@klaytn/kds-oracles v0.0.5

Oracle Starter Kit

• Oracle Starter Kit
  • Install
  • Quick Usage
  • Setup Hardhat configurations Baobab Klaytn network and variables
    • 1. Hardhat configurations
    • 2. Environment Variables
  • Deploy contracts
  • Interacting with Deployed Contracts
    • Chainlink Price Feeds
      • Parameters
      • Returns
      • Example
    • Change Chainlink price feed address
      • Parameters
      • Returns
      • Example
    • Chainlink Request \& Receive Data
      • Fund ChainLinkAPI contract
      • Parameters
        • Returns
      • Request ChainLinkAPI Data
        • Parameters
        • Returns
        • Example
      • Request ChainLinkAPI Data
        • Parameters
        • Returns
        • Example
    • Chainlink VRF Get a random number
      • Prerequisite
      • Request Chainlink Random number
        • Parameters
        • Returns
        • Example
      • Read Chainlink Random number
        • Parameters
        • Returns
        • Example
    • Chainlink Keepers
    • Witnet Price Feeds
      • Parameters
      • Returns
      • Example
    • Witnet Randomness
      • 1. Request new randomness
      • Parameters
        • Returns
        • Example
      • 2. Fetch Witnet random number
      • Parameters
        • Returns
        • Example
      • 3. Get the latest randomizing block
      • Parameters
        • Returns
        • Example
      • 4. Get the generated random number
      • Parameters
        • Returns
        • Example
    • Witnet Web Oracle Request
      • Compile the Witnet queries into Solidity contracts
        • Example
      • Execute Witnet Queries
        • Parameters
        • Returns
        • Example 1 - Fetch Coinprice
        • Example 2 - Post Request
  • Resources

Oracles take data from the outside world and put it into the blockchain for other smart contracts to consume. This is a hardhat project containing contracts and scripts for Chainlink and Witnet integrations.

Install

npm install -g @klaytn/kds-cli --force

Quick Usage

For a default set of contracts and tests, run the following within the required project directory:

> kds-cli oracle init

> cd oracle-starter-kit
> npm install --force

Above commands downloads the oracle-starter-kit folder structure in the current project directory. Enter inside the generated folder and install the packages as mentioned

From there you can run hardhat commands to compile your contracts, deploy those contracts to the network and run their associated unit tests.

Setup Hardhat configurations Baobab Klaytn network and variables

The default hardhat configurations can be modified in helper-hardhat-config.json Default configurations of baobab network 1001 are already using Klaytn vrf configurations.

1. Hardhat configurations

Hardhat configuration variables can be found in helper-hardhat-config.json in the root directory. Below is the configuration explaination for 1001 network.

• name - hardhat network name Ex: baobab
• linkToken - chainlink linktoken address. see Link Token Address for reference.
• keyHash - chainlink keyHash. see KeyHash Configurations for reference.
• chainLinkPriceFeed - chainlink pricefeed address for contract deployment. Ex: 0xf49f81b3d2F2a79b706621FA2D5934136352140c. see Chainlink Pricefeed Addresses for reference.
• oracle - chainlink oracle contract address. see Klaytn Operator Contracts for reference.
• jobId - chainlink jobId. Ex: ca98366cc7314957b8c012c72f05aeeb. see Chainlink JobID's for reference.
• vrfCoordinator - vrfCoordinator. see VRF Coordinator for reference.
• witnetPriceRouter - witnetPriceRouter Address Ex: 0xeD074DA2A76FD2Ca90C1508930b4FB4420e413B0 for Klaytn Testnet. See WitnetPriceRouter for reference.
• witnetRandomness - witnetRandomness Address. Ex: 0xb4b2e2e00e9d6e5490d55623e4f403ec84c6d33f for Klaytn Testnet. See WitnetRandomness Contract Addresses for reference.
• fee - fee

• fundAmount - fundAmount

2. Environment Variables

We will need to set environment variables by following below steps 1. copy .env.example file and rename to .env 2. Modify environment variables. Below is the explaination of each variable

• BAOBAB_RPC_URL - string https://api.baobab.klaytn.net:8651/ can be used. its the rpc url of blockchain.
• PRIVATE_KEY - string This is private key from wallet, ie MetaMask. This is required for deploying contracts to public networks.
• AUTO_FUND - boolean provide true, if needs to autofund
• VRF_SUBSCRIPTION_ID - number VRF Subscription id. Head over to VRF Subscription Page and create the new subscription.

