mongodb.js

"use strict";

const http = require("http");
const MongoClient = require('mongodb').MongoClient;

let collection = null;
let documentId = null;

MongoClient.connect("mongodb://user:pass@hostname:port/dbName", (err, db) => {
    
    if (err) {
        console.error(err);
        process.exit();
        return;
    }
    
    db.collection("test", (err, _collection) => {
        collection = _collection;
        collection.findOne()
            .then(doc => {
                if (doc) {
                    return Promise.resolve(doc);
                } else {
                    return collection.insert({ count: 0 });
                }
            })
            .then(doc => {
                documentId = doc._id; 
            })
            .catch(err => {
                console.error(err);
            });
    });
});

const server = http.createServer((req, res) => {
    
    res.setHeader("Content-Type", "text/plain");
    res.writeHead(200);
    
    if (!documentId) {
        res.end("documentId is null. retry please.");
        return;
    }
    
    let startAt = Date.now();
    let readTime = -1;
    let count = -1;
    
    collection.findOne(documentId)
        .then(doc => {
            readTime = Date.now() - startAt;
            ++doc.count;
            count = doc.count;
            startAt = Date.now();
            return collection.updateOne({ _id: documentId }, doc);
        })
        .then(() => {
            res.end(`This is DocumentDB protocol support for MongoDB Read/Update Demo. -> count=${count} (r/w: ${readTime}/${Date.now() - startAt} ms)`);
        })
        .catch(err => {
            console.error("error!", err);
            res.end(JSON.stringify(err));
        });
});

server.listen(process.env.PORT);