Functions are subject to a 10-second execution limit before being terminated. Keep this limit in mind when evaluating if this method suits your use case.
Adding a delay to your Function's response is useful in certain use cases, particularly when it comes to interacting with Twilio Studio. One such case is if you are creating a chatbot and want longer, more realistic pauses between responses. Or perhaps you are making an HTTP request in a Studio Flow and want to add a delay to the retry loop on failure.
In all of these situations, the ability to add a delay is incredibly helpful. While Studio does not provide a native "Delay" widget, you can combine the Run Function widget with a Function that has a delayed response to emulate such behavior.
Below are some examples of what such a Function may look like. Before getting deeper into the examples, first, create a Service and Function so that you have a place to write and test your Function code.
In order to run any of the following examples, you will first need to create a Function into which you can paste the example code. You can create a Function using the Twilio Console or the Serverless Toolkit as explained below:
If you prefer a UI-driven approach, creating and deploying a Function can be done entirely using the Twilio Console and the following steps:
https://<service-name>-<random-characters>-<optional-domain-suffix>.twil.io/<function-path>
test-function-3548.twil.io/hello-world
.
Your Function is now ready to be invoked by HTTP requests, set as the webhook of a Twilio phone number, invoked by a Twilio Studio Run Function Widget, and more!
The act of delaying a Function's response is mostly just a matter of using a built-in method, such as setTimeout
, to delay the act of calling the callback
method and signaling that the Function has completed. If this Function were to be called by a Run Function widget, the Studio Flow containing that call would be delayed until this Function returns a response.
It's also quite possible to provide the value for delay
, by defining a value (or dynamic variable) under the Function Parameters config for the Run Function Widget that calls this Function.
To provide a more async
/await
friendly syntax in your Functions, this example demonstrates how to write a sleep
helper method that wraps setTimeout
in a Promise.
If your Function has no other actions to execute or if you don't see the need for Promises in this case, the next example demonstrates the same functionality, but without the async
/await
abstraction.
_14// Helper function for quickly adding await-able "pauses" to JavaScript_14const sleep = (delay) => new Promise((resolve) => setTimeout(resolve, delay));_14_14exports.handler = async (context, event, callback) => {_14 // A custom delay value could be passed to the Function, either via_14 // request parameters or by the Run Function Widget_14 // Default to a 5-second delay_14 const delay = event.delay || 5000;_14 // Pause Function for the specified number of ms_14 await sleep(delay);_14 // Once the delay has passed, return a success message, TwiML, or_14 // any other content to whatever invoked this Function._14 return callback(null, `Timer up: ${delay}ms`);_14};
Without async/await or Promises
_10exports.handler = (context, event, callback) => {_10 // A custom delay value could be passed to the Function, either via_10 // request parameters or by the Run Function Widget_10 // Default to a 5-second delay_10 const delay = event.delay || 5000;_10 // Set a timer for the specified number of ms. Once the delay has passed,_10 // return a success message, TwiML, or any other content to whatever_10 // invoked this Function._10 setTimeout(() => callback(null, `Timer Up: ${delay}ms`), delay);_10};
The sleep
method that we created for the previous example is also a great example of a method that could be used across a number of Functions in your Service. In Functions, it's best practice to store shared JavaScript methods such as these in Private Functions, and import them into the various Functions that will make use of them.
To see this in action, first create a new Function named utils
, and set its privacy level to Private. Paste in the following code, which exports the sleep
helper from before.
A delayed Function that leverages a utility method instead of defining it inline
_14exports.handler = async (context, event, callback) => {_14 // You can import shared code from a Private Function_14 // using the Runtime.getFunctions() helper + require_14 const { sleep } = require(Runtime.getFunctions().utils.path);_14 // A custom delay value could be passed to the Function, either via_14 // request parameters or by the Run Function Widget_14 // Default to a 5-second delay_14 const delay = event.delay || 5000;_14 // Pause Function for the specified number of ms_14 await sleep(delay || 5000);_14 // Once the delay has passed, return a success message, TwiML, or_14 // any other content to whatever invoked this Function._14 return callback(null, `Timer up: ${delay}ms`);_14};