oracle9iAS features even if your corporate standard requires you to use IIS or NES as the web server!  

OHS: The 'Supporting' Application Server

'Webification' of PLSQL Stored Procedures
Oracle HTTP Server includes a module that enables making requests to database stored procedures from the browser, which then gets routed to the correct place, and the output is send back to the browser. This, in addition to the performance improvement due to the disk based cache and the associated security, has made this feature one of the most popular in Oracle9iAS HTTP Server. 

PLSQL Server Pages
Similar in concept to the Java Server Pages, this module allows PLSQL to be used as the scripting language within an HTML page. It gets translated into a stored procedure, which then uses the module described above (for PLSQL stored procedures), to send the output to the browser.  

Server Side Include
Server Side Includes provide an easy way of adding some dynamic, or uniform static content, across all the site's pages. It is typically used for header / footer information. Oracle HTTP Server supports special directives to enable these only for certain types of files or for a given virtual host. 

Perl
Perl is one of the most common ways scripts and cgi programs were developed for the web initially. However, the Perl interpreter is large and starting and stopping it is time consuming. Hence, Oracle HTTP Server optimizes the execution by keeping the perl interpreter always running and in memory. It also enables extending the web server functionality by adding new perl modules that can process a web request.

C / C++ (CGI and FastCGI).
CGI programs have been commonly used to program web applications. OHS improves on them by providing a mechanism to keep them alive beyond the request lifecycle, thus improving the performance tremendously. 

Java Object Cache 
OHS provides a new caching framework for Java objects. This caching mechanism allows you to distribute state (such as session variables) across an array of machine and supports group membership protocols. Thus, the framework not only provides performance improvement by caching Java objects, but can also provide improved fault tolerance by having those objects available on different machines. There are several different cache invalidation schemes supported. While bundled with OHS, the common usage of these files will indeed be through OC4J (Oracle9iAS Containers for J2EE).

Dynamic Monitoring Service 
OHS includes relevant libraries to instrument applications - and then monitor them over the web. OHS itself, as well as several of Oracle9iAS components have already been instrumented using these. Several metrics and events information is already available and exported in this fashion. 

OHS: The Clustering Framework

Distributed Configuration Management [New in Release 2]
OHS now includes associated infrastructure module - Distributed Configuration Manager [DCM] - that enables cluster wide deployments in a very simple way. J2EE applications for OC4J can now be deployed to a cluster, or a new node can be added to the cluster with ease.

High Availability Framework [New in Release 2]
Oracle Process Monitor and Notification Server - OPMN, is included with OHS. This process monitors not only OHS but OC4J also, and ensures that these processes are up. The death detection and event notification features in OPMN ensures that all components in the cluster have the latest cluster-wide view of the system.

Load Balancing [New in Release 2]
OHS now includes a new module - mod_oc4j - that routes requests to the OC4J in a cluster in a round robin fashion. OPMN helps ensure that mod_oc4j knows of all the OC4J in the system - without requiring a system administrator to do any configuration. 

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