Content Group Test

The integrated cache provides in-memory storage on the Citrix ADC appliance and serves Web content to users without requiring a round trip to an origin server.

When you first enable the integrated cache, cacheable objects are stored in a content group named Default. A content group is a container for cached objects that can be served in a response. You can create content groups that have unique properties. For example, you can define separate content groups for image data, bug reports, and stock quotes, and you can configure the stock quote content group to be refreshed more often than the other groups. You can configure expiration of an entire content group or selected entries in a content group.

  • A user enters search criteria for an item, such as a bug report, and clicks the Find button in an HTML form.

  • The browser issues one or more HTTP GET requests. These requests contain parameters (for example, the bug owner, bug ID, and so on).

  • When the Citrix ADC appliance receives the requests, it searches for a matching policy, and if it finds a caching policy that matches these requests, it directs the requests to a content group.

  • The content group looks for appropriate objects in the content group, based on criteria that you configure in a selector.

  • If it finds matching objects, the Citrix ADC appliance can serve them to the user’s browser, where they are assembled into a complete response (for example, a bug report).

Higher the number of requests serviced by content groups, happier will be users. On the other hand, if most requests are serviced only by the origin server and not by the content groups, users will experience significant slowness in their interactions with applications. To ensure optimum cache usage, administrators need to ensure that the cache is sized right and cached objects are flushed out periodically from the content groups to make room for new ones. With the help of the Content Group test, administrators can monitor how well each content group (default and user-configured) services requests to it. In the process, they can figure out if any content group does not contain enough response objects to service requests effectively. The test also helps administrators zoom into the reasons for the poor usage of a content group - is it because the content group is not sized with enough memory to hold many objects in cache? or is it because the content group is not flushing enough objects from memory?

Agent deploying the test : A remote agent

Outputs of the test : One set of results for each content group configured on the Citrix ADC VPX/MPX appliance being monitored.

Configurable parameters for the test
Parameter Description

Test Period

How often should the test be executed.

Host

The IP address of the host for which the test is being configured.

NetScaler Username, NetScaler Password, and Confirm Password

To monitor a NetScaler device, the eG agent should be configured with the credentials of a user with read-only privileges to the target NetScaler device. Specify the credentials of such a user in the NetScaler Username and NetScaler Password text boxes. Then, confirm the password by retyping it in the Confirm Password text box.

SSL

The eG agent collects performance metrics by invoking NITRO (NetScaler Interface Through Restful interfaces and Objects) APIs on the target NetScaler device. Typically, the NITRO APIs can be invoked through the HTTP or the HTTPS mode. By default, the eG agent invokes the NITRO APIs using the HTTPS mode. This is why, the SSL flag is set to Yes by default. If the target NetScaler device is not SSL-enabled, then the NITRO APIs can be accessed through the HTTP mode only. In this case, set the SSL flag to No.

Measurements made by the test
Measurement Description Measurement Unit Interpretation

Non 304 hits for content group

Indicates the total number of full (non-304) responses served from this content group during the last measurement period.

Number

A 304 status code indicates that a response has not been modified since the last time it was served.

 

304 hits for content group

Indicates the count of object not modified responses served from this content group during the last measurement period.

Number

Number of objects in content group

Indicates the number of objects in this content group during the last measurement period.

Number

The value of this measure includes responses that have not yet been fully downloaded and responses that have been expired but not yet flushed.

A high value is desired for this measure. A low value indicates that not enough objects have been cached to effectively service requests.

Number of marker objects in content group

Indicates the number of marker objects in this content group during the last measurement period.

Number

A marker object is cacheable, but it does not yet meet all the criteria for being cached. For example, the object may exceed the maximum response size for the content group. A marker cell is created for objects of this type. The next time a user sends a request for this object, a cache miss is served.

Number of times content group is flushed

Indicates the number of times this content group was flushed during the last measurement period.

Number

If objects are not flushed / do not expire fast enough, then the content group will soon run out of space for new objects. This is why, the value of this measure should be high.

Current memory usage

Indicates the amount of memory this content group is utilizing currently.

MB

 

Maximum memory usage limit

Indicates the maximum amount of memory that this content group can use.

MB

If the value of the Current memory usage measure is equal to or grows very close to the value of the Maximum memory usage limit measure, it means that the content group is rapidly running out of memory to store objects. Without sufficient memory, the content group will not be able to respond to requests it receives, forcing such requests to the routed to the origin server. To avoid this, you may want to increase the memory usage limit of the content group.