390 lines
13 KiB
Nim
390 lines
13 KiB
Nim
# nimbus-eth1
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# Copyright (c) 2021 Status Research & Development GmbH
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# Licensed under either of
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# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
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# http://www.apache.org/licenses/LICENSE-2.0)
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# * MIT license ([LICENSE-MIT](LICENSE-MIT) or
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# http://opensource.org/licenses/MIT)
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# at your option. This file may not be copied, modified, or distributed
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# except according to those terms.
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## Aristo DB -- Patricia Trie Merkleisation
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## ========================================
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##
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## For the current state of the `Patricia Trie`, keys (equivalent to hashes)
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## are associated with the vertex IDs. Existing key associations are checked
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## (i.e. recalculated and compared) unless the ID is locked. In the latter
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## case, the key is assumed to be correct without checking.
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##
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## The association algorithm is an optimised version of:
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##
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## * For all leaf vertices, label them with parent vertex so that there are
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## chains from the leafs to the root vertex.
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##
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## * Apply a width-first traversal starting with the set of leafs vertices
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## compiling the keys to associate with by hashing the current vertex.
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##
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## Apperently, keys (aka hashes) can be compiled for leaf vertices. For the
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## other vertices, the keys can be compiled if all the children keys are
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## known which is assured by the nature of the width-first traversal method.
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##
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## For production, this algorithm is slightly optimised:
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##
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## * For each leaf vertex, calculate the chain from the leaf to the root vertex.
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## + Starting at the leaf, calculate the key for each vertex towards the root
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## vertex as long as possible.
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## + Stash the rest of the partial chain to be completed later
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##
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## * While there is a partial chain left, use the ends towards the leaf
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## vertices and calculate the remaining keys (which results in a width-first
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## traversal, again.)
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{.push raises: [].}
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import
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std/[sequtils, sets, strutils, tables],
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chronicles,
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eth/common,
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stew/results,
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"."/[aristo_constants, aristo_desc, aristo_get, aristo_hike,
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aristo_transcode, aristo_vid]
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type
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BackVidValRef = ref object
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root: VertexID ## Root vertex
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onBe: bool ## Table key vid refers to backend
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toVid: VertexID ## Next/follow up vertex
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BackVidTab =
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Table[VertexID,BackVidValRef]
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logScope:
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topics = "aristo-hashify"
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# ------------------------------------------------------------------------------
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# Private helpers
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# ------------------------------------------------------------------------------
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template logTxt(info: static[string]): static[string] =
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"Hashify " & info
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func getOrVoid(tab: BackVidTab; vid: VertexID): BackVidValRef =
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tab.getOrDefault(vid, BackVidValRef(nil))
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func isValid(brv: BackVidValRef): bool =
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brv != BackVidValRef(nil)
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# ------------------------------------------------------------------------------
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# Private functions
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# ------------------------------------------------------------------------------
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proc toNode(vtx: VertexRef; db: AristoDb): Result[NodeRef,void] =
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case vtx.vType:
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of Leaf:
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return ok NodeRef(vType: Leaf, lPfx: vtx.lPfx, lData: vtx.lData)
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of Branch:
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let node = NodeRef(vType: Branch, bVid: vtx.bVid)
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for n in 0 .. 15:
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if vtx.bVid[n].isValid:
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let key = db.getKey vtx.bVid[n]
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if key.isValid:
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node.key[n] = key
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continue
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return err()
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else:
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node.key[n] = VOID_HASH_KEY
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return ok node
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of Extension:
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if vtx.eVid.isValid:
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let key = db.getKey vtx.eVid
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if key.isValid:
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let node = NodeRef(vType: Extension, ePfx: vtx.ePfx, eVid: vtx.eVid)
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node.key[0] = key
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return ok node
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proc updateHashKey(
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db: AristoDb; # Database, top layer
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root: VertexID; # Root ID
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vid: VertexID; # Vertex ID to check for
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expected: HashKey; # Hash key for vertex address by `vid`
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backend: bool; # Set `true` id vertex is on backend
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): Result[void,AristoError] =
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## Update the argument hash key `expected` for the vertex addressed by `vid`.
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##
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# If the Merkle hash has been cached locally, already it must match.
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block:
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let key = db.top.kMap.getOrVoid(vid).key
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if key.isValid:
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if key != expected:
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let error = HashifyExistingHashMismatch
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debug logTxt "hash update failed", vid, key, expected, error
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return err(error)
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return ok()
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# If the vertex had been cached locally, there would be no locally cached
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# Merkle hash key. It will be created at the bottom end of the function.
