prevent uint64 to int64-induced RangeError/RangeDefects in metrics (#2358)

* prevent uint64 to int64-induced RangeError/RangeDefects in metrics

* remove redundant min(foo, int64.high)

* adjust spacing to be consistent

beacon_chain/block_pools/chain_dag.nim

@@ -885,32 +885,32 @@ proc updateHead*(
       finalized = shortLog(dag.headState.data.data.finalized_checkpoint)
 
   # https://github.com/ethereum/eth2.0-metrics/blob/master/metrics.md#additional-metrics
-  if dag.headState.data.data.eth1_data.deposit_count < high(int64).uint64:
-    beacon_pending_deposits.set(
-      dag.headState.data.data.eth1_data.deposit_count.int64 -
-      dag.headState.data.data.eth1_deposit_index.int64)
-    beacon_processed_deposits_total.set(
-      dag.headState.data.data.eth1_deposit_index.int64)
+  # both non-negative, so difference can't overflow or underflow int64
+  beacon_pending_deposits.set(
+    dag.headState.data.data.eth1_data.deposit_count.toGaugeValue -
+    dag.headState.data.data.eth1_deposit_index.toGaugeValue)
+  beacon_processed_deposits_total.set(
+    dag.headState.data.data.eth1_deposit_index.toGaugeValue)
 
   beacon_head_root.set newHead.root.toGaugeValue
-  beacon_head_slot.set newHead.slot.int64
+  beacon_head_slot.set newHead.slot.toGaugeValue
 
   if lastHead.slot.epoch != newHead.slot.epoch:
     # Epoch updated - in theory, these could happen when the wall clock
     # changes epoch, even if there is no new block / head, but we'll delay
     # updating them until a block confirms the change
     beacon_current_justified_epoch.set(
-      dag.headState.data.data.current_justified_checkpoint.epoch.int64)
+      dag.headState.data.data.current_justified_checkpoint.epoch.toGaugeValue)
     beacon_current_justified_root.set(
       dag.headState.data.data.current_justified_checkpoint.root.toGaugeValue)
     beacon_previous_justified_epoch.set(
-      dag.headState.data.data.previous_justified_checkpoint.epoch.int64)
+      dag.headState.data.data.previous_justified_checkpoint.epoch.toGaugeValue)
     beacon_previous_justified_root.set(
       dag.headState.data.data.previous_justified_checkpoint.root.toGaugeValue)
 
     let epochRef = getEpochRef(dag, newHead, newHead.slot.epoch)
     beacon_active_validators.set(
-      epochRef.shuffled_active_validator_indices.lenu64().int64)
+      epochRef.shuffled_active_validator_indices.lenu64().toGaugeValue)
 
   if finalizedHead != dag.finalizedHead:
     block: # Remove states, walking slot by slot
@@ -977,7 +977,7 @@ proc updateHead*(
       heads = dag.heads.len
 
     beacon_finalized_epoch.set(
-      dag.headState.data.data.finalized_checkpoint.epoch.int64)
+      dag.headState.data.data.finalized_checkpoint.epoch.toGaugeValue)
     beacon_finalized_root.set(
       dag.headState.data.data.finalized_checkpoint.root.toGaugeValue)
 

beacon_chain/eth1_monitor.nim

@@ -260,12 +260,6 @@ proc fixupWeb3Urls*(web3Url: var string) =
     web3Url = "ws://" & normalizedUrl.substr(pos)
     warn "Only WebSocket web3 providers are supported. Rewriting URL", web3Url
 
-func toGaugeValue(x: uint64): int64 =
-  if x > uint64(int64.high):
-    int64.high
-  else:
-    int64(x)
-
 template toGaugeValue(x: Quantity): int64 =
   toGaugeValue(distinctBase x)
 

beacon_chain/nimbus_beacon_node.nim

@@ -963,10 +963,12 @@ proc onSlotStart(
   # Check before any re-scheduling of onSlotStart()
   checkIfShouldStopAtEpoch(wallSlot, node.config.stopAtEpoch)
 
-  beacon_slot.set wallSlot.int64
-  beacon_current_epoch.set wallSlot.epoch.int64
+  beacon_slot.set wallSlot.toGaugeValue
+  beacon_current_epoch.set wallSlot.epoch.toGaugeValue
 
-  finalization_delay.set wallSlot.epoch.int64 - finalizedEpoch.int64
+  # both non-negative, so difference can't overflow or underflow int64
+  finalization_delay.set(
+    wallSlot.epoch.toGaugeValue - finalizedEpoch.toGaugeValue)
 
   if node.config.verifyFinalization:
     verifyFinalization(node, wallSlot)

beacon_chain/spec/datatypes.nim

@@ -852,6 +852,12 @@ template lenu64*(x: untyped): untyped =
 func `$`*(v: ForkDigest | Version): string =
   toHex(array[4, byte](v))
 
+func toGaugeValue*(x: uint64 | Epoch | Slot): int64 =
+  if x > uint64(int64.high):
+    int64.high
+  else:
+    int64(x)
+
 # TODO where's borrow support when you need it
 func `==`*(a, b: ForkDigest | Version): bool =
   array[4, byte](a) == array[4, byte](b)

beacon_chain/validator_duties.nim

@@ -589,7 +589,7 @@ proc updateValidatorMetrics*(node: BeaconNode) =
       total += balance
 
     node.attachedValidatorBalanceTotal = total
-    attached_validator_balance_total.set(min(total, int64.high.uint64).int64)
+    attached_validator_balance_total.set(total.toGaugeValue)
   else:
     discard