Prefetches content from origin servers to points of presence (POPs). This reduces workloads on origin servers because users can hit cache upon their first visits.
Operation description
- You can call the RefreshDcdnObjectCaches operation to refresh content and call the PreloadDcdnObjectCaches operation to prefetch content.
- Dynamic Content Delivery Network (DCDN) supports POST requests in which parameters are sent as a form.
- By default, each Alibaba Cloud account can submit up to 1,000 URLs per day. If the daily peak bandwidth value of your workloads exceeds 200 Mbit/s, you can submit a ticket to increase your daily quota. Alibaba Cloud reviews your application and then increases the quota accordingly.
- You can specify up to 100 URLs to prefetch.
- The prefetch queue of each Alibaba Cloud account can contain up to 100,000 URLs. DCDN executes prefetch tasks based on the time at which you submit the URLs.
- You can call this operation up to 15 times per second per account.
Description
- After a refresh task is submitted and completed, the POPs immediately start to retrieve resources from the origin server. Therefore, a large number of refresh tasks cause a large number of concurrent download tasks. This increases the number of requests that are redirected to the origin server. The back-to-origin routing process consumes more bandwidth resources and the origin server may be overwhelmed.
- The time required for a prefetch task to complete is proportional to the size of the prefetched file. In actual practice, most prefetch tasks require 5 to 30 minutes to complete. A task with a smaller average file size requires less time.
- To allow RAM users to perform this operation, you need to first grant them the required permissions. For more information, see Authorize a RAM user to prefetch and refresh resources.
Debugging
Authorization information
The following table shows the authorization information corresponding to the API. The authorization information can be used in the Action policy element to grant a RAM user or RAM role the permissions to call this API operation. Description:
- Operation: the value that you can use in the Action element to specify the operation on a resource.
- Access level: the access level of each operation. The levels are read, write, and list.
- Resource type: the type of the resource on which you can authorize the RAM user or the RAM role to perform the operation. Take note of the following items:
- For mandatory resource types, indicate with a prefix of * .
- If the permissions cannot be granted at the resource level,
All Resourcesis used in the Resource type column of the operation.
- Condition Key: the condition key that is defined by the cloud service.
- Associated operation: other operations that the RAM user or the RAM role must have permissions to perform to complete the operation. To complete the operation, the RAM user or the RAM role must have the permissions to perform the associated operations.
| Operation | Access level | Resource type | Condition key | Associated operation |
|---|---|---|---|---|
| dcdn:PreloadDcdnObjectCaches | none | *domain acs:dcdn:*:{#accountId}:domain/{#domainName} |
| none |
Request parameters
| Parameter | Type | Required | Description | Example |
|---|---|---|---|---|
| ObjectPath | string | Yes | The path of the content that you want to prefetch. Separate multiple URLs with line feed characters (\n) or a pair of carriage return and line feed characters (\r\n). | example.com/examplefile.txt |
| Area | string | No | The acceleration region in which you want to prefetch content. If you do not specify a region, the value overseas is used.
| domestic |
| L2Preload | boolean | No | Specifies whether to prefetch content to POPs. Valid values:
| true |
| WithHeader | string | No | The custom header for prefetch in the JSON format. | { "Accept-Encoding": [ "gzip" ] } |
Response parameters
Examples
Sample success responses
JSONformat
{
"PreloadTaskId": "95248880",
"RequestId": "E5BD4B50-7A02-493A-AE0B-97B9024B4135"
}Error codes
| HTTP status code | Error code | Error message | Description |
|---|---|---|---|
| 400 | SingleRequest.OverLimit | A maximum of 1000 URLs are supported for each request. | - |
| 400 | QuotaExceeded.Preload | Your refresh attempts have exceeded the daily limit. | The maximum number of refresh and prefetch requests on the current day has been reached. |
| 400 | InvalidObjectPath.Malformed | The specified ObjectPath is invalid. | The ObjectPath parameter is set to an invalid value. Specify a valid value and try again. |
| 400 | InvalidExtensiveDomain.ValueNotSupported | The specified ExtensiveDomain is not supported. | Wildcard domain names are not supported. |
| 400 | PreloadQueueFull | The warming queue is full; please try again later. | The maximum number of URLs of the objects that are being prefetched has been reached. Try again later. |
For a list of error codes, visit the Service error codes.
Change history
| Change time | Summary of changes | Operation |
|---|---|---|
| 2024-11-21 | API Description Update. The Error code has changed | View Change Details |
| 2024-11-03 | The Error code has changed. The request parameters of the API has changed | View Change Details |
| 2023-07-25 | The Error code has changed | View Change Details |