629 lines
22 KiB
Nim
629 lines
22 KiB
Nim
import
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bitops, chronicles, options, sequtils, tables,
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ssz, beacon_chain_db, state_transition, extras,
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beacon_node_types,
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spec/[crypto, datatypes, digest, helpers]
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proc parent*(bs: BlockSlot): BlockSlot =
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BlockSlot(
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blck: if bs.slot > bs.blck.slot: bs.blck else: bs.blck.parent,
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slot: bs.slot - 1
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)
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proc link(parent, child: BlockRef) =
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doAssert (not (parent.root == Eth2Digest() or child.root == Eth2Digest())),
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"blocks missing root!"
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doAssert parent.root != child.root, "self-references not allowed"
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child.parent = parent
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parent.children.add(child)
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proc init*(T: type BlockRef, root: Eth2Digest, slot: Slot): BlockRef =
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BlockRef(
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root: root,
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slot: slot
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)
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proc init*(T: type BlockRef, root: Eth2Digest, blck: BeaconBlock): BlockRef =
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BlockRef.init(root, blck.slot)
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proc findAncestorBySlot*(blck: BlockRef, slot: Slot): BlockSlot =
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## Find the first ancestor that has a slot number less than or equal to `slot`
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assert(not blck.isNil)
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var ret = blck
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while ret.parent != nil and ret.slot > slot:
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ret = ret.parent
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BlockSlot(blck: ret, slot: slot)
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proc init*(T: type BlockPool, db: BeaconChainDB): BlockPool =
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# TODO we require that the db contains both a head and a tail block -
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# asserting here doesn't seem like the right way to go about it however..
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let
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tailBlockRoot = db.getTailBlock()
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headBlockRoot = db.getHeadBlock()
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doAssert tailBlockRoot.isSome(), "Missing tail block, database corrupt?"
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doAssert headBlockRoot.isSome(), "Missing head block, database corrupt?"
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let
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tailRoot = tailBlockRoot.get()
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tailBlock = db.getBlock(tailRoot).get()
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tailRef = BlockRef.init(tailRoot, tailBlock)
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headRoot = headBlockRoot.get()
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var
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blocks = {tailRef.root: tailRef}.toTable()
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latestStateRoot = Option[Eth2Digest]()
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headStateBlock = tailRef
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headRef: BlockRef
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if headRoot != tailRoot:
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var curRef: BlockRef
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for root, blck in db.getAncestors(headRoot):
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if root == tailRef.root:
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doAssert(not curRef.isNil)
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link(tailRef, curRef)
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curRef = curRef.parent
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break
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let newRef = BlockRef.init(root, blck)
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if curRef == nil:
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curRef = newRef
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headRef = newRef
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else:
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link(newRef, curRef)
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curRef = curRef.parent
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blocks[curRef.root] = curRef
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if latestStateRoot.isNone() and db.containsState(blck.state_root):
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latestStateRoot = some(blck.state_root)
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doAssert curRef == tailRef,
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"head block does not lead to tail, database corrupt?"
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else:
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headRef = tailRef
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var blocksBySlot = initTable[uint64, seq[BlockRef]]()
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for _, b in tables.pairs(blocks):
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let slot = db.getBlock(b.root).get().slot
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blocksBySlot.mgetOrPut(slot.uint64, @[]).add(b)
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let
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# The head state is necessary to find out what we considered to be the
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# finalized epoch last time we saved something.
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headStateRoot =
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if latestStateRoot.isSome():
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latestStateRoot.get()
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else:
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db.getBlock(tailRef.root).get().state_root
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# TODO right now, because we save a state at every epoch, this *should*
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# be the latest justified state or newer, meaning it's enough for
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# establishing what we consider to be the finalized head. This logic
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# will need revisiting however
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headState = db.getState(headStateRoot).get()
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finalizedHead =
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headRef.findAncestorBySlot(
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headState.finalized_checkpoint.epoch.compute_start_slot_of_epoch())
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justifiedSlot =
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headState.current_justified_checkpoint.epoch.compute_start_slot_of_epoch()
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justifiedHead = headRef.findAncestorBySlot(justifiedSlot)
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head = Head(blck: headRef, justified: justifiedHead)
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doAssert justifiedHead.slot >= finalizedHead.slot,
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"justified head comes before finalized head - database corrupt?"
