The Problem

Asynchronous function calls made within the initialization block of a Lambda function are not guaranteed to complete prior to invocation. This limits the effectiveness of Provisioned Concurrency for latency sensitive customers.

Proposed Solution

In this proof of concept application, I introduce the concept of a lifecycle hook to AWS Lambda. The initializeFunction lifecycle hook enables customers to gain greater control over their runtime environment by allowing them to run and complete initialization code during function startup. The Lambda Runtime Interface Client calls the initializeFunction lifecycle hook a single time prior to the first invocation. Notably, the await keyword is honored within this function block, enabling customers to create blocking calls.

Review the Code

The easiest way to review the code is to download the application and then search for the string dfox. I have numbered the sequence of changes for review.

Run the App Locally

1. Install the Runtime Interface Emulator

2. Open a terminal and execute ./run.sh

3. Open a second terminal and execute ./curl.sh

Enhancements

The function name is currently selected by convention, but could be customized by the customer.