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Serverless Flask and Serverless Express-ts

July 19, 2023

Aws

Serverless

Contents

1. Prerequisite

We assume the reader has installed the npm package serverless globally. Make sure you can run sls or serverless at your terminal.

2. Python Flask

2.1. Template Repo

2.2. How to test Locally and Deploy

  • yarn to install serverless-wsgi and serverless-python-requirements

  • Now if you run sls wsgi serve, a flask api server should be up and running. It also provides hot reload for code changes.

  • After your api implement are done, you can sls deploy to deploy your application.

  • You can sls remove to undo everything.

2.3. Size Reduction for Python Lambdas

You can reduce the size by modifying serverless.yml.

  • Add custom.pythonRequirements.noDeploy.

  • By default serverless will copy compiled binary from your virtual environment.

  • If you add autopep8 in noDeploy, make sure to remove that from requirements.txt as well because serverless will make a copy of requirements.txt and copy compiled binary accordingly.

  • dockerizePip: true is necessary for package PILLOW because the compiled binary in windows is not compatible with linux.

  • Layers! I haven't tried to Flask yet, we may add noDeploy in the list once we find suitable lambda layers available in our region:

    provider:
name: aws
runtime: python3.8
layers:
  - arn:aws:lambda:us-east-1:xxxxxxxxxxxxx:layer:xxxxx:mylayer1
  - arn:aws:lambda:us-east-1:xxxxxxxxxxxxx:layer:xxxxx:mylayer2

    The list of layers available at our region can be found in here.

3. Nodejs Express (ts)

3.1. Template Repo

3.2. How to test Locally and Deploy

  • yarn to install

    • serverless-http
    • serverless-offline
    • serverless-plugin-common-excludes
    • serverless-plugin-typescript-express

  • To run locally we run yarn start, which just use traditional nodemon and ts-node src/app.ts.

  • We run yarn deploy to deploy our app using our ~/.aws credentials.

  • We run yarn remove to sls remove everything according to cloudformation record.

3.3. Size Reduction for Nodejs Lambdas

Compared to python we have much fewer things to modify in serverless.yml as we don't have such options. The best thing we may try is:

package:
  patterns:
    - src/** # include only files from ./src/**/*
    - "!node_modules/some-package/**" # exclude files from ./node_modules/some-package/**/*

and add layers in provider option, but I don't have such convenient resource yet.

3.4. Manual Bug Fix before Deployment

Before deployment, a manual bug fix must be held on our own. From this thread, we need to modify

node_modules/serverless/bin/serverless.js

which in my case my serverless.js is held at the following absolute path

C:\Users\user\AppData\Local\Yarn\Data\global\node_modules\serverless\bin\serverless.js

in that file we add the following line right after use strict;:

require("../../graceful-fs/graceful-fs").gracefulify(require("fs"));