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BlockPool(
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pending: initTable[Eth2Digest, BeaconBlock](),
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missing: initTable[Eth2Digest, MissingBlock](),
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blocks: blocks,
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blocksBySlot: blocksBySlot,
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tail: tailRef,
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head: head,
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finalizedHead: finalizedHead,
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db: db,
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heads: @[head]
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)
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proc addSlotMapping(pool: BlockPool, slot: uint64, br: BlockRef) =
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proc addIfMissing(s: var seq[BlockRef], v: BlockRef) =
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if v notin s:
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s.add(v)
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pool.blocksBySlot.mgetOrPut(slot, @[]).addIfMissing(br)
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proc updateStateData*(
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pool: BlockPool, state: var StateData, bs: BlockSlot) {.gcsafe.}
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proc add*(
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pool: var BlockPool, state: var StateData, blockRoot: Eth2Digest,
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blck: BeaconBlock): BlockRef {.gcsafe.}
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proc addResolvedBlock(
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pool: var BlockPool, state: var StateData, blockRoot: Eth2Digest,
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blck: BeaconBlock, parent: BlockRef): BlockRef =
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let blockRef = BlockRef.init(blockRoot, blck)
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link(parent, blockRef)
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pool.blocks[blockRoot] = blockRef
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pool.addSlotMapping(blck.slot.uint64, blockRef)
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# Resolved blocks should be stored in database
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pool.db.putBlock(blockRoot, blck)
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# TODO this is a bit ugly - we update state.data outside of this function then
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# set the rest here - need a blockRef to update it. Clean this up -
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# hopefully it won't be necessary by the time hash caching and the rest
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# is done..
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doAssert state.data.data.slot == blockRef.slot
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state.blck = blockRef
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# This block *might* have caused a justification - make sure we stow away
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# that information:
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let justifiedSlot =
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state.data.data.current_justified_checkpoint.epoch.compute_start_slot_of_epoch()
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var foundHead: Option[Head]
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for head in pool.heads.mitems():
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if head.blck.root == blck.parent_root:
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if head.justified.slot != justifiedSlot:
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head.justified = blockRef.findAncestorBySlot(justifiedSlot)
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foundHead = some(head)
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break
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if foundHead.isNone():
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foundHead = some(Head(
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blck: blockRef,
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justified: blockRef.findAncestorBySlot(justifiedSlot)))
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pool.heads.add(foundHead.get())
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info "Block resolved",
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blck = shortLog(blck),
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blockRoot = shortLog(blockRoot),
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justifiedRoot = shortLog(foundHead.get().justified.blck.root),
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justifiedSlot = humaneSlotNum(foundHead.get().justified.slot)
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# Now that we have the new block, we should see if any of the previously
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# unresolved blocks magically become resolved
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# TODO there are more efficient ways of doing this that don't risk
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# running out of stack etc
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let retries = pool.pending
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for k, v in retries:
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discard pool.add(state, k, v)
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blockRef
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proc add*(
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pool: var BlockPool, state: var StateData, blockRoot: Eth2Digest,
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blck: BeaconBlock): BlockRef {.gcsafe.} =
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## return the block, if resolved...
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## the state parameter may be updated to include the given block, if
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## everything checks out
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# TODO reevaluate passing the state in like this
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doAssert blockRoot == signing_root(blck)
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# Already seen this block??
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if blockRoot in pool.blocks:
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debug "Block already exists",
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blck = shortLog(blck),
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blockRoot = shortLog(blockRoot)
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return pool.blocks[blockRoot]
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pool.missing.del(blockRoot)
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# If the block we get is older than what we finalized already, we drop it.
