mirror of
https://gitlab.com/pulsechaincom/erigon-pulse.git
synced 2024-12-22 11:41:19 +00:00
56 lines
3.5 KiB
Markdown
56 lines
3.5 KiB
Markdown
# Merry-Go-Round sync (Erigon design)
|
|
|
|
Initial discussion here: https://ethresear.ch/t/merry-go-round-sync/7158
|
|
|
|
## Participants
|
|
|
|
We divide participants into two types: seeders and leechers. Seeders are the ones who have the full copy of the current Ethereum
|
|
state, and they also keep updating it as new blocks appear. Leechers are the ones that join the Merry-Go-Round network to
|
|
either acquire the full copy of the state, or "sift" through it to acquire some part of the state (this is what some "Stateless"
|
|
node might like to do in the beginning).
|
|
|
|
## Syncing cycles
|
|
|
|
The process of syncing happens in cycles. During each cycle, all participants attempt to distribute the entire content of the
|
|
Ethereum state to each other. Therefore the duration of one cycle for the Ethereum mainnet is likely to be some hours.
|
|
Cycle is divided into ticks. For convenience, we can say that each ticks starts after the mining of certain block, and lasts
|
|
for some predetermined amount of time, let's say, 30 seconds. This definition means that the ticks will often overlap, but not
|
|
always, as shown on the picture below.
|
|
|
|
|
|
|
|
If chain reorgs occur, and the timings of recent Ethereum blocks change as a result, we can accept these rules to prevent
|
|
the reorgs to be used to disrupt the sync. Imagine the tick started at block A (height H), and then due to reorg, block A
|
|
was replaced by block B (also height H).
|
|
|
|
* If timestamp(B) < timestamp(A), the tick does not shorten, but proceeds until timestamp(A) + tick_duration.
|
|
|
|
* If timestamp(B) >= timestamp(A), the tick gets extended to proceed until timestamp(B) + tick_duration.
|
|
|
|
As one would guess, we try to distribute the entire Ethereum state into as many pieces as many ticks there are in one cycle.
|
|
Each piece would be exchanged over the duration of one tick. Obviously, we would like to make the distribution as even as possible.
|
|
Therefore, there is still a concern about situations when the blocks are coming in quick succession, and the ticks corresponding
|
|
to those blocks would largely overlap.
|
|
|
|
## Sync schedule
|
|
|
|
When we split the entire Ethereum state into pieces and plan to exchange each piece during one tick, we are creating a sync
|
|
schedule. Sync schedule is a mapping from the tick number (which can be derived from the block number) to the piece of state.
|
|
These pieces need to be efficient to extract from the State Database (for a seeder), and add to the State Database (for a leecher).
|
|
Probably the most convenient way of specifying such a piece of state is a pair of bounds - lower bound and upper bound.
|
|
Each of the bounds would correspond to either Keccak256 hash of an address, or to a combination of Keccak256 hash of an address,
|
|
and Keccak256 hash of a storage location in some contract. In other words, there could be four types of specification for a piece
|
|
of state:
|
|
|
|
1. `[ keccak256(address1); keccak256(address2) )`
|
|
2. `[ keccak256(address1), keccak256(location1); keccak256(address2) )`
|
|
3. `[ keccak256(address1); keccak256(address2), keccak256(location2) )`
|
|
4. `[ keccak256(address1), keccak256(location1); keccak256(address2), keccak256(location2) )`
|
|
|
|
In the last type, addresses `address1` and `address2` may mean the same address. If they mean different addresses, then `location1` and `location2` may mean the same locations.
|
|
|
|
## How will seeders produce sync schedule
|
|
|
|
Seeders should have the ability to generate the sync schedule by the virtue of having the entire Ethereum state available. No
|
|
extra coordination should be necessary.
|