Add Delay
Execution time limit
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.
Before you run any of the examples on this page, create a Function and paste the example code into it. You can create a Function in the Twilio Console or by using the Serverless Toolkit.
If you prefer a UI-driven approach, complete these steps in the Twilio Console:
- Log in to the Twilio Console and navigate to Develop > Functions & Assets. If you're using the legacy Console, open the Functions tab.
- Functions are contained within Services. Click Create Service to create a new Service.
- Click Add + and select Add Function from the dropdown.
- The Console creates a new protected Function that you can rename. The filename becomes the URL path of the Function.
- Copy one of the example code snippets from this page and paste the code into your newly created Function. You can switch examples by using the dropdown menu in the code rail.
- Click Save.
- Click Deploy All to build and deploy the Function. After deployment, you can access your Function at
https://<service-name>-<random-characters>-<optional-domain-suffix>.twil.io/<function-path>
For example:test-function-3548.twil.io/hello-world.
You can now invoke your Function with HTTP requests, configure it as the webhook for a Twilio phone number, call it from 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.
1// Helper function for quickly adding await-able "pauses" to JavaScript2const sleep = (delay) => new Promise((resolve) => setTimeout(resolve, delay));34exports.handler = async (context, event, callback) => {5// A custom delay value could be passed to the Function, either via6// request parameters or by the Run Function Widget7// Default to a 5-second delay8const delay = event.delay || 5000;9// Pause Function for the specified number of ms10await sleep(delay);11// Once the delay has passed, return a success message, TwiML, or12// any other content to whatever invoked this Function.13return callback(null, `Timer up: ${delay}ms`);14};
Without async/await or Promises
1exports.handler = (context, event, callback) => {2// A custom delay value could be passed to the Function, either via3// request parameters or by the Run Function Widget4// Default to a 5-second delay5const delay = event.delay || 5000;6// Set a timer for the specified number of ms. Once the delay has passed,7// return a success message, TwiML, or any other content to whatever8// invoked this Function.9setTimeout(() => 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
1exports.handler = async (context, event, callback) => {2// You can import shared code from a Private Function3// using the Runtime.getFunctions() helper + require4const { sleep } = require(Runtime.getFunctions().utils.path);5// A custom delay value could be passed to the Function, either via6// request parameters or by the Run Function Widget7// Default to a 5-second delay8const delay = event.delay || 5000;9// Pause Function for the specified number of ms10await sleep(delay || 5000);11// Once the delay has passed, return a success message, TwiML, or12// any other content to whatever invoked this Function.13return callback(null, `Timer up: ${delay}ms`);14};