From 0e9cc20cfe34a9dc10eaa2831b5603fd4c49a3d4 Mon Sep 17 00:00:00 2001
From: Jacek Sieka <arnetheduck@gmail.com>
Date: Fri, 15 Feb 2019 10:33:32 -0600
Subject: [PATCH] beacon node simplifications (#116)

* remove previous randao scheme code
* fix some epoch logging
* move genesis time selection to state generation
---
 beacon_chain/beacon_node.nim             | 13 ++++++++++---
 beacon_chain/conf.nim                    |  7 +++++--
 beacon_chain/spec/beaconstate.nim        |  5 -----
 beacon_chain/spec/datatypes.nim          |  3 +++
 beacon_chain/spec/helpers.nim            |  5 +++++
 beacon_chain/spec/validator.nim          | 11 +++++++++--
 beacon_chain/time.nim                    | 13 +++++++------
 beacon_chain/trusted_state_snapshots.nim | 10 ++++++----
 beacon_chain/validator_keygen.nim        |  3 +--
 tests/simulation/start.sh                |  6 +++---
 10 files changed, 49 insertions(+), 27 deletions(-)

diff --git a/beacon_chain/beacon_node.nim b/beacon_chain/beacon_node.nim
index e313f46c5..25a01c9ca 100644
--- a/beacon_chain/beacon_node.nim
+++ b/beacon_chain/beacon_node.nim
@@ -102,6 +102,11 @@ proc sync*(node: BeaconNode): Future[bool] {.async.} =
     if t < node.beaconState.genesisTime * 1000:
       await sleepAsync int(node.beaconState.genesisTime * 1000 - t)
 
+    # TODO: change this to a full sync / block download
+    info "Syncing state from remote peers",
+      finalized_epoch = humaneEpochNum(node.beaconState.finalized_epoch),
+      target_slot_epoch = humaneEpochNum(targetSlot.slot_to_epoch)
+
     while node.beaconState.finalized_epoch < targetSlot.slot_to_epoch:
       var (peer, changeLog) = await node.network.getValidatorChangeLog(
         node.beaconState.validator_registry_delta_chain_tip)
@@ -284,7 +289,7 @@ proc scheduleEpochActions(node: BeaconNode, epoch: uint64) =
   ## attestations from our attached validators.
   doAssert node != nil
 
-  debug "Scheduling epoch actions", epoch
+  debug "Scheduling epoch actions", epoch = humaneEpochNum(epoch)
 
   # TODO: this copy of the state shouldn't be necessary, but please
   # see the comments in `get_beacon_proposer_index`
@@ -320,7 +325,7 @@ proc scheduleEpochActions(node: BeaconNode, epoch: uint64) =
 
   node.lastScheduledEpoch = epoch
   let
-    nextEpoch = epoch + 1
+    nextEpoch = humaneEpochNum(epoch + 1)
     at = node.beaconState.slotMiddle(nextEpoch * EPOCH_LENGTH)
 
   info "Scheduling next epoch update",
@@ -416,7 +421,9 @@ when isMainModule:
 
   case config.cmd
   of createChain:
-    createStateSnapshot(config.chainStartupData, config.outputStateFile.string)
+    createStateSnapshot(
+      config.chainStartupData, config.genesisOffset,
+      config.outputStateFile.string)
     quit 0
 
   of noCommand:
diff --git a/beacon_chain/conf.nim b/beacon_chain/conf.nim
index e42d56282..5fad6e1ab 100644
--- a/beacon_chain/conf.nim
+++ b/beacon_chain/conf.nim
@@ -16,7 +16,6 @@ type
 
   ChainStartupData* = object
     validatorDeposits*: seq[Deposit]
-    genesisTime*: Timestamp
 
   PrivateValidatorData* = object
     privKey*: ValidatorPrivKey
@@ -69,6 +68,11 @@ type
         desc: ""
         shortform: "c".}: ChainStartupData
 
+      genesisOffset* {.
+        desc: "Seconds from now to add to genesis time"
+        shortForm: "g"
+        defaultValue: 0 .}: int
+
       outputStateFile* {.
         desc: "Output file where to write the initial state snapshot"
         longform: "out"
@@ -96,4 +100,3 @@ template handledAsJsonFilename(T: untyped) {.dirty.} =
 handledAsJsonFilename BeaconState
 handledAsJsonFilename ChainStartupData
 handledAsJsonFilename PrivateValidatorData
-
diff --git a/beacon_chain/spec/beaconstate.nim b/beacon_chain/spec/beaconstate.nim
index 27a128eed..2017ad510 100644
--- a/beacon_chain/spec/beaconstate.nim
+++ b/beacon_chain/spec/beaconstate.nim
@@ -334,11 +334,6 @@ func update_validator_registry*(state: var BeaconState) =
 
   process_penalties_and_exits(state)
 
