Edge FunctionsCache API-Edge Security Acceleration(ESA)-阿里云帮助中心

Working mechanism

The built-in Cache API of EdgeRoutine caches processed results or origin server data on Dynamic Content Delivery Network (DCDN) POPs. Other requests that access the same POPs can reuse the cached data, which reduces repetitive calculations and network requests. The following figure shows the relationship between EdgeRoutine and DCDN cache. How it works

API standards

The Cache API follows the standard Cache API as closely as possible. However, because EdgeRoutine reuses the DCDN cache engine, the semantics are not identical.

API definition

cache.put(request/string, response)

Adds a Response object to Cache.
- If the PUT method is successful, the returned Promise resolves to undefined.
- If the cache engine fails, the Promise is rejected with an error.
- If the cache engine quota is exhausted, the Promise is rejected with an error.
The cache key is set to the URL of the Request object, or you can use a string to specify the URL. Only HTTP URLs are supported due to DCDN cache engine limitations.
This is an asynchronous function. You can use await to wait until the Response object is added to the cache.，awaitFor usage, seeawaitsyntax
Configure the Cache-Control header on the Response object to define the cache TTL. The Cache-Control header must conform to Cache standards.

Examples

Add content to Cache

async function doPut() {
  await cache.put("http://www.example.com", new Response("Hello World"));
}

Add content to Cache and configure TTL

async function doPut() {
  await cache.put("http://www.example.com", 
    new Response("Hello World", {headers: [["cache-control", "max-age=10"]]})
  );
}

cache.get(request/string)

Returns the cached Response object that matches the input request or string. If no match exists, the Promise resolves to undefined.
This is an asynchronous function. You can use await to wait until the Response object is returned.
The GET method may not return an object that was added by a preceding PUT call. A cached object may be evicted by the least recently used (LRU) algorithm.

Examples

Obtain a Response object

async function doGet() {
    let resp = await cache.get("http://www.example.com");
}

Parse the stored results into JSON

async function doGet() {
    let resp = await cache.get("http://www.example.com");
    let j = await resp.json();
}

cache.delete(request/string)

Deletes a Response object whose key is the input request.
- On success, the Promise resolves to true.
- On failure, the Promise resolves to false.
This is an asynchronous function. You can use await to wait until the deletion completes.

Example: Delete the resource for a key

async function doDelete() {
  let resp = await cache.delete("http://www.example.com");
  
  if (resp) {
        console.alert("done");
  } else {
        console.alert("failed");
  }
}

Limits

Cache API calls are subrequests that share the EdgeRoutine subrequest quota. By default, the total number of cache.put, cache.get, cache.delete, and fetch subrequests cannot exceed 32 per request context. This quota may change when EdgeRoutine is put into commercial use.
cache.put, cache.get, and cache.delete are subject to concurrency control. If concurrent requests target the same URL, one request may return a pending state. Retry the request later if this occurs.

Note
If a cache.put, cache.get, or cache.delete request is rejected and the Promise resolves to true, the rejection is caused by concurrency control.

Cache refresh

The Cache API does not support active cache refresh. You must specify an appropriate TTL when you add an item to the cache with the cache.put() method.