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Manual Chapter: Configuring Proxying Rules
Manual Chapter
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Proxying rules identify the elements in a HTTP requests URL that indicate whether the WebAccelerator system should send a request to your origin web servers, instead of attempting to service it from its cache.
Always proxy
This option overrides all other proxying rules and options.
Proxy rules
This option is where you can define specific parameters for proxying rules. In general, proxy rules options are only relevant to requests that match their node, rather than to matched responses.
Proxy overrides rules
This option is where you define parameters and associated conditions under which the WebAccelerator system should ignore proxying rules options.
You organize proxying rules in the Policy Tree, with any associated proxying rules assigned to the leaf node. The WebAccelerator system applies proxying rules against only leaf nodes in the Policy Tree. The proxying rules defined for a leaf node are a combination of the proxying rules and data parameter types defined locally at the node, and any proxying rules and data parameter types that are inherited from the nodes ancestors. For information about inheritance support in the Policy Tree, see Understanding rule inheritance within the Policy Tree.
The always proxy option prompts the WebAccelerator system to always send requests that match the specified node, to the origin server for content. When the WebAccelerator system matches a response to a node that has the always proxy option enabled, it caches the response in accordance to the nodes acceleration rules; however, when the WebAccelerator system receives a subsequent request for the same content, it checks its cache and notes that the always proxy option is enabled. This prompts the WebAccelerator system to send the request to the origin web server.
1.
In the navigation pane, expand WebAccelerator, and then click Policies.
The Policies screen opens, displaying a table of user-defined and pre-defined acceleration policies.
2.
On the User-defined Acceleration Policies table, click the name of the acceleration policy that you want to edit.
The Policy Editor screen opens.
4.
From the Matching Rules list on the Policy Editor menu bar, select Acceleration Rules.
The acceleration rules display on the Policy Editor menu bar.
5.
On the Policy Editor menu bar, click Proxying.
The Proxying rules screen opens.
6.
7.
Click the Save button.
For the new policy to be in effect for your site, you must publish it. See Publishing acceleration policies, for more information. Once you publish the acceleration policy, the WebAccelerator system sends all matched requests to the origin server for content.
In general, the WebAccelerator system attempts to service all HTTP requests from its cache. If you have certain types of requests that you do not want the WebAccelerator system to service content from its cache, you can configuring proxy rules options to specify the conditions that prompt the WebAccelerator system to send specific requests to the origin server.
Proxy rules options are based on specific values for HTTP request data type parameters. When defining options for proxy rules, you identify the parameter that the WebAccelerator system should look for in a request, and specify the value it must have in order for the WebAccelerator system to send the request to the origin server. When the WebAccelerator system matches a request to the proxy rules option that you defined, it sends the request to the origin web servers.
For example, you can set session tracking information in a cookie or segment parameter. When you do this, the WebAccelerator system sends any request that it receives without the tracking information, to the origin server so that it can set the tracking information.
For this example, you create a proxying rule based on a cookie named version, and define a proxy rules option that specifies that the WebAccelerator system must send the request to the origin server if one of the following is true:
The version cookie does not appear on the request.
The version cookie appears on the request, but has no value set for it (version is empty).
1.
On the Main tab of the navigation pane, expand WebAccelerator and click Applications.
The Applications screen opens in a new window.
2.
On the Main tab of the navigation pane in the new window, click Policies.
The Policies screen opens, displaying a table of user-defined and pre-defined acceleration policies.
3.
On the User-defined Acceleration Policies table, click the name of the acceleration policy that you want to edit.
The Policy Editor screen opens.
5.
From the Matching Rules list on the Policy Editor menu bar, select Acceleration Rules.
The acceleration rules display on the Policy Editor menu bar.
6.
On the Policy Editor menu bar, click Proxying.
The Proxying Rules screen opens.
7.
In the Proxy Rules area, select Cookie from the Add Parameter list, and click the Add button.
The Parameter Identity screen opens.
8.
In the Name box, type version.
9.
From the Value(s) list, select Value does not match, and check the associated check box.
11.
Check the box for Value is an empty string.
12.
Click the Save button.
The Proxying Rules screen refreshes and the new rule appears in the Proxy Rules summary table.
Like proxy rules options, proxy override rules are based on specific values for HTTP request data type parameters. When configuring options for proxy override rules, you identify the parameter that the WebAccelerator system should look for in an HTTP request, and specify the value it must have in order for the WebAccelerator system to override the matched proxying rules. When the WebAccelerator system matches a request to a node for which the proxy override rules option is configured, it services the request from its cache, even if the matched proxying rule dictates that the WebAccelerator should send the request to the origin server.
