80/20 #4 — Building a notification app for BAYC transactions on ethereum

Published in

Coinmonks

3 min readMar 13, 2022

Goals

Last blog we wrote could not create a lottery app because the original design required the full history of buyers of a token of a smart which cannot easily be obtained from the contract. This project is an attempt to create a store of the transaction events in Kafka to solve for this general problem
Create a platform that can be used to solve this problem generally i.e. can connect to any smart contract and subscribe and store the emitted events in a kafka topic which can then be consumed in whatever way the client requires
To prove the concept we chose to use the platform to consume the BAYC transaction events, store them in Kafka and then publish those events to a Discord channel

Technologies

Value prop

Enable accessible history of events to support many realtime event-based smart contract use cases
Consumers have flexibility to choose how they want to consume e.g. publish to database for product-based queries, analytics platform for analytical queries or consume the events directly e.g. our BAYC use case
If anything goes wrong in their downstream they can replay events

Github link with instructions to setup the Penrose App — https://github.com/olwflynn/penrose-app

Discord channel to receive Bored Ape Yacht Club transfer notifications — https://discord.gg/sfj2KjqS

Watch Demo — Making storing state easier in blockchains

User journey to subscribe to a new contract event

Add contract address (and ABI optionally) and event name in the admin UI. This will add the contract event to the platform but it will be inactive i.e. not listening to events
Click on subscribe button in order to start listening to the defined events
Successfully stored events for the chosen smart contract can then be viewed in the Kowl UI. These are accessible via the relevant Kafka topic.

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