AssumeUTXO update
Speakers: James O'Beirne
Date: April 27, 2023
Transcript By:
Tags: Bitcoin core, Assumeutxo
Category: Core dev tech
Goals
- allow nodes to get a utxo set quickly (1h)
- at the same time, no major security concessions
Approach
- Provide serialized utxo snapshot
- get headers chain first, load snapshot and deserialize, sync to tip from that
- then start background verification with a 2nd snapshot
- finally, compare hashes when background IBD hits snapshot base
Progress update
- lots of refactoring has been done;
ChainStateManagerwas introduced, globals removed, mempool / blockstorage refactored - init / shutdown logic changes have been merged
- wallet changes done
- p2p changes still under review (i.e. picking the chainstate to which to append new blocks )
Open issues
nFile order gets fragmented, potential problems with pruning and/or reindex
-> Introduce blockfile nFile counter per chainstate types (simple change)
Pruning
- currently, pruning target w/ trailing window
- do the same, but with two tips - different possiblities to achieve this
Indexing
validationinterface signals are picked up by indices
could build out of order, but some indexes (coinstats) cant be build out of order
simple solution: just disable all indexes until sync completes
fancy solution: disable some indexers only
Introduce rpc to load chainstate
Put actual assumeutxo hashes into chainparams
In total, only ~1k loc left, although mostly in important places
Approach re-ack discussion
- Do we really need background sync?
- not doing the background sync is simpler, but changes security assumptions
- Also, it would remove the necessity that every node must be able to sync the chain