NodeJS Lambda for Processing Video from S3 Event

index.js

const s3Util = require("./s3-util");
const childProcessPromise = require("./child-process-promise");
const path = require("path");
const os = require("os");
const fs = require("fs");
const https = require("https");

const OUTPUT_BUCKET = process.env.OUTPUT_BUCKET;
const VIDEO_MIME_TYPE = process.env.VIDEO_MIME_TYPE;
const LAMBDA_SHARED_SECRET = process.env.LAMBDA_SHARED_SECRET;

exports.handler = async (eventObject, context) => {
  const eventRecord = eventObject.Records && eventObject.Records[0];
  const inputBucket = eventRecord.s3.bucket.name;
  const key = eventRecord.s3.object.key;
  const id = context.awsRequestId;
  const workdir = os.tmpdir();

  // Get the filename without the path
  const filename = path.basename(key); // /path/1/.../n/filename

  // Names for files once they are placed in the output S3 bucket
  const lowResKey = "processed/lowRes/" + filename;

  // Names for files while they reside in Lambda prior to uploading to output bucket
  const inputFile = path.join(workdir, id + path.extname(key));
  const lowResOutputFile = path.join(workdir, "lowRes-" + id + ".mp4");

  console.log("Download file from S3...");
  await s3Util.downloadFileFromS3(inputBucket, key, inputFile);

  // lowRes
  console.log("Generate lowRes optimized (plays on Chrome) video file...");
  await childProcessPromise.spawn(
    "/opt/bin/ffmpeg",
    [
      "-loglevel",
      "error",
      "-y",
      "-i",
      inputFile,
      "-movflags",
      "faststart",
      "-vf",
      "scale=480:-2",
      lowResOutputFile,
    ],
    { env: process.env, cwd: "./" }
  );

  console.log("Upload lowRes file...");
  await s3Util.uploadFileToS3(
    OUTPUT_BUCKET,
    lowResKey,
    lowResOutputFile,
    VIDEO_MIME_TYPE
  );

  // callback to the API to signal that this file is finished processing
  console.log("Informing server lowRes derivative is ready...");
  await informServerOfCompletion({ key: key, low_res_key: lowResKey });

  // Clean up remaining artifacts
  console.log(
    "Delete unused files to avoid running out of space on future runs..."
  );
  fs.unlinkSync(inputFile); // Original
  fs.unlinkSync(lowResOutputFile);

  console.log(`Signaling post process complete for ${key}`);
};

// Helper method
const informServerOfCompletion = async (data) => {
  data = JSON.stringify(data);

  const options = {
    hostname: process.env.API_HOSTNAME,
    port: 443,
    path: "/api/videos/derivative",
    method: "PUT",
    headers: {
      "Content-Type": "application/json",
      Accept: "application/json",
      "Content-Length": data.length,
      "User-Agent": "Lambda-PreviewGenerator",
      Authorization: LAMBDA_SHARED_SECRET,
    },
  };

  console.log("Callback to server...", data);
  await new Promise((resolve) => {
    const req = https.request(options, (res) => {
      console.log(`/api/videos/derivative statusCode: ${res.statusCode}`);

      res.on("data", (d) => {
        process.stdout.write(d);
        resolve();
      });
    });

    req.on("error", (error) => {
      console.log(`/api/videos/derivative failed ${error}`);
      resolve();
    });

    req.write(data);
    req.end();
  });
};