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Re: h2 proxy and connection flow control

Tatsuhiro Tsujikawa <tatsuhiro.t@gmail.com> Thu, 21 August 2014 14:14 UTC

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From: Tatsuhiro Tsujikawa <tatsuhiro.t@gmail.com>
Date: Thu, 21 Aug 2014 23:09:57 +0900
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To: Patrick McManus <mcmanus@ducksong.com>
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Subject: Re: h2 proxy and connection flow control
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On Thu, Aug 21, 2014 at 10:59 PM, Patrick McManus <mcmanus@ducksong.com>
wrote:

>
> On Thu, Aug 21, 2014 at 9:39 AM, Tatsuhiro Tsujikawa <
> tatsuhiro.t@gmail.com> wrote:
>
>>
>>
>> Since Browser's receive window is 0, Frontend Proxy cannot send
>> more DATA for stream A to Browser.  Meanwhile, Frontend Proxy
>> continues to receive DATA for stream B from Backend.  Since
>> stream A's stream window is 0, Frontend Proxy cannot proceed and
>> just buffer the received data and eventually Frontend Proxy's
>> receive window for connection becomes 0.
>>
>> After this happens, Browser can still issue new request, but
>> Backend cannot send response to Frontend Proxy because its recive
>> window is 0.  This means that if Browser stalls one stream, it
>> stalls all streams in entire session.
>>
>
> The proxy cannot receive more data because its resources (the session
> window) are exhausted.
>
>
​Yes
​

> If it did receive more data where would it put it?
>
> If it actually has room for more data then it should just increase its
> session window with a window update.
>
>
​In this scenario, proxy has no room to expand. Therefore I wrote that​ all
streams on backend connections are stalled.

Best regards,
Tatsuhiro Tsujikawa

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