Concordium Contracts Events Indexer

What it is?

On Concordium Chain. The contracts can be coded to emit events. Which are the source for Off chain products to analyze whats happening on chain. This project provides a reference implementation for Node JS in Typescript to listen to such events and index them in database to be queried account to the business logic.

Components

• Server : Its the backend code for a web service to which the users can connect and query for aggregated events and listener which has the code for long running process to listen for contract events.
• Server Rust Bindings : Rust code that compiles to wasm and provides helper methods to deserialize the events.

Build

cd server-rust-bindings
yarn run build

Execute

The following command will execute the listener and will continuously run and look for new events.

NODE_ENDPOINT=localhost
NODE_PORT=20002
DB_CONN_STRING="mongodb://root:example@localhost:27017/"
STARTING_BLOCK_HASH="f44a796e78dafe98d669e3aa9c5bc8770f224f5236adc7a3cd90fdecf1d4b361"

cd server
yarn run dev:listener

The following command will run the web backend and allows the user to query for aggregated events.

DB_CONN_STRING="mongodb://root:example@localhost:27017/"
cd server
yarn run dev:web

How to use?

This repository is meant as a template repository / boilerplate code for creating a custom events listener for Concordium Blockchain. Read more about it.

Prerequisites

• yarn : Used to build and run listener and web server.
• cargo & Rust : Used to build WASM dependencies for listener & web server.

Build

yarn && yarn run build

Execute

• Listener

cd server
yarn run dev-listener

• Web Server

cd server
yarn run dev-web

Debug

Typescript files can be executed with any typescript debugger. We have been using kakumei.ts-debug

Customize

To be able to listen to custom events The files that would need changing are

• listener-config.ts : This are listener configuration file and contains documented functions to be able to configure various aspects of the process related to listener.

• app.ts : This file is the web server. The developer needs to edit this file to be able to query the aggregated events from the database. Currently there are following 2 methods added for the developer to be able to query the events which are persisted

  • '/supply/index/:index/subindex/:subindex/token/:tokenId' : Returns the aggregated total supply of the token.

    • :index : Index of the CIS2 contract.
    • :subindex : Sub Index of CIS2 contract.
    • :tokenId : Token Id.

  • '/market/index/:index/subindex/:subindex/tokens' : Returns list of tokens listed on the marketplace with their quantities.

    • :index : Index of the market contract.
    • :subindex : Sub Index of the market contract.