Proxy Round Robin

// @NO_AUTO_TRANSPILE
import ccxt from '../../js/ccxt.js';
import ololog from 'ololog';
import ansicolor from 'ansicolor';
const log = ololog.configure({ locate: false });
ansicolor.nice;
//-----------------------------------------------------------------------------
// this script loads markets from all exchanges
// if it cannot connect to an exchange, it falls back to an alternative route via proxy
// it will retry to load a exchange until it either reaches the exchange or runs out of proxies
//-----------------------------------------------------------------------------
process.on('uncaughtException', e => { log.bright.red.error(e); process.exit(1); });
process.on('unhandledRejection', e => { log.bright.red.error(e); process.exit(1); });
//-----------------------------------------------------------------------------
let loadExchange = async (exchange) => {
    await exchange.loadMarkets();
    log(exchange.id.green, 'loaded', exchange.symbols.length.toString().bright.green, 'symbols', (exchange.proxy ? exchange.proxy : '_').blue);
};
//-----------------------------------------------------------------------------
let tryAllProxies = async function (exchange, proxies) {
    let currentProxy = 0;
    let maxRetries = proxies.length;
    // a special case for ccex
    if (exchange.id == 'ccex')
        currentProxy = 1;
    for (let numRetries = 0; numRetries < maxRetries; numRetries++) {
        try {
            exchange.proxy = proxies[currentProxy];
            await loadExchange(exchange);
            break;
        }
        catch (e) {
            currentProxy = ++currentProxy % proxies.length;
            if (e instanceof ccxt.DDoSProtection) {
                log.bright.yellow(exchange.id, '[DDoS Protection] ' + e.message);
            }
            else if (e instanceof ccxt.RequestTimeout) {
                log.bright.yellow(exchange.id, '[Request Timeout] ' + e.message);
            }
            else if (e instanceof ccxt.AuthenticationError) {
                log.bright.yellow(exchange.id, '[Authentication Error] ' + e.message);
            }
            else if (e instanceof ccxt.ExchangeNotAvailable) {
                log.bright.yellow(exchange.id, '[Exchange Not Available] ' + e.message);
            }
            else if (e instanceof ccxt.ExchangeError) {
                log.bright.yellow(exchange.id, '[Exchange Error] ' + e.message);
            }
            else if (e instanceof ccxt.NetworkError) {
                log.bright.yellow(exchange.id, '[Network Error] ' + e.message);
            }
            else {
                throw e;
            }
        }
    }
};
//-----------------------------------------------------------------------------
let proxies = [
    '',
    'https://cors-anywhere.herokuapp.com/',
    'https://crossorigin.me/',
];
let exchanges = [];
async function main() {
    // instantiate all exchanges
    await Promise.all(ccxt.exchanges.map(async (id) => {
        let exchange = new (ccxt)[id]();
        exchanges.push(exchange);
        await tryAllProxies(exchange, proxies);
    }));
    let succeeded = exchanges.filter(exchange => exchange.markets ? true : false).length.toString().bright.green;
    let failed = exchanges.filter(exchange => exchange.markets ? false : true).length;
    let total = ccxt.exchanges.length.toString().bright.white;
    console.log(succeeded, 'of', total, 'exchanges loaded', ('(' + failed + ' errors)').red);
}
main();