http-alive/server.js

keep your web service always online

"use strict";
var __importStar = (this && this.__importStar) || function (mod) {
    if (mod && mod.__esModule) return mod;
    var result = {};
    if (mod != null) for (var k in mod) if (Object.hasOwnProperty.call(mod, k)) result[k] = mod[k];
    result["default"] = mod;
    return result;
};
Object.defineProperty(exports, "__esModule", { value: true });
const http = __importStar(require("http"));
const http_proxy_lite_1 = require("http-proxy-lite");
const util_1 = require("./util");
const port = process.env.PORT;
const proxy = http_proxy_lite_1.createProxyServer();
const endpoints = [
    { url: `http://localhost:${process.env.MASTER_PORT}`, healthy: true, fall: 0 },
    { url: `http://localhost:${process.env.SLAVE_PORT}`, healthy: true, fall: 0 }
];
http
    .createServer((req, res) => {
    const ep1 = util_1.sample(endpoints.filter(e => e.healthy));
    if (!ep1) {
        res.writeHead(500, { 'Content-Type': 'text/plain' });
        res.end('Internal Server Error');
        return;
    }
    proxy
        .web(req, res, { target: ep1.url })
        .on('error', e => {
        console.error(e);
        ep1.healthy = false;
        ep1.fall++;
        setTimeout(() => {
            ep1.healthy = true;
        }, 10 * 1000 * ep1.fall);
        const ep2 = endpoints.find(e => e.url !== ep1.url);
        proxy
            .web(req, res, { target: ep2.url })
            .on('error', e => {
            console.error(e);
            res.writeHead(500, { 'Content-Type': 'text/plain' });
            res.end('Internal Server Error');
        })
            .on('end', () => {
            ep2.fall = 0;
        });
    })
        .on('end', () => {
        ep1.fall = 0;
    });
})
    .listen(port);
console.log(`Listening on http://localhost:${port} ..`);
process.on('uncaughtException', err => {
    console.error('uncaughtException:', err);
});