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Nbb on AWS Lambda

Creating an nbb lambda

All you need to do to get nbb running on AWS Lambda is the following:

package.json:

{"dependencies": {"nbb": "^0.6.129"}}

It's recommend to always use the newest version of nbb, so be sure to execute:

$ npm install nbb@latest

index.mjs:

import { loadFile, addClassPath } from 'nbb';

addClassPath('.'); // This is necessary when you require another .cljs file

const { handler } = await loadFile('./example.cljs');

export { handler }

example.cljs:

(ns example)

(defn handler [event _ctx]
  (js/console.log event)
  (js/Promise.resolve #js{:hello "world"}))

#js {:handler handler}

Test if the code runs locally:

$ node index.mjs

Zip the directory: zip -r app.zip .

Go to the AWS Console. Choose Lambda -> Author from Scratch -> Runtime Node.s 16.x + arm64. The default 128 MB should be sufficient for fast response times after cold start, but for fast cold starts, higher memory (which comes with higher CPU) is better.

Then choose Upload from and choose the zip file.

You can test the lambda function by creating a test event and invoking it.

To be able to invoke the function via HTTP, you'll first have to Publish it.

The API Gateway response has to be a little different so adjust your handler code like this...

example.cljs:

(ns example)
(defn handler [event _ctx]
      (js/console.log event)
      (js/Promise.resolve
        (clj->js {:statusCode 200
                  :body       (js/JSON.stringify #js{:hello "world"})})))
#js {:handler handler}

After uploading the updated code, under Configuration > Trigger you can add an API Gateway trigger. Create one and choose HTTP API and Security Open (make sure you change this when it becomes a private production lambda rather than just for the sake of trying nbb on lambda!).

After that you should end up with a public URL like https://9fov8nrv4f.execute-api.eu-central-1.amazonaws.com/default/... which you can then call from curl or via a browser. The response times I got after the cold start were around 100ms.

As a nice bonus, you can edit the CLJS code directly in the console.

Also check out these resources: