PHP Lambda

Introduction

This repo is a bit of a self-training project, and a bit of an exercise of curiosity - I wanted to see how to run AWS lambdas in PHP, now that they can be backed by a Docker container. I have a use-case where I want to call some APIs on a schedule, and running a lambda based on an EventBridge seems like an interesting, serverless, and low-cost way to do that.

The project isn't all PHP - I use TypeScript to deploy the project using the AWS CDK library.

Another interesting side-project here shall be the bridging of EFS to Lambda in order to make use of SQLite. Yes, you heard that right - I want to try out SQLite for a real project, and to demonstrate that there are cheaper serverless alternatives to RDS for low-volume use-cases. Have a read of the SQLite docs for many interesting real-world uses.

This project can be thought of a PHP equivalent to my StackWatcher project, which is an unfinished JavaScript version that runs in the Mongo Stitch environment. I'd like to get back to that, but that environment forces the involvement of Mongo, and I have mixed feelings about NoSQL - it seems to often be used because it is cheap, rather than because it is appropriate.

Ideas

From a toolkit perspective it would be great to set up these things:

• A config file to specify what AWS features are required (EFS, pdo_sqlite, Cron, etc.)
• A simple way to kick off CDK on a dev machine with only Docker as a dependency
• A command to deploy a lambda via an AWS call and run a "ping" command

Status

At the time of writing:

• the Docker image builds
• the image can be pushed to AWS ECR
• I have built some AWS infra (Lambda, VPC, ECR, EFS)
• the PHP lambda is callable from the AWS dashboard
• the lambda mediator code is unit-tested
• the lambda can write to EFS
• the CDK deployment creates a working PHP lambda with EFS write access

Here is what does not work:

• The lambda doesn't do anything useful
• SQLite isn't yet in use
• The CDK needs a cron

However, I think there is enough code here for it to be interesting to readers.

Warning on AWS costs

I was rather hoping this project was going to be inexpensive to run, but sadly it is not. It seems to attract these rates:

• $0.05 per NAT Gateway Hour
• $0.176 per GB-Mo for One Zone Storage in EU (London) (very trivial in this case)
• $0.05 per GB Data Processed by NAT Gateways (very trivial in this case)

When I set this up, it was charging $2.40 (USD) per day, which would result in a monthly bill of $72. This isn't nearly good enough - while there are other reasons to use lambdas, one might as well just set up a small VPS with any cloud provider.