One common application for the proxy override rules option is for sites that receive a high volume of traffic related to web crawlers and robots clients, because proxy override rules ensure that your origin server does not have to manage the that traffic. It is especially important to consider a proxy override rule for this application if your proxy rules are based on a set cookie, because web crawlers and robots rarely present cookies in their requests.
For this example, you use a cookie to contain session tracking information. If the session tracking cookie is not presented on an HTTP request, you want the WebAccelerator system to send the request to the origin web servers so that the origin web servers can set cookie. As a result, you created a proxying rule based on the cookie. This rule indicates that the WebAccelerator system must send any request that does not include the cookie, or for which the cookie is empty, to the origin server. However, since your site experiences a lot of traffic from a web crawler, this proxy rule forces your origin server to handle every request from the web crawler, because the web crawler never presents a cookie. This places an unnecessary load on your origin web servers.
You examine the origin servers log files and look to see if the web crawler presents a specific a string. For example, the web crawler might present a string for the HTTP USER_AGENT request header that looks very much like the value presented for MSIE 5.0 browsers. However, the web crawler adds badcrawler to the HTTP USER_AGENT string.
For this example, you add a proxy override rule option to the nodes proxying rules, and base this rule on the user agent parameter to match the regular expression .*badcrawler.*
1.
On the Main tab of the navigation pane, expand WebAccelerator and click Applications.
The Applications screen opens in a new window.
2.
On the Main tab of the navigation pane in the new window, click Policies.
The Policies screen opens, displaying a table of user-defined and pre-defined acceleration policies.
3.
On the User-defined Acceleration Policies table, click the name of the acceleration policy that you want to edit.
The Policy Editor screen opens.
5.
From the Matching Rules list on the Policy Editor menu bar, select Acceleration Rules.
The acceleration rules display on the Policy Editor menu bar.
6.
On the Policy Editor menu bar, click Proxying.
The Proxying Rules screen opens.
7.
In the Proxy Override Rules area, select User Agent from the Add Parameter list, and click the Add button.
The Parameter Identity screen opens.
8.
In the Value(s) area, select Values matches from the list and check the Values matches check box
9.
In the value matches box, type the regular expression that matches the user agent value. For this example, type .*badcrawler.*
10.
Click the Save button.
The Proxying Rules screen refreshes, and the new rule appears in the Proxy Override Rules summary table.
Once published, the WebAccelerator system attempts to service, from its cache, all request that it receives with a HTTP USER_AGENT value that matches .*badcrawler.*, regardless of any proxy rules that the request matches.
This section of the chapter provides information about how to configure an example proxying rule. For this example site, you have three top-level nodes in the Policy Tree as follows:
Home
This branch node specifies the rules related to the home page.
Applications
This branch node specifies the rules related to the applications for the site, with the following leaf nodes:
Default
This leaf node specifies the rules related to non-search related applications.
Search
This leaf node specifies the rules related to your sites search application.
Images
This branch node specifies the rules related to graphics images.
Note: See To create the Home, Application, and Images nodes for the example Policy Tree, for specific instructions about how to create the Policy Tree.
For this example, you use a segment parameter to contain identifying information for your shopping cart application. Requests for your applications are all in the following form:
If the session tracking string does not appear in the segment parameter at the end of the URI, you want the WebAccelerator system to send the request to the origin web servers for special handling.
For this example, you create a proxying rule for your Applications node with just one parameter based on the path segment data type. This rule should identify the subject as being:
Note: See Path segment, for information about path segments and their ordinals.
1.
On the Main tab of the navigation pane, expand WebAccelerator and click Applications.
The Applications screen opens in a new window.
2.
On the Main tab of the navigation pane in the new window, click Policies.
The Policies screen opens, displaying a table of user-defined and pre-defined acceleration policies.
3.
On the User-defined Acceleration Policies table, click the name of the acceleration policy that you want to edit.
The Policy Editor screen opens.
4.
5.
From the Matching Rules list on the Policy Editor menu bar, select Acceleration Rules.
The acceleration rules display on the Policy Editor menu bar.
6.
On the Policy Editor menu bar, click Proxying.
The Proxying Rules screen opens.
7.
In the Proxy Rules area, select Path Segment from the Add Parameter list, and click the Add button.
The Parameter Identify screen opens.
8.
In the Alias box, type a meaningful name for the parameter.
9.
In the Segment Ordinal box, type 1 and from the list, select Numbering Right-to-Left in the Full Path.
10.
In the Parameter Ordinal box, type 1.
12.
Click the Save button.
The Proxying Rules screen refreshes and the new rule appears in the Proxy Rules summary table.

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