Specifications

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Cisco Internet Streamer CDS 2.0-2.3 Software Configuration Guide
OL-13493-04
Appendix B Creating Manifest Files
Working with Manifest Files
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Refreshing and Removing Content
Use the ttl (time-to-live) and expires attributes of the Manifest file to monitor and control the freshness
of content objects, and remove them.
The ttl attribute is expressed in minutes and specifies how frequently the software checks the freshness
of the content at the origin server. If the ttl attribute is specified inside an <item> tag, it applies to that
item; if it is specified inside a <crawler> tag, the attribute applies to the crawl job.
For example, if you give the ttl attribute a value of 10, the software checks the item or crawl job every
10 minutes. If the item has been updated, then the updated file is reacquired.
Caution Sometimes a crawl job can be very large, crawling over thousands of files. The recrawl speed is 5000
files per hour for small files. It is time-consuming to recheck so many files. We strongly recommend that
you specify a large ttl value for such crawl jobs (for example, 1440 minutes [daily]). Otherwise, the
software continues to crawl the site over and over again, blocking other acquisition tasks.
If you omit the ttl attribute in the Manifest file, the time-to-live is assumed to be zero and the software
does not recheck that item after it is acquired. A value of 0 (zero) for ttl means that the content is fetched
only once and is never checked again unless you click the Fetch Manifest Now button in the CDSM or
use the acquirer start-delivery-service EXEC command in the Content Acquirer CLI.
The Fetch Manifest Now button is located in the Delivery Service Content page in the CDSM. When
you click this button, the software checks to see if the Manifest file has been updated, and the updated
Manifest file is downloaded and reparsed. Also, regardless of whether the Manifest file has been
updated, all content in the delivery service is rechecked and the updated content is downloaded.
If you assign a negative value to the ttl attribute, such as –1, that item is never to be rechecked. A negative
ttl attribute value prevents the software from checking item freshness, even if you click the Fetch
Manifest Now button or use the acquirer start-delivery-service command.
Note Configuring the update interval in the CDSM GUI (Services > Service Definition > Delivery Services
> Delivery Service Content) sets the interval for checking updates to the Manifest file itself. This
setting only pertains to checking the Manifest file; it does not pertain to checking the content.
The failRetryInterval attribute is sometimes confused with the ttl attribute. The fail and retry feature acts
upon failed content or failed updates. If the acquisition of a single item or of some crawled content fails,
the software automatically tries to refetch these failed objects after a default interval of 5 minutes. The
fail and retry interval can also be specified by using the failRetryInterval attribute in the Manifest file.
The difference between the failRetryInterval attribute and the ttl attribute is that the ttl attribute is for
successfully acquired content and the failRetryInterval attribute is for content acquisition failures. The
ttl attribute must be specified for the software to recheck the content freshness, whereas the
failRetryInterval attribute does not need to be specified unless you want to change the retry interval.
The expires attribute specifies the time the content is to be removed from the CDS network. If you do
not specify a time when you set the expires attribute, content is stored in the CDS network until it is
explicitly removed when you modify the Manifest file. The expires attribute uses the format
yyyy-mm-dd hh:mm:ss (year-month-day hour:minute:second). In the following example, the content
expires on June 12, 2003 at 2:00 p.m.
expires="2003-06-12 14:00:00 PST"