IMPORTANT: MAKE SURE YOU DON'T EXPOSE THE KEYS YOU PUT IN THIS .env FILE saved in the package node_modules. By that, I mean don't push them to a public repo, and please try to keep them keys you use in development not associated with any real funds.

Don't commit and push any changes to .env files that may contain sensitive information, such as a private key! If this information reaches a public GitHub repository, someone can use it to check if you have any Mainnet funds in that wallet address, and steal them!

Get some Baobab Testnet KLAY and LINK Go to the Klaytn faucets to get some KLAY to configured private key account. Head over to the Chainlink faucets and get some LINK to configured private key account. Please follow the chainlink documentation if unfamiliar.

Deploy contracts

You should now be all setup! You can run any method now! Since we configured the environment variables and hardhat configurations so you don't really need to pass any configurations.

To comple contracts

npx hardhat compile

To deploy all contracts

npx hardhat deploy --network baobab

To run tests

npm run test

Interacting with Deployed Contracts

After deploying your contracts, the deployment output will give you the contract addresses as they are deployed.You can then use these contract addresses in conjunction with Hardhat tasks to perform operations on each contract.

Chainlink Price Feeds

The Price Feeds consumer contract has one task, to read the latest price of a specified price feed contract

npx hardhat read-price-feed --contract <deployedContractAddress> --network baobab

Parameters

deployedContractAddress - string Deployed Price feed consumer contract.

Returns

• price - price

Example

  npx hardhat read-price-feed --contract 0x6883956A235f8b823d547575812B08F4a720D76A --network baobab

  // By default it returns LINK/KLAY price feed value. 1 LINK = 32.9 KLAY
  /*
    Price is: 32915338976573950000
  */

Change Chainlink price feed address

The price feed address used while deployment can be changed using below method.

npx hardhat change-price-feed --contract <deployedContractAddress> --pricefeedaddress <pricefeedAddress> --network baobab

Parameters

deployedContractAddress - string Deployed Price feed consumer contract. pricefeedAddress - string pricefeed address. see Klaytn Pricefeed Addresses for reference.

Returns

• transaction hash - string transaction hash

Example

  // Change pricefeedaddress to WEMIX/USD 0x76Aa17dCda9E8529149E76e9ffaE4aD1C4AD701B price feed contract. 1 WEMIX = 0.8 USD
  npx hardhat change-price-feed --contract 0x6883956A235f8b823d547575812B08F4a720D76A --pricefeedaddress 0x76Aa17dCda9E8529149E76e9ffaE4aD1C4AD701B --network baobab
  /*
    Transaction Hash: 0x0741df94b257a29f73ff4b94d2f0d5cd91dae20f2bc9946dd00a954905d85936
  */

  npx hardhat read-price-feed --contract 0x6883956A235f8b823d547575812B08F4a720D76A --network baobab
  /*
    Price is: 800625678041836600
  */

Chainlink Request & Receive Data

The APIConsumer contract has two tasks, one to request external data based on a set of parameters, and one to check to see what the result of the data request is. Currently fetches the volume24hour data from https://min-api.cryptocompare.com/data/pricemultifull?fsyms=KLAY&tsyms=USD.

Fund ChainLinkAPI contract

This chainLinkApiData contract needs to be funded with link tokens first.

npx hardhat fund-link --contract <deployedContractAddress> --network baobab

Parameters

deployedContractAddress - string Deployed API consumer contract.

Returns

• transaction hash - string transaction hash

WARNING: chainlink-plugin-fund-link have not supported baobab network. You have to fund link tokens manually to the deployed chainLinkApiData contract. Get deployed contracts list using console.log(OracleSDK.readDeployedContracts()) method.

