IRC meeting summary for 2015-11-19



Main topics

  • transaction priority
  • dealing with mempool eviction
  • Sequence numbers

Short topics/notes

Opt-in replace by fee needs some extra testing, but otherwise seems ready to go. Some wallet developers are onboard and actively participating, for example GreenAddress.

transaction priority


Each transaction is assigned a priority, determined by the age, size, and number of inputs. Which currently makes some transactions free.
This currently has a large amount of code, which makes it harder to maintain, and is not that optimal since you can’t expect miners to include 0-fee transactions.

meeting comments

If we don’t stop support for priority in transaction creation we also need a mempool area for priority, or those transactions will always get evicted.
If we develop a better framework to support these kind of metrics we can add it back.
Plan is to remove the priority transaction creation from the wallet, not the mining part.

meeting conclusion

Creation of priority transactions should be removed from the wallet.

dealing with mempool eviction


When a transaction is relayed across the network it is held by the nodes in memory, until it gets into a block. All these transactions that sit in memory are called the memorypool or mempool for short.
Like we could see during the spam-attack if there’s a big back-log of transactions that couldn’t make it in the blockchain this mempool can get pretty big resulting in nodes crashing.

To stop this from happening devs created a mechanism to reject and/or remove transactions from the mempool.

meeting comments

Current problem: when a wallet transaction is rejected by the mempool, the wallet considers the resulting transaction as “conflicting” and will happily respend the inputs.
sipa proposes to make the wallet only treat a transaction as conflicting if it has non-existing inputs.
It should however consider it respendable at some time later on.
You could add a way to manually remove transactions, or tag is as removed, or archive it.
You could also do something separate that marks the transaction as respendable, as removal gives the impression the transaction can’t be mined in the future.
Options that are wanted: a “respend with higher fee” option and an option to forget about a transaction completely, we need a minimum viable idea for 0.12 though.

meeting conclusion

Given the tight deadline for 0.12 we detect actual conflict instead of mempool eviction and leave the coins immediately respendable.

Sequence numbers**


BIP 68 repurposes some of the unused nSequence field to a relative locktime, meaning locking inputs until a certain time or blockheight has passed.

meeting comments

We need to wait for BIP113 to be deployed as standardness so BIP 68, 112 and 113 can go in a softfork.
There’s upcoming projects that already use sequence numbers.
Merging BIP68 would make BIP112 easier to review and would stop the need to rebase all the time.
If we feel the 68/112 are sufficiently reviewed and mature they could go in as standardness rules.
The BIP text doesn’t seem to reflect what’s written in the code.

meeting conclusion

Check BIP68 to match the implementation


sipa               Pieter Wuille  
gmaxwell           Gregory Maxwell  
morcos             Alex Morcos  
jtimon             Jorge Timón  
wumpus             Wladimir J. van der Laan  
btcdrak            btcdrak  
jgarzik            Jeff Garzik  
petertodd          Peter Todd   
Luke-Jr            Luke Dashjr   
BlueMatt           Matt Corallo   
jonasschnelli      Jonas Schnelli  
CodeShark          Eric Lombrozo  
sdaftuar           Suhas Daftuar   
gavinand1esen      Gavin Andresen   


This summary was originally compiled by Stefan Gilis aka “G1lius” and posted to the bitcoin-discuss mailing list with the disclaimer, “Please bear in mind I’m not a developer so some things might be incorrect or plain wrong.” and placed copyright in the Public Domain.

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