Substrate Events Listener & Storage Adapter

A simple node.js based web-socket listener which subscribes to Parity Substrate runtime events and stores them in a data store. At the moment, MongoDB is supported but new stores can be added easily.

Substrate node and data sink related config lives in the .env file.

Why?

Ideally, we should avoid running iterators and loops on the on-chain data stored in a blockchain runtime or contracts. The chain should store the minimum amount of data which is needed for conflict resolution. Everything else can and should be stored off-chain with it's hash on the chain. In cases where on-chain data is stored in lists or maps and needs to be shown on a UI, an event based approach can be used to build an off-chain storage which can be queried from the UI.

This app listens to all Substrate runtime events using the web-socket connection, parses each event based on (extensible) custom rules and then stores the processed event data in one or more data stores. This off-chain storage can then be used for data analysis, querying, showing it on the UI, etc.

Usage

1. Clone this repository.
2. Make sure your Substrate node and MongoDB is running. Update the .env file with the server and ports, if needed.
3. Set event section filters (comma separated list of module names, no spaces) in the .env file to filter events,

SUBSTRATE_EVENT_SECTIONS=all

SUBSTRATE_EVENT_SECTIONS=balances,assets,token

4. Run the following docker command to build the image,

docker build -t substrate-listener .

5. Run the following docker command to start the listener in a container,

docker run -d substrate-listener

Add new data stores

To use a new data store with the listener,

1. Create the storage client in the adaptors dir (similar to existing mongo client)
2. Add the connection config in .env and use it in the js client
3. Import the new js client in dataService.js
4. Use init() for initializing the client - connection, priming, etc.
5. Use insert() for (of course) inserting substrate events data

Note

This app is not for production usage. It is mainly built to suggest an event based pattern for priming an off-chain storage. Please feel free to extend and use as needed.