Problem

EC2 instances are very handy for personal computing needs but they get a bit expensive just sitting there idling. For most tasks I find that I only need the instance up for a few minutes or hours anyway. Typical examples for me are:

• Check my TT-RSS feed
• Use Wireguard VPN server to log into Home Assistant when I'm not at home.
• Use my remote workstation machine (a.k.a "box") for some work if I'm currently running into local compute or bandwidth constraints, or running tools not supported on the M1 architecture.

But logging into the AWS console or app every time just to start and stop the instance is annoying. I wanted a convenient yet still secure way to do this.

Solution

Key insight:

• Humans integrate easily with chat (e.g. Telegram)
• Telegram integrates easily with AWS Lambda with zero uptime cost.
• AWS Lambda makes it easy and safe to control other AWS resources using boto3 combined with fine-grained IAM policies.

This is approach is broadly referred to as "ChatOps". Specifically my solution is to use a Telegram bot hosted using AWS Lambda as a cheap, convenient and safe way to manage and query this infrastructure. I call it "TLI" for "Telegram Line Interface". The name is currently way more ambitious than the application since it only supports a few simple prompts specific only to me. But I use it every day so that has to count for something.

Getting started

Install serverless cli

npm install -g serverless

Use the env var template to populate your details

cp example.env .env 

Restore dependencies

python3 -m pip install -r requirements.txt -t vendored

Deploy

# Set your AWS env vars AWS_PROFILE, AWS_REGION etc
serverless deploy

Creating a new Telegram bot

• Go to BotFather and send /newbot
• Choose a name (e.g FSO TLI) and username (e.g. fso_tli_bot) for your bot
• Copy the example.config.json file add the key and add the bot key
• Create a new telegram group and add the bot there
• Promote bot as administrator to group. If admin, a bot can see messages with /setprivacy enabled which is the default
• Disable the bot from joining other groups on BotFather /setjoingroups
• Add menu items to the bot
• Restore the dependencies

Use the registerWebhook.sh script to link the Bot to the lambda.

References

https://hackernoon.com/serverless-telegram-bot-on-aws-lambda-851204d4236c https://github.com/Andrii-D/serverless-telegram-bot?ref=hackernoon.com https://github.com/python-telegram-bot/python-telegram-bot/wiki/Extensions-%E2%80%93-Your-first-Bot https://sarafian.github.io/low-code/2020/03/24/create-private-telegram-chatbot.html https://stackoverflow.com/questions/45889405/how-to-read-messages-from-telegram-group-with-bot