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Date: Thu, 31 Oct 2013 13:01:37 +0100
Message-ID: <CANEZrP3hMe_1moKDZKjxcB_okJqzmDJprnskMnts59ED18JsEg@mail.gmail.com>
From: Mike Hearn <mike@plan99.net>
To: Gregory Maxwell <gmaxwell@gmail.com>
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Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>,
	kjj <bitcoin-devel@jerviss.org>
Subject: Re: [Bitcoin-development] Feedback requested: "reject" p2p message
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On Wed, Oct 30, 2013 at 6:13 PM, Gregory Maxwell <gmaxwell@gmail.com> wrote:

> If a node is using priority queued rate limiting for its relaying then
> it might "accept" a transaction from you, but have it fall out of its
> memory pool (due to higher priority txn arriving, or getting
> restarted, etc.) before it ever gets a chance to send it on to any
> other peers.
>

That's a good point, however, I would hope that this fairly trivial race
condition can be resolved. There's no requirement that a transaction be
placed into a buffer from which it can be removed before relaying. After
relaying - sure. But the gap of a few seconds between that shouldn't cause
any issues to eliminate.

I believe Gavin's smartfees branch adds mempool persistence to disk, so
restarting nodes won't clear the mempool in future. Or at least that's a
part of the longer term plan once mempool limiting is done.


> Finding out that it rejected is still useful information, but even
> assuming all nodes are honest and well behaved I don't think you could
> count on its absence to be sure of forwarding.
>

I think measuring propagation will be a part of bitcoin wallets for the
forseeable future, although if all nodes reject that allows for a more
responsive and more helpful UI than just waiting for some arbitrary timeout
to elapse.

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<div dir=3D"ltr">On Wed, Oct 30, 2013 at 6:13 PM, Gregory Maxwell <span dir=
=3D"ltr">&lt;<a href=3D"mailto:gmaxwell@gmail.com" target=3D"_blank">gmaxwe=
ll@gmail.com</a>&gt;</span> wrote:<br><div class=3D"gmail_extra"><div class=
=3D"gmail_quote">
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div class=3D"im"><span style=3D"color:rgb(3=
4,34,34)">If a node is using priority queued rate limiting for its relaying=
 then</span><br>
</div>
it might &quot;accept&quot; a transaction from you, but have it fall out of=
 its<br>
memory pool (due to higher priority txn arriving, or getting<br>
restarted, etc.) before it ever gets a chance to send it on to any<br>
other peers.<br></blockquote><div><br></div><div>That&#39;s a good point, h=
owever, I would hope that this fairly trivial race condition can be resolve=
d. There&#39;s no requirement that a transaction be placed into a buffer fr=
om which it can be removed before relaying. After relaying - sure. But the =
gap of a few seconds between that shouldn&#39;t cause any issues to elimina=
te.</div>
<div><br></div><div>I believe Gavin&#39;s smartfees branch adds mempool per=
sistence to disk, so restarting nodes won&#39;t clear the mempool in future=
. Or at least that&#39;s a part of the longer term plan once mempool limiti=
ng is done.</div>
<div>=C2=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8=
ex;border-left:1px #ccc solid;padding-left:1ex">Finding out that it rejecte=
d is still useful information, but even<br>
assuming all nodes are honest and well behaved I don&#39;t think you could<=
br>
count on its absence to be sure of forwarding.<br>
</blockquote></div><br></div><div class=3D"gmail_extra">I think measuring p=
ropagation will be a part of bitcoin wallets for the forseeable future, alt=
hough if all nodes reject that allows for a more responsive and more helpfu=
l UI than just waiting for some arbitrary timeout to elapse.</div>
</div>

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