A New Clone Army:

ClojureScript on Lambda

Presented at @clojureireland on 7th Sept 2016.

Hit the [right-arrow] key to proceed.

"Serverless usually refers to an architectural pattern where the server-side logic is run in stateless compute containers that are event-driven and ephemeral."

- Software Engineering Daily podcast.

Colour Me Blue!

(set! (.. js/document -body -style
          -backgroundColor)
      "blue")

3 Runtimes for Lambda

NodeJS

Java Virtual Machine

Python 2.7

Amazon Cloud Jargon

AWS - Amazon Web Services

S3 - file storage service

API Gateway - give a Lambda function a public URL

EC2 - Amazon's virtual server.

Sample applications for Lambda

Process photo / video (trigger: upload to S3 bucket)

Scheduled jobs for data-analytics, etc.

API backend for mobile or web app

Why not Clojure?

Delay for cold starts of the container & JVM.

The frequency of cold starts is unpredictable.

OK for a 'background task' (startup time isn't critical).

Clojure rocks and JavaScript reaches.

Rich Hickey, NYC Clojure meet up 20 July 2011

Requirements to run ClojureScript on Lambda

Amazon Web Services account

aws-cli (command-line tools)

Node

Leiningen

Lambda creation on AWS console

(This is not required. We'll create the lambda on the command-line shortly.)

Triggers for a Lambda function

Prep local environment for AWS

Create a new project

`lein new cljs-lambda clonezero`

(NB: no need to download cljs-lambda in advance.)

Key elements of `project.clj`

{ ;; ...
:defaults {:role "FIXME"} ;; security role
:functions
[{:name   "work-magic"    ;; name of Lambda function
:invoke clonezero.core/work-magic}]} ;; entry-point to code
;; ...

Create a security role on AWS for the Lambda

`lein cljs-lambda default-iam-role`

This is just enough to run the Lambda. It'll need more for database-access etc.

'Main' function for Lambda

(deflambda work-magic [ input ctx ] ;; two arguments: input and context ;; input from the trigger for the Lambda ;; ctx is a library-handle to call Amazon's environment (e.g. time remaining) )

My Lambda's 'Main' function

(deflambda work-magic [{:keys [magic-word x y] :as input} ctx] (when (not= magic-word (config :magic-word)) (throw (js/Error. "Your magic word is garbage"))) (if (= (input :spell) "adder") (+ x y) (ctx/environment ctx)))