title: AWS Lambda thumbnail generator not working on larger file sizes
body: <p>So I followed this tutorial by amazon:  <a href="https://docs.aws.amazon.com/lambda/latest/dg/with-s3-example.html" rel="nofollow noreferrer">https://docs.aws.amazon.com/lambda/latest/dg/with-s3-example.html</a> to make a thumbnail generator for every image that I upload to my S3 bucket.  It works fine on small images around 500KB, and it correctly puts them in the thumbnail bucket, but I attempted to upload a 300MB image file to my S3 bucket, and my lambda function doesn't seem to work correctly. </p>
  
  <p>I looked through other forums and I have attempted to fiddle with some timeout and memory size settings in AWS Lambda becuase I thought that the function maybe needed more memory, but that wasn't the case and I personally don't know what else I have left to go off of.</p>
  
  <p>Here is the copy of the lambda function straight from the link I used, the error occurs at line 57 when the MAX_HEIGHT and MAX_WIDTH are being set. It seems that size in the case of large files seems to always be undefined.</p>
  
  <pre><code>// dependencies
  var async = require('async');
  var AWS = require('aws-sdk');
  var gm = require('gm')
              .subClass({ imageMagick: true }); // Enable ImageMagick integration.
  var util = require('util');
  
  // constants
  var MAX_WIDTH  = 100;
  var MAX_HEIGHT = 100;
  
  // get reference to S3 client 
  var s3 = new AWS.S3();
  
  exports.handler = function(event, context, callback) {
      // Read options from the event.
      console.log("Reading options from event:\n", util.inspect(event, {depth: 5}));
      var srcBucket = event.Records[0].s3.bucket.name;
      // Object key may have spaces or unicode non-ASCII characters.
      var srcKey    =
      decodeURIComponent(event.Records[0].s3.object.key.replace(/\+/g, " "));  
      var dstBucket = srcBucket + "resized";
      var dstKey    = "resized-" + srcKey;
  
      // Sanity check: validate that source and destination are different buckets.
      if (srcBucket == dstBucket) {
          callback("Source and destination buckets are the same.");
          return;
      }
  
      // Infer the image type.
      var typeMatch = srcKey.match(/\.([^.]*)$/);
      if (!typeMatch) {
          callback("Could not determine the image type.");
          return;
      }
      var imageType = typeMatch[1];
      if (imageType != "jpg" &amp;&amp; imageType != "png") {
          callback('Unsupported image type: ${imageType}');
          return;
      }
  
      // Download the image from S3, transform, and upload to a different S3 bucket.
      async.waterfall([
          function download(next) {
              // Download the image from S3 into a buffer.
              s3.getObject({
                      Bucket: srcBucket,
                      Key: srcKey
                  },
                  next);
              },
          function transform(response, next) {
              gm(response.Body).size(function(err, size) {
                  // Infer the scaling factor to avoid stretching the image unnaturally.
                  var scalingFactor = Math.min(
                      MAX_WIDTH / size.width,
                      MAX_HEIGHT / size.height
                  );
                  var width  = scalingFactor * size.width;
                  var height = scalingFactor * size.height;
  
                  // Transform the image buffer in memory.
                  this.resize(width, height)
                      .toBuffer(imageType, function(err, buffer) {
                          if (err) {
                              next(err);
                          } else {
                              next(null, response.ContentType, buffer);
                          }
                      });
              });
          },
          function upload(contentType, data, next) {
              // Stream the transformed image to a different S3 bucket.
              s3.putObject({
                      Bucket: dstBucket,
                      Key: dstKey,
                      Body: data,
                      ContentType: contentType
                  },
                  next);
              }
          ], function (err) {
              if (err) {
                  console.error(
                      'Unable to resize ' + srcBucket + '/' + srcKey +
                      ' and upload to ' + dstBucket + '/' + dstKey +
                      ' due to an error: ' + err
                  );
              } else {
                  console.log(
                      'Successfully resized ' + srcBucket + '/' + srcKey +
                      ' and uploaded to ' + dstBucket + '/' + dstKey
                  );
              }
  
              callback(null, "message");
          }
      );
  };
  </code></pre>
  
  <p>Here is the error message directly from AAWS Cloud Watch logs:</p>
  
  <pre><code>2019-05-14T22:31:28.731Z    b5fccf54-e55f-49f2-9206-462fa5769149    TypeError: Cannot read property 'width' of undefined
  at gm.&lt;anonymous&gt; (/var/task/index.js:57:38)
  at emitMany (events.js:147:13)
  at gm.emit (events.js:224:7)
  at gm.&lt;anonymous&gt; (/var/task/node_modules/gm/lib/getters.js:70:16)
  at cb (/var/task/node_modules/gm/lib/command.js:322:16)
  at gm._spawn (/var/task/node_modules/gm/lib/command.js:226:14)
  at gm._exec (/var/task/node_modules/gm/lib/command.js:190:17)
  at gm.proto.(anonymous function) [as size] (/var/task/node_modules/gm/lib/getters.js:68:12)
  at transform (/var/task/index.js:54:31)
  at nextTask (/var/task/node_modules/async/dist/async.js:5324:14)
  </code></pre>
  
  <p>EDIT: In addition I also seem to get this error which alternated between the two:</p>
  
  <pre><code>2019-05-14T22:55:25.923Z    7a7f1ec2-cd78-4fa5-a296-fee58033aea6    Unable to resize MYBUCKET/image.png and upload to MYBUCKETRESIZE/resize-image.png due to an error: Error: Stream yields empty buffer
  
  </code></pre>
  
  <p>EDIT: Added the report line:</p>
  
  <pre><code>REPORT RequestId: a67e1e79-ebec-4b17-9832-4049ff31bd89  Duration: 7164.64 ms    Billed Duration: 7200 ms Memory Size: 1024 MB   Max Memory Used: 810 MB
  </code></pre>