node.js - 使用节点js的aws lambda中的pdf缩略图

Question

我正在将此节点 js 脚本用作 aws lambda 脚本，以在将 pdf 上传到 s3 存储桶后立即创建 pdf 文件的缩略图。

var async = require('async');
var s3 = new AWS.S3();
var ffmpeg = require('fluent-ffmpeg');
var fs = require('fs');
var util = require('util');
var mktemp = require("mktemp");
var gm = require('gm').subClass({ imageMagick: true });
const https = require('https');


var mediaconvert = new AWS.MediaConvert({
    apiVersion: '2017-08-29',
});

p1 = process.env['LAMBDA_TASK_ROOT'];

process.env['FFMPEG_PATH'] = p1 + '/ffmpeg-git-20180111-64bit-static/ffmpeg';
process.env['FFPROBE_PATH'] = p1 + '/ffmpeg-git-20180111-64bit-static/ffprobe';

var imageResolutions = Object.freeze({
    thumbnail: 0,
    type1: 1,
    type2: 2
});



function processPdf(srcBucket, srcKey, fileType, format) {

    var lastSlash = srcKey.lastIndexOf('/');
    var dotIndex = srcKey.lastIndexOf('.');
    var parentPath = srcKey.slice(0, lastSlash + 1);
    var fileName = srcKey.slice(lastSlash + 1, dotIndex);
    var dstKey = parentPath + 'scaled/' + fileName + '_thumbnail.png';
    console.log('lastSlash:' + lastSlash + ' dotIndex ' + dotIndex + ' parentPath ' + parentPath + ' fileName ' + fileName);

    async.waterfall([
        function download(next) {
            // Download the pdf from S3 into a buffer.
            s3.getObject({
                Bucket: srcBucket,
                Key: srcKey
            },
            next);
        },
    function thumbnail(response, next) {
        console.log('generating thumbnail for pdf');
        var temp_file, image;
        temp_file = mktemp.createFileSync("/tmp/XXXXXXXXXX.pdf");
        fs.writeFileSync(temp_file, response.Body);
        image = gm(temp_file + "[0]").flatten().colorspace("CMYK");
        console.log("image is " + image);
        image.size(function(err, size) {

            // Transform the image buffer in memory.
            this.resize(200, 200)
                .toBuffer("jpeg", function(err, buffer) {
                if (err) {
                    console.log("error buffer " + err);
                    next(err);
                } else {
                    next(null, response.ContentType, buffer);
                }
            });

        });
    },
    function upload(contentType, data, next) {
        // Stream the thumbnail
        console.log('uploading thumbnail');
        s3.putObject({
            Bucket: srcBucket,
            Key: dstKey,
            ACL:"public-read",
            Body: data,
            ContentType: "image/jpeg"
        },
        next);
    }
    ], function (err) {
        if (err) {
            console.log(
                'Unable to create thumbnail for ' + srcBucket + '/' + dstKey +
                ' and upload to ' + srcBucket + '/' + dstKey +
                ' due to an error: ' + err
                );
        } else {
            console.log(
                'Successfully resized ' + srcBucket + '/' + dstKey +
                ' and uploaded to ' + srcBucket + '/' + dstKey
                );
        }
    }
    );
}

exports.handler = function(event, context, callback) {
    console.time('Total time taken');
    var srcBucket = event.Records[0].s3.bucket.name;
    console.log('Source Bucket: ' + srcBucket);
    var format = "png";
    var srcKey = decodeURIComponent(event.Records[0].s3.object.key.replace(
        /\+/g, " "));
    console.log('Source Key: ' + srcKey);

    var pathComponents = srcKey.split('/');

    if (srcKey.indexOf('scaled/') > -1) {
        console.log('Already scaled....Skipping');
        return;
    }
    var dstBucket = srcBucket;

    var typeMatch = srcKey.match(/\.([^.]*)$/);
    var imageType = typeMatch[1].toLowerCase();

    if (imageType == "mp4") {
        console.log('Processing video ' + srcKey);
        processVideo(srcBucket, srcKey, imageType);
    } 
    else if(imageType == "pdf"){
        console.log('Processing video ' + srcKey);
        processPdf(srcBucket, srcKey, imageType, format);
    }else if(imageType == "png"){
        var params = {
            Bucket: srcBucket,
            Key: srcKey
        };
        s3.getObjectTagging(params, function(err, data) { //get Tags for this object
            if (err) console.log(err, err.stack); // an error occurred
            else {
                var isAlreadyProcessed = false;
                var lastSlash = srcKey.lastIndexOf('/');
                var parentPath = srcKey.slice(0, lastSlash + 1);
                var name = srcKey.slice(lastSlash + 1, srcKey.indexOf('.' + imageType));
                var tagSet = data.TagSet;

                console.log('isAlreadyProcessed ' + isAlreadyProcessed);
                console.log('lastSlash ' + lastSlash);
                console.log('parentPath ' + parentPath);
                console.log('name ' + name);
                console.log('tagSet ' + tagSet);

                tagSet.forEach(function(value) {
                    if (value['Key'] == 'processed' && value['Value'] == 'true') { //if 'processed' tag is set to 'true'
                        isAlreadyProcessed = true;
                    }
                });

                if (isAlreadyProcessed) {
                    console.log("Alreay processed.....Skipping");
                    return;
                }

                tagSet.push({
                    Key: "processed",
                    Value: "true"
                })
                scale(params, srcBucket, parentPath, name, 200, imageType, imageResolutions.thumbnail, tagSet);

            }
        });
    }
    else{
        console.log("no valid data type");
        return;
    }
};

每当我将文件上传到 s3 存储桶时，我都会收到此错误错误：流产生空缓冲区。我已将内存增加到 2 GB 仍然存在问题。请帮忙，让我知道这里出了什么问题。