-# https://github.com/ethereum/eth2.0-specs/blob/v0.2.0/specs/core/0_beacon-chain.md#get_epoch_start_slot
-func get_epoch_start_slot*(epoch: EpochNumber): SlotNumber =
-  # Return the starting slot of the given ``epoch``.
-  epoch * EPOCH_LENGTH
-
 ## https://github.com/ethereum/eth2.0-specs/blob/v0.2.0/specs/core/0_beacon-chain.md#attestations-1
 proc checkAttestation*(
     state: BeaconState, attestation: Attestation, flags: UpdateFlags): bool =
diff --git a/beacon_chain/spec/datatypes.nim b/beacon_chain/spec/datatypes.nim
index 7266e6148..a900cb513 100644
--- a/beacon_chain/spec/datatypes.nim
+++ b/beacon_chain/spec/datatypes.nim
@@ -487,6 +487,9 @@ func shortValidatorKey*(state: BeaconState, validatorIdx: int): string =
 func humaneSlotNum*(s: SlotNumber): SlotNumber =
   s - GENESIS_SLOT
 
+func humaneEpochNum*(e: EpochNumber): EpochNumber =
+  e - GENESIS_EPOCH
+
 export
   writeValue, readValue
 
diff --git a/beacon_chain/spec/helpers.nim b/beacon_chain/spec/helpers.nim
index 9bc4979fd..d820f1c6a 100644
--- a/beacon_chain/spec/helpers.nim
+++ b/beacon_chain/spec/helpers.nim
@@ -102,6 +102,11 @@ func merkle_root*(values: openArray[Eth2Digest]): Eth2Digest =
 func slot_to_epoch*(slot: SlotNumber): EpochNumber =
   slot div EPOCH_LENGTH
 
+# https://github.com/ethereum/eth2.0-specs/blob/v0.2.0/specs/core/0_beacon-chain.md#get_epoch_start_slot
+func get_epoch_start_slot*(epoch: EpochNumber): SlotNumber =
+  # Return the starting slot of the given ``epoch``.
+  epoch * EPOCH_LENGTH
+
 # https://github.com/ethereum/eth2.0-specs/blob/v0.2.0/specs/core/0_beacon-chain.md#is_double_vote
 func is_double_vote*(attestation_data_1: AttestationData,
                      attestation_data_2: AttestationData): bool =
diff --git a/beacon_chain/spec/validator.nim b/beacon_chain/spec/validator.nim
index f461250cb..15399e7b9 100644
--- a/beacon_chain/spec/validator.nim
+++ b/beacon_chain/spec/validator.nim
@@ -144,8 +144,15 @@ func get_crosslink_committees_at_slot*(state: BeaconState, slot: uint64,
     previous_epoch = get_previous_epoch(state)
     next_epoch = current_epoch + 1
 
-  assert previous_epoch <= epoch, "Previous epoch: " & $previous_epoch & ", epoch: " & $epoch & ", Next epoch: " & $next_epoch 
-  assert epoch <= next_epoch, "Previous epoch: " & $previous_epoch & ", epoch: " & $epoch & ", Next epoch: " & $next_epoch 
+  assert previous_epoch <= epoch,
+    "Previous epoch: " & $humaneEpochNum(previous_epoch) &
+    ", epoch: " & $humaneEpochNum(epoch) &
+    ", Next epoch: " & $humaneEpochNum(next_epoch)
+
+  assert epoch <= next_epoch,
+    "Previous epoch: " & $humaneEpochNum(previous_epoch) &
+    ", epoch: " & $humaneEpochNum(epoch) &
+    ", Next epoch: " & $humaneEpochNum(next_epoch)
   # TODO - Hack: used to be "epoch < next_epoch" (exlusive interval)
   # until https://github.com/status-im/nim-beacon-chain/issues/97
 
diff --git a/beacon_chain/time.nim b/beacon_chain/time.nim
index d2e3fd34a..972ae7733 100644
--- a/beacon_chain/time.nim
+++ b/beacon_chain/time.nim
@@ -1,7 +1,7 @@
 import
   random,
   chronos,
-  spec/datatypes
+  spec/[datatypes, helpers]
 
 type
   Timestamp* = uint64 # Unix epoch timestamp in millisecond resolution
@@ -20,17 +20,18 @@ proc getSlotFromTime*(s: BeaconState, t = now()): SlotNumber =
   GENESIS_SLOT + uint64((int64(t - s.genesis_time * 1000) - detectedClockDrift) div
                          int64(SLOT_DURATION * 1000))
 
-template slotStart*(s: BeaconState, slot: uint64): Timestamp =
+func slotStart*(s: BeaconState, slot: SlotNumber): Timestamp =
   (s.genesis_time + (slot * SLOT_DURATION)) * 1000
 
