From: "Michael Grønager" <gronager@ceptacle•com>
To: Bitcoin Dev <bitcoin-development@lists•sourceforge.net>
Subject: [Bitcoin-development] Trickle in CNode::SendMessages
Date: Thu, 29 Dec 2011 23:05:55 +0100 [thread overview]
Message-ID: <AB205206-AC96-4A95-B100-E8F4461B08C5@ceptacle.com> (raw)
In CNode::SendMessages there is a trickle algorithm. Judging from the comments it is supposed to:
* at each update round a new (random) trickle node is chosen, with 120 nodes and an average round time of 100ms (the sleep) we will have moved through roughly all nodes every 12-15 seconds.
* when a node is the trickle node it will get to send all its pending addresses to its corresponding peer.
* when a node is not trickle node (the rest of the nodes) we send transaction-invs, however, only 1/4 of them - the rest is pushed to wait for the next round and would eventually get sent.
However, the way the 1/4 of the invs are chosen is by:
(inv.getHash() ^ hashSalt) & 3 == 0
As hashSalt is a constant (static, generated on start up) and as the hash of an inv is constant for the inv too, the other 3/4 will never get sent and hence it does not make sense to carry them around from round to round:
if (fTrickleWait) vInvWait.push_back(inv);
and:
pto->vInventoryToSend = vInvWait;
The hashSalt will be different for each node in the peer-to-peer network and hence as long as we have much more than 4 nodes all tx'es will be sent around.
Ironically, this (wrong?) implementation divides the inv forwarding hash space into 4, along the same lines as we discussed last week for DHTs...
I suggest to either keep the algorithm as is, but remove the redundant vInvWait stuff, or to change the algorithm to e.g. push the tx'es into a multimap (invHash^hashSalt, invHash) and choose the first 25% in each round.
The last alternative is that I have misunderstood the code... - if so please correct me ;)
Happy New Year!
Michael
next reply other threads:[~2011-12-29 22:06 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-29 22:05 Michael Grønager [this message]
2011-12-30 7:38 ` Michael Grønager
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