使用Express从S3流式传输文件，包括有关长度和文件类型的信息 [英] Streaming file from S3 with Express including information on length and filetype

问题描述

使用aws-sdk模块和Express 4.13，可以通过多种方式从S3代理文件.

Using the aws-sdk module and Express 4.13, it's possible to proxy a file from S3 a number of ways.

此回调版本将返回文件主体作为缓冲区，以及其他相关的标头，例如Content-Length:

This callback version will return the file body as a buffer, plus other relevant headers like Content-Length:

function(req,res){

  var s3 = new AWS.S3();

  s3.getObject({Bucket: myBucket, Key: myFile},function(err,data){

    if (err) {
      return res.status(500).send("Error!");
    }

    // Headers
    res.set("Content-Length",data.ContentLength)
       .set("Content-Type",data.ContentType);

    res.send(data.Body); // data.Body is a buffer

  });

}

此版本的问题在于，您必须在发送文件之前先获取整个文件，这并不好，尤其是在视频之类的大文件中.

The problem with this version is that you have to get the entire file before sending it, which is not great, especially if it's something large like a video.

此版本将直接流式传输文件:

This version will directly stream the file:

function(req,res){

  var s3 = new AWS.S3();

  s3.getObject({Bucket: myBucket, Key: myFile})
    .createReadStream()
    .pipe(res);

}

但与第一个不同，它不会对标头做任何事情，浏览器可能需要正确处理标头.

But unlike the first one, it won't do anything about the headers, which a browser might need to properly handle the file.

是否有一种方法可以通过从S3传递正确的标头，但将文件作为流发送，从而获得两全其美的方法?可以通过首先向S3发出HEAD请求以获取元数据来完成，但是可以通过一个API调用来完成吗?

Is there a way to get the best of both worlds, passing through the correct headers from S3 but sending the file as a stream? It could be done by first making a HEAD request to S3 to get the metadata, but can it be done with one API call?

推荐答案

一种方法是监听httpHeaders事件并在其中创建流.

One approach is listening the httpHeaders event and creating a stream within it.

s3.getObject(params)
    .on('httpHeaders', function (statusCode, headers) {
        res.set('Content-Length', headers['content-length']);
        res.set('Content-Type', headers['content-type']);
        this.response.httpResponse.createUnbufferedStream()
            .pipe(res);
    })
    .send();

这篇关于使用Express从S3流式传输文件，包括有关长度和文件类型的信息的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！