Purging Cached Assets (Overview)

Cached content can be purged from:

• Our entire network (i.e., all POPs).
• Specific regions (i.e., subset of POPs).

The purpose of purging content is to force the CDN to request a new version of the content in question from an origin server. This ensures that the latest version of the content in question is delivered to your clients.

Purging does not delete content from the origin server. A file management tool (e.g., SFTP or rsync) may be used to delete content from an origin server.

Purging Content

Cached content may be purged from our network (i.e., edge servers) through the Purge/Load page.

Key information:

• Specify a full URL when purging content:

  Example:

  Purging the following URL purges both the HTTP and HTTPS version of this URL:

  http://cdn.example.com/resources/logo.jpg

• A request to purge content is specific to the following criteria:

  • Directory: A URL must be specified when purging content. This URL identifies the directory where the content to be purged is stored.

    Purging is not URL-specific. In other words, it affects all CDN and edge CNAME URLs that point to the same assetA file is the most commonly known example of an asset. Refers to any collection of data that is typically stored as a single unit on a storage unit (e.g., disk drive). An example of an asset that is not physically stored on a disk drive occurs when dynamically generated content is not cached..

    View example.

    This example assumes the following setup:

    Edge CNAME	Points To
    cdn.example.com	Customer Origin: myorigin Relative Path: /
    sales.example.com	Customer Origin: myorigin Relative Path: /sales

    Purging any of the following URLs will purge brochure.pdf:

    http://cdn.example.com/sales/brochure.pdf

    http://sales.example.com/brochure.pdf

    http://can.0001Represents your customer account number..transactcdn.com/800001Represents your customer account number./myorigin/sales/brochure.pdf

  • Region: Purging by region is an advanced option that should only be used to address specialized cache management needs. It allows the selection of one or more regions when purging content. The asset in question will only be purged from the selected region(s).

    Learn more.

    By default, purging is applied to the entire network (i.e., all regions).

• An assetA file is the most commonly known example of an asset. Refers to any collection of data that is typically stored as a single unit on a storage unit (e.g., disk drive). An example of an asset that is not physically stored on a disk drive occurs when dynamically generated content is not cached. only needs to be purged a single time per protocolHTTP or HTTPS, path, and region.

• Use purge syntax to determine the scope of the purge request.

  • Individual assets
  • Multiple assets
  • Directory
  • Directory (Recursive)
• Each purge request needs to be applied to edge servers throughout our network. As a result, each request will be placed in a queue. The Purge/Load page tracks when a request was submitted and completed.
• There is a default limit of 50 concurrent purge requests.
• A URL containing a dollar sign symbol (i.e., $) cannot be added to the purge queue. The dollar sign symbol must be encoded as %24 before such a URL can be added to the queue.
• By default, content requested through the CAN platform is not cached. This means that a cached version of an asset will typically not reside on a CAN Gateway or edge server. As a result, it is typically unnecessary to purge content from the CAN platform.
• Purge is only supported for GET requests. Although you may use the Cacheable HTTP Methods feature to enable caching for POST and PUT requests, cached POST and PUT requests cannot be purged.

• Automate purging content via a script that leverages our REST API.

  View our REST API Help Center

• View best practices for updating cached content.

To purge content

1. Navigate to the Purge/Load page.
2. From the URL option, which can be found under the Purge From Edge section, select the base URL where the desired content can be found.
3. Directly below the URL option, type the path to the directory containing the asset(s) to be purged. Since a forward slash (/) has been added for your convenience, make sure that this relative path starts after the forward slash.

4. Perform one of the following:
   

   Purge	Procedure	Sample Syntax
   Asset	Append the name of the asset that you would like to purge to the relative path specified in step 3.	presentations/Gala_01.flv
   Set of Assets	Determine the naming convention and/or file type that will be used to identify the assets that will be purged. Append that pattern to the relative path specified in step 3.	presentations/gala*.fl*
   Directory	Append an asterisk (i.e., /*.*), a period, and another asterisk to the relative path specified in step 3.	presentations/*.*
   Directory (Recursive)	Append an asterisk (i.e., /*) to the relative path specified in step 3.	presentations/*

5. From the Regions option, perform one of the following steps:

   • Purge All Regions (Recommended): Select All.

   • Purge Specific Regions:

     1. Select Custom.
     2. Mark the regions that should be purged.
     3. Clear all other regions.
6. Click Purge Content.

To perform a bulk purge

1. Navigate to the Purge/Load page.
2. Click the "Bulk Purge" link, which can be found under the Purge From Edge section, to display the URLs option.
3. In the URLs option, type the CDN or edge CNAME URL that points to the asset(s) that will be purged.
4. Add another purge request by pressing ENTER and then specifying the desired CDN or edge CNAME URL. Repeat this step as needed.
5. From the Regions option, perform one of the following steps:
   • Purge All Regions (Recommended): Select All.

   • Purge Specific Regions:

     1. Select Custom.
     2. Mark the regions that should be purged.
     3. Clear all other regions.
6. Click Purge Content.

Each CDN or edge CNAME URL specified in the URLs option must be placed on a separate line. This can be accomplished by using a carriage return to delimit each CDN or edge CNAME URL. Using any other type of character (e.g., a comma) as a delimiter may prevent the asset from being purged.

Purge Syntax: Individual Assets

An individual assetA file is the most commonly known example of an asset. Refers to any collection of data that is typically stored as a single unit on a storage unit (e.g., disk drive). An example of an asset that is not physically stored on a disk drive occurs when dynamically generated content is not cached. may be purged by specifying a CDN or an edge CNAME URL that points to it. This type of purge request will also purge all query string variations of the specified asset at that location. Sample URLs are provided below.

