Backend for grammY Free Sessions

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Introduction

This repo contains the backend setup which powers grammY's free sessions. It is hosted on Deno Deploy.

Bots can authenticate themselves using their bot token on the /login endpoint. In turn, they will receive a JWT which contains their bot identifier.

When reading or writing session data via the /session endpoint, the bot sends this token in a header. We can use it to identify the bot and perform the respective action.

Session data is stored in an S3 bucket.

We enforce hard limits on the storage space that a bot can consume.

• Session keys each max 64 UTF-16 code units
• Session data per key max 16 KiB
• Max 50K sessions

We keep track of the session keys for each bot in a MongoDB database.

This backend can be used from the respective storage adapter.

Development

If you want to run this project locally, you can simply execute deno run src/main.ts.

You will need to set a number of environment variables for this project to function.

1. Generate a secret key by running deno run genkey.ts. Store it in the environment variable SECRET_KEY, e.g. using SECRET_KEY="$(deno run genkey.ts)".
2. Create an S3 bucket at any S3-compatible hosting provider of your choice. You should now have those values for your S3 bucket:
   • A URL endpoint, must be stored in S3_ENDPOINT.
   • A region name, must be stored in S3_REGION.
   • A bucket name, must be stored in S3_BUCKET.
   • An access key, must be stored in S3_ACCESS_KEY.
   • A secret key, must be stored in S3_SECRET_KEY.
3. Create a MongoDB database at any hosting provider of your choice. Store the srv string in MONGO_URL.

See the .env.example file, too.