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# One way this can happen is that we start resolving a block and finalization
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# happens in the meantime - the block we requested will then be stale
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# by the time it gets here.
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if blck.slot <= pool.finalizedHead.slot:
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debug "Old block, dropping",
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blck = shortLog(blck),
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tailSlot = humaneSlotNum(pool.tail.slot),
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blockRoot = shortLog(blockRoot)
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return
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let parent = pool.blocks.getOrDefault(blck.parent_root)
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if parent != nil:
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# The block might have been in either of these - we don't want any more
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# work done on its behalf
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pool.pending.del(blockRoot)
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# The block is resolved, now it's time to validate it to ensure that the
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# blocks we add to the database are clean for the given state
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# TODO if the block is from the future, we should not be resolving it (yet),
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# but maybe we should use it as a hint that our clock is wrong?
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updateStateData(pool, state, BlockSlot(blck: parent, slot: blck.slot - 1))
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if not state_transition(state.data, blck, {}):
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# TODO find a better way to log all this block data
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notice "Invalid block",
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blck = shortLog(blck),
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blockRoot = shortLog(blockRoot)
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return
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return pool.addResolvedBlock(state, blockRoot, blck, parent)
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pool.pending[blockRoot] = blck
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# TODO possibly, it makes sense to check the database - that would allow sync
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# to simply fill up the database with random blocks the other clients
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# think are useful - but, it would also risk filling the database with
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# junk that's not part of the block graph
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if blck.parent_root in pool.missing or
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blck.parent_root in pool.pending:
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return
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# This is an unresolved block - put its parent on the missing list for now...
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# TODO if we receive spam blocks, one heurestic to implement might be to wait
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# for a couple of attestations to appear before fetching parents - this
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# would help prevent using up network resources for spam - this serves
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# two purposes: one is that attestations are likely to appear for the
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# block only if it's valid / not spam - the other is that malicious
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# validators that are not proposers can sign invalid blocks and send
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# them out without penalty - but signing invalid attestations carries
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# a risk of being slashed, making attestations a more valuable spam
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# filter.
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# TODO when we receive the block, we don't know how many others we're missing
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# from that branch, so right now, we'll just do a blind guess
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debug "Unresolved block (parent missing)",
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blck = shortLog(blck),
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blockRoot = shortLog(blockRoot)
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let parentSlot = blck.slot - 1
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pool.missing[blck.parent_root] = MissingBlock(
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slots:
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# The block is at least two slots ahead - try to grab whole history
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if parentSlot > pool.head.blck.slot:
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parentSlot - pool.head.blck.slot
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else:
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# It's a sibling block from a branch that we're missing - fetch one
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# epoch at a time
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max(1.uint64, SLOTS_PER_EPOCH.uint64 -
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(parentSlot.uint64 mod SLOTS_PER_EPOCH.uint64))
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)
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proc getRef*(pool: BlockPool, root: Eth2Digest): BlockRef =
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## Retrieve a resolved block reference, if available
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result = pool.blocks.getOrDefault(root)
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proc get*(pool: BlockPool, blck: BlockRef): BlockData =
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## Retrieve the associated block body of a block reference
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doAssert (not blck.isNil), "Trying to get nil BlockRef"
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let data = pool.db.getBlock(blck.root)
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doAssert data.isSome, "BlockRef without backing data, database corrupt?"
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BlockData(data: data.get(), refs: blck)
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proc get*(pool: BlockPool, root: Eth2Digest): Option[BlockData] =
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## Retrieve a resolved block reference and its associated body, if available
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let refs = pool.getRef(root)
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if not refs.isNil:
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some(pool.get(refs))
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else:
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none(BlockData)
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proc getOrResolve*(pool: var BlockPool, root: Eth2Digest): BlockRef =
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## Fetch a block ref, or nil if not found (will be added to list of
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## blocks-to-resolve)
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result = pool.getRef(root)
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if result.isNil:
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pool.missing[root] = MissingBlock(slots: 1)
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iterator blockRootsForSlot*(pool: BlockPool, slot: uint64|Slot): Eth2Digest =
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for br in pool.blocksBySlot.getOrDefault(slot.uint64, @[]):
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yield br.root
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proc checkMissing*(pool: var BlockPool): seq[FetchRecord] =
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## Return a list of blocks that we should try to resolve from other client -
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## to be called periodically but not too often (once per slot?)
