Recently, the Indian govt announced vaccination for 18-45 age group from 1st May ✨

Anyone who wants to vaccinate in this age group can visit official website or install Arogya Setu App from Google Play to book a slot for vaccination.

The problem is vaccination is limited and slots are also limited, so whenever anyone wanted to book a slot, it always shows booked on official website 😢

After visiting website multiple times in a day to book my slot, I was unable to find any available slots because it always shows booked 🥺

Now, on the same website when you click on a search to find slots, it calls one API which is used to get availability of slots for selected district -

Cowin already have Public APIs available, which anyone can use to check slots availability.

Out of all public APIs, I used calendarByDistrict API which returns planned vaccination sessions for 7 days from a specific date for a given district.

Which returns response that contains all required information like center details, session details and available slot details 🙌🏼

{
  "centers": [
    {
      "center_id": 1234,
      "name": "District General Hostpital",
      "state_name": "Maharashtra",
      "district_name": "Pune",
      "pincode": "411057",
      "lat": 28.7,
      "long": 77.1,
      "from": "09:00:00",
      "to": "18:00:00",
      "fee_type": "Free",
      "sessions": [
        {
          "session_id": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
          "date": "10-05-2021",
          "available_capacity": 50,
          "min_age_limit": 18,
          "vaccine": "COVISHIELD",
          "slots": [
            "FORENOON",
            "AFTERNOON"
          ]
        }
      ]
    }
  ]
}

You may visit this link to get an idea about detailed response here.

For sending web requests in ruby language, Net::HTTP class available. For above request, you can execute below code in your rails console for getting center list JSON -

# District - Pune, Date 10th May, 2021. You can modify it as per your requirement
uri = URI.parse("https://cdn-api.co-vin.in/api/v2/appointment/sessions/public/calendarByDistrict?district_id=363&date=10-05-2021")

results = Net::HTTP.get(uri) 
results = JSON.parse(result).with_indifferent_access

It'll give you a list of centers like this in your rails console.

Now we have results hash variable available in which root element is centers like this -

{
  "centers": [
    {
      "center_id": 1234,
      "name": "District General Hostpital"
      "sessions": [
        {
          "date": "10-05-2021",
          "available_capacity": 50,
          "min_age_limit": 18
        }
      ]
    }
  ]
}

Basically, from above data, we need to compare following attributes to get available slots -

1. min_age_limit attribute comparison with 18 (min_age_limit == 18)
2. available_capacity is greater than 0 (available_capacity > 0)

Alright, let's search for available slots then -

availability = {}
result[:centers].each do |center|
    # 1st condition - Checking Age
    sessions = center[:sessions].select{ |c| c[:min_age_limit] == 18 }
    # 2nd condition - Checking Availability
    sessions_with_availability = sessions.select{ |s| s[:available_capacity] > 0 }
    # Collect date for specific pincode if there's vaccine availability
    availability[center[:pincode]] = sessions_with_availability.collect{ |s| s[:date] } if sessions_with_availability.any?
end

That's it 🥳 availability variable will have following hash value if any availability found.

❯ availability
❯ {413102=>["02-05-2021"], 411044=>["02-05-2021"]}

It contains dates on which slots available for particular Pincode 🔖

Now, as we have all the required data with us, we can do following thing with this script -

1. Write a fancy output, maybe create mail/SMS to send notification.
2. Create a cron-job to run it every 1 minute and notify if there's avaibility.

Apart from this, you may also create a minimal rails app to get user details from users and send notifications to help them find available slots -

Conclusion

Automation is good sometimes if used properly. In this case also, if you wanted to run your cron-job in large intervals, say once in 10 minutes, it's fine.

But, if you run it on a very small interval and access cowin API frequently, there might be a chance that your IP might be blocked to access those API and you're no more able to access it. So use it wisely ✌🏼

Reference

• You can find whole script here.

If you found this article insightful and helpful, then do let me know your views in the comments 🙂

In case you want to connect with me, here's my twitter - rishipi

Original article available over here - rishi.tips/p/find-vaccine-slots