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#
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# So there remains tha case when vertex is available on the backend only.
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# The Merkle hash not cached locally. It might be overloaded (and eventually
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# overwitten.)
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if backend:
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# Ok, vertex is on the backend.
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let rc = db.getKeyBackend vid
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if rc.isOk:
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let key = rc.value
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if key == expected:
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return ok()
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# This step is a error in the sense that something the on the backend
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# is fishy. There should not be contradicting Merkle hashes. Throwing
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# an error heres would lead to a deadlock so we correct it.
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debug "correcting backend hash key mismatch", vid, key, expected
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# Proceed `vidAttach()`, below
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elif rc.error != GetKeyNotFound:
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debug logTxt "backend key fetch failed", vid, expected, error=rc.error
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return err(rc.error)
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else:
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discard
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# Proceed `vidAttach()`, below
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# Othwise there is no Merkle hash, so create one with the `expected` key
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db.vidAttach(HashLabel(root: root, key: expected), vid)
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ok()
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proc leafToRootHasher(
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db: AristoDb; # Database, top layer
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hike: Hike; # Hike for labelling leaf..root
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): Result[int,(VertexID,AristoError)] =
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## Returns the index of the first node that could not be hashed
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for n in (hike.legs.len-1).countDown(0):
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let
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wp = hike.legs[n].wp
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bg = hike.legs[n].backend
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rc = wp.vtx.toNode db
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if rc.isErr:
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return ok n
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# Vertices marked proof nodes need not be checked
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if wp.vid in db.top.pPrf:
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continue
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# Check against existing key, or store new key
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let
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key = rc.value.encode.digestTo(HashKey)
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rx = db.updateHashKey(hike.root, wp.vid, key, bg)
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if rx.isErr:
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return err((wp.vid,rx.error))
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ok -1 # all could be hashed
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# ------------------------------------------------------------------------------
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# Public functions
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# ------------------------------------------------------------------------------
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proc hashifyClear*(
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db: AristoDb; # Database, top layer
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locksOnly = false; # If `true`, then clear only proof locks
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) =
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## Clear all `Merkle` hashes from the `db` argument database top layer.
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if not locksOnly:
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db.top.pAmk.clear
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db.top.kMap.clear
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db.top.pPrf.clear
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proc hashify*(
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db: AristoDb; # Database, top layer
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): Result[HashSet[VertexID],(VertexID,AristoError)] =
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## Add keys to the `Patricia Trie` so that it becomes a `Merkle Patricia
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## Tree`. If successful, the function returns the key (aka Merkle hash) of
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## the root vertex.
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var
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roots: HashSet[VertexID]
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completed: HashSet[VertexID]
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# Width-first leaf-to-root traversal structure
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backLink: BackVidTab
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downMost: BackVidTab
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for (lky,vid) in db.top.lTab.pairs:
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let hike = lky.hikeUp(db)
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if hike.error != AristoError(0):
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return err((vid,hike.error))
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roots.incl hike.root
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# Hash as much of the `hike` as possible
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let n = block:
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let rc = db.leafToRootHasher hike
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if rc.isErr:
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return err(rc.error)
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rc.value
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if 0 < n:
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# Backtrack and register remaining nodes. Note that in case *n == 0*, the
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# root vertex has not been fully resolved yet.
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#
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# hike.legs: (leg[0], leg[1], .., leg[n-1], leg[n], ..)
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# | | | |
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# | <---- | <---- | <---- |
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# | | |
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# | backLink[] | downMost |
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#
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downMost[hike.legs[n].wp.vid] = BackVidValRef(
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root: hike.root,
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onBe: hike.legs[n].backend,
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toVid: hike.legs[n-1].wp.vid)
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for u in (n-1).countDown(1):
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backLink[hike.legs[u].wp.vid] = BackVidValRef(
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root: hike.root,
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onBe: hike.legs[u].backend,
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toVid: hike.legs[u-1].wp.vid)
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elif n < 0:
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completed.incl hike.root
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# At least one full path leaf..root should have succeeded with labelling
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# for each root.
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if completed.len < roots.len:
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return err((VertexID(0),HashifyLeafToRootAllFailed))
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# Update remaining hashes
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while 0 < downMost.len:
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var
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redo: BackVidTab
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done: HashSet[VertexID]
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for (vid,val) in downMost.pairs:
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# Try to convert vertex to a node. This is possible only if all link
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# references have Merkle hashes.