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var done: seq[Eth2Digest]
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for k, v in pool.missing.mpairs():
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if v.tries > 8:
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done.add(k)
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else:
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inc v.tries
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for k in done:
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# TODO Need to potentially remove from pool.pending - this is currently a
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# memory leak here!
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pool.missing.del(k)
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# simple (simplistic?) exponential backoff for retries..
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for k, v in pool.missing.pairs():
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if v.tries.popcount() == 1:
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result.add(FetchRecord(root: k, historySlots: v.slots))
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proc skipAndUpdateState(
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state: var HashedBeaconState, blck: BeaconBlock, flags: UpdateFlags,
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afterUpdate: proc (state: HashedBeaconState)): bool =
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process_slots(state, blck.slot - 1)
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afterUpdate(state)
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let ok = state_transition(state, blck, flags)
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afterUpdate(state)
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ok
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proc maybePutState(pool: BlockPool, state: HashedBeaconState, blck: BlockRef) =
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# TODO we save state at every epoch start but never remove them - we also
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# potentially save multiple states per slot if reorgs happen, meaning
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# we could easily see a state explosion
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if state.data.slot mod SLOTS_PER_EPOCH == 0:
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if not pool.db.containsState(state.root):
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info "Storing state",
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stateSlot = humaneSlotNum(state.data.slot),
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stateRoot = shortLog(state.root)
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pool.db.putState(state.root, state.data)
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# TODO this should be atomic with the above write..
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pool.db.putStateRoot(blck.root, state.data.slot, state.root)
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proc rewindState(pool: BlockPool, state: var StateData, bs: BlockSlot):
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seq[BlockData] =
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var ancestors = @[pool.get(bs.blck)]
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# Common case: the last block applied is the parent of the block to apply:
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if not bs.blck.parent.isNil and state.blck.root == bs.blck.parent.root and
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state.data.data.slot < bs.slot:
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return ancestors
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# It appears that the parent root of the proposed new block is different from
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# what we expected. We will have to rewind the state to a point along the
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# chain of ancestors of the new block. We will do this by loading each
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# successive parent block and checking if we can find the corresponding state
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# in the database.
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var
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stateRoot = pool.db.getStateRoot(bs.blck.root, bs.slot)
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curBs = bs
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while stateRoot.isNone():
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let parBs = curBs.parent()
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if parBs.blck.isNil:
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break # Bug probably!
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if parBs.blck != curBs.blck:
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ancestors.add(pool.get(parBs.blck))
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if (let tmp = pool.db.getStateRoot(parBs.blck.root, parBs.slot); tmp.isSome()):
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if pool.db.containsState(tmp.get):
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stateRoot = tmp
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break
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curBs = parBs
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if stateRoot.isNone():
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# TODO this should only happen if the database is corrupt - we walked the
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# list of parent blocks and couldn't find a corresponding state in the
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# database, which should never happen (at least we should have the
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# tail state in there!)
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error "Couldn't find ancestor state root!",
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blockRoot = shortLog(bs.blck.root)
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doAssert false, "Oh noes, we passed big bang!"
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let
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ancestor = ancestors[^1]
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ancestorState = pool.db.getState(stateRoot.get())
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if ancestorState.isNone():
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# TODO this should only happen if the database is corrupt - we walked the
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# list of parent blocks and couldn't find a corresponding state in the
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# database, which should never happen (at least we should have the
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# tail state in there!)
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error "Couldn't find ancestor state or block parent missing!",
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blockRoot = shortLog(bs.blck.root)
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doAssert false, "Oh noes, we passed big bang!"
