Edge Security Acceleration:Prefetch cache

Scenarios

• Support for major events

  Before a big event, you can prefetch the static resources of the event page to POPs. When the event starts, visitors can access the static resources that are already cached on POPs. This accelerates content delivery.

• Release of installation packages

  Before you release an installation or upgrade package of a product, you can prefetch the package to POPs. After the product is launched, visitors can download the package from POPs. This accelerates content delivery and reduces loads on the origin server when a large number of visitors access your resources.

Prefetch methods

ESA supports instant prefetch and scheduled prefetch.

• Instant prefetch: prefetches resources to POPs immediately after you configure URLs to fetch resources from.

• Scheduled prefetch: prefetches resources as scheduled and at specified time intervals. Scheduled prefetch helps prevent fetching during peak hours, control origin traffic generated from prefetching, and reduce pressure on the origin server.

Usage notes

• After a prefetch task is submitted and run, ESA fetches required resources from the origin server to POPs. Submitting a large number of instant prefetch tasks at a time generates a large number of download tasks, which burdens the origin server due to a surge in origin bandwidth and requests. We recommend that you use scheduled prefetch.

• The period of time required to complete a prefetch task is proportional to the size of the files that you want to prefetch. In most cases, most prefetch tasks require 5 to 30 minutes to complete. A task that prefetches a smaller file requires less time to complete.

• By default, prefetch requests include the Accept-Encoding:gzip header. If you want a prefetch request to include other headers or implement multi-replica prefetch, you can call the PreloadCaches operation and specify a custom prefetch header by configuring the Header parameter.

• If the origin server returns a redirection-related status code, such as 301, the prefetch task does not follow the redirected address and fails. If the origin server returns status code 301 or 302, submit a ticket to enable 301/302 redirection.

Feature availability

Procedure

1. Log on to the ESA console.

2. In the left-side navigation pane, click Websites.

3. On the Websites page, find the website that you want to manage, and click the website name or View Details in the Actions column.

4. In the left-side navigation tree, choose Caching > Prefetch Cache.

5. Select instant prefetch or scheduled prefetch.

   Instant prefetch

   Instant prefetch retrieves resources from the origin server immediately after you submit the URLs of resources and caches retrieved resources to POPs.

   You can select Manual Input to specify URLs one by one or Upload File to specify URLs collectively by uploading a file that contains a list of URLs.

   Method	Description
   Manual Input	Enter one or more URLs in the text box and click Submit. Each specified URL must be a complete path to the resource. You can specify up to 100 URLs at a time, with each line holding one single URL. Example: https://www.example.com/cat.jpg https://www.example.com/image/cat.jpg
   Upload File	If a large number of URLs need to be prefetched, you can specify the URLs in a TXT file and then upload the file. Each specified URL must be a complete path to the resource. One URL per line. The size of the TXT file cannot exceed 10 MB.

   Scheduled prefetch

   Scheduled prefetch retrieves resources as scheduled and at specified time intervals to prevent fetching during peak hours, control origin traffic generated from prefetching, and reduce pressure on the origin server.

   1. Write complete URLs of resources to prefetch into a TXT file, with each URL in a separate line. The size of the TXT file cannot exceed 10 MB.

   2. Click Create Prefetch Task.

   3. In the Upload File Step, specify a prefetch task name, upload the TXT file, and then click Next.

      Note

      You can create up to 100 prefetch tasks.

      

   4. In the Create Prefetch Plan step, create a prefetch plan. You need to specify the time range, prefetch time intervals (at least 1 second), and number of URLs for each prefetch (at most 100 URLs).

      Note

      You can create up to 10 prefetch plans.

      

   5. Click OK.

6. View the prefetch progress.

   After you submit a prefetch task, you can view the task progress and details on the Prefetch Records tab. The prefetch task is complete when the progress reaches 100%. The prefetch task may require a long period of time to complete if you have a lot of resources to prefetch.