log-viewer/backend/server.js

const { MongoClient } = require("mongodb");
const express = require('express');
const minio = require('minio');

/*============== VARIABLE DECLARATION ==============*/
// Mongo set-up variables
const mongoCollection = process.env.MONGO_COLLECTION || 'eventlog';
const mongoUri = process.env.MONGO_URI || 'mongodb://127.0.0.1:27017/default?replicaSet=rs0';

// Minio set-up variables
const minioAccessKey = process.env.MINIO_ACCESS_KEY || 'kspace-mugshot';
const minioSecretKey = process.env.MINIO_SECRET_KEY || '2mSI6HdbJ8';
const minioHostname = process.env.MINIO_HOSTNAME || '127.0.0.1';
const minioPort = process.env.MINIO_PORT || 9000;
const minioScheme = process.env.MINIO_SCHEME || 'http';
const minioBucket = process.env.MINIO_BUCKET || 'kspace-mugshot';
console.info("Using bucket:", minioBucket);
const historyNumber = parseInt(process.env.HISTORY_AMOUNT) || 10;

// Stream set-up variables
let changeStream;
const options = { fullDocument: "updateLookup" };
const pipeline = [];
const PORT = process.env.PORT || 3002;

// Create Mongo client
const mongoClient = new MongoClient(mongoUri);


/*============== CODE ==============*/
async function run() {

  console.log('server.js has been launched');
  const app = express();

  await mongoClient.connect();
  const collection = mongoClient.db().collection(mongoCollection);

  changeStream = collection.watch(pipeline, options);
  console.log("Started watching changes in database");
  console.log("Minio hostname:", minioHostname);
  console.log("Minio port:", minioPort);
  console.log("Minio protocol:", minioScheme);

  // Triggers on GET at /event route
  app.get('/events', async function (request, response) {
    let minioClient = new minio.Client({
      endPoint: minioHostname,
      port: parseInt(minioPort),
      useSSL: minioScheme == 'https',
      accessKey: minioAccessKey,
      secretKey: minioSecretKey
    });

    async function wrapEvent(doc) {
      let arr = [];
      let blob;
      if (doc && doc.screenshot_count) {
        for (let i = 1; i <= doc.screenshot_count ; i++) {
          arr.push({
            url: await minioClient.presignedUrl('GET', minioBucket,
              `${doc.camera}/${doc._id}/${i}.jpg`, 60 * 60)
          });
        }
      } else if (doc && doc.screenshots) {
        for (let j = 0; j < doc.screenshots.length; j++) {
          let path = doc.screenshots[j];
          arr.push({
            url: await minioClient.presignedUrl('GET', minioBucket,
              `thumb/${path}`, 60 * 60),
            orig: await minioClient.presignedUrl('GET', minioBucket,
              `${path}`, 60 * 60)
          });
        }
      };

      if (arr.length > 0) {
        blob = JSON.stringify({...doc, screenshots: [...arr]});
      } else {
        blob = JSON.stringify({...doc});
      }
      return `event: log-entry\ndata: ${blob}\n\n`
    }

    // Notify SSE to React
    const header = { 'Content-Type': 'text/event-stream', 'Connection': 'keep-alive' };
    response.writeHead(200, "OK", header);

    const historyCursor = collection.find().sort({$natural:-1}).limit(historyNumber);

    historyCursor.forEach(async (document) => {
      response.write(await wrapEvent(document));
    })

    changeStream.on("change", async(data) => {
      response.write(await wrapEvent(data.fullDocument));
    });
  });

  app.listen(PORT);
  console.log(`Server listening at 127.0.0.1:${PORT}`);
}

run().catch(console.dir);