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debug "Replaying state transitions",
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stateSlot = humaneSlotNum(state.data.data.slot),
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ancestorStateRoot = shortLog(ancestor.data.state_root),
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ancestorStateSlot = humaneSlotNum(ancestorState.get().slot),
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slot = humaneSlotNum(bs.slot),
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blockRoot = shortLog(bs.blck.root),
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ancestors = ancestors.len
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state.data.data = ancestorState.get()
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state.data.root = stateRoot.get()
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state.blck = ancestor.refs
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ancestors
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proc updateStateData*(pool: BlockPool, state: var StateData, bs: BlockSlot) =
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## Rewind or advance state such that it matches the given block and slot -
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## this may include replaying from an earlier snapshot if blck is on a
|
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## different branch or has advanced to a higher slot number than slot
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## If slot is higher than blck.slot, replay will fill in with empty/non-block
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## slots, else it is ignored
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# We need to check the slot because the state might have moved forwards
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# without blocks
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if state.blck.root == bs.blck.root and state.data.data.slot <= bs.slot:
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if state.data.data.slot != bs.slot:
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# Might be that we're moving to the same block but later slot
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process_slots(state.data, bs.slot)
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pool.maybePutState(state.data, bs.blck)
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return # State already at the right spot
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let ancestors = rewindState(pool, state, bs)
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# If we come this far, we found the state root. The last block on the stack
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# is the one that produced this particular state, so we can pop it
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# TODO it might be possible to use the latest block hashes from the state to
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# do this more efficiently.. whatever!
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# Time to replay all the blocks between then and now. We skip one because
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# it's the one that we found the state with, and it has already been
|
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# applied
|
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for i in countdown(ancestors.len - 2, 0):
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let ok =
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skipAndUpdateState(state.data, ancestors[i].data, {skipValidation}) do(
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state: HashedBeaconState):
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pool.maybePutState(state, ancestors[i].refs)
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doAssert ok, "Blocks in database should never fail to apply.."
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process_slots(state.data, bs.slot)
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pool.maybePutState(state.data, bs.blck)
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state.blck = bs.blck
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proc loadTailState*(pool: BlockPool): StateData =
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## Load the state associated with the current tail in the pool
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let stateRoot = pool.db.getBlock(pool.tail.root).get().state_root
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StateData(
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data: HashedBeaconState(
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data: pool.db.getState(stateRoot).get(),
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root: stateRoot),
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blck: pool.tail
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)
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func isAncestorOf*(a, b: BlockRef): bool =
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if a == b:
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true
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elif a.slot >= b.slot or b.parent.isNil:
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false
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else:
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a.isAncestorOf(b.parent)
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proc updateHead*(pool: BlockPool, state: var StateData, blck: BlockRef) =
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## Update what we consider to be the current head, as given by the fork
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## choice.
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## The choice of head affects the choice of finalization point - the order
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## of operations naturally becomes important here - after updating the head,
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## blocks that were once considered potential candidates for a tree will
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## now fall from grace, or no longer be considered resolved.
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if pool.head.blck == blck:
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debug "No head update this time",
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headBlockRoot = shortLog(blck.root),
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headBlockSlot = humaneSlotNum(blck.slot)
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return
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let
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lastHead = pool.head
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pool.db.putHeadBlock(blck.root)
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# Start off by making sure we have the right state
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updateStateData(pool, state, BlockSlot(blck: blck, slot: blck.slot))
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let justifiedSlot =
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state.data.data.current_justified_checkpoint.epoch.compute_start_slot_of_epoch()
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pool.head = Head(blck: blck, justified: blck.findAncestorBySlot(justifiedSlot))
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if lastHead.blck != blck.parent:
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notice "Updated head with new parent",
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lastHeadRoot = shortLog(lastHead.blck.root),
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parentRoot = shortLog(blck.parent.root),
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stateRoot = shortLog(state.data.root),
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headBlockRoot = shortLog(state.blck.root),
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stateSlot = humaneSlotNum(state.data.data.slot),
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justifiedEpoch =
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humaneEpochNum(state.data.data.current_justified_checkpoint.epoch),
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finalizedEpoch =
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humaneEpochNum(state.data.data.finalized_checkpoint.epoch)
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else:
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info "Updated head",
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stateRoot = shortLog(state.data.root),
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headBlockRoot = shortLog(state.blck.root),
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stateSlot = humaneSlotNum(state.data.data.slot),
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justifiedEpoch =
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humaneEpochNum(state.data.data.current_justified_checkpoint.epoch),
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finalizedEpoch =
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humaneEpochNum(state.data.data.finalized_checkpoint.epoch)
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let
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# TODO there might not be a block at the epoch boundary - what then?
