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Configuring OracleAS Web Cache for Session Binding and Load Balancing

Purpose

This tutorial describes how to configure OracleAS Web Cache for sesison binding and load balancing.

Time to Complete

Approximately 20 minutes

Topics

This tutorial covers the following topics:

	Overview
	Prerequisites
	Defining a Second Origin Server
	Defining a Ping URL for Application Detection and Origin Server Capacity
	Configuring OracleAS Web Cache to use Cookie-Based Sessions
	Confirming the Configuration for Session Binding
	Configuring OracleAS Web Cache to use JSESSIONID
	Summary
	Related Information

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Overview

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OracleAS Web Cache can distribute load among multiple origin servers via HTTP or HTTPS. For applications that use sessions, OracleAS Web Cache performs session binding to the origin servers as well.

Prerequisites

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Before starting this tutorial, you should:

1.	Have completed the OBE titled "Configuring OracleAS Web Cache for Caching a J2EE Application"

Defining a Second Origin Server

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Recollect that one of the prerequisites for performing Web Cache OBEs is that you should have two instances of Application Server Mid Tier (J2EE and Web Cache). For these OBEs, we have installed both the instances on the same machine. You have worked on the first instance in the first OBE titled "Configuring OracleAS Web Cache for Caching a J2EE Application." The default origin server for instance 1 is localhost 7778. The default origin server for instance 2 will be localhost 7779 because the instances are on the same machine. In this section you will define a second origin server localhost 7779 and map OracleAS Web Cache with the origin servers for load balancing.

1.	From the Oracle Enterprise Manager 10g Application Server Control Console, go to the OracleAS Web Cache Home page. Click the Administration tab. Click Origin Servers under Properties.
2.	Click Create to create the second origin server.
3.	Enter the following parameter values in their respective fields: Host: localhost Port: 7779 Capacity: 100 Routing: Enabled Failover Threshold: 5 Ping URL: / Ping Frequency: 10 Leave all other parameters as default and click OK.
4.	Click Restart Web Cache to restart Web Cache. Click Yes when prompted for confirmation.
5.	Click Sites. Under Named Sites Definitions, select localhost:7777 and click Edit.
6.	A new origin server should appear under the Available Origin Servers column. Select that origin server and move it to the Selected Origin Servers column. Click OK.
7.	Click Restart Web Cache to restart Web Cache. Click Yes when prompted for confirmation.

Defining a Ping URL for Application Detection and Origin Server Capacity

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OracleAS Web Cache detects the availability of the application by sending a user-defined URL to the origin server periodically. If there is no response, then OracleAS Web Cache assumes that the origin server is unavailable. The fact that the origin server fails to respond can also mean that there is a problem with the application. Therefore, the Ping URL serves for application detection as well.

1.	Click Web Cache in the breadcrumbs to return to the OracleAS Web Cache Home page. Click Administration tab and then click Origin Servers under Properties.
2.	Select one of the origin servers and click Edit.
3.	In the Ping URL field, enter /hrapp. /hrapp is a redirect header with zero byte size from the origin server. Because /hrapp does not require much resources from the origin server, it is an ideal candidate for ping URL.
4.	For the purpose of this OBE, the load at origin server is expected to be low. To lower the number of maximum concurrent connections that OracleAS Web Cache can establish with a particular origin server, change the Capacity to 50. Click OK.
5.	Repeat steps 2 through 4 for the other origin server (localhost:7779). Click Restart Web Cache to restart Web Cache. Click Yes when prompted for confirmation.

Configuring OracleAS Web Cache to Use Cookie-Based Sessions

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In Oracle Application Server 10g Release 2, OracleAS Web Cache offers three options for session binding mechanism: Cookie-Based, OC4J-Based, and Internal Tracking.
The cookie-based session binding mechanism is applicable for all types of Web applications. OracleAS Web Cache generates its own cookie to perform session stickiness to the origin servers, so the session stickiness still persists even if the application changes its session ID.
The OC4J-based mechanism is used if the application you are trying to cache is based on OC4J. OracleAS Web Cache forwards routing information with each request to OC4J through Oracle HTTP Server.
The Internal Tracking mechanism is used if the application does not support cookies or is not OC4J-based. In this case, OracleAS Web Cache maintains an in-memory routing table.
In this section, you will configure Web Cache to use cookie-based sessions.

1.	Navigate to the OracleAS Web Cache Home page. Click the Adminsitration tab and then click Sites under Properties.
2.	Under Named Site Definitions, select the site, localhost:7777 and click Edit.
3.	Click the Advanced tab to go to advanced section.
4.	Under Session Binding, make sure that Enable session binding for this site is selected. Select Any Set Cookies from the Session drop-down list and select Cookie-Based from the Session Binding Mechanism drop-down list. Click OK.
5.	Click Restart Web Cache to restart Web Cache. Click Yes when prompted for confirmation.

Confirming the Configuration for Session Binding

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1.	Open a browser window and browse the application at http://localhost:7777/hrapp. OracleAS Web Cache serves the cached pages and forwards any requests to the origin servers.
2.	Switch back to the Application Server Control Console browser window. Navigate to OracleAS Web Cache Home page. Go to Performance tab and click Origin Servers.
3.	Click the link for the first origin server. Check Total Requests under Request Throughput.
4.	Click the Back button on your browser and click the link for the second origin server. Check Total Requests under Request Throughput. Note that most of the requests are going to only one of the origin servers. Session binding is working correctly.

Configuring OracleAS Web Cache to use JSESSIONID

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For J2EE applications, OracleAS Web Cache can use JSESSIONID for session binding. You will have to change the setting for session binding.

1.	Navigate back to the OracleAS Web Cache Home page and click the Administration tab. Click Sites under Properties. Select the site localhost:7777 and click Edit.
2.	Click the Advanced tab to go to the advanced section. Under Session Binding, make sure that Enable session binding for this site is selected. Select JSESSIONID from the Session drop-down menu and select OC4J-Based from the Session Binding Mechanism drop-down menu. Click OK.
3.	Click Restart Web Cache to restart Web Cache. Click Yes when prompted for confirmation.
4.	Switch to the browser window that you used to browse the application. Browse the pages again at http://localhost:7777/hrapp.
5.	Switch back to the Application Server Control Console browser window and verify whether most of the requests are going to one of the origin servers. To verify, follow steps 2 through 4 of the topic titled "Confirming the Configuration for Session Binding."