Building a Telegram Bot for Cowin Shot Slots

Cowin Shot Slot availability chase has become an extremely competitive space with the gap in supply and demand in India . Several techies are doing their best to educate and empower people with one of the largest vaccination drive in the world’s 2nd most populous country.

Here is my recipe to provide timely alerts to those in search for a CoWin slot .

Assumptions: I assume you have some idea about oth AWS Lambda , Python programming and Telegram to proceed further.

Remember to read the last section of this article

Architecture

Architecture

I was motivated to use AWS Lambda given the simplicity of deploying the code and being able to scale up and scale down .

Telegram was my choice to broadcast the messages given the flexibility it has in creating a bot , channel and the “200,000” subscribers limit to any broadcast channel you create. That’s convenient.

Step 1: Bot Creation with Telegram

If you have not already signed up for Telegram , I think its time you do one . Proceed after you have created your Telegram ID and signed up.

Telegram provided the ultra-simple way to create your own bot . You can chat with “@botfather“ a specialized Telegram Bot that can assist you .

First , open up your Telegram app on phone and search for “ @botfather ”

botfather

Click “Start” to communicate

communicated started with botfather

Now we want to create a newbot . Use the command “/newbot” and proceed with the process.

Ensure the following.

a. Select a unique name for your bot

b. Get the Authorization token ( save it some where we need it shortly )

c. Set up a Description for your bot

Step 2: Channel Creation with Telegram

A Bot account can be used to respond to messages ( essentially reply ) . However that’s not convenient if we have to transmit messages to large audience . In such situations it’s useful to use “Channels” . So let’s create one.

New Channel

Name your Channel

Once the channel is created , you need to add the Bot created in step 1 as an administrator to enable sending broadcast messages .

It’s such a good idea to limit the rights the bot will have for this channel.

Step 3: Create Lambda Function

I’m not going to deep dive about how to create the Lambda Function .

Note : The script I have provided may not be the most optimized one . I have purposefully left it generic for customization . Please feel free to use it as you please.

Things to note while creating the Lambda Function

1. Ensure to create your Lambda Function in ap-south-1 “Mumbai Region”
2. Ensure to keep your execution trigger to not exceed 100 API calls within a 5 minute interval .

The lambda function has 2 critical steps

a. Fetching data from the Cowin API for the district / districts defined in the districts variable ( lines 15–48 )

b. Broadcasting the message to Telegram . ( lines 57–74 )

Observe that in line 67 I’m invoking the Telegram API with the botapikey (parameter botapikey ) from step 1 and the channel ID ( parameter chatid ) from step 2 and the message to be transmitted ( which is essentially the records that i fetched from the Cowin API )

url = f”https://api.telegram.org/{botapikey}/sendMessage?chat_id={chatid}&text={finalmessage}"

Step 4: Schedule the Lambda Function

For this I’m using AWS CloudWatch .

Click on Rules

Create a New Rule

Use a Cron Expression here to specify how frequently you want to run the function. Other considerations such as concurrency , scaling can be done at the Lambda function window.

Use Crontab.guru if in doubt .

Crontab.guru - The cron schedule expression editor

My Bot is broadcasting

Strategy Points to keep in mind :

1. The same approach is being used by several tech enthusiasts to provide customized updates . And this means the Cowin API Server is taking a lot of hits.
2. Avoid throttling your requests to the API . You may end up getting blocked interim.
3. Set your schedule for fetching the API sensibly. Sometimes the data can be in cache and upto 30 minutes old ( refer to the API Documentation )
4. If possible group with other like minded enthusiasts to narrow down your scope of search like a particular district , city , pincode whatever it is .
5. Respect fair use policies of all the involved technologies such as AWS , Telegram , API Setu . It’s a beautiful thing that almost all of these services are free of cost . Let’s respect that and dont get greedy with it.
6. Secure your bot API Keys with environment variables to avoid bot ID getting misused.

If you come across a suggestion , alternative approach , help please shout out. Glad to help .

Inspiration :

Berty Thomas on Twitter : @BertyThomas

Thanks.