AWS S3 Select Demo

This project showcases the rich AWS S3 Select feature to stream a large data file in a paginated style.

Currently, S3 Select does not support OFFSET and hence we cannot paginate the results of the query. Hence, we use scanrange feature to stream the contents of the S3 file.

Background

Importing (reading) a large file leads Out of Memory error. It can also lead to a system crash event. There are libraries viz. Pandas, Dask, etc. which are very good at processing large files but again the file is to be present locally i.e. we will have to import it from S3 to our local machine. But what if we do not want to fetch and store the whole S3 file locally at once? :thinking:

Well, we can make use of AWS S3 Select to stream a large file via it's ScanRange parameter. This approach is similar to how a pginated API works. Instead of limit and offset on records, we provide the limit and offset on the bytes to stream. S3 Select is intelligent enough to skip the whole row of the file if it does not fit in the byte range.

You can find an in-depth article on this implementation here.

Getting Started

Prerequisites

• Python 3.9.13 or higher
• Up and running Redis client
• AWS account with an S3 bucket and an object (or upload from /data/data.csv)
• aws-cli configured locally (having read access to S3)

:scroll: This project is a clone of one of my projects Flask Boilerplate to quickly get started on the topic :satisfied:

Project setup

# clone the repo
$ git clone https://github.com/idris-rampurawala/s3-select-demo.git
# move to the project folder
$ cd s3-select-demo

If you want to install redis via docker

# at the root of this project 
$ docker run -d --name="flask-boilerplate-redis" -p 6379:6379 redis

Creating virtual environment

• Install pipenv a global python project pip install pipenv
• Create a virtual environment for this project

# creating pipenv environment for python 3.9 (if you have multiple python versions, then check last command)
$ pipenv --three
# activating the pipenv environment
$ pipenv shell
# install all dependencies (include -d for installing dev dependencies)
$ pipenv install -d

# if you have multiple python 3 versions installed then
$ pipenv install -d --python 3.9

Configuration

• There are 3 configurations development, staging and production in config.py. Default is development
• Create a .env file from .env.example and set appropriate environment variables before running the project

Running app

• Run flask app python run.py
• Logs would be generated under log folder

Running celery workers

• Run redis locally before running celery worker
• Celery worker can be started with following command

# run following command in a separate terminal
$ celery -A celery_worker.celery worker -l INFO
# (append `--pool=solo` for windows)

Test

Test if this app has been installed correctly and it is working via following curl commands (or use in Postman)

• Check if the app is running via status API

$ curl --location --request GET 'http://localhost:5000/status'

• Check if core app API and celery task is working via

$ curl --location --request GET 'http://localhost:5000/api/v1/core/test'

• Check if authorization is working via (change API Key as per you .env)

$ curl --location --request GET 'http://localhost:5000/api/v1/core/restricted' --header 'x-api-key: 436236939443955C11494D448451F'

• To test the file streaming task, please upload the /data/data.csv on your AWS S3 and then update the .env with its bucket, key and profile-name

$ curl --location --request GET 'http://localhost:5000/api/v1/core/s3_select'

• To test the file parallel processing task, please upload the /data/data.csv on your AWS S3 and then update the .env with its bucket, key and profile-name

$ curl --location --request GET 'http://localhost:5000/api/v1/core/s3_select_parallel'

Resouces

• My post explaining this approach
• AWS S3 Select userguide
• AWS S3 Select Example
• AWS S3 Select boto3 reference

License

This program is free software under MIT license. Please see the LICENSE file in our repository for the full text.