在响应节点中发送数据流。使用node.js的Azure文件服务

I am using node.js to create file service for Azure File storage. I am using azure-storage-node (http://azure.github.io/azure-storage-node/) for this.

我用节点。为Azure文件存储创建文件服务。我使用的是azure.github. io/az-storage -node/)节点。

I am trying to download a file from Azure file storage. Below is my code snippet

我正在尝试从Azure file storage下载一个文件。下面是我的代码片段

// Download a file from Share
exports.get = function(request, response){
    var shareName = request.headers.sharename;
    var dirPath = request.headers.directorypath;
    var fileName = request.headers.filename;

    var fileService = azure.createFileService();

    var readStream = fileService.createReadStream(shareName, dirPath, fileName);

    var dataLength = 0;
    var body = '';
    readStream.on('data', function (chunk) {
    dataLength += chunk.length;
  })

    readStream.on('end', function(){
      console.log('The length was:', dataLength);
    });

    response.setHeader('Content-Type', 'application/json');
    response.send(statusCodes.OK, JSON.stringify("Success!"));

}

I able to get the stream of data. But how can I sent the stream in the response so that we can get it in the rest call.

我能得到数据流。但是我如何在响应中发送流以便在rest调用中获得它。

I tried readStream.pipe(response); and

我试着readStream.pipe(响应);和

response.write(typeof chunk);
response.end() but it doesnt work; 

I am new to node.js. Please help me on this.

我是新手。请在这方面帮助我。

Updated:

更新:

I tried the following.

我试着以下。

response.writeHead(200, {'Content-Type': 'application/json'});

var readStream = fileService.createReadStream(shareName, dirPath, fileName);
readStream.pipe(response);

But its throwing follwing error.

但它犯了一个错误。

    ERROR
An unhandled exception occurred. Error: Can't set headers after they are sent.
    at ServerResponse.OutgoingMessage.setHeader (http.js:679:11)
    at ServerResponse.res.setHeader (D:\home\site\wwwroot\node_modules\express\node_modules\connect\lib\patch.js:59:22)
    at ServerResponse.res.set.res.header (D:\home\site\wwwroot\node_modules\express\lib\response.js:518:10)
    at addDefaultHeaders (D:\home\site\wwwroot\runtime\request\requesthandler.js:582:9)
    at ServerResponse.<anonymous> (D:\home\site\wwwroot\runtime\request\requesthandler.js:291:13)
    at ServerResponse._.wrap [as end] (D:\home\site\wwwroot\node_modules\underscore\underscore.js:692:22)
    at ChunkStream.onend (stream.js:66:10)
    at ChunkStream.EventEmitter.emit (events.js:126:20)
    at ChunkStream.end (D:\home\site\wwwroot\App_Data\config\scripts\node_modules\azure-storage\lib\common\streams\chunkstream.js:90:8)
    at Request.onend (stream.js:66:10)

The return datatype of fileService.createReadStream(shareName, dirPath, fileName); is ChunkStream

fileService的返回数据类型。createReadStream(shareName dirPath,文件名);是ChunkStream

Updated:

更新:

This is my updated code which works.

这是我更新过的代码。

    var option = new Object();
    option.disableContentMD5Validation = true;
    option.maximumExecutionTimeInMs = 20 * 60000;
    option.timeoutIntervalInMs = 20 * 6000;

    fileService.getFileToStream(shareName, dirPath, fileName, response, option, function(error, result, res) {
        if(!error) {
            if(res.isSuccessful) {
                console.log(result);
        console.log(res);
        console.log("Success!");
      }
        }
    });

But more frequently I am getting below error.

但更常见的是，我在错误以下。

ERROR
An unhandled exception occurred. Error: Can't set headers after they are sent.
at ServerResponse.OutgoingMessage.setHeader (http.js:679:11)
at ServerResponse.res.setHeader (D:\home\site\wwwroot\node_modules\express\node_modules\connect\lib\patch.js:59:22)
at ServerResponse.res.set.res.header (D:\home\site\wwwroot\node_modules\express\lib\response.js:518:10)
at addDefaultHeaders (D:\home\site\wwwroot\node_modules\azure-mobile-services\runtime\request\requesthandler.js:590:9)
at ServerResponse. (D:\home\site\wwwroot\node_modules\azure-mobile-services\runtime\request\requesthandler.js:299:13)
at ServerResponse._.wrap as end
at Request.onend (stream.js:66:10)
at Request.EventEmitter.emit (events.js:126:20)
at IncomingMessage.Request.onRequestResponse.strings (D:\home\site\wwwroot\App_Data\config\scripts\node_modules\azure-storage\node_modules\request\request.js:1153:12)
at IncomingMessage.EventEmitter.emit (events.js:126:20)

2 个解决方案

#1

The NodeJS Class http.ServerResponse implements the Writable Stream interface, please refer to the NodeJS API https://nodejs.org/api/http.html#http_class_http_serverresponse and https://nodejs.org/api/stream.html#stream_class_stream_writable_1.

