获得S3对象元数据创建流

Question

我从S3下载对象，并创建从中读取流对象来处理视频：

s3.getObject(params).createReadStream() 

不过，我需要从中获得的元数据是如果可能，我只是通过访问其“元数据”属性获取对象：

s3.getObject() 

我将如何之一：

1. 通过s3.getObject()获取对象，从其元数据属性中获取元数据，然后将其转换为读取流？

   var stream = fs.createReadStream(response);不工作 - 输入必须是字符串

- 或 -

获取经由s3.getObject().createReadStream()该流，并提取来自流的元数据？

据我所知，元数据不在流内传递。

---

告诉我，如果我的假设是错误的，但我目前坚持这两个需求：

• 获取元数据
• 使其成为一个流

Answer 1

所以我找到了解决方案。这适用于大多数10 MB以下的文件。如果它们大于缓冲流在文件完成写入之前结束。我试图把bufferStream.end内完成对功能，但后来我回电话犯规经历....

function download(s3Event, srcKey, cb){ 

    console.log('Starting download'); 

    s3.getObject({ 
     Bucket: s3Event.bucket.name, 
     Key: srcKey 
    }, cb); 
} 



function writeToFile(data, cb){ 

    var dlFile = path.join(tempDir, 'download'); 

    console.log('data = ', data); 
    console.log('data.Body = ', data.Body); 
    var stream = bufferStream.pipe(fs.createWriteStream(dlFile)).on('finish', function() { 
    console.log('finished writing stream'); 
    cb(null, data); 
    }); 

    bufferStream.end(data.Body); 
} 


exports.handler = function(event, context) { 

// Read options from the event. 

console.log("Reading options from event:\n", util.inspect(event, {depth: 5})); 

var s3Event = event.Records[0].s3; 
var srcKey = decodeURIComponent(s3Event.object.key); 
var keyPrefix = srcKey.replace(/\.[^/.]+$/, '');   
var dstBucket = "jump-lambda"; 


async.waterfall([ 

    function (cb){ 
     download(s3Event, srcKey, cb); 
    }, 

    function (data, cb){ 
     writeToFile(data, cb); 
    }, 

    function (data, cb){ 
     fluentffmpegProcess(data, cb); 
    }, 

    function (data, cb){ 
     transform(data, cb); 
    }, 

    function (data, buffer, cb){ 
     thumbnailUpload(data, buffer, dstBucket, keyPrefix, cb); 
    }, 

    function (data, cb){ 
     updateParse(data, srcKey, keyPrefix, cb); 
    }, 

], 

    function (err) { 
     if (err) { 
      console.error(
       'Unable to convert video to scene object, with error code: ' + err.description 
      ); 
     } else { 
      console.log(
       'Successfully created scene object, updated venue, and created thumbnail' 
      ); 
     } 
    } 
); 
}; 

Answer 2

你可以通过请求的httpHeaders事件的元数据。

let fs = require('fs') 
let aws = require('aws-sdk') 
let s3 = new aws.S3() 

let request = s3.getObject({ 
    Bucket: 'my-bucket', 
    Key: 'my-key' 
}) 

let stream 

request.on('httpHeaders', (statusCode, httpHeaders) => { 
    // object metadata is represented by any header in httpHeaders starting with 'x-amz-meta-' 
    // you can use the stream object that this point 
    stream.pipe(fs.createWriteStream('./somepath')) 
    stream.on('end',() => { 
     console.log('were done') 
    }) 
}) 

stream = request.createReadStream() 

另外，您也可以拨打s3.headObject获得元数据，而无需下载对象，然后下载使用s3.getObject