Testnet stability (#451)

* Change reduced tree for adding weightless node

* Add more comments for reduced tree fork choice

* Small refactor on reduced tree for readability

* Move test_harness forking logic into itself

* Add new `AncestorIter` trait to store

* Add unfinished tests to fork choice

* Make `beacon_state.genesis_block_root` public

* Add failing lmd_ghost fork choice tests

* Extend fork_choice tests, create failing test

* Implement Debug for generic ReducedTree

* Add lazy_static to fork choice tests

* Add verify_integrity fn to reduced tree

* Fix bugs in reduced tree

* Ensure all reduced tree tests verify integrity

* Slightly alter reduce tree test params

* Add (failing) reduced tree test

* Fix bug in fork choice

Iter ancestors was not working well with skip slots

* Put maximum depth for common ancestor search

Ensures that we don't search back past the finalized root.

* Add basic finalization tests for reduced tree

* Change fork choice to use beacon_block_root

Previously it was using target_root, which was wrong

* Change reduced tree for adding weightless node

* Add more comments for reduced tree fork choice

* Small refactor on reduced tree for readability

* Move test_harness forking logic into itself

* Add new `AncestorIter` trait to store

* Add unfinished tests to fork choice

* Make `beacon_state.genesis_block_root` public

* Add failing lmd_ghost fork choice tests

* Extend fork_choice tests, create failing test

* Implement Debug for generic ReducedTree

* Add lazy_static to fork choice tests

* Add verify_integrity fn to reduced tree

* Fix bugs in reduced tree

* Ensure all reduced tree tests verify integrity

* Slightly alter reduce tree test params

* Add (failing) reduced tree test

* Fix bug in fork choice

Iter ancestors was not working well with skip slots

* Put maximum depth for common ancestor search

Ensures that we don't search back past the finalized root.

* Add basic finalization tests for reduced tree

* Add network dir CLI flag

* Simplify "NewSlot" log message

* Rename network-dir CLI flag

* Change fork choice to use beacon_block_root

Previously it was using target_root, which was wrong

* Update db dir size for metrics

* Change slog to use `FullFormat` logging

* Update some comments and log formatting

* Add prom gauge for best block root

* Only add known target blocks to fork choice

* Add finalized and justified root prom metrics

* Add CLI flag for setting log level

* Add logger to beacon chain

* Add debug-level CLI flag to validator

* Allow block processing if fork choice fails

* Create warn log when there's low libp2p peer count

* Minor change to logging

* Make ancestor iter return option

* Disable fork choice test when !debug_assertions

* Fix type, removed code fragment

* Tidy some borrow-checker evading

* Lower reduced tree random test iterations

beacon_node/beacon_chain/src/fork_choice.rs

@@ -18,6 +18,7 @@ pub enum Error {
 
 pub struct ForkChoice<T: BeaconChainTypes> {
     backend: T::LmdGhost,
+    store: Arc<T::Store>,
     /// Used for resolving the `0x00..00` alias back to genesis.
     ///
     /// Does not necessarily need to be the _actual_ genesis, it suffices to be the finalized root
@@ -36,6 +37,7 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
         genesis_block_root: Hash256,
     ) -> Self {
         Self {
+            store: store.clone(),
             backend: T::LmdGhost::new(store, genesis_block, genesis_block_root),
             genesis_block_root,
         }
@@ -125,13 +127,6 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
         state: &BeaconState<T::EthSpec>,
         attestation: &Attestation,
     ) -> Result<()> {
-        let validator_indices = get_attesting_indices_unsorted(
-            state,
-            &attestation.data,
-            &attestation.aggregation_bitfield,
-        )?;
-        let block_slot = state.get_attestation_slot(&attestation.data)?;
-
         let block_hash = attestation.data.beacon_block_root;
 
         // Ignore any attestations to the zero hash.
@@ -147,7 +142,22 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
         // (1) becomes weird once we hit finality and fork choice drops the genesis block. (2) is
         // fine because votes to the genesis block are not useful; all validators implicitly attest
         // to genesis just by being present in the chain.
-        if block_hash != Hash256::zero() {
+        //
+        // Additionally, don't add any block hash to fork choice unless we have imported the block.
+        if block_hash != Hash256::zero()
+            && self
+                .store
+                .exists::<BeaconBlock>(&block_hash)
+                .unwrap_or(false)
+        {
+            let validator_indices = get_attesting_indices_unsorted(
+                state,
+                &attestation.data,
+                &attestation.aggregation_bitfield,
+            )?;
+
+            let block_slot = state.get_attestation_slot(&attestation.data)?;
+
             for validator_index in validator_indices {
                 self.backend
                     .process_attestation(validator_index, block_hash, block_slot)?;