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#OpenWhisk - Web Actions

Functions can be turned into "web actions" which return HTTP content without use of an API Gateway. This feature is enabled by setting an annotation (web-export) in the configuration file.

    handler: index.main
      web-export: true

Functions with this annotation can be invoked through a URL template with the following parameters.

  • APIHOST - platform endpoint e.g. openwhisk.ng.bluemix.net.
  • USER_NAMESPACE - this must be an explicit namespace and cannot use the default namespace (_).
  • PACKAGE - action package or default.
  • ACTION_NAME - default form ${servicename}-${space}-${name}.
  • TYPE - .json, .html, .text or .http.

Return values from the function are used to construct the HTTP response. The following parameters are supported.

  1. headers: a JSON object where the keys are header-names and the values are string values for those headers (default is no headers).
  2. code: a valid HTTP status code (default is 200 OK).
  3. body: a string which is either plain text or a base64 encoded string (for binary data).

Here is an example of returning HTML content:

function main(args) {
    var msg = "you didn't tell me who you are."
    if (args.name) {
        msg = `hello ${args.name}!`
    return {body:

Here is an example of returning binary data:

function main() {
   let png = <base 64 encoded string>
   return {
      headers: { "Content-Type": "image/png" },
      body: png };

Functions can access request parameters using the following environment variables.

  1. **__ow_meta_verb:** the HTTP method of the request.
  2. **__ow_meta_headers:** the request headers.
  3. **__ow_meta_path:** the unmatched path of the request.

Full details on this new feature are available in this blog post.

*IMPORTANT: Web Actions is currently experimental and may be subject to breaking changes.*