如何通过Yaws流式传输内容？

Question

I read about Yaws: streaming data to the client . 我读到有关Yaws的内容：将数据流传输到客户端。 I created a simple example shown below, but it doesn't work. 我创建了一个如下所示的简单示例，但是它不起作用。 I get an error and the process is dying. 我收到一个错误，过程即将结束。

Here is my yaws-file: 这是我的偏航文件：

<erl>
out(A) ->
    Self = self(),  
    spawn(fun() ->
        yaws_api:stream_chunk_deliver_blocking(Self, "Hello"),
        yaws_api:stream_chunk_end(Self, "Thanks"),
        exit(normal)
    end),
    {streamcontent, "text/html; charset=utf-8", "First\r\n"}.
</erl>

I also tried with yaws_api:stream_chunk_deliver/2 but I got the same error. 我也尝试了yaws_api:stream_chunk_deliver/2但是遇到了同样的错误。 Here is the error message I get in the command prompt: 这是我在命令提示符下收到的错误消息：

=ERROR REPORT==== 13-Feb-2012::09:23:30 ===
Error in process <0.117.0> with exit value: {undef,[{yaws_api,stream_chunk_end,[
\n"],[]}]}"Thanks

1>
=ERROR REPORT==== 13-Feb-2012::09:24:00 ===
Yaws process died: {stream_timeout,
                       [{yaws_server,stream_loop_send,5,
                            [{file,"yaws_server.erl"},{line,2821}]},
                        {yaws_server,aloop,3,
                            [{file,"yaws_server.erl"},{line,1167}]},
                        {yaws_server,acceptor0,2,
                            [{file,"yaws_server.erl"},{line,1025}]},
                        {proc_lib,init_p_do_apply,3,
                            [{file,"proc_lib.erl"},{line,227}]}]}
1>

The last chunk doesn't seem to be sent to the client: 最后一块似乎没有发送给客户端：

HTTP/1.1 200 OK
Server: Yaws 1.92
Date: Mon, 13 Feb 2012 07:31:18 GMT
Content-Type: text/html; charset=utf-8
Transfer-Encoding: chunked

7
First

7
Hello

Here is the JavaScript client code I use (only working with IE8 and IE9), using XDomainRequest : 这是我使用的JavaScript客户端代码（仅适用于IE8和IE9）以及XDomainRequest ：

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"/>
<script>
window.onload = function() {
    var el = document.getElementById("requestbutton");
    if(el.attachEvent) {
        el.attachEvent('onclick', doXDR);
    }
}

function writeStatus(message) {
    var html = document.createElement("div");
    html.setAttribute("class", "message");
    html.innerHTML = message;
    document.getElementById("status").appendChild(html);
}

function doXDR() {
    if(!window.XDomainRequest) {
        writeStatus("No XDR support in your browser");
        return;
    }

    writeStatus("Beginning XDR");
    try {
        var xdr = new XDomainRequest();
        xdr.open("GET", "http://localhost:8090/stream.yaws");
        xdr.send();
        xdr.onload = function() {
            writeStatus("XDR response: " + xdr.responseText);
        };
        xdr.onerror = function() {
            writeStatus("XDR error");
        };
        xdr.onprogress = function() {
            writeStatus("XDR intermediate: " + xdr.responseText);
        };
    } catch (e) {
        writeStatus("XDR Exception: " + e);
    }
}
</script>
</head>
<body>
<h1>Test page</h1>
<button id="requestbutton">Send request</button><br>
<div id="status"></div>
</body>
</html>

On the JavaScript client, the xdr.onerror = function() method is called. 在JavaScript客户端上，将xdr.onerror = function()方法。 The client should not show any data in this example since it need a 2k prelude , but it should be sent, as how I understand it. 在此示例中，客户端不应显示任何数据，因为它需要2k的前奏 ，但应按照我的理解发送。

Update 更新资料

After fixing the Erlang issues pointed out by Steve Vinoski and removing \\r\\n on my data, the Yaws server send the correct data. 解决了Steve Vinoski指出的Erlang问题并删除了我的数据\\r\\n ，Yaws服务器发送了正确的数据。 But I still get xdr.onerror = function() error on the JavaScript client. 但是我在JavaScript客户端上仍然出现xdr.onerror = function()错误。 And it seems that I need to add another header to the response Access-Control-Allow-Origin: * as documented in XDomainRequest Object : 似乎我需要向响应Access-Control-Allow-Origin: *添加另一个标头Access-Control-Allow-Origin: *如XDomainRequest对象中所述：

The document will request data from the domain's server by sending an Origin header with the value of the origin. 该文档将通过发送带有标头值的标头来向域的服务器请求数据。 It will only complete the connection if the server responds with an Access-Control-Allow-Origin header of either * or the exact URL of the requesting document . 仅当服务器使用*或请求文档的确切URL的Access-Control-Allow-Origin标头响应时，它才会完成连接。 This behavior is part of the World Wide Web Consortium (W3C)'s Web Application Working Group's draft framework on client-side cross-domain communication that the XDomainRequest object integrates with. 此行为是XDomainRequest对象与之集成的万维网联盟（W3C）的Web应用程序工作组的客户端跨域通信框架的一部分。

How do I add this header to the HTTP response? 如何将此标头添加到HTTP响应中？ It looks like I only can set the MIME type in the return value: {streamcontent, MimeType, FirstChunk} ? 看来我只能在返回值中设置MIME类型： {streamcontent, MimeType, FirstChunk} ？

Answer 1

Anytime you see an undef error, like this one you showed above: 每当您看到undef错误时，就像您在上面显示的那样：

Error in process <0.117.0> with exit value: {undef,[{yaws_api,stream_chunk_end,

it means you're either calling a function in a module that isn't on your load path, or you're calling a function that doesn't exist. 这意味着您正在调用不在加载路径上的模块中的函数，或者正在调用不存在的函数。 In your code, you're calling yaws_api:stream_chunK_end/2 , which doesn't exist. 在您的代码中，您正在调用yaws_api:stream_chunK_end/2 ，该名称不存在。 What you want instead is yaws_api:stream_chunk_end/1 . 您想要的是yaws_api:stream_chunk_end/1 。 Change your code to the following: 将您的代码更改为以下内容：

<erl>
  out(A) ->
    Self = self(),  
      spawn(fun() ->
        yaws_api:stream_chunk_deliver_blocking(Self, "Hello\r\n"),
        yaws_api:stream_chunk_deliver_blocking(Self, "Thanks\r\n"),
        yaws_api:stream_chunk_end(Self),
        exit(normal)
      end),
    {streamcontent, "text/html; charset=utf-8", "First\r\n"}.
</erl>

and then I think your example will work fine. 然后我认为您的示例会很好。

Update: 更新：

To answer the new part of your question, you use a list return value rather than just a single tuple, making sure the streamcontent tuple is last in the list: 为了回答问题的新部分，您可以使用列表返回值，而不仅仅是一个元组，请确保streamcontent元组在列表中位于最后：

[{header, {"Access-Control-Allow-Origin", "*"}},
 {streamcontent, "text/html; charset=utf-8", "First"}].

如何通过Yaws流式传输内容？

问题描述

Update 更新资料

1 个解决方案

解决方案1
3 已采纳 2012-02-13 15:35:20

如何通过Yaws流式传输内容？

问题描述

Update 更新资料

1 个解决方案

解决方案1 3 已采纳 2012-02-13 15:35:20

解决方案1
3 已采纳 2012-02-13 15:35:20