Request ChainLinkAPI Data

Once the deployed chainlinkAPI contract it's funded with link tokens, you can request external data by passing in a number of parameters to the request-data task.

npx hardhat request-data --contract <deployedContractAddress> --coinsymbol <coinsymbol> --coindecimals <coindecimals> --network baobab

Parameters

1. deployedContractAddress - string Deployed API consumer contract.
2. coinsymbol - string coinsymbol. see Coin Symbols for reference.
3. coindecimals - number coin supported decimals. Ex: 18 for KLAY

Returns

• transaction hash - string transaction hash

Example

  npx hardhat request-data --contract 0xddDC43f1ae46757C94Ec6dCDAa7E9b6738e0db0b --coinsymbol KLAY --coindecimals 18 --network baobab

  /*
    Transaction Hash: 0xe8f3d600a4789d16b0a0a9a739d67bbefcb088aebbc038687c4c9e7b1d56373a
  */

Request ChainLinkAPI Data

Once you have successfully made a request for external data, you can see the result via the read-data task. it retrives VOLUME24 from https://min-api.cryptocompare.com/data/pricemultifull?fsyms=KLAY&tsyms=USD from the contract

npx hardhat read-data --contract <deployedContractAddress> --network baobab

Parameters

1. deployedContractAddress - string Deployed API consumer contract.

Returns

• data - string Receives volume24 data without decimals

Example

  // Receives volume24 from RAW.KLAY.USD.VOLUME24HOUR in "https://min-api.cryptocompare.com/data/pricemultifull?fsyms=KLAY&tsyms=USD" result without decimals
  npx hardhat read-data --contract 0xddDC43f1ae46757C94Ec6dCDAa7E9b6738e0db0b  --network baobab

  /*
    Data is: 76993244391264860000000000
  */

Chainlink VRF Get a random number

The VRFConsumer contract has two tasks, one to request a random number, and one to read the result of the random number request.

Prerequisite

To start, go to VRF Subscription Page and create the new subscription. Save your subscription ID and put it in .env file as VRF_SUBSCRIPTION_ID:

  VRF_SUBSCRIPTION_ID=subscription_id

Then, deploy your VRF V2 contract consumer(if its not deployed already with the subscription id) to the network with your recent subscription using subscription id as constructor argument.

npx hardhat deploy --network baobab

Finally, you need to go to your subscription page one more time and add the address of deployed contract as a new consumer (https://vrf.chain.link/klaytn-testnet/). Once that's done, you can perform a VRF request with the request-random-number task.

NOTE: Make sure to add LINK funds to the subscription from the chainlink UI screen:

Request Chainlink Random number

npx hardhat request-random-number --contract <deployedContractAddress> --numwords <randomNumbersCount> --network baobab

Parameters

deployedContractAddress - string Deployed RandomNumberConsumer contract address randomNumbersCount - number No of random numbers to be generated

Returns

• transaction hash - string Transaction hash

Example

  npx hardhat request-random-number --contract 0x3AFb1Ce6B16EcB1e367cCC23d99Ea4D9Ef497BE3 --numwords 3 --network baobab
  /*
    Transaction Hash: 0x770892fb09f00fbc25aa4118c4e59bae8f106e550d9295ddab62db79d708821a
  */

Read Chainlink Random number

Once you have successfully made a request for a random number, you can see the result via the read-random-number task:

  npx hardhat read-random-number --contract <deployedContactAddress> --network baobab

Parameters

deployedContractAddress - string Deployed RandomNumberConsumer contract address

Returns

• randomNumbers - random numbers

Example

  npx hardhat read-random-number --contract 0x3AFb1Ce6B16EcB1e367cCC23d99Ea4D9Ef497BE3 --network baobab
  /*
    Random Numbers are: 25039093979060057973217505519617231457599792522931877947740225763662111327605,66221833599132925893563674221180186695699650058371972286077266023247996014608,62169596737219453842215058746401741770368274717351892705020984286494216685598
  */

Chainlink Keepers

WARNING: The Baobab network is not supported by Chainlink Automation (aka Chainlink Keepers) yet. Because of that, the response of the Keeper will always be 0. You can ignore this feature in the current version.

Witnet Price Feeds

The Witnet Price Feeds consumer contract has one task, to read the latest price of a specified price feed contract

  npx hardhat read-witnet-price-feed --contract <deployedContractAddress> --id <id> --network baobab

Parameters

deployedContractAddress - string Deployed WitnetPriceFeed contract address id - string id4 is the witnet pricefeed ID. Ex: 0x6cc828d1 for Price-KLAY/USD-6. See Klaytn Witnet PriceFeeds for reference.

Returns

• price - price of KLAY/USD.

Example

  // 1 KLAY = 0.20 USD
  npx hardhat read-witnet-price-feed --contract 0x37291E5036db32DFe714823dE7A96253676e6487 --id 0x6cc828d1 --network baobab

  /*
    Last price is: 209744
  */

Witnet Randomness

The Witnet Randomness has 4 tasks. Make sure the deployWitnetRandomNumber method successful execution.