-template slotMiddle*(s: BeaconState, slot: uint64): Timestamp =
+func slotMiddle*(s: BeaconState, slot: SlotNumber): Timestamp =
   s.slotStart(slot) + SLOT_DURATION * 500
 
-template slotEnd*(s: BeaconState, slot: uint64): Timestamp =
+func slotEnd*(s: BeaconState, slot: SlotNumber): Timestamp =
+  # TODO this is actually past the end, by nim inclusive semantics (sigh)
   s.slotStart(slot + 1)
 
 proc randomTimeInSlot*(s: BeaconState,
-                       slot: uint64,
+                       slot: SlotNumber,
                        interval: HSlice[float, float]): Timestamp =
   ## Returns a random moment within the slot.
   ## The interval must be a sub-interval of [0..1].
@@ -39,7 +40,7 @@ proc randomTimeInSlot*(s: BeaconState,
 
 proc slotDistanceFromNow*(s: BeaconState): int64 =
   ## Returns how many slots have passed since a particular BeaconState was finalized
-  int64(s.timeSinceGenesis() div (SLOT_DURATION * EPOCH_LENGTH * 1000)) - int64(s.finalized_epoch)
+  int64(s.getSlotFromTime() - s.finalized_epoch.get_epoch_start_slot)
 
 proc synchronizeClock*() {.async.} =
   ## This should determine the offset of the local clock against a global
diff --git a/beacon_chain/trusted_state_snapshots.nim b/beacon_chain/trusted_state_snapshots.nim
index 772da77bc..da1abe62f 100644
--- a/beacon_chain/trusted_state_snapshots.nim
+++ b/beacon_chain/trusted_state_snapshots.nim
@@ -29,10 +29,12 @@ proc obtainTrustedStateSnapshot*(db: BeaconChainDB): Future[BeaconState] {.async
 
   assert(false, "Not implemented")
 
-proc createStateSnapshot*(startup: ChainStartupData, outFile: string) =
-  let initialState = get_initial_beacon_state(startup.validatorDeposits,
-                                              startup.genesisTime,
-                                              Eth1Data(), {})
+proc createStateSnapshot*(
+    startup: ChainStartupData, genesisOffset: int, outFile: string) =
+  let initialState = get_initial_beacon_state(
+    startup.validatorDeposits,
+    uint64(int(fastEpochTime() div 1000) + genesisOffset),
+    Eth1Data(), {})
 
   var vr: Validator
   Json.saveFile(outFile, initialState, pretty = true)
diff --git a/beacon_chain/validator_keygen.nim b/beacon_chain/validator_keygen.nim
index b6e2029f4..012f8cdeb 100644
--- a/beacon_chain/validator_keygen.nim
+++ b/beacon_chain/validator_keygen.nim
@@ -12,6 +12,7 @@ proc genSingleValidator(path: string): (ValidatorPubKey,
                                         ValidatorPrivKey) =
   var v: PrivateValidatorData
   v.privKey = newPrivKey()
+
   writeFile(path, v)
 
   assert v.privKey != ValidatorPrivKey(), "Private key shouldn't be zero"
@@ -61,7 +62,5 @@ cli do (validators: int,
           proof_of_possession: proofOfPossession,
           withdrawal_credentials: withdrawalCredentials)))
 
-  startupData.genesisTime = uint64(int(now() div 1000) + startupDelay)
-
   writeFile(outputDir / "startup.json", startupData)
 
diff --git a/tests/simulation/start.sh b/tests/simulation/start.sh
index e030965ff..d5695e455 100755
--- a/tests/simulation/start.sh
+++ b/tests/simulation/start.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-set -eu
+set -eux
 
 # Kill children on ctrl-c
 trap "trap - SIGTERM && kill -- -$$" SIGINT SIGTERM EXIT
@@ -37,13 +37,13 @@ if [[ -z "$SKIP_BUILDS" ]]; then
 fi
 
 if [ ! -f $STARTUP_FILE ]; then
-  $VALIDATOR_KEYGEN_BIN --validators=$NUMBER_OF_VALIDATORS --outputDir="$SIMULATION_DIR" # --startupDelay=2
+  $VALIDATOR_KEYGEN_BIN --validators=$NUMBER_OF_VALIDATORS --outputDir="$SIMULATION_DIR"
 fi
 
 if [ ! -f $SNAPSHOT_FILE ]; then
   $BEACON_NODE_BIN createChain \
     --chainStartupData:$STARTUP_FILE \
-    --out:$SNAPSHOT_FILE
+    --out:$SNAPSHOT_FILE # --genesisOffset=2
 fi
 
 MASTER_NODE_ADDRESS_FILE="$SIMULATION_DIR/node-0/beacon_node.address"