Implement voluntary exits pool (#4610)

beacon-chain/operations/voluntaryexits/BUILD.bazel

@@ -0,0 +1,31 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "go_default_library",
+    srcs = [
+        "doc.go",
+        "service.go",
+    ],
+    importpath = "github.com/prysmaticlabs/prysm/beacon-chain/operations/voluntaryexits",
+    visibility = ["//beacon-chain:__subpackages__"],
+    deps = [
+        "//beacon-chain/blockchain:go_default_library",
+        "//beacon-chain/core/helpers:go_default_library",
+        "//shared/params:go_default_library",
+        "@com_github_prysmaticlabs_ethereumapis//eth/v1alpha1:go_default_library",
+    ],
+)
+
+go_test(
+    name = "go_default_test",
+    size = "small",
+    srcs = ["service_test.go"],
+    embed = [":go_default_library"],
+    deps = [
+        "//beacon-chain/blockchain/testing:go_default_library",
+        "//proto/beacon/p2p/v1:go_default_library",
+        "//shared/params:go_default_library",
+        "@com_github_gogo_protobuf//proto:go_default_library",
+        "@com_github_prysmaticlabs_ethereumapis//eth/v1alpha1:go_default_library",
+    ],
+)

beacon-chain/operations/voluntaryexits/doc.go

@@ -0,0 +1,2 @@
+// Package voluntaryexits defines the operations management of voluntary exits.
+package voluntaryexits

beacon-chain/operations/voluntaryexits/service.go

@@ -0,0 +1,94 @@
+package voluntaryexits
+
+import (
+	"context"
+	"sort"
+	"sync"
+
+	ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
+	"github.com/prysmaticlabs/prysm/beacon-chain/blockchain"
+	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
+	"github.com/prysmaticlabs/prysm/shared/params"
+)
+
+// Pool implements a struct to maintain pending and recently included voluntary exits. This pool
+// is used by proposers to insert into new blocks.
+type Pool struct {
+	lock     sync.RWMutex
+	pending  []*ethpb.SignedVoluntaryExit
+	included map[uint64]bool
+	chain    blockchain.HeadFetcher
+}
+
+// NewPool accepts a head fetcher (for reading the validator set) and returns an initialized
+// voluntary exit pool.
+func NewPool(chain blockchain.HeadFetcher) *Pool {
+	return &Pool{
+		pending:  make([]*ethpb.SignedVoluntaryExit, 0),
+		included: make(map[uint64]bool),
+		chain:    chain,
+	}
+}
+
+// PendingExits returns exits that are ready for inclusion at the given slot.
+func (p *Pool) PendingExits(slot uint64) []*ethpb.SignedVoluntaryExit {
+	p.lock.RLock()
+	defer p.lock.RUnlock()
+	pending := make([]*ethpb.SignedVoluntaryExit, 0)
+	for _, e := range p.pending {
+		if e.Exit.Epoch > helpers.SlotToEpoch(slot) {
+			continue
+		}
+		pending = append(pending, e)
+	}
+	return pending
+}
+
+// InsertVoluntaryExit into the pool. This method is a no-op if the pending exit already exists,
+// has been included recently, or the validator is already exited.
+func (p *Pool) InsertVoluntaryExit(ctx context.Context, exit *ethpb.SignedVoluntaryExit) {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+
+	// Has this validator index been included recently?
+	if p.included[exit.Exit.ValidatorIndex] {
+		return
+	}
+
+	// Has the validator been exited already?
+	if h, _ := p.chain.HeadState(ctx); h == nil || len(h.Validators) <= int(exit.Exit.ValidatorIndex) || h.Validators[exit.Exit.ValidatorIndex].ExitEpoch != params.BeaconConfig().FarFutureEpoch {
+		return
+	}
+
+	// Does this validator exist in the list already? Use binary search to find the answer.
+	if found := sort.Search(len(p.pending), func(i int) bool {
+		e := p.pending[i].Exit
+		return e.ValidatorIndex == exit.Exit.ValidatorIndex
+	}); found != len(p.pending) {
+		// If an exit exists with this validator index, prefer one with an earlier exit epoch.
+		if p.pending[found].Exit.Epoch > exit.Exit.Epoch {
+			p.pending[found] = exit
+		}
+		return
+	}
+
+	// Insert into pending list and sort again.
+	p.pending = append(p.pending, exit)
+	sort.Slice(p.pending, func(i, j int) bool {
+		return p.pending[i].Exit.ValidatorIndex < p.pending[j].Exit.ValidatorIndex
+	})
+}
+
+// MarkIncluded is used when an exit has been included in a beacon block. Every block seen by this
+// node should call this method to include the exit.
+func (p *Pool) MarkIncluded(exit *ethpb.SignedVoluntaryExit) {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+	i := sort.Search(len(p.pending), func(i int) bool {
+		return p.pending[i].Exit.ValidatorIndex == exit.Exit.ValidatorIndex
+	})
+	if i != len(p.pending) {
+		p.pending = append(p.pending[:i], p.pending[i+1:]...)
+	}
+	p.included[exit.Exit.ValidatorIndex] = true
+}