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ETH-USDT Oracle

The Oracle works on the basis of publisher-subscriber technique. Any dApp can generate request to get latest ETH price in USDT. Node (client) listens for generated request and reports price.

Contracts

  1. EthPriceOracle.sol - Used by nodes(client).
  2. Caller.sol - Used by dApp.

Working

  1. dApp calls updateLatestPrice() of Caller.sol contract which returns a randomly generated id.
  2. Node listens for GetLatestEthPrice event of EthPriceOracle.sol contract and starts reporting latest ETH price in USDT for request from Binance ticker.
  3. As soon as responses for request id reaches to threshold value, mean of all the reported responses is considered as final price.
  4. dApp listens for PriceUpdated event of Caller.sol to get the updated price.
  5. dApp can also access the latest price reported by oracle by calling getEthPrice().

Environment Variables

To run node(client), you will need to add the following environment variables to your .env file:

  • ORACLE_PRIVATE_KEY
  • PROVIDER_URL
  • ETH_ORACLE_ADDRESS

To deploy contracts, you will need to add the following environment variables to your .env file:

  • PRIVATE_KEY
  • MUMBAI_URL

Deployment

To deploy the contracts run

  npm install
  npx hardhat run scripts/deploy.ts --network [NETWORK_NAME]

Running a node

To start node on local run

  npm start

Running Tests

To run tests, run the following command

  npm run test

Usage

  1. Deploy the contract to matic mumbai.(Add PRIVATE_KEY and MUMBAI_URL in .env)
  npx hardhat run scripts/deploy.ts --network mumbai

The above command will deploy EthPriceOracl.sol and Caller.sol contract. It will also update threshold to 1.

  1. Add/Update ETH_ORACLE_ADDRESS and CALLER_ADDRESS in .env file which you get from above command.
  2. Add/Update ORACLE_PRIVATE_KEY in .env file.
  3. Grant ORACLE_ROLE to ORACLE_PRIVATE_KEY address. Change ORACLE_ADDRESS in scripts/addOracle.ts file.
  npx hardhat run --network mumbai scripts/addOracle.ts
  1. Start running node.
  npm start
  1. Generate a requestId to be reported by oracle
  npx hardhat run scripts/getEthPrice.ts --network mumbai

As soon as the above tx is confirmed the node will report eth price from API and report to oracle.

  1. Latest eth price reported by oracle can be retrieved with the following command.
npx hardhat run scripts/getLatestEthPrice.ts --network mumbai