Part 1 of proto array fork choice - docs and interfaces (#4615)

* Docs

* Interface definitions

* Fmt and gazelle

* Rename interface to interfaces

beacon-chain/cache/skip_slot_cache_test.go

@@ -5,8 +5,8 @@ import (
 	"testing"
 
 	"github.com/gogo/protobuf/proto"
-	pb "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
 	"github.com/prysmaticlabs/prysm/beacon-chain/cache"
+	pb "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
 	"github.com/prysmaticlabs/prysm/shared/featureconfig"
 )
 

beacon-chain/forkchoice/BUILD.bazel

@@ -0,0 +1,11 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = [
+        "doc.go",
+        "interfaces.go",
+    ],
+    importpath = "github.com/prysmaticlabs/prysm/beacon-chain/forkchoice",
+    visibility = ["//beacon-chain:__subpackages__"],
+)

beacon-chain/forkchoice/doc.go

@@ -0,0 +1,7 @@
+/*
+Package forkchoice implements the service to support fork choice for the eth2 beacon chain. This contains the
+necessary components to track latest validators votes, and balances. Then a store object to be used
+to calculate head. High level fork choice summary:
+https://notes.ethereum.org/@vbuterin/rkhCgQteN?type=view#LMD-GHOST-fork-choice-rule
+*/
+package forkchoice

beacon-chain/forkchoice/interfaces.go

@@ -0,0 +1,33 @@
+package forkchoice
+
+import (
+	"context"
+)
+
+// ForkChoice represents the full fork choice interface composed of all of the sub-interfaces.
+type ForkChoice interface {
+	HeadRetriever        // to compute head.
+	BlockProcessor       // to track new block for fork choice.
+	AttestationProcessor // to track new attestation for fork choice.
+	Pruner               // to clean old data for fork choice.
+}
+
+// HeadRetriever retrieves head root of the current chain.
+type HeadRetriever interface {
+	Head(context.Context, uint64, [32]byte, uint64, []uint64) ([32]byte, error)
+}
+
+// BlockProcessor processes the block that's used for accounting fork choice.
+type BlockProcessor interface {
+	ProcessBlock(context.Context, uint64, [32]byte, [32]byte, uint64, uint64) error
+}
+
+// AttestationProcessor processes the attestation that's used for accounting fork choice.
+type AttestationProcessor interface {
+	ProcessAttestation(context.Context, []uint64, [32]byte, uint64)
+}
+
+// Pruner prunes the fork choice upon new finalization. This is used to keep fork choice sane.
+type Pruner interface {
+	Prune(context.Context, [32]byte)
+}

beacon-chain/forkchoice/protoarray/BUILD.bazel

@@ -0,0 +1,8 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["doc.go"],
+    importpath = "github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/protoarray",
+    visibility = ["//beacon-chain:__subpackages__"],
+)

beacon-chain/forkchoice/protoarray/doc.go

@@ -0,0 +1,7 @@
+/*
+Package protoarray implements proto array fork choice as outlined:
+https://github.com/protolambda/lmd-ghost#array-based-stateful-dag-proto_array
+This was motivated by the following light house implementation:
+https://github.com/sigp/lighthouse/pull/804
+*/
+package protoarray

beacon-chain/sync/initial-sync/round_robin.go

@@ -9,12 +9,12 @@ import (
 	"sync/atomic"
 	"time"
 
-	"github.com/prysmaticlabs/prysm/beacon-chain/flags"
 	"github.com/libp2p/go-libp2p-core/peer"
 	"github.com/paulbellamy/ratecounter"
 	"github.com/pkg/errors"
 	eth "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
+	"github.com/prysmaticlabs/prysm/beacon-chain/flags"
 	prysmsync "github.com/prysmaticlabs/prysm/beacon-chain/sync"
 	p2ppb "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
 	"github.com/prysmaticlabs/prysm/shared/bytesutil"

validator/db/attestation_history_test.go

@@ -75,7 +75,7 @@ func TestSaveAttestationHistory_OK(t *testing.T) {
 	if savedHistory == nil || !reflect.DeepEqual(history, savedHistory) {
 		t.Fatalf("Expected DB to keep object the same, received: %v", history)
 	}
-	if savedHistory.TargetToSource[epoch] != newMap[epoch]{
+	if savedHistory.TargetToSource[epoch] != newMap[epoch] {
 		t.Fatalf("Expected target epoch %d to have the same marked source epoch, received %d", epoch, savedHistory.TargetToSource[epoch])
 	}
 	if savedHistory.TargetToSource[epoch-1] != farFuture {
@@ -145,11 +145,11 @@ func TestSaveAttestationHistory_Overwrites(t *testing.T) {
 		if history == nil || !reflect.DeepEqual(history, tt.history) {
 			t.Fatalf("Expected DB to keep object the same, received: %v", history)
 		}
-		if history.TargetToSource[tt.epoch] != tt.epoch - 1 {
+		if history.TargetToSource[tt.epoch] != tt.epoch-1 {
 			t.Fatalf("Expected target epoch %d to be marked with correct source epoch %d", tt.epoch, history.TargetToSource[tt.epoch])
 		}
-		if history.TargetToSource[tt.epoch - 1] != farFuture {
-			t.Fatalf("Expected target epoch %d to not be marked as attested for, received %d", tt.epoch-1, history.TargetToSource[tt.epoch - 1])
+		if history.TargetToSource[tt.epoch-1] != farFuture {
+			t.Fatalf("Expected target epoch %d to not be marked as attested for, received %d", tt.epoch-1, history.TargetToSource[tt.epoch-1])
 		}
 	}
 }