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Using OracleAS Discoverer Viewer with OracleAS Web Cache

6.1 Using OracleAS Discoverer Viewer with OracleAS Web Cache

This chapter describes how to use OracleAS Web Cache to enhance OracleAS Discoverer Viewer performance, and contains the following topics:

• Section 6.2, "About OracleAS Web Cache"

• Section 6.3, "What are the benefits of OracleAS Web Cache?"

• Section 6.4, "How does OracleAS Web Cache work?"

• Section 6.5, "When to use Discoverer Viewer with OracleAS Web Cache"

• Section 6.6, "How to use Discoverer Viewer with OracleAS Web Cache"

• Section 6.7, "How to turn on OracleAS Web Cache"

• Section 6.8, "How to restart OracleAS Web Cache"

• Section 6.9, "How to display the Rerun Query link, hide the Preferences link, and hide the Presentation Options link"

• Section 6.10, "How to turn off Discoverer Viewer's 'sticky worksheet' behavior"

• Section 6.11, "Notes about using Discoverer Viewer with OracleAS Web Cache"

6.2 About OracleAS Web Cache

OracleAS Web Cache is a content-aware server accelerator, or reverse proxy server, that improves the performance, scalability, and availability of Web sites that run on OracleAS and Oracle9i. By storing frequently accessed pages in memory, OracleAS Web Cache eliminates the need to repeatedly process requests for those pages on middle tier servers and databases.

You can also use OracleAS Web Cache to load balance OracleAS machines in a multiple machine installation (for more information, see Section 5.1, "Installing OracleAS Discoverer in a multiple machine environment").

You manage OracleAS Web Cache using the OracleAS Web Cache Administration page.

Figure 6-1 OracleAS Web Cache Administration page

Text description of the illustration mm5.gif

OracleAS Web Cache sits in front of application Web servers, caching their content, and providing that content to Web browsers that request it. When Web browsers access the Web site, they send HTTP protocol or HTTPS protocol requests to OracleAS Web Cache. OracleAS Web Cache, in turn, acts as a virtual server to the application Web servers. If the requested content has changed, OracleAS Web Cache retrieves the new content from the application Web servers.

Figure 6-2 OracleAS Web Cache overview

Text description of the illustration webcachc.gif

For more information about OracleAS Web Cache, see Oracle Application Server Web Cache Administration and Deployment Guide.

Notes

• When deploying Discoverer, you typically add the Discoverer client tier components to an OracleAS farm, and use OracleAS Web Cache as a proxy server (for more information, see Section 5.1, "Installing OracleAS Discoverer in a multiple machine environment").

6.3 What are the benefits of OracleAS Web Cache?

Using OracleAS Web Cache:

• improves performance

  Running on inexpensive hardware, OracleAS Web Cache can increase the throughput of a Web site by several orders of magnitude. In addition, OracleAS Web Cache significantly reduces response time to browser requests by storing documents in memory and by serving compressed versions of documents to browsers that support the GZIP encoding method.

• improves scalability

  In addition to unparalleled throughput, OracleAS Web Cache can sustain thousands of concurrent browser connections. The result is that visitors to a site see fewer application Web server errors, even during periods of peak load.

• offers high availability

  OracleAS Web Cache supports content-aware load balancing and fail-over detection. These features ensure that documents not in the cache (referred to as 'cache misses') are directed to the most available, highest-performing Web server in the cluster. Further features guarantee performance and provide surge protection when application Web server load increases.

• offers cost savings

  Fewer application Web servers are required to meet the challenges posed by traffic spikes and denial of service attacks. As a result, OracleAS Web Cache offers a simple and inexpensive means of reducing a Web site's cost for each request.

• reduces network traffic

  Most requests are resolved by OracleAS Web Cache, reducing traffic to the application Web servers. The cache also reduces traffic to backend databases located on computers other than the application Web server.

For more information about the benefits of using OracleAS Web Cache, see Oracle Application Server Web Cache Administration and Deployment Guide.

6.4 How does OracleAS Web Cache work?

OracleAS Web Cache uses cacheability rules to determine which documents to cache. A cacheability rule indicates whether you want the documents specified within a particular URL to be cached or not cached. Cacheability rules are defined using regular expressions (for more information about Oracle's implementation of regular expressions, see Oracle Application Server Web Cache Administration and Deployment Guide).

