Price feed adapter

Fetches price from exchanges, takes median and writes them to chain. Currently supported price sources are Coinmarketcap, Coingecko, Cryptocompare and Binance. All the actions are written as small tasks.

This repo holds several components:

• the adapter, which is the js module in ./src, gets deployed to a chainlink node (by node operators) under the bridge name dock_usd_bridge
• the jobspecs, which define when the adapter function get scheduled to run
• the server, which acts as a middleware for price data APIs (Coinmarketcap, Coingecko, etc.), and exposes:
  • each price data API endpoint
  • an endpoint that returns the median of all these APIs' prices

Deploying the adapter

The default adapter is the module in ./src. This is for chainlink node operators to deploy on their node.

This bridge should be deployed under the name dock_usd_bridge. This can be checked in the admin dashboard of the oracle's chainlink node.

Customizing the adapter deployment

Alternatively, node operators can tweak the deployment and jobspec in the following ways:

To get price for DOCK/USD pair

import { execute } from './adapter';
import { coinmarketcap } from './endpoint';
import { coingecko } from './endpoint';

// Get price from coinmarketcap
const data = await execute({ id: "1", data: {endpoint: coinmarketcap.NAME}} as AdapterRequest );

// Get price from coingecko
const data = await execute({ id: "1", data: {endpoint: coingecko.NAME}} as AdapterRequest );

// To get median price from multiple exchanges, the choice of exchanges is hardcoded in code
import { MEDIAN_PRICE } from './adapter';
const data = await execute({ id: "1", data: {endpoint: MEDIAN_PRICE}} as AdapterRequest );

The result key of data will contain the price.

To write price for DOCK/USD pair on chain

import { execute, WRITE_CMC_PRICE, WRITE_MEDIAN_PRICE } from './adapter';

// To write coinmarketcap price
const data = await execute({ id: "1", data: {endpoint: WRITE_CMC_PRICE}} as AdapterRequest );

// To write median price
const data = await execute({ id: "1", data: {endpoint: WRITE_MEDIAN_PRICE}} as AdapterRequest );

// To write the price on chain when the current price has either deviated by 5% or is stale by 30 seconds
const data = await execute({ id: "1", data: {endpoint: WRITE_MEDIAN_PRICE, thresholdPct: 5, idleTime: 30}} as AdapterRequest );

The result key of data will contain the block number.

HTTP server

Running the server. By default, runs at port 8080

ts-node scripts/run-server.ts

Eg. To fetch price at Binance, send GET request as

curl -X POST -H "Content-Type: application/json" http://localhost:8080 --data '{"id":"1","data": {"endpoint": "Binance"}}'

Eg. To fetch median price of all sources, send GET request as

curl -X POST -H "Content-Type: application/json" http://localhost:8080 --data '{"id":"1","data": {"endpoint": "median_price"}}'

Eg. To write median price of all sources on chain, send GET request as

curl -X POST -H "Content-Type: application/json" http://localhost:8080 --data '{"id":"1","data": {"endpoint": "write_median_price"}}'

Jobspecs

There are 2 jobspecs. Each of them is initiated by a cron trigger each minute. They assume the adapter has been deployed with the bridge named dock_usd_bridge.
Spec 1 will always write on the chain.
Spec 2 will write on the chain when either the price deviates by 1% or 3600 seconds (1 hour) has passed.

Running the server

ts-node scripts/run-server.ts

Env variables

The following environment variables need to be set for the adapter to work.

CMC_API_KEY=<Coinmarketcap API key>
MinimumAnswersForPriceFeed = <Minimum answers (from different sources) required for price feed>
MinGasPrice = <Minimum gas price>
MaxGas = <Maximum allowed gas for a txn>
NODE_ENDPOINT=<TCP endpoint of the blockchain node>
ORACLE_SK=<Secret key for Oracle's account>
ORACLE_ADDRESS=<EVM address of the Oracle>
PROXY_ADDRESS=<EVM address of the proxy to price aggregator contract>