Functions FAQ

Why does my Function return 'runtime application timed out'?

There are two possible reasons for why your Function has completed with the error: 'runtime application timed out'.

The most common reason is that your Function has exceeded the 5 second execution time limit. You can determine this by looking at the execution logs on the Function instance page. The last log line after execution will tell you how many milliseconds the Function took to execute. If the processing time is greater than 5,000 milliseconds then your Function was terminated by Twilio.

The other more subtle reason your Function ended with an application timeout is because of an incorrect invocation of callback(). If the callback() method is not being called or is unreachable your Function will continue executing until it reaches the timelimit and ultimately fail. The Function Execution documentation provides extensive details on the functionality and usage of the callback() method. Below are several examples of how to correctly use callback() to complete execution and emit a response.

Why isn't my code running?

The most common reason we have seen that a Function appears not to run is misuse of callback(). If the callback() method is not being called or is unreachable your Function will continue to execute until it reaches the timelimit and ultimately fail. This makes it appear as if your Function is not executing because there is no response emitted. The Function Execution documentation provides extensive details on the functionality and usage of the callback() method. Below are several examples of how to correctly use callback() to complete execution and emit a response.

How do I construct Voice TwiML?

You can generate Voice TwiML using the Twilio Node library which comes packaged within your Function.

How do I construct Messaging TwiML?

You can generate Messaging TwiML using the Twilio Node library which comes packaged within your Function.

How do I return JSON?

Simply return your object as outlined in the Function Execution documentation.

How do I send CORS headers?

You can send CORS headers by using the Twilio Response object described in the Function Execution documentation.

Is there a Functions or Assets REST API?

Not yet, currently, Functions and Assets can only be accessed through the Twilio Console. But keep and eye on this space for updates. Please reach out to us via support or our Google Group to express interest in this feature.

Can I execute my Functions on a schedule?

Not today, currently, Functions are event driven and can only be invoked by HTTP.

Can I see examples of existing Functions?

Absolutely! In addition to our Programmable SMS and Programmable Voice quickstarts, you can find a variety of templates within our catalogue within the Create Function page.

How many Functions can I create?

During the beta period, we currently have a limit of 100 functions per account.