The document specified within a URL included in a cacheability rule is not actually cached until a browser requests it.

Figure 6-3 The URL and document request process

Text description of the illustration webcacha.gif

Key to figure:

1. The first time a browser requests a particular URL, OracleAS Web Cache detects that the required document is not in the cache (referred to as a cache miss). OracleAS Web Cache therefore forwards the request to an application Web server, which sends the request to the database.

2. The database returns the data to the application Web server, which forwards a document and its URL to OracleAS Web Cache. If the URL is specified as one of the URLs to cache, OracleAS Web Cache caches the document for subsequent requests.

3. The next time a browser requests the URL, OracleAS Web Cache detects that the document is already in the cache (referred to as a cache hit).

4. OracleAS Web Cache serves the document from the cache to the browser.

6.5 When to use Discoverer Viewer with OracleAS Web Cache

With Oracle Application Server 10g (9.0.4), using Discoverer Viewer with OracleAS Web Cache to improve Web site performance, scalability, and availability will be most appropriate in the following cases:

• where Web sites only use public workbooks

• where Web sites access data that is relatively static

• where the Discoverer manager and/or workbook creator has access to OracleAS Web Cache and can refresh the cache after changes to workbooks

OracleAS Web Cache is particularly suitable for optimizing Discoverer Viewer performance when controlling access to data is relatively unimportant (e.g. where the same public connections are used by several users to access workbooks). OracleAS Web Cache is less suitable in restricted environments where controlling access to data is an issue (e.g. where private connections are used by individuals to access their own workbooks). If you are considering using OracleAS Web Cache in a restricted environment, note that a malicious user might be able to access pages that have been cached for another user (for more information about OracleAS Discoverer security in general, see Section 12.1, "Maintaining security with OracleAS Discoverer").

In Oracle Application Server 10g (9.0.4), using Discoverer Viewer and OracleAS Web Cache together requires a number of compromises, as follows:

• the removal of the following links from Discoverer Viewer:
  • the Preferences link, which enables users to configure how Discoverer Viewer behaves

  • the Presentation Options link, which enables users to change the appearance of Discoverer Viewer

• the turning off of sticky worksheet functionality (for more information about sticky worksheet functionality, see Section 6.10, "How to turn off Discoverer Viewer's 'sticky worksheet' behavior")

• data synchronization issues might arise where cached data is not purged after changes in underlying database tables

6.6 How to use Discoverer Viewer with OracleAS Web Cache

To use Discoverer Viewer with OracleAS Web Cache, you must perform the following configuration tasks:

• you must turn on OracleAS Web Cache for Discoverer Viewer, by setting the 'webcache' attribute of the Discoverer configuration element to 'true' in the configuration.xml file (for more information, see Section 6.7, "How to turn on OracleAS Web Cache").

• you must edit the ui_config.xml file to:
  • display the Rerun Query link, hide the Preferences link, and hide the Presentation Options link (for more information, see Section 6.9, "How to display the Rerun Query link, hide the Preferences link, and hide the Presentation Options link").

    Note: Removing these links prevents Discoverer Viewer end users accessing parts of the Discoverer Viewer user interface that interfere with OracleAS Web Cache.

  • turn off Discoverer Viewer's 'sticky worksheet' behavior (for more information, see Section 6.10, "How to turn off Discoverer Viewer's 'sticky worksheet' behavior").

  Note: If you have a multiple machine Discoverer environment, you need to make the changes specified above on each Discoverer machine.

Having specified that you want to use Discoverer Viewer with OracleAS Web Cache, you might want to remove files from the cache because workbook data has changed (for more information, see Section 6.11.1, "How to remove Discoverer Viewer documents from the cache")

Notes

• OracleAS Web Cache is automatically pre-configured on installation with an cacheability rule for Discoverer Viewer (for more information, see Section 6.11.3, "About the OracleAS Web Cache cacheability rule that is pre-configured for Discoverer Viewer").