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#
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# Also `db.getVtx(vid)` => not nil as it was fetched earlier, already
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let rc = db.getVtx(vid).toNode(db)
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if rc.isErr:
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# Cannot complete with this vertex, so do it later
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redo[vid] = val
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else:
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# Update Merkle hash
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let
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key = rc.value.encode.digestTo(HashKey)
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rx = db.updateHashKey(val.root, vid, key, val.onBe)
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if rx.isErr:
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return err((vid,rx.error))
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done.incl vid
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# Proceed with back link
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let nextItem = backLink.getOrVoid val.toVid
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if nextItem.isValid:
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redo[val.toVid] = nextItem
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# Make sure that the algorithm proceeds
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if done.len == 0:
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let error = HashifyCannotComplete
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return err((VertexID(0),error))
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# Clean up dups from `backLink` and restart `downMost`
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for vid in done.items:
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backLink.del vid
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downMost = redo
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ok completed
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# ------------------------------------------------------------------------------
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# Public debugging functions
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# ------------------------------------------------------------------------------
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proc hashifyCheck*(
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db: AristoDb; # Database, top layer
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relax = false; # Check existing hashes only
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): Result[void,(VertexID,AristoError)] =
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## Verify that the Merkle hash keys are either completely missing or
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## match all known vertices on the argument database layer `db`.
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if not relax:
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for (vid,vtx) in db.top.sTab.pairs:
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let rc = vtx.toNode(db)
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if rc.isErr:
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return err((vid,HashifyCheckVtxIncomplete))
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let lbl = db.top.kMap.getOrVoid vid
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if not lbl.isValid:
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return err((vid,HashifyCheckVtxHashMissing))
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if lbl.key != rc.value.encode.digestTo(HashKey):
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return err((vid,HashifyCheckVtxHashMismatch))
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let revVid = db.top.pAmk.getOrVoid lbl
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if not revVid.isValid:
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return err((vid,HashifyCheckRevHashMissing))
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if revVid != vid:
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return err((vid,HashifyCheckRevHashMismatch))
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elif 0 < db.top.pPrf.len:
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for vid in db.top.pPrf:
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let vtx = db.top.sTab.getOrVoid vid
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if not vtx.isValid:
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return err((vid,HashifyCheckVidVtxMismatch))
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let rc = vtx.toNode(db)
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if rc.isErr:
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return err((vid,HashifyCheckVtxIncomplete))
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let lbl = db.top.kMap.getOrVoid vid
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if not lbl.isValid:
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return err((vid,HashifyCheckVtxHashMissing))
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if lbl.key != rc.value.encode.digestTo(HashKey):
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return err((vid,HashifyCheckVtxHashMismatch))
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let revVid = db.top.pAmk.getOrVoid lbl
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if not revVid.isValid:
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return err((vid,HashifyCheckRevHashMissing))
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if revVid != vid:
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return err((vid,HashifyCheckRevHashMismatch))
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else:
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for (vid,lbl) in db.top.kMap.pairs:
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if lbl.isValid: # Otherwise to be deleted
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let vtx = db.getVtx vid
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if vtx.isValid:
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let rc = vtx.toNode(db)
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if rc.isOk:
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if lbl.key != rc.value.encode.digestTo(HashKey):
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return err((vid,HashifyCheckVtxHashMismatch))
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let revVid = db.top.pAmk.getOrVoid lbl
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if not revVid.isValid:
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return err((vid,HashifyCheckRevHashMissing))
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if revVid != vid:
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return err((vid,HashifyCheckRevHashMismatch))
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# Some `kMap[]` entries may ne void indicating backend deletion
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let kMapCount = db.top.kMap.values.toSeq.filterIt(it.isValid).len
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if db.top.pAmk.len != kMapCount:
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var knownKeys: HashSet[VertexID]
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for (key,vid) in db.top.pAmk.pairs:
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if not db.top.kMap.hasKey(vid):
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return err((vid,HashifyCheckRevVtxMissing))
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if vid in knownKeys:
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return err((vid,HashifyCheckRevVtxDup))
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knownKeys.incl vid
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return err((VertexID(0),HashifyCheckRevCountMismatch)) # should not apply(!)
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if 0 < db.top.pAmk.len and not relax and db.top.pAmk.len < db.top.sTab.len:
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# Cannot have less changes than cached entries
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return err((VertexID(0),HashifyCheckVtxCountMismatch))
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for vid in db.top.pPrf:
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if not db.top.kMap.hasKey(vid):
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return err((vid,HashifyCheckVtxLockWithoutKey))
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ok()
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# ------------------------------------------------------------------------------
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# End
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# ------------------------------------------------------------------------------
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