Comment by foob | Hacker News Reader

Comment by foob | Hacker News Reader

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I'm kind of surprised that the article doesn't mention aws-serverless-express [1], a node module provided by Amazon which makes it fairly trivial to expose an existing Express app as a Lambda function via AWS API Gateway. The Lambda handler module basically just consists of the following code.

    const awsServerlessExpress = require('aws-serverless-express');
    const app = require('./app');
    const server = awsServerlessExpress.createServer(app);

    exports.handler = (event, context) => (
      awsServerlessExpress.proxy(server, event, context)
    );

It's really convenient to be able to develop simple APIs using Express, and then to expose them via Lambda functions using aws-serverless-express. After you've done it once or twice, it's really easy to throw together single-purpose APIs and deploy them in a matter of minutes. For example, I was recently frustrated with the fact that CircleCI's API for accessing build artifacts is perpetually broken, and I wrote a little microservice to expose the same functionality [2]. It's definitely awesome to be able to deploy one-off projects like that without needing to worry about any sort of server maintenance.

[1] - https://github.com/awslabs/aws-serverless-express

[2] - https://intoli.com/blog/circleci-artifacts/

Hey, I didn't mentioned it in this article because I have another article dedicated to serverless-express (https://medium.freecodecamp.org/express-js-and-aws-lambda-a-...), also we dedicated whole chapter of our book to it too with explanation how does it work, etc. (livebook link: https://livebook.manning.com/#!/book/serverless-apps-with-no...)

You might be interested in trying out https://github.com/tobiipro/http-lambda (disclaimer: I'm the author)

for reasons that I've explained in a README section https://github.com/tobiipro/http-lambda#a-word-on-httpsgithu...

Your snippet becomes

    const {httpLambda} = require('http-lambda');
    const app = require('./app');
    exports.handler = httpLambda((http, _event, _context) => (
      http.createServer(app);
    ));

How's the latency when using this method? I'd imagine if you foresee your site being low usage, startup times would be quite bad. At least, on the order of seconds rather than milliseconds.

It depends a little bit on whether there's a warm container or not, but I think that the overhead is much closer to ~100 milliseconds than to multiple seconds. The CircleCI artifacts API that I linked to takes less than one second to return an artifact, and there's a lot more going on there than a single request/response pair. The endpoint makes an external request to CircleCI's API, does some processing on the response, returns a 301 redirect, and then the redirect is followed by the client and another request is made to actually download the file from S3. You can test this directly by running

    time curl -L 'https://circleci.intoli.com/artifacts/intoli/exodus/coverage-report/total-coverage.json'

which outputs something like the following (the timing will vary a bit obviously).

    { "coverage": "92.43%" }

    real	0m0.798s
    user	0m0.046s
    sys	0m0.010s

I just ping my functions every 4 minutes to keep them warm. I am still in the free quota doing that

It is not. You obviously get into a different set of problems than you're accustomed with, but it is not seconds, even on "cold" lambdas. https://read.acloud.guru/cold-starting-lambdas-2c663055589e

From your linked article: "In the absolute worst case it could be as high as 2.8 seconds."

One is the latency of starting up the "cold" lambda, one is the latency of actually starting it up and running your code. The latter is a moving target, subject to the setup i.e. size of loaded code, available memory/CPU, etc, and subject to the actual computation and the latency of its dependencies e.g. network calls, database queries, etc.

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