6.7 How to turn on OracleAS Web Cache

Although OracleAS Web Cache is installed with OracleAS, it is turned off by default. To make use of OracleAS Web Cache, you must turn it on. For example, you might want to cache Discoverer Viewer pages, or use a Discoverer machine to provide load balancing.

To turn on OracleAS Web Cache for Discoverer Viewer:

1. Open the configuration.xml file in text editor or XML editor (for more information about the location of configuration files, see Section A.2, "List of Discoverer file locations").

2. Change the value of the 'webcache' attribute of the Discoverer configuration element from false to true (i.e. webcache="true").

   For example, after the change the configuration element might look like this:

   <disco:configuration 
   xmlns:disco="http://oracle.com/xmlns/discoverer/configuration" 
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
   xsi:schemaLocation="http://oracle.com/xmlns/discoverer/configuration 
   configuration.xsd" locale="en" webcache="true" rmi="true">
   
   

3. Save the configuration.xml file.

4. Restart OracleAS Web Cache in Application Server Control (for more information, see Section 6.8, "How to restart OracleAS Web Cache").

   OracleAS Web Cache is now turned on for Discoverer Viewer and OracleAS Discoverer Viewer performance will improve.

6.8 How to restart OracleAS Web Cache

You restart OracleAS Web Cache to re-initialize the component. For example, you might want to restart OracleAS Web Cache after making changes to the configuration.xml file.

To restart OracleAS Web Cache:

1. Display Application Server Control (for more information, see Section 4.2.2, "How to display Application Server Control").

   Application Server Control displays a list of OracleAS instances available.

2. In the Name column, select the OracleAS instance containing the OracleAS Business Intelligence and Forms installation where OracleAS Discoverer is installed.

3. When prompted, enter an Application Server Control user name and password.

   Application Server Control displays a list of OracleAS System Components available for the OracleAS Business Intelligence and Forms installation (e.g. Discoverer, Forms, Web Cache).

   
   
   Text description of the illustration wc4.gif

4. In the Select column, select the check box next to the Web Cache link.

5. Click Restart.

Application Server Control displays a notification message when OracleAS Web Cache is has restarted.

6.9 How to display the Rerun Query link, hide the Preferences link, and hide the Presentation Options link

When you use Discoverer Viewer with OracleAS Web Cache, you must modify the Discoverer Viewer user interface by:

• displaying the Rerun Query link

• hiding the Preferences link

• hiding the Presentation Options link

Figure 6-4 Discoverer Viewer showing Rerun Query link, Preferences link, and Presentation Options link

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Key to figure:

1. Rerun Query link

2. Preferences link

3. Presentation Options link

Notes

• Displaying the Rerun Query link is recommended where data changes frequently and users will therefore want to execute a new server request instead of using cached data.

• Hiding the Preferences link and the Presentation Options link is recommended because OracleAS Web Cache does not recognize changes in these values. Any such changes could therefore result in inconsistent workbook behavior and appearance.

To display and hide links:

1. Open the ui_config.xml file in a text editor or XML editor (for more information about the location of configuration files, see Section A.2, "List of Discoverer file locations").

2. Locate the <appearance> tag in the file.

3. Change the value of the following <appearance> tags:
   • change the value of the display_rerun_query_link tag to true

   • change the value of the display_preferences_link tag to false

   • change the value of the display_presentation_options_link tag to false

   After the change the tags will look like this:

   .
   .
     <option id="display_rerun_query_link" state="true"/>
     <option id="display_preferences_link" state="false"/>
     <option id="display_presentation_options_link" state="false"/
   

4. Save the ui_config.file.

When end users next run Discoverer Viewer, the user interface will be updated accordingly.

6.10 How to turn off Discoverer Viewer's 'sticky worksheet' behavior

Discoverer Viewer enables worksheet drills and pivot operations to be remembered between worksheet visits in a single session. This functionality is sometimes referred to as Discoverer Viewer's 'sticky worksheet' behavior. Discoverer Viewer's sticky worksheet behavior is not supported when used with OracleAS Web Cache. You must therefore turn off this behavior.

To turn off Discoverer Viewer's sticky worksheet behavior:

1. Open the ui_config.xml file in a text editor (for more information about the location of configuration files, see Section A.2, "List of Discoverer file locations").