This 2-step process preserves unpredictability of the random numbers that you get because it guarantees that the number is derived from a seed that was generated only after the request was sent.

NOTE: Initially 1 and 2nd step has to be completed sequentially. Only after that 3rd or 4th can be executed for fetching a random number.

1. Request new randomness

Requesting the new randomness. Once the the request to new randomness is performed successfully. The other tasks can be performed after transaction submission.

  npx hardhat request-witnet-randomness --contract <deployedContractAddress> --network baobab

Parameters

deployedContractAddress - string Deployed Deployed Witnet RandomNumber contract address

Returns

• transaction hash - Transaction hash

Example

  npx hardhat request-witnet-randomness --contract 0x8937C127F3060fF8a23E9a0fb5AEA10bc30e28be --network baobab
  /*
    Transaction Hash: 0x809addb235dc953c90a563c396c11978a359b574336564c7ec890514c961e050
  */

2. Fetch Witnet random number

Initiate fetch witnet random number transaction.

WARNING: Calling fetch-witnet-random-number right after request-witnet-randomness will most likely cause the transaction to revert. Please allow 5-10 minutes for the randomization request to complete

  npx hardhat fetch-witnet-random-number --contract <deployedContractAddress> --network baobab

Parameters

deployedContractAddress - string Deployed Witnet RandomNumber contract address

Returns

• transaction hash - Transaction hash

Example

  npx hardhat fetch-witnet-random-number --contract 0x8937C127F3060fF8a23E9a0fb5AEA10bc30e28be --network baobab
  /*
    Transaction Hash: 0x0eb8fe1217ecdc3860009bc49f5319cab6ffdedd80877c39df02899a3542db24'
  */

3. Get the latest randomizing block

  npx hardhat read-latest-randomizing-block --contract <deployedContractAddress> --network baobab

Parameters

deployedContractAddress - string Deployed Witnet RandomNumber contract address

Returns

• randomizingBlock - randomized block value

Example

  npx hardhat read-latest-randomizing-block --contract 0x8937C127F3060fF8a23E9a0fb5AEA10bc30e28be --network baobab
  /*
    The latest randomizing block is: 113690138
  */

4. Get the generated random number

fetches the generated random number

NOTE: Make sure first 2 steps are executed sequentially.

  npx hardhat read-witnet-random-number --contract <deployedContractAddress> --network baobab

Parameters

deployedContractAddress - string Deployed Witnet RandomNumber contract address

Returns

• randomNumber - generated random number

Example

  npx hardhat read-witnet-random-number --contract 0x8937C127F3060fF8a23E9a0fb5AEA10bc30e28be --network baobab
  /*
    Random Number is: 1392104028
  */

Witnet Web Oracle Request

We have 2 examples for Witnet HTTP Request:

• KlayPrice: a GET request example to get Klay token price in USD
• postRequestExample: a POST request example echoes back any data and headers that you send in your POST requests (based on this tutorial)

Inside witnet-queries folder you will find predefined Witnet oracle queries.

You can follow this link to learn how to create other queries.

Compile the Witnet queries into Solidity contracts

npx rad2sol --target ./witnet-queries --write-contracts ./contracts/witnet-requests

Example

  npx rad2sol --target ./witnet-queries --write-contracts ./contracts/witnet-requests

Execute Witnet Queries

After the contracts have been created, you can query locally to preview the result by running:

npx witnet-toolkit try-query --from-solidity ./contracts/witnet-requests/<contractFileName>

Parameters

contractFileName - string generatedSolFileName

Returns

• Result - string

Example 1 - Fetch Coinprice

  // 1 KLAY = 0.19 USD. Divide the return value by 10^6 to get actual coin price result.
  npx witnet-toolkit try-query --from-solidity ./contracts/witnet-requests/coinPrice.sol
  /*
    Result: 195467
  */

Example 2 - Post Request

  // Gets parsed data of headers.Header-Name from the post api 
  npx witnet-toolkit try-query --from-solidity ./contracts/witnet-requests/postAPI.sol
  /*
    Result: "Header-Value"
  */

NOTE: If above tryWitnetQueries is stuck, please try to run command shown in below snapshot npx witnet-toolkit, install the binary once in the machine and retry above method

Resources

• Chainlink Documentation
• Witnet Documentation
• Hardhat Documentation