genswiftsyncbitmap, chaincfg, blockchain: implement swiftsync #2478
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for clients In order for the clients to take advantage of swiftsync, we need provide the bitmap to the clients. This tool generates the bitmap and writes it in the data directory of the given network (mainnet, signet, etc).
Add the SwiftSyncData structure which contains precomputed bitmap data for fast UTXO set bootstrapping. The bitmap indicates which transaction outputs have been spent up to a certain block height, allowing nodes to skip transaction replay during initial sync. Include embedded bitmap data for signet covering blocks 1 through 285205. The bitmap is stored in chaincfg/data/ and embedded at compile time using go:embed.
Implement swift sync which uses precomputed bitmap data to rapidly construct the UTXO set during initial block download. Instead of replaying all historical transactions, swift sync checks each output against the bitmap: bit 0 means unspent (add to UTXO cache), bit 1 means spent (skip). Key features: - Skip all transaction validation during swift sync range - Persist bitmap bit index for resumability across restarts - Verify block hash at swift sync boundary to ensure chain correctness - Safety check prevents enabling swift sync on existing chain data Swift sync is automatically enabled when checkpoints are enabled and SwiftSyncData is available in chain parameters.
Add a checkpoint at the swift sync boundary height (285205) for signet. Swift sync requires at least one checkpoint to be enabled as a security measure to validate the chain before trusting the precomputed bitmap.
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Change Description
This is a first implementation of SwiftSync for btcd. SwiftSync enables fast UTXO set bootstrapping during initial block download by using a precomputed bitmap that indicates which transaction outputs have been spent.
Instead of replaying and validating all historical transactions from genesis, nodes can use the bitmap to directly construct the UTXO set:
The main benefit is performance improvement during ibd. On this PR when testing on signet, it was 3.3x faster than on master.
Without SwiftSync on master to block height 285,205 took 22m 59s.
Ran with command:
pprof:
With SwiftSync on this PR to block height 285,205 took 6m 56s.
Ran with command:
One caveat is that we can't generate the SpendJournals for the blocks that are processed with SwiftSync.
Note that the aggregator part of SwiftSync is not yet implemented which makes this not safe to run for production uses.
This is a first pass at the implementation and is not final. Feedback welcome.
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