Add missed blocks to monitored validators (#4731)

* add missed_block metric

* init missed_block in constructor

* declare beaconproposercache in ValidatorMonitor

* refacto proposer_shuffling_decision_root to use epoch instead of current.epoch

* imple new proposer_shuffling_decision_root in callers

* push missed_blocks

* prune missed_blocks

* only add to hashmap if it's a monitored validator

* remove current_epoch dup + typos

* extract in func

* add prom metrics

* checkpoint is not only epoch but slot as well

* add safeguard if we start a new chain at slot 0

* clean

* remove unnecessary negative value for a slot

* typo in comment

* remove unused current_epoch

* share beacon_proposer_cache between validator_monitor and beacon_chain

* pass Hash256::zero()

* debug objects

* fix loop: lag is at the head

* sed s/get_slot/get_epoch

* fewer calls to cache.get_epoch

* fix typos

* remove cache first call

* export TYPICAL_SLOTS_PER_EPOCH and use it in validator_monitor

* switch to gauge & loop over missed_blocks hashset

* fix subnet_service tests

* remove unused var

* clean + fix nits

* add beacon_proposer_cache + validator_monitor in builder

* fix store_tests

* fix builder tests

* add tests

* add validator monitor set of tests

* clean tests

* nits

* optimise imports

* lint

* typo

* added self.aggregatable

* duplicate proposer_shuffling_decision_root

* remove duplication in passing beacon_proposer_cache

* remove duplication in passing beacon_proposer_cache

* using indices

* fmt

* implement missed blocks total

* nits

* avoid heap allocation

* remove recursion limit

* fix lint

* Fix valdiator monitor builder pattern

Unify validator monitor config struct

* renaming metrics

* renaming metrics in validator monitor

* add log if there's a missing validator index

* consistent log

* fix loop

* better loop

* move gauge to counter

* fmt

* add error message

* lint

* fix prom metrics

* set gauge to 0 when non-finalized epochs

* better wording

* remove hash256::zero in favour of block_root

* fix gauge total label

* fix last missed block validator

* Add `MissedBlock` struct

* Fix comment

* Refactor non-finalized block loop

* Fix off-by-one

* Avoid string allocation

* Fix compile error

* Remove non-finalized blocks metric

* fix func clojure

* remove unused variable

* remove unused DEFAULT_INDIVIDUAL_TRACKING_THRESHOLD

* remove unused DEFAULT_INDIVIDUAL_TRACKING_THRESHOLD in builder

* add validator index depending on the fork name

* typos

---------

Co-authored-by: Paul Hauner <paul@paulhauner.com>

consensus/types/src/beacon_state.rs

@@ -626,6 +626,25 @@ impl<T: EthSpec> BeaconState<T> {
         cache.get_all_beacon_committees()
     }
 
+    /// Returns the block root which decided the proposer shuffling for the epoch passed in parameter. This root
+    /// can be used to key this proposer shuffling.
+    ///
+    /// ## Notes
+    ///
+    /// The `block_root` must be equal to the latest block applied to `self`.
+    pub fn proposer_shuffling_decision_root_at_epoch(
+        &self,
+        epoch: Epoch,
+        block_root: Hash256,
+    ) -> Result<Hash256, Error> {
+        let decision_slot = self.proposer_shuffling_decision_slot(epoch);
+        if self.slot() <= decision_slot {
+            Ok(block_root)
+        } else {
+            self.get_block_root(decision_slot).map(|root| *root)
+        }
+    }
+
     /// Returns the block root which decided the proposer shuffling for the current epoch. This root
     /// can be used to key this proposer shuffling.
     ///
@@ -634,7 +653,7 @@ impl<T: EthSpec> BeaconState<T> {
     /// The `block_root` covers the one-off scenario where the genesis block decides its own
     /// shuffling. It should be set to the latest block applied to `self` or the genesis block root.
     pub fn proposer_shuffling_decision_root(&self, block_root: Hash256) -> Result<Hash256, Error> {
-        let decision_slot = self.proposer_shuffling_decision_slot();
+        let decision_slot = self.proposer_shuffling_decision_slot(self.current_epoch());
         if self.slot() == decision_slot {
             Ok(block_root)
         } else {
@@ -643,11 +662,9 @@ impl<T: EthSpec> BeaconState<T> {
     }
 
     /// Returns the slot at which the proposer shuffling was decided. The block root at this slot
-    /// can be used to key the proposer shuffling for the current epoch.
-    fn proposer_shuffling_decision_slot(&self) -> Slot {
-        self.current_epoch()
-            .start_slot(T::slots_per_epoch())
-            .saturating_sub(1_u64)
+    /// can be used to key the proposer shuffling for the given epoch.
+    fn proposer_shuffling_decision_slot(&self, epoch: Epoch) -> Slot {
+        epoch.start_slot(T::slots_per_epoch()).saturating_sub(1_u64)
     }
 
     /// Returns the block root which decided the attester shuffling for the given `relative_epoch`.