Configure custom cache tags - Edge Security Acceleration

When Edge Security Acceleration (ESA) points of presence (POPs) receive a resource from an origin server, they check for a cache tag, which is marked in the Cache-Tag header by default. By configuring custom cache tags, you can change the cache tag name and ignore the case of tag values.

Introduction

How filter interaction works

When you submit a Purge cache by tag task, ESA refreshes cached content based on the cache tags and the case-sensitivity setting. The refresh process is as follows:

Note

The origin server response must include a cache tag. Otherwise, this feature does not work.

Check whether the origin server response includes a cache tag
- No cache tag: You cannot use the purge-by-tag feature.
- Cache tag present: Proceed to check the site's cache tag configuration.
Check the site's cache tag configuration
- No custom name configured
  - The origin server response includes the default cache tag (Cache-Tag):
    - Case-insensitive mode is disabled: Resources cached at ESA nodes are tagged with Cache-Tag: Cat,Dog. You can use the tag values Cat or Dog to refresh the cache.
    - If case-insensitivity is enabled, a resource cached on ESA nodes is assigned the tag Cache-Tag: cat,dog, and you can use the tag value cat or dog to refresh the cache.
  - If a response from the origin server contains a custom cache tag, such as Edge-Cache-Tag, you cannot use the cache refresh by tag feature because the tag is not added when the resource is cached on an ESA node.
- Custom name configured (for example, Edge-Cache-Tag)
  - Resources in the origin server's response carry the default cache tag (Cache-Tag). When these resources are cached on ESA nodes, this tag is not added. Because the tag is not added, you cannot use the refresh cache by tag feature.
  - The origin server response includes the custom-named cache tag (for example, Edge-Cache-Tag):
    - Case-insensitive matching is disabled: When resources are cached on ESA nodes, the system adds the tag Edge-Cache-Tag: Cat,Dog. You can use the tag values Cat or Dog to refresh the cache.
    - Case-insensitive mode is enabled: When resources are cached on ESA nodes, the tag Edge-Cache-Tag: cat,dog is added, allowing you to use the tag values cat or dog to refresh the cache.

Key configuration settings

Cache tags have the following parameters:

Cache tag name

The default name is Cache-Tag.
A custom cache tag name must be 1 to 64 characters long.
A custom cache tag name can contain uppercase letters (A–Z), lowercase letters (a–z), digits (0–9), and hyphens (-).

Ignore Case

This feature is disabled by default, so ESA treats CAT and cat as different values during a cache refresh operation.
After you enable this feature, ESA converts cache tag values in origin responses to lowercase and treats CAT and cat as identical values during a Refresh Cache operation.

Configure cache tags

Procedure

In the ESA console, choose Websites. In the Website column, click the target site.
In the navigation pane on the left, choose Caching > Settings.
In the Cache Tag section, click the Configuration button on the right.
Configure the Tag Name and the tag value case-insensitive parameter:
- Tag Name: Select Use Custom Cache Tag Name and enter the custom tag name ESA-Cache-Tag.
- Ignore Case: Enable or disable this setting as needed.

Cache purge examples

When you update images or page files on an e-commerce website, you need to delete the files and purge the corresponding ESA cache. An e-commerce website may have many cropped versions of an image in different sizes. When you delete an image, enumerating all of its cropped versions is inconvenient. Therefore, you can batch-delete the image files and the corresponding ESA cache by the image name. In addition, when you prepare for a promotional event, you need to continuously iterate on the event page during development. When you publish a new version of the page, you can delete all related files and the corresponding ESA cache by a specified version. Purging cache by tag significantly improves cache management efficiency:

Purge by image name

Scenario

The following three images are cropped versions of the original dog.jpg. The origin adds the tag ESA-Cache-Tag:dog.jpg to responses for all three:

dog_100_200.jpg
dog_200_200.jpg
dog_300_200.jpg

The following three images are cropped versions of the original cat.jpg. The origin adds the tag ESA-Cache-Tag:cat.jpg to responses for all three:

cat_100_200.jpg
cat_200_200.jpg
cat_300_200.jpg

Delete the original images and purge all cached variants at the same time.

Configuration example

In the ESA console, choose Site Management. In the Website column, click your target site.
In the navigation pane on the left, choose Caching > Settings.
In the Cache Tag section, click the Configuration button on the right.
Configure the Tag Name and the tag value case-insensitive parameter:
- Tag Name: Select Use Custom Cache Tag Name and enter the custom tag name ESA-Cache-Tag.
- Ignore Case: Enable or disable this setting as needed.
In the navigation pane on the left, choose Caching > Purge Cache.
On the Purge Cache tab, configure the purge rule and click Submit:
- Type: Select By Tag.
- Purge Method: Select Delete.
- Purge Content: Enter the tag values to purge: cat.jpg,dog.jpg.

Purge by version number

Scenario

The following six images were generated for version v0820. The origin adds the tag ESA-Cache-Tag:v0820 to responses for all six:

dog_100_200_v0820.jpg
dog_200_200_v0820.jpg
dog_300_200_v0820.jpg
cat_100_200_v0820.jpg
cat_200_200_v0820.jpg
cat_300_200_v0820.jpg

Configuration example

In the ESA console, choose Site Management. In the Website column, click your target site.
In the navigation pane on the left, choose Caching > Settings.
In the Cache Tag section, click the Configuration button on the right.
Configure the Tag Name and the tag value case-insensitive parameter:
- Tag Name: Select Use Custom Cache Tag Name and enter the custom tag name ESA-Cache-Tag.
- Ignore Case: Enable or disable this setting as needed.
In the navigation pane on the left, choose Caching > Purge Cache.
On the Purge Cache tab, configure the purge rule and click Submit:
- Type: Select By Tag.
- Purge Method: Select Delete.
- Purge Content: Enter the tag value to purge: v0820.