From 2a3694991305aefff6c27d6f77ab2cd6472e56e5 Mon Sep 17 00:00:00 2001
From: Jacek Sieka <jacek@status.im>
Date: Mon, 10 Aug 2020 15:21:31 +0200
Subject: [PATCH] use epochcache for attesting (#1478)

---
 beacon_chain/block_pools/spec_cache.nim | 30 ++++++++++-
 beacon_chain/validator_duties.nim       | 70 +++++++++++++++----------
 beacon_chain/validator_pool.nim         |  4 +-
 3 files changed, 74 insertions(+), 30 deletions(-)

diff --git a/beacon_chain/block_pools/spec_cache.nim b/beacon_chain/block_pools/spec_cache.nim
index 3930bc6a8..3fec5b3c1 100644
--- a/beacon_chain/block_pools/spec_cache.nim
+++ b/beacon_chain/block_pools/spec_cache.nim
@@ -12,7 +12,7 @@ import
     beaconstate, crypto, datatypes, digest, helpers, presets, signatures,
     validator],
   ../extras,
-  ./block_pools_types
+  ./block_pools_types, ./chain_dag
 
 # Spec functions implemented based on cached values instead of the full state
 func count_active_validators*(epochInfo: EpochRef): uint64 =
@@ -122,3 +122,31 @@ proc is_valid_indexed_attestation*(
       return false
 
   true
+
+func makeAttestationData*(
+    epochRef: EpochRef, bs: BlockSlot,
+    committee_index: uint64): AttestationData =
+  ## Create an attestation / vote for the block `bs` using the
+  ## data in `epochRef` to fill in the rest of the fields.
+  ## `epochRef` is the epoch information corresponding to the `bs` advanced to
+  ## the slot we're attesting to.
+
+  let
+    slot = bs.slot
+    current_epoch = slot.compute_epoch_at_slot()
+    epoch_boundary_slot = compute_start_slot_at_epoch(current_epoch)
+    epoch_boundary_block = bs.blck.atSlot(epoch_boundary_slot)
+
+  doAssert current_epoch == epochRef.epoch
+
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/validator.md#attestation-data
+  AttestationData(
+    slot: slot,
+    index: committee_index,
+    beacon_block_root: bs.blck.root,
+    source: epochRef.current_justified_checkpoint,
+    target: Checkpoint(
+      epoch: current_epoch,
+      root: epoch_boundary_block.blck.root
+    )
+  )
diff --git a/beacon_chain/validator_duties.nim b/beacon_chain/validator_duties.nim
index 9006c1bae..42f1ba283 100644
--- a/beacon_chain/validator_duties.nim
+++ b/beacon_chain/validator_duties.nim
@@ -18,7 +18,7 @@ import
   eth/[keys, async_utils], eth/p2p/discoveryv5/[protocol, enr],
 
   # Local modules
-  spec/[datatypes, digest, crypto, beaconstate, helpers, validator, network],
+  spec/[datatypes, digest, crypto, helpers, validator, network],
   spec/state_transition,
   conf, time, validator_pool,
   attestation_pool, block_pools/[spec_cache, chain_dag, clearance],
@@ -60,11 +60,29 @@ proc addLocalValidators*(node: BeaconNode) =
 
   info "Local validators attached ", count = node.attachedValidators.count
 
+proc getAttachedValidator*(node: BeaconNode,
+                           pubkey: ValidatorPubKey): AttachedValidator =
+  node.attachedValidators.getValidator(pubkey)
+
 proc getAttachedValidator*(node: BeaconNode,
                            state: BeaconState,
                            idx: ValidatorIndex): AttachedValidator =
-  let validatorKey = state.validators[idx].pubkey.initPubKey
-  node.attachedValidators.getValidator(validatorKey)
+  if idx < state.validators.len.ValidatorIndex:
+    node.getAttachedValidator(state.validators[idx].pubkey)
+  else:
+    warn "Validator index out of bounds",
+      idx, stateSlot = state.slot, validators = state.validators.len
+    nil
+
+proc getAttachedValidator*(node: BeaconNode,
+                           epochRef: EpochRef,
+                           idx: ValidatorIndex): AttachedValidator =
+  if idx < epochRef.validator_keys.len.ValidatorIndex:
+    node.getAttachedValidator(epochRef.validator_keys[idx])
+  else:
+    warn "Validator index out of bounds",
+      idx, epoch = epochRef.epoch, validators = epochRef.validator_keys.len
+    nil
 