2. Locate the <behavior> tag in the file.

3. Change the value of the sticky_worksheets tag true to false.

After the change the element will look like this:

.
.
  <option id="sticky_worksheets" state="false"/>
.
.

4. Save the ui_config.xml file.

When end users next run Discoverer Viewer, the sticky worksheet behavior will be turned off.

6.11 Notes about using Discoverer Viewer with OracleAS Web Cache

This section contains miscellaneous information about using OracleAS Web Cache with OracleAS Discoverer.

6.11.1 How to remove Discoverer Viewer documents from the cache

You might want to remove Discoverer Viewer cached documents for a number of reasons, including:

• because the data in a workbook has changed

• because a calculation shared by multiple workbooks has changed

To remove a Discoverer Viewer document from the cache:

1. If it is not already running, start OracleAS Web Cache Manager and login.

   If you are not sure of the user name and password to use, contact the OracleAS system administrator.

2. Select the Advanced Content Invalidation link to display the Advanced Content Invalidation page.

3. In the Advanced Invalidation section:
   1. Type /discoverer/ in the URL Path Prefix field.

   2. Enter an appropriate regular expression in the URL Expression field and select the adjacent regular expression radio button.

      The regular expression that you enter depends on the Discoverer Viewer document(s) you want to remove from the cache. The table below gives some examples:

      URL regular expression	Description
      viewer	This will remove all cached Discoverer documents.
      viewer.+(wbk=X)	Where X is the name of the workbook. This will remove cached Discoverer documents that have X as the workbook name.
      viewer.+(eul=X)	Where X is the name of the EUL. This will remove cached Discoverer documents that have X as the EUL name.
      viewer.+(ac=X)	Where X is the account name. This will remove cached Discoverer documents that have X as the account name.
      viewer.+(nlsl=en-us)	This will remove all United States English cached documents.

4. Click the Submit button to clear the selected document(s) from the cache.

Notes

• For a full list of regular OracleAS Web Cache expressions, see Oracle Application Server Web Cache Administration and Deployment Guide.

6.11.2 About preventing unauthorized access to cached pages

It is likely that OracleAS Web Cache will cache HTML pages for different Discoverer Viewer users. To prevent unauthorized users accessing cached pages, OracleAS Web Cache is pre-configured to use Discoverer Viewer's authentication mechanism, and requires no further configuration.

6.11.3 About the OracleAS Web Cache cacheability rule that is pre-configured for Discoverer Viewer

OracleAS Discoverer Viewer is pre-configured with a cacheability rule to cache pages served by the Discoverer servlet, except the following types of page:

• error pages

• scheduled workbook pages

• progress pages

• list of connections pages

A cacheability rule comprises a regular expression. OracleAS Web Cache evaluates each expression to a string, and tests whether a particular URL contains that string. If the URL does contain the string, OracleAS Web Cache performs the actions specified by the cacheability rule (e.g. cache or do not cache the page). If the URL does not contain the string, the page is not cached.

Notes

• Cacheability rules are configured automatically when you install OracleAS. Do not change the Web Cache configuration unless explicitly advised to do so by Oracle Corporation.

6.11.3.1 Cacheability rule to cache all pages served by the Discoverer Servlet

This cacheability rule caches all Discoverer Viewer pages.

Cacheability rule - discoverer\/viewer

Rule Details	Value
Method	GET, GET with query string
POST Body Expression
Cache/Don't Cache	Cache
Expiration Policy	Default: Never Expire
Multiple Documents with the Same Selector by Cookies*	Cache based on value of cookie "oracle-disco-account", also cache documents whose requests don't contain this cookie
Multiple Documents with the Same Selector by Other Headers*	Accept-Language, User-Agent
Session/Personalized Attribute Related Caching Rules	For session/attribute "ViewerCookie": cache documents whose requests contain this session, AND cache documents whose requests don't contain this session.
Simple Personalization	NO
HTTP Error Caching
ESI Output Permission	YES
Compression	On for non-Netscape browsers
Comment	Caches all pages served by the Discoverer servlet

* For more information about this option, see Section 6.11.2, "About preventing unauthorized access to cached pages".