Edge Security Acceleration:Fetch API

Method definition

Fetch is fully asynchronous and does not block script execution unless you use await. Up to four concurrent subrequests are supported. Persistent connections are managed internally.

Fetch supports HTTP and HTTPS requests. Each redirect counts as one subrequest, with a maximum of 12 redirect operations per request.

• Method definition

  fetch(arg, init). The method follows the MDN WorkerOrGlobalScope.fetch() specification.

• Method limits

  • The Fetch API supports domain names only, not IP addresses. Default ports: 80 (HTTP), 443 (HTTPS).

  • The credentials, referrer, referrerPolicy, cache, and integrity properties of the init parameter have no effect.

  • redirect defaults to follow, which follows 3xx responses from the origin. Set redirect to manual to disable redirect following.

  Note

  • Browser-specific Fetch modes do not apply. On CDN, DCDN, or ESA, CROS fetch can retrieve data from any origin.

  • To send four or more subrequests, submit a ticket to request a quota increase.

  • The total length of a request URL cannot exceed 4 KB.

  • Fetched gzip-compressed resources are decompressed by default. Add the manual parameter to disable decompression. The Decompress section covers details.

• Set a timeout period

  • Timeout function

    /**
     * Request timeout control implementation
     *
     * @param {Number} timeout Timeout period, in ms
     * @param {Object} config Timeout configuration
     *   - @param {Object|Funtion} handler Value to return on timeout
     * @returns
     */
    const RequestTimeout = (timeout, config) => {
      return new Promise((resolve) => {
        const { handler = null } = config;
        let timer = setTimeout(() => {
          clearTimeout(timer);
          timer = null;
    
          const defaultRes = (typeof handler === 'function' ? handler() : handler) || {};
          resolve(defaultRes);
        }, timeout);
      });
    };

  • Example call

    const KV_TIMEOUT = 1000;
    let edgekv = new EdgeKV({
      namespace: KV_NS,
    });
    
    let kvRequest = edgekv.get(key, getType);
    let timeoutPromise = RequestTimeout(KV_TIMEOUT, {
      handler: {
        res: {},
        errorMessage: `kv request timeout (${KV_TIMEOUT}ms)`,
      }
    });
    
    let resp = await Promise.race([
      kvRequest,
      timeoutPromise,
    ]);
    
    if (resp === undefined) {
      return "kv not found, key = " + key;
    } else {
      return resp;
    }

Redirect

Decompress

content-length

Headers

• Definition

  For more information about the Headers object, see Headers.

• Limits

  A header records the amount of memory resources that are consumed. The maximum size of a Headers object is 8 KB. If the size of a Headers object exceeds this limit, a JavaScript exception is thrown.

• Blacklist

  The Fetch API uses a header blacklist. If you attempt to read or write a header that is in the blacklist, an exception is thrown. The following table describes the headers that are included in the blacklist.

  • expect

  • te

  • trailer

  • upgrade

  • proxy-connection

  • connection

  • keep-alive

  • dnt

  • host

  • Reserved headers

Request

• Definition

  Follows the MDN Request specification.

• Limits

  The following Request properties are not supported in CDN, DCDN, or ESA.

  • context

  • credentials

  • destination

  • integrity

  • mode

  • referrer

  • referrerPolicy

  • cache

• Common uses

  • Retrieve the request method: request.method.

  • Retrieve the request URL: request.url.

  • Retrieve the request headers: request.headers.

  • Retrieve the request payload: request.body. The body is a ReadableStream object.

  • Retrieve JSON: await request.json().

  • Retrieve form data: await request.formData().

  • Retrieve a UTF-8 string: await request.text().

  As a non-standard extension, request.ignore drains the body stream at the socket level without loading it into JavaScript VM memory, avoiding GC delays. Call await request.ignore() when you do not need the request body. The runtime returns the connection to the pool after the body is fully read.

Response

• Definition

  Follows the MDN Response specification.

• Limits

  The useFinalURLS and error properties are not supported in CDN, DCDN, or ESA.

• Common uses

  • Retrieve the response code: response.status.

  • Retrieve the response reason phrase: response.statusText.

  • Retrieve the response headers: response.headers.

  • Retrieve the response URL: response.url. This is the final URL after all redirects.

  • Retrieve all redirect URLs (non-standard): response.urlList. Response implements a body mixin like Request, so the same body-retrieval methods apply.

FormData

• Definition

  For more information about the FormData operation, see FormData.

• Limits

  The FormData operation is similar to the Headers operation. FormData limits the size of headers. If the size of a header exceeds the upper limit, an exception is thrown. If you send FormData as an HTTP request body, content-type is set to form-data/multipart by default.

URLSearchParams

• Definition

  For more information about the URLSearchParams operation, see URLSearchParams().

• Limits

  If you send URLSearchParams as an HTTP request body, content-type is set to application/x-www-form-urlencode by default. The data size cannot exceed 1,000 bytes.

Blob and File

• Definition

  • For more information about the Blob operation, see Blob.

  • For more information about the File operation, see File.

• Limits

  ER supports the Blob and File classes, which meet the standards of the Blob and File operations. ER cannot read or write files. You can pass the Blob and File classes supported by ER to the response body. The value of the content-type header is the same as the MIME type in the Blob or File operation.