 proc isSynced*(node: BeaconNode, head: BlockRef): bool =
   ## TODO This function is here as a placeholder for some better heurestics to
@@ -318,32 +336,30 @@ proc handleAttestations(node: BeaconNode, head: BlockRef, slot: Slot) =
   # In case blocks went missing, this means advancing past the latest block
   # using empty slots as fillers.
   # https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/validator.md#validator-assignments
-  # TODO we could cache the validator assignment since it's valid for the entire
-  #      epoch since it doesn't change, but that has to be weighed against
-  #      the complexity of handling forks correctly - instead, we use an adapted
-  #      version here that calculates the committee for a single slot only
-  node.chainDag.withState(node.chainDag.tmpState, attestationHead):
-    var cache = getEpochCache(attestationHead.blck, state)
-    let
-      committees_per_slot =
-        get_committee_count_per_slot(state, slot.epoch, cache)
-      num_active_validators =
-        count_active_validators(state, slot.compute_epoch_at_slot, cache)
+  let
+    epochRef = node.chainDag.getEpochRef(
+      attestationHead.blck, slot.compute_epoch_at_slot())
+    committees_per_slot =
+      get_committee_count_per_slot(epochRef)
+    num_active_validators = count_active_validators(epochRef)
+    fork = node.chainDag.headState.data.data.fork
+    genesis_validators_root =
+      node.chainDag.headState.data.data.genesis_validators_root
 
-    for committee_index in 0'u64..<committees_per_slot:
-      let committee = get_beacon_committee(
-        state, slot, committee_index.CommitteeIndex, cache)
+  for committee_index in 0'u64..<committees_per_slot:
+    let committee = get_beacon_committee(
+      epochRef, slot, committee_index.CommitteeIndex)
 
-      for index_in_committee, validatorIdx in committee:
-        let validator = node.getAttachedValidator(state, validatorIdx)
-        if validator != nil:
-          let ad = makeAttestationData(state, slot, committee_index, blck.root)
-          attestations.add((ad, committee.len, index_in_committee, validator))
+    for index_in_committee, validatorIdx in committee:
+      let validator = node.getAttachedValidator(epochRef, validatorIdx)
+      if validator != nil:
+        let ad = makeAttestationData(epochRef, attestationHead, committee_index)
+        attestations.add((ad, committee.len, index_in_committee, validator))
 
-    for a in attestations:
-      traceAsyncErrors createAndSendAttestation(
-        node, state.fork, state.genesis_validators_root, a.validator, a.data,
-        a.committeeLen, a.indexInCommittee, num_active_validators)
+  for a in attestations:
+    traceAsyncErrors createAndSendAttestation(
+      node, fork, genesis_validators_root, a.validator, a.data,
+      a.committeeLen, a.indexInCommittee, num_active_validators)
 
 proc handleProposal(node: BeaconNode, head: BlockRef, slot: Slot):
     Future[BlockRef] {.async.} =
@@ -359,7 +375,7 @@ proc handleProposal(node: BeaconNode, head: BlockRef, slot: Slot):
     return head
 
   let validator =
-    node.attachedValidators.getValidator(proposer.get()[1].initPubKey())
+    node.attachedValidators.getValidator(proposer.get()[1])
 
   if validator != nil:
     return await proposeBlock(node, validator, proposer.get()[0], head, slot)
diff --git a/beacon_chain/validator_pool.nim b/beacon_chain/validator_pool.nim
index 101f504f4..a4164d275 100644
--- a/beacon_chain/validator_pool.nim
+++ b/beacon_chain/validator_pool.nim
@@ -20,9 +20,9 @@ proc addLocalValidator*(pool: var ValidatorPool,
 
   info "Local validator attached", pubKey, validator = shortLog(v)
 
-func getValidator*(pool: ValidatorPool,
+proc getValidator*(pool: ValidatorPool,
                    validatorKey: ValidatorPubKey): AttachedValidator =
-  pool.validators.getOrDefault(validatorKey)
+  pool.validators.getOrDefault(validatorKey.initPubKey)
 
 # TODO: Honest validator - https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/validator.md
 proc signBlockProposal*(v: AttachedValidator, fork: Fork,