A fork of https://gist.github.com/sararob/275b252d1eda3a5baa27d6464d2f2198 to use async/await rather than callbacks

image-queue.js

'use strict';

// Dependencies
// we can remove a dependency by using the vision
// package directly
const vision = require('@google-cloud/vision')({
  projectId: 'sara-bigquery',
  keyfileName: 'keyfile.json'
});
const fs = require('fs');
const async = require('async');


// Convert the newline delimited JSON file into JSON to send to our queue
let imageIds = [];
const data = fs.readFileSync('./image-ids.json').toString();
imageIds = data.split("\n").map(function(obj) {
  return JSON.parse(obj);
});

let imageData = [];
const features = [
  { "type": "FACE_DETECTION" },
  { "type": "LABEL_DETECTION" },
  { "type": "LANDMARK_DETECTION" },
  { "type": "WEB_DETECTION" },
  { "type": "IMAGE_PROPERTIES" }
];

// specify this function as async and remove the callback param
// as it will no longer be needed. The async library will implicitly
// convert any thrown errors to be the resulting error of the function
// and any returned value to be the result.
async function callVision(task) {
  console.log(`processing ${task.object_id}`);

  let visionReq = {
    "image": {
      "source": {
        "imageUri": `gs://gcs-storage-bucket/${task.id}.jpg`
      }
    },
    "features": features
  }

  // As this function is async we can use try/catch and
  // await on functions that return promises
  try {
    // use the version of the api that returns a promise
    // i.e. do not pass a callback. we can then 'await' the
    // result
    let data = await vision.annotate(visionReq);
    let annotations = data[0];
    let imgMetadata = annotations[0];

    if (!imgMetadata['imagePropertiesAnnotation']) {
      throw new Error('no data');
    }

    imgMetadata['object_id'] = task.name;
    imageData.push(imgMetadata);

    // we are not returning anything so return
    // is called implicitly. No need to call
    // callback
  catch (err) {
      // with await we can catch errors in the 'normal'
      // way and throw them to the calling code
      throw err;
    }
  }

// The queue sends the image ID to callVision() and writes the response to a local file
// once the entire queue has finished processing
let q = async.queue(callVision, 20);

// any thrown errors in the callVision function
// will be err here. Any returned values would
// also be available here as a second parameter
q.push(imageIds, (err) => {
  if (err) {
    console.log(err)
  }
});

function done() {
  q.drain = null;
  fs.writeFileSync('./responses.json', JSON.stringify(imageData));
}

// Will only be executed when the queue is drained
q.drain = done;