URL Type	Sample URL
CDN URL	http://can.0001.transactcdn.com/000001/resources/homepage.html
Edge CNAME URL	http://cdn.sampleurl.net/resources/homepage.html

Purge Syntax: File Name Patterns

One or more asterisks may be used to restrict purging to content whose filename matches the specified pattern.

Key information:

• An asterisk may only be used when defining a filename pattern. It may not be used to define a directory name pattern.
• Each asterisk represents one or more characters.
• Specify /* will always result in a recursive purge. Restrict the purge to the current directory by defining a more restrictive patternExamples: /*a, /*.pdf, or /*.*.
• A particular file type may be purged by appending an asterisk, a period, and the desired file extension to the purge URL (e.g., http://cdn.sampleurl.net/*.html).

Learn how to purge directories.

Sample purges are provided below.

Scope	Syntax/Example
All files that reside in the specified directory.	Syntax: Append the following value to the URL that points to the desired directory: /*.* Example: http://cdn.sampleurl.net/sales/*.*
All files that meet both of the following conditions: Match the specified file extension. Reside within the specified directory.	Syntax: Append the following value to the URL that points to the desired directory: /*.extReplace this term with the desired file extension. Example: http://cdn.sampleurl.net/sales/*.htm
All files that meet both of the following conditions: Match the specified filename pattern. Reside within the specified directory.	Syntax: URL to the desired directory plus a filename pattern that identifies the desired files. Example: http://cdn.sampleurl.net/sales/a*.ht*

Purge Syntax: Query String Variations

By default, our CDN service does not take into account query strings when caching content. However, query string caching may be enabled through either of the following:

• Unique-caching
• Cache-Key Query String feature (Rules Engine)

Several examples on how query string variations of an asset may be purged are provided below.

Scope	Syntax/Example
Purge: Original asset All of its query string variations.	Syntax: Full URL (including filename) Example: http://cdn.sampleurl.net/path/sampleasset.htm
Purge original asset only. Query string variations of the specified asset will not be purged.	Syntax: Full URL plus a question mark Example: http://cdn.sampleurl.net/path/sampleasset.htm?
Purge a specific query string variation of an asset. The original asset and all other query string variations of that asset will not be purged.	Syntax: Full URL plus query string Example: http://cdn.sampleurl.net/path/sampleasset.htm?user=Joe

Purge Syntax: Directory's Default Cached Asset

The default asset cached for a particular directory (i.e., directory index) may be purged through the use of the syntax described below.

Scope	Syntax/Example
Purge: Default cached asset for a directory All of its query string variations.	Syntax: Append / to the URL that points to the desired directory. Example: http://cdn.sampleurl.net/path/
Purge the default cached asset for a directory. Query string variations of the specified asset will not be purged.	Syntax: Append the following value to the URL that points to the desired directory: /? Example: http://cdn.sampleurl.net/path/?
Purge a specific query string variation of the default cached asset for a directory. The default cached asset for that directory and all other query string variations of that asset will not be purged.	Syntax: Append a query string to the URL that points to the desired directory. Example: http://cdn.sampleurl.net/path/?user=Joe

When purging the default asset that was cached for a particular directory, keep in mind that there are certain conditions that may cause an asset other than the default asset for that directory to be purged. For example, specifying /path/ may not be the same as specifying /path/index.html even if index.html is the default asset for that directory. For example, this occurs when the specified URL is redirected or if URL rewriting is used.

Purge Syntax: Directory

The contents of a directory can be purged through the use of wildcards (i.e., *.*). This syntax will purge all of the assetA file is the most commonly known example of an asset. Refers to any collection of data that is typically stored as a single unit on a storage unit (e.g., disk drive). An example of an asset that is not physically stored on a disk drive occurs when dynamically generated content is not cached.s contained in the specified directory. It will not purge assets stored in subdirectories of the purge path.

Sample purge request:

Purge Syntax: Directory (Recursive)

All of the assets contained in a specified directory and its subfolders can be purged by appending /* to the purge directory.

Sample purge request:

An asterisk cannot be used to specify a directory pattern. It can only be used as specified above or when defining a pattern that will be used to define the set of assets that will be purged (e.g., /*.css).

Regions

Content may be purged from our entire network or solely from specific regions. Purging by region provides additional flexibility for determining when updated content may be served to clients.

Regional purging is designed to meet specialized cache management needs. When in doubt, purge content from all regions.

By default, purges are applied across the entire CDN network.

The available set of regions are described below.

Region	Description
North America	This region encompasses all POPs in North America.
US: Eastern Time Zone	This region encompasses all POPs in the Eastern Time zone of the United States. View map.
US: Central Time Zone	This region encompasses all POPs in the Central Time zone of the United States. View map.
US: Pacific Time Zone	This region encompasses all POPs in the Pacific Time zone of the United States. View map.
Europe	This region encompasses all POPs in Europe.
Asia	This region encompasses all POPs in Asia and Australia.

View a list of POPs and their corresponding regions.

Key information:

• The Regions option determines whether cached content will be purged from:

  • Entire Network: Select All.

  • Specific Regions:

    1. Select Custom.
    2. Mark each region from which content should be purged.
    3. Clear each region from which content should not be purged.
    4. Click Purge Content to submit the purge request.

• Selecting the North America region will purge content from all POPs in North America. This takes place regardless of whether other US regions have been cleared.

  Purge content from specific regions in the US by clearing the North America option and then marking the desired regions.

More Information

• FAQs - Cache Management: Updating Cached Content
• TTL and Cache Revalidation (Leveraging a Cache Policy to Update Stale Content)

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