Re: WGLC: p1 MUST NOT pipeline until connection is persistent

Alex Rousskov <rousskov@measurement-factory.com> Wed, 01 May 2013 07:35 UTC

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Date: Wed, 01 May 2013 01:34:12 -0600
From: Alex Rousskov <rousskov@measurement-factory.com>
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Subject: Re: WGLC: p1 MUST NOT pipeline until connection is persistent
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On 05/01/2013 12:52 AM, Willy Tarreau wrote:
> On Tue, Apr 30, 2013 at 05:22:39PM -0600, Alex Rousskov wrote:

>>>>> A client [...] MUST NOT pipeline on a retry connection until it
>>>>> knows the connection is persistent.

> I think that it was the reason why it's suggested somewhere that pipelining
> should only be done on connections that we know are persistent (ie after a
> first response)

That "somewhere" may be the above MUST NOT requirement we are discussing
on this thread :-).


>> Let's start with (a): To know that a connection "is persistent", the
>> client has to receive a response on that connection. This implies that
>> the client MUST NOT retry a failed pipelined request on a connection it
>> just opened.

I know what I was missing: The client may send a retry request on a new
connection. The above MUST NOT prohibits _pipelining_ on a new
connection, but does not prohibit sending a single request on that
connection. That resolves my concern about stuck clients.

I am still not sure why we are prohibiting retry pipelining on new
connections though. Why do we have to reuse an old connection if we want
to retry a failed pipeline?


Thank you,

Alex.