swift-lambda.json manifest

Projects utilising the swift-lambda project include a swift-lambda.json manifest file in their root directory alongside SwiftPM’s Package.swift. This file is mandatory and includes information that swift-lambda needs in order to successfully deploy your function to AWS Lambda.

Basic

In its basic form, this is a JSON file that looks like the following:

{
    "Name": "Swifty McLambdaface",
    "Description": "My awesome new backend function written in Swift",
    "Memory": 128,
    "Timeout": 30,
    "AptDependencies": [
        "openssl-dev"
    ]
}

• The Name field is how we refer to our function. AWS Lambda lets you define as many functions as you need, so being able to refer to them by name is helpful.
• The Description field is similarly useful for distinguishing between Lambda functions when you have many defined.
• The Memory field is mandatory and should be an integer between 128 and 1536. This is how much memory Lambda will make available to your Swift program while it runs. CPU performance is also allocated to your function proportionate to the amount of memory allocated.
• The Timeout field is a mandatory integer between 1 and 300. This is how many seconds that Lambda will wait before considering your function to have timed out and be forcibly terminated. You are billed per 100ms of actual runtime, not how much time you allocate.
• The AptDependencies field is optional. It is an array of native dependencies that your Swift program (or its packages) needs in order to compile.

Advanced

Eventually your needs may exceed that provided by the basic manifest file format. In this case, you can upgrade to using an AWS CloudFormation template to describe your function and infrastracture-as-code.

CloudFormation allows you to describe database tables, push notification topics, S3 file upload buckets and any other AWS resources you might need in addition to your Lambda function to support your mobile application.

Here is an example of a CloudFormation swift-lambda manifest file:

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Metadata": {
        "Name": ""
    },
    "Resources": {

    },
}

CloudFormation rationale

Our rationale for exposing raw CloudFormation is that a) you shouldn’t have to learn a new standard when an existing one will do and b) we don’t want to reinvent the wheel.