S3 + Lambda Image Handling

This is just a proof of concept of handling images using S3 + Lambda + serverless.

How to install for local development

1. Install the required node modules:

   npm install
   

2. Start the app (replace YOUR_AWS_* accordingly):

   BUCKET=YOUR_AWS_BUCKET_NAME AWS_KEY=YOUR_AWS_KEY AWS_SECRET=YOUR_AWS_SECRET node app.js
   

How to deploy

1. Install serverless:

   npm i -g serverless
   

2. Configure serverless (replace AWS_KEY and AWS_SECRET accordingly):

   serverless config credentials --provider aws --key AWS_KEY --secret AWS_SECRET
   

3. Copy serverless_dist.yml to serverless.yml and adjust accordingly.

4. Copy config/serverless/environment/dev_dist.yml to config/serverless/environment/dev.yml and adjust accordingly.

5. Build node_modules using an AWS Lambda environment with Docker (some packages like Sharp require compiled files in an environment similar to AWS Lambda - by executing this command, the local version will stop working, so in order to make it work locally again you have to delete node_modules and npm install):

   docker run --rm -v "$PWD":/var/task lambci/lambda:build-nodejs6.10
   

6. Deploy:

   serverless deploy
   

7. Make sure that the environment variables (BUCKET, AWS_KEY and AWS_SECRET) exist at https://console.aws.amazon.com/lambda/home?region=YOUR_REGION#/functions/YOUR_LAMBDA_FUNCTION

Status

Endpoint	Status	Comment
/add-images	Done
/delete-image	Done
/fetch-image	Done
/list-images	Done
/resize-image	Done
/zip-image	Done
/zip-images	Done

Tips

• sls is a shortcut for serverless. So you can use sls deploy instead of serverless deploy etc.
• In case of local development, consider installing nodemon (npm i -g nodemon) to make the development process easier (using nodemon app.js will restart the server every time a file changes).
• When adding new routes/functions remember to create the environment variables (BUCKET, AWS_KEY and AWS_SECRET).

Troubleshooting

In case you face problems you can try one of the followings:

• Make sure the two config files exist and contain the correct values.
• If already deployed code stopped working right after a deploy, try to remove (sls remove) and re-deploy. In that case remember to create the environment variables again (BUCKET, AWS_KEY and AWS_SECRET).

Coding Style

Just follow the default guidelines from http://standardjs.com.

If you want to automate your code formatting and be able to detect unused and deprecated code:

1. Install standard globally:

   npm install -g standard
   

2. Execute this periodically:

   standard --fix
   

3. Add this in the pre-commit hook:

   # Ensure all JavaScript files staged for commit pass standard code style
   function xargs-r() {
   # Portable version of "xargs -r". The -r flag is a GNU extension that
   # prevents xargs from running if there are no input files.
   if IFS= read -r -d $'\n' path; then
       { echo "$path"; cat; } | xargs $@
   fi
   }
   git diff --name-only --cached --relative | grep '\.jsx\?$' | sed 's/[^[:alnum:]]/\\&/g' | xargs-r -E '' -t standard
   if [[ $? -ne 0 ]]; then
   echo 'JavaScript Standard Style errors were detected. Aborting commit.'
   exit 1
   fi
   

Resources

• https://read.acloud.guru/serverless-image-optimization-and-delivery-510b6c311fe5
• https://iiaku.com/2017/06/06/aws-lambda-part-ii-how-to-create-zip-from-files/
• https://github.com/iiAku/zip-aws-lambda
• https://github.com/amazon-archives/serverless-image-resizing
• https://medium.freecodecamp.org/express-js-and-aws-lambda-a-serverless-love-story-7c77ba0eaa35