[erlang-questions] Why does having SNDBUF too low break HTTP?

[Alec Mocatta]

Headers as reported by tcpick, with address, host, referrer and cookie
asterisked:

1      SYN-SENT       x.108.161.x:62793 > 10.144.11.241:http
1      SYN-RECEIVED   x.108.161.x:62793 > 10.144.11.241:http
1      ESTABLISHED    x.108.161.x:62793 > 10.144.11.241:http
GET /1/****** HTTP/1.1
Host: ****.*******.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:16.0)
Gecko/20100101 Firefox/16.0
Accept: */*
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: keep-alive
Referer: http://****.*******.com/*******
Cookie: ******

HTTP/1.1 200 OK
Transfer-Encoding: chunked
Date: Sat, 24 Nov 2012 18:45:49 GMT

5d4dd
jsonpCallback([...


Thanks,

Alec


On Sat, Nov 24, 2012 at 8:52 AM, Dmitry Kolesnikov
<dmkolesnikov@REDACTED>wrote:

> Hello,
>
> Could you please share HTTP headers for request and response?
>
> - Dmitry
>
> On Nov 24, 2012, at 2:09 AM, Max Lapshin <max.lapshin@REDACTED> wrote:
>
> Nobody have replied to you yet.
>
> It is a very strange issue. Show your full reply headers. Do you have
> Content-Length in them?
>
> On Wednesday, November 21, 2012, Alec Mocatta wrote:
>
>> I've got a simple http server running, with gen_tcp options as follows:
>>
>> [
>> binary,
>> {active, false},
>> {packet, http_bin},
>> {reuseaddr, true},
>>  {keepalive, true},
>> {delay_send, false},
>> {nodelay, true}
>> ]
>>
>> With one response in particular that sends a single 300000 byte http
>> chunk with a single gen_tcp:send call, I'm seeing some clients failing to
>> receive it, or only receiving the first 150000 - 250000 bytes.
>>
>> Firefox, Chrome and Cocoa's NSURLConnection all have problems while
>> receiving the response, with Firefox and NSURLConnection truncating the
>> response, and Chrome not accepting it at all and giving an error. Curl and
>> wget however receive the response fine.
>>
>> tcpick -C -yP "tcp port 80" shows the connection being closed before all
>> the data's sent, printing the data truncated at the same place as Firefox,
>> followed by:
>> 1      FIN-WAIT-2     x.108.161.x:65438 > 10.144.11.241:http
>> 1      TIME-WAIT      x.108.161.x:65438 > 10.144.11.241:http
>> 1      CLOSED         x.108.161.x:65438 > 10.144.11.241:http
>>
>> Setting sndbuf to 512000 however seems to solve the problem, at least for
>> the 300000 byte chunk size I'm sending.
>>
>> Why would sndbuf affect the validity of the TCP/HTTP stream? Someone
>> suggested this looks like the return value of write(2) isn't being checked,
>> or EAGAIN isn't being dealt with correctly? gen_tcp:send is returning ok,
>> however.
>>
>> Erlang version: Erlang R15B02 (erts-5.9.2) [source] [64-bit]
>> [async-threads:0] [hipe] [kernel-poll:true]
>>
>> Any ideas what could be causing this?
>>
>> Thanks,
>>
>> Alec
>
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