104 lines
4.3 KiB
Markdown
104 lines
4.3 KiB
Markdown
# Collected change log from Jamie's snap branch squash merge
|
|
|
|
The comments are collected in chronological order, oldest first (as opposed to
|
|
squash merge order which is oldest last.)
|
|
|
|
If a similar comment is found in a source file it was deleted here.
|
|
|
|
|
|
## Sync: Chain head: Promote peer chain head updates to debug level
|
|
|
|
This way, you can see peer chain head updates at `--log-level:DEBUG` without
|
|
being flooded by trace messages.
|
|
|
|
These occur about once every 15 seconds from each good peer.
|
|
|
|
|
|
## Sync: Chain head: Rate limit "blocked overlapping" error states
|
|
|
|
Under some conditions when a peer is not responding (but stays connected),
|
|
these messages happen continuously. Don't output them and don't waste CPU
|
|
trying.
|
|
|
|
|
|
## Sync: Update protocol code to use `BlockHash`, `TxHash`, `NodeHash`
|
|
|
|
New hash type aliases added and used. They're not `distinct` because that
|
|
would be disruptive, but perhaps they will be eventually, when code is
|
|
harmonised around using them.
|
|
|
|
Changes:
|
|
|
|
- Use `BlockHash` more consistently, to match the rest of the sync code.
|
|
|
|
- Use `BlockNumber` where currently `uint64` is used in the protocol (and
|
|
`uint` was used before that, which was 32-bit on 32-bit targets).
|
|
|
|
- New alias `TxHash` is for transactions and is used in
|
|
`NewPooledTransactionHashes` and `GetPooledTransactions`.
|
|
|
|
- New alias `NodeHash` is for trie nodes (or contract bytecode)
|
|
and is used in `GetNodeData`.
|
|
|
|
|
|
## Sync: Set and update `syncStateRoot` for each peer
|
|
|
|
State syncing requires the `stateRoot` value of the selected block to sync to.
|
|
|
|
The chain head tracker selects a block and uses `block.stateRoot`. State sync
|
|
reads that value to sync to. It can change at any time, but that's ok, the
|
|
state sync algorithm is designed around that idea.
|
|
|
|
Aside from getting an initial `stateRoot`, the regular updates are essential
|
|
because state sync is so slow.
|
|
|
|
On Mainnet, it is normal for the initial selected block to become too old
|
|
before state sync is complete, and then peers stop providing data in their
|
|
replies. The solution is for `stateRoot` to be updated by the chain head
|
|
tracker so it's always recent enough. (On Goerli and a fast peer we can fetch
|
|
the whole state just in time without this.)
|
|
|
|
There are a number of issues with the simple implementation here:
|
|
|
|
- The selected `stateRoot` block shouldn't be the most recent canonical head,
|
|
because it is prone to change due to small reorgs. It should be a more stable
|
|
block choice, slightly further back in time.
|
|
|
|
However, any block close to the head is reasonably harmless during the state
|
|
"snap" phase. Small block differences cause a small state delta, which are
|
|
patched automatically during "heal" traversals.
|
|
|
|
- During the state "heal" phase, `stateRoot` should not be updated on every
|
|
block change, because it disrupts the "heal" traversal when this happens.
|
|
|
|
It should be kept the same for longer, but not too long because the `snap/1`
|
|
protocol does not provide state older than 128 blocks ago.
|
|
|
|
So during "heal", `stateRoot` should be updated roughly every N blocks where
|
|
N is close to 128, except when the heal is disrupted due to chain reorgs
|
|
taking place or other loss of available state from the peer.
|
|
|
|
- During the state "heal" phase, `stateRoot` must be coordinated among all
|
|
the peers. This is because "heal" converges a patchwork of states from
|
|
different times into a unified point-in-time whole state, so that execution
|
|
can proceed using entirely local data from there.
|
|
|
|
|
|
## Sync: Add `genesisStateRoot` for state syncing
|
|
|
|
State syncing requires the `stateRoot` value of the selected block to sync to.
|
|
Normally the chain head tracker selects a block and uses `block.stateRoot`.
|
|
|
|
However, in some cases in test environments, the chain head tracker finds the
|
|
sync block is 0, the genesis block, without receiving that block from a peer.
|
|
Of course this only happens when connecting to peers that are on block 0
|
|
themselves, but it can happen and must be handled.
|
|
|
|
Perhaps we should not run state sync on block 0, and instead the local trie.
|
|
But to get the correct "flat" or "snap sync" style representation that requires
|
|
special code.
|
|
|
|
In order to exercise the state sync code and see how peers behave when block 0
|
|
is selected, and avoid special code, use the genesis `stateRoot` found locally,
|
|
and sync that state from peers like any other.
|