Purge cache by tag

Benefits

Tag-based cache purge simplifies bulk purging of related cached resources:

• Efficient batch operations: Assign the same tag to a group of related resources—such as a news page with its images, JS, and CSS files—and purge them all with one action.

• Simplified O&M: Manage logical groups of resources by tag instead of tracking individual URLs.

• Scenario isolation: Assign different tags to different scenarios within the same application. Purging by tag affects only the targeted scenario—such as a promotion page—without impacting others.

• Consistent updates: Ensure tightly coupled resources—such as frontend pages and their static assets—update together, avoiding mismatches like new pages with old styles.

Use cases

Common use cases:

• Updating e-commerce promotion pages and associated assets

• Taking down special-topic content on news or media sites

• Switching content for multilingual or multi-version websites

• Purging sub-application resources in a micro-frontend architecture

How it works

ESA uses HTTP response headers as cache tags. A cache tag consists of a header name and a header value separated by a colon :, for example, Cache-Tag:tag1,tag2,tag3. When you submit a tag-based cache purge task:

1. ESA checks whether the cached file on the POP has a cache tag (default: Cache-Tag). If no cache tag exists, ESA skips the file. Otherwise, ESA matches the tag value.

2. ESA checks whether the tag value matches the Purge Content you submitted. If the value matches, ESA purges the cache (default behavior: Mark as Expired). If not, ESA skips the file.

Prerequisites

ESA tag-based cache purge works by checking whether cached content on ESA POPs contains specific cache tags set by the origin. Before using this feature, configure your origin server to add the corresponding cache tag response headers:

# /etc/nginx/nginx.conf

server {
    listen 80;
    server_name your-origin-domain.com;
    # Add tag to all resources under /images/
    location /images/ {
        add_header Cache-Tag "images";
        # ... other configuration
    }
    # ... other location blocks
}

Procedure

1. In the ESA console, choose Site Management. In the Website column, click your target site.

2. In the navigation pane on the left, choose Caching > Purge Cache.

3. On the Purge Cache tab, configure the purge rule and click Submit:

   • Type: Select By Tag.

   • Purge Method: You can choose between two methods: Mark as Expired and Delete.

     Refresh method	Description
     Mark as Expired	Nodes are processed according to the following flow: The ESA POP sends an origin request with the If-Modified-Since and If-None-Match request headers. The origin server compares the file modification time. If the file is not modified, the origin server returns a 304 status code. The ESA POP can then use the existing cache file to respond to the client request. If the file is modified, the origin server returns a 200 status code and the latest file. The ESA POP returns the latest file to the client and caches the resource.
     Delete	If a user requests content that matches a resource to be refreshed, the ESA POP directly fetches the new resource from the origin, returns it to the user, and caches the new resource.

   • Purge Content: Enter the tag value to purge. Separate multiple values with ,, such as images.

   

4. After you submit a purge task, track its progress on the Purge Records tab. 100% indicates completion. Large tasks may take longer.

   

Examples

When you update images or pages on an e-commerce website, you may need to purge the corresponding ESA cache. For images with multiple cropped versions, enumerating each variant is impractical—instead, batch-purge the ESA cache for all variants by image name. Similarly, when iterating on event pages, purge all related ESA cache by version tag:

Cache tag description

Availability