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finalizedHead =
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blck.findAncestorBySlot(
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state.data.data.finalized_checkpoint.epoch.compute_start_slot_of_epoch())
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doAssert (not finalizedHead.blck.isNil),
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"Block graph should always lead to a finalized block"
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if finalizedHead != pool.finalizedHead:
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info "Finalized block",
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finalizedBlockRoot = shortLog(finalizedHead.blck.root),
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finalizedBlockSlot = humaneSlotNum(finalizedHead.slot),
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headBlockRoot = shortLog(blck.root),
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headBlockSlot = humaneSlotNum(blck.slot)
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var cur = finalizedHead.blck
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while cur != pool.finalizedHead.blck:
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# Finalization means that we choose a single chain as the canonical one -
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# it also means we're no longer interested in any branches from that chain
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# up to the finalization point
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# TODO technically, if we remove from children the gc should free the block
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# because it should become orphaned, via mark&sweep if nothing else,
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# though this needs verification
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# TODO what about attestations? we need to drop those too, though they
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# *should* be pretty harmless
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# TODO remove from database as well.. here, or using some GC-like setup
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# that periodically cleans it up?
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for child in cur.parent.children:
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if child != cur:
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pool.blocks.del(child.root)
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cur.parent.children = @[cur]
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cur = cur.parent
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pool.finalizedHead = finalizedHead
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let hlen = pool.heads.len
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for i in 0..<hlen:
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let n = hlen - i - 1
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if pool.heads[n].blck.slot < pool.finalizedHead.blck.slot and
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not pool.heads[n].blck.isAncestorOf(pool.finalizedHead.blck):
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pool.heads.del(n)
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proc latestJustifiedBlock*(pool: BlockPool): BlockRef =
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## Return the most recent block that is justified and at least as recent
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## as the latest finalized block
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|
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doAssert pool.heads.len > 0,
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"We should have at least the genesis block in heaads"
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doAssert (not pool.head.blck.isNil()),
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|
"Genesis block will be head, if nothing else"
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|
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# Prefer stability: use justified block from current head to break ties!
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result = pool.head.justified.blck
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for head in pool.heads[1 ..< ^0]:
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if head.justified.blck.slot > result.slot:
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result = head.justified.blck
|
|
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|
proc preInit*(
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T: type BlockPool, db: BeaconChainDB, state: BeaconState, blck: BeaconBlock) =
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# write a genesis state, the way the BlockPool expects it to be stored in
|
|
# database
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|
# TODO probably should just init a blockpool with the freshly written
|
|
# state - but there's more refactoring needed to make it nice - doing
|
|
# a minimal patch for now..
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|
let
|
|
blockRoot = signing_root(blck)
|
|
|
|
notice "Creating new database from snapshot",
|
|
blockRoot = shortLog(blockRoot),
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|
stateRoot = shortLog(blck.state_root),
|
|
fork = state.fork,
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|
validators = state.validators.len()
|
|
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|
db.putState(state)
|
|
db.putBlock(blck)
|
|
db.putTailBlock(blockRoot)
|
|
db.putHeadBlock(blockRoot)
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db.putStateRoot(blockRoot, blck.slot, blck.state_root)
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