获取s3对象元数据，然后创建流

问题描述

我正在从s3下载一个对象，并从中创建一个读取流对象以处理视频:

I'm downloading an object from s3 and creating a read stream object from it to process a video:

s3.getObject(params).createReadStream()

但是，我需要从中获取元数据，当我仅通过访问其元数据"属性来获取对象时，这是可能的:

However, I need to get the metadata from it which is possible when i just get the object by accessing its 'metadata' property:

s3.getObject()

我该怎么办

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

1. Get the object via s3.getObject(), grab the metadata from its metadata property, and then turn it into a read stream?

var stream = fs.createReadStream(response);不起作用-输入必须为字符串

var stream = fs.createReadStream(response); isn't working - input must be a string

-或-

1. 通过s3.getObject().createReadStream()获取流，并从流中提取元数据吗?

1. Get the stream via s3.getObject().createReadStream(), and extract the metadata from the stream?

据我所知，元数据未在流中传递.

To my knowledge metadata isn't passed within streams.

---

如果我的假设是错误的，请告诉我，但是我目前仍然满足以下两个需求:

---

Tell me if my assumptions are wrong, but I am currently stuck with these two needs:

• 获取元数据
• 将其制作为流

推荐答案

您可以通过请求的httpHeaders事件获取元数据.

You can get the metadata via the request's httpHeaders event.

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()

或者，您也可以调用s3.headObject来获取元数据而不下载对象，然后使用s3.getObject

Alternatively you can also call s3.headObject to get the metadata without downloading the object and then download the object using s3.getObject

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