Discovery

TDEX clients often use multiple daemons. These daemons can provide the same market to the trader client. In this case, it is up to the trader to choose the provider that best suits his needs. For instance if two daemons provides a market LBTC<->USDT, the trader might want to choose the daemon that offers him the lowest price for instance.

For this kind of use case, the SDK provides a class named Discoverer. It allows to "discover" the best daemon (among a list) according to a given strategy. The "strategy" using to select daemons is called Discovery. It is basically a function with the following signature:

export type Discovery = (  clients: TraderClientInterface[], // 1 client = 1 provider  discoveryOpts: DiscoveryOpts, // data about the trade  errorHandler?: (err: any) => Promise<void> // optional async error handler, if `undefined` errors will be ignored) => Promise<TraderClientInterface[]>;
export interface DiscoveryOpts {  market: MarketInterface; // which market the trader is targetting  amount: number; // using for preview  asset: string; // using for preview  type: TradeType; // type of trade BUY or SELL}

Discoverer takes Discovery function in constructor. the SDK exports two discovery functions: bestBalanceDiscovery and bestPriceDiscovery. However, feel free to write your own according to your needs.

Best balance discovery

bestBalanceDiscovery will make gRPC calls on balances endpoints for each providers. Then, it compares all the balances and return the one with the greater amount. In other words, it allows you to select the provider that has the most liquidity for the targeted market.

import { Discoverer, bestBalanceDiscovery } from "tdex-sdk";
const myProvidersClients: TraderClientInterface[] = [...]
const discoverer = new Discoverer(  myProvidersClients,  bestBalanceDiscovery,);
const discoveryOpts = ... // discoveryOpts describes the tradeconst bestBalanceProviderClient = (await discoverer.discover(discoveryOpts))[0];// make your trade on the daemon with the greatest liquidity

Best price discovery

bestPriceDiscovery will make gRPC calls on marketPrice endpoints for each providers. Then, it compares all the prices and return the client with the lowest price.

import { Discoverer, bestPriceDiscovery } from "tdex-sdk";
const myProvidersClients: TraderClientInterface[] = [...]
const discoverer = new Discoverer(  myProvidersClients,   bestPriceDiscovery,);
const discoveryOpts = ... // discoveryOpts describes the tradeconst bestPriceProviderClient = (await discoverer.discover(discoveryOpts))[0];// make your trade on the daemon with the lowest price

Combine Discovery

The Javascript SDK provides also an utility function using to combine several Discovery functions.

import { combineDiscovery, bestPriceDiscovery, bestBalanceDiscovery } from "tdex-sdk";
const lowestPriceThenGreatestBalance = combineDiscovery(bestPriceDiscovery, bestBalanceDiscovery);// this discovery function will firt look at the lowest price for each providers (bestPriceDiscovery)// then, if there is several providers providing the lowest price, the function will use bestBalanceDiscovery to select the provider.
const discoverer = new Discoverer(  myProvidersClients,   lowestPriceThenGreatestBalance,);