PHP ON LAMBDA

Ian Littman / @iansltx

AustinPHP January 2019

https://ian.im/lambatx19

WHY LAMBDA?

• No servers to manage
• Quick automatic scaling
• High levels of concurrency
• Very granular billing
• Fair-sized free tier
• Stateless per-request, shared-nothing-ish
• Integrates with other AWS functions
  • Application Load Balancer (billed for capacity + time)
  • API Gateway (billed per request)

Shared-nothing-ish?

• "Cold starts"
• AWS keeps Lambda containers around for a bit
• 500 MB in /tmp is available per-instance
• Instances != invocations
• Cache on disk if you want/need it

Wait, I thought Lambda Didn't Do PHP

• Custom runtime support became available late last year
• Build the file system needed to run your function code
• Store the file system as one or more (up to 5) Layers
  • Extracted to /opt
  • Versioned
  • Can include library dependencies (e.g. /vendor)
  • Zipped + submitted to AWS API (like functions)
• Worker/polling model, NOT HTTP request based

Lambda Custom Runtime Lifecycle

• bootstrap runs once on instance start
  • Initializes runtime
  • Preps function for execution
  • Passed env vars including file/method for fn handler
  • If there's an error init-ing, make an API call
• One bootstrapped, instance calls APIs to process work
  • Next invocation (GET); invocation ID in headers
  • Invocation response (POST), includes invocation ID
  • Invocation error
• Lambda decides when to kill the instance

Wait, this isn't shared-nothing?!?

That's a good thing for billable exec time

The Easy Way

stackery/php-lambda-layer

php-lambda-layer

• Bootstrap written in PHP
• Forks, then runs PHP built-in web server in fork
• Only works for ALB/API Gateway
• Rebuilds API Gateway request context, then curl-calls the forked web server to execute
• Calls the PHP file specified in the handler
• Reformats the result and pushes back to AWS
• Feels a bit more shared-nothing-y
• Enable extensions via function config ini overrides

Why PHP 7.1?

OpenSSL version conflict

Demo time!

(code)

...and then Michael Moussa did a thing

• PHP 7.3 (compiled, including OpenSSL)
• Shared execution environment from CLI init
• Handled by method calls rather than HTTP
• Much lower overhead
• Rob Allen riffed on this bit...
• ...and set up a version to use Serverless Framework

Can we combine the two?

Not quite. Compiled binary doesn't have pcntl.

// TODO see if building a binary with --enable-pcntl works

Honorable Mention: Bref

version 0.3 will use custom runtimes

...with some speedy benchmarks!

Thanks! Questions?