Handle Timeouts

When a lambda times out, it throws an error that cannot be caught by middy. To work around this, middy maintains an AbortController that can be signalled early to allow time to clean up and log the error properly.

You can set timeoutEarlyInMillis to 0 to disable this functionality. If you want to override during testing, mock the lambda context to set getRemainingTimeInMillis to a function that returns a very large value (e.g. () => 99999).

import middy from '@middy/core'

const lambdaHandler = (event, context, { signal }) => {
  signal.onabort = () => {
    // cancel events
  }
  // ...
}

export const handler = middy({
  timeoutEarlyInMillis: 50,
  timeoutEarlyResponse: () => {
    return {
      statusCode: 408
    }
  }
}).handler(lambdaHandler)

Notes

Do not mistake timeoutEarlyInMillis for a “timeout threshold”, as this is not something middy can control. The actual timeout of a Lambda function is controlled by AWS and you can configure it at the infrastructure level (with a hard limit of 15 minutes), see docs https://docs.aws.amazon.com/lambda/latest/dg/configuration-timeout.html

timeoutEarlyInMillis gives you a small buffer of time to perform cleanup or logging before Lambda forcibly terminates the function.

Example: If your Lambda timeout is 10s and you set timeoutEarlyInMillis: 1000, middy will abort at approximately 9s, leaving about 1s for cleanup.