NodeJS类http。服务器响应实现了可写流接口，请参考NodeJS API https://nodejs.org/api/http.html#http_class_http_serverresponse和https://nodejs.org/api/stream.html# stream_class_writable_1。

So you just need to use the object response instead of the stream writer fs.createStreamWriter(...) in the sample code "getFileToStream" http://azure.github.io/azure-storage-node/#toc8 when you send data stream into response for NodeJS.

因此，您只需要在示例代码“getFileToStream”http://azure.github中使用对象响应而不是流编写器fs.createStreamWriter(…)。当您将数据流发送到NodeJS的响应中时，io/ az-storage -node/#toc8。

This is my sample code as below:

这是我的示例代码如下:

var http = require('http');
var azure = require('azure-storage');
var fileService = azure.createFileService('<storage_key_name>','<storage_access_key>');

http.createServer(function (request, response) {
    var shareName = request.headers.sharename;
    var dirPath = request.headers.directorypath;
    var fileName = request.headers.filename;
    response.setHeader('Content-Type', 'application/json');
    fileService.getFileToStream(shareName, dirPath, fileName, response, {disableContentMD5Validation: true}, function(error, result, response) {
            if(!error) {
                    //console.log(result);
                    //console.log(response);
                   if(response.isSuccessful) {
                                console.log("Success!");
                   }
            }
    });
}).listen(1337, "127.0.0.1");

console.log('Server running at http://127.0.0.1:1337/');

Best Regards.

致以最亲切的问候。

---

For getting File greater than 4MB from Azure File Storage, there is a request header x-ms-range-get-content-md5 that it will cause the status code 400(Bad Request) error, please refer to the Get File REST API doc of Azure File Storage https://msdn.microsoft.com/en-us/library/azure/dn194274.aspx, see below:

对于从Azure文件存储中获取大于4MB的文件，有一个请求头x-ms-range-get-content-md5会导致状态码400(错误请求)错误，请参阅Azure文件存储的Get File REST API doc https://msdn.microsoft.com/en- us/library/azure/azure/dn1944.aspx，参见下面:

So I reviewed the source of Azure File Storage SDK for Node (https://github.com/Azure/azure-storage-node/blob/master/lib/services/file/fileservice.js). For the function getFileToText, getFileToLocalFile, createReadStream and getFileToStream, you need to set the options.disableContentMD5Validation attribute to avoid the error, see below.

因此，我回顾了Node的Azure文件存储SDK的源代码(https://github.com/Azure/azure-storage-node/blob/master/lib/services/file/fileservice.js)。对于函数getFileToText、getFileToLocalFile、createReadStream和getFileToStream，您需要设置选项。为了避免错误，请参见下面的内容。

• @param {boolean} [options.disableContentMD5Validation] When set to true, MD5 validation will be disabled when downloading files.
• @param {布尔}[选项。当设置为true时，在下载文件时将禁用MD5验证。

And refer to the source of getFileToStream as example:

并以getFileToStream的源代码为例:

In my sample code, need to add the code {disableContentMD5Validation: true} as options at the front of invoking the function getFileToStream.

在我的示例代码中，需要在调用函数getFileToStream之前添加代码{disableContentMD5Validation: true}作为选项。

#2

You might want to try in this way:

你可能想这样尝试:

exports.get = function(request, response) {
  var shareName = request.headers.sharename;
  var dirPath = request.headers.directorypath;
  var fileName = request.headers.filename;

  var fileService = azure.createFileService();
  var readStream = fileService.createReadStream(shareName, dirPath, fileName);    

  var dataLength = 0;
  readStream.on('data', function (chunk) {
    dataLength += chunk.length;
  })

  readStream.on('end', function(){
    response.setHeader('Content-Type', 'application/json');
    response.setHeader('Content-Length', dataLength);
  });

  readStream.pipe(response);

  response.on('finish', function (chunk) {
    response.send(statusCodes.OK, JSON.stringify("Success!"));
  })
}