Reduce deposit memory (#7478)

* remove deposit proof and pending deposits

* wip

* wip

* wip

* clean up logs/comments

* function for pruning deposits and feature flag

* remove log

* add flag to beacon flags

* addressed PR feedback from terence

* add test assertions for errors

Co-authored-by: prylabs-bulldozer[bot] <58059840+prylabs-bulldozer[bot]@users.noreply.github.com>

beacon-chain/blockchain/process_block.go

@@ -125,7 +125,17 @@ func (s *Service) onBlock(ctx context.Context, signed *ethpb.SignedBeaconBlock,
 		if err != nil {
 			return errors.Wrap(err, "could not fetch finalized state")
 		}
-		s.depositCache.InsertFinalizedDeposits(ctx, int64(finalizedState.Eth1Data().DepositCount-1))
+		// We update the cache up to the last deposit index in the finalized block's state.
+		// We can be confident that these deposits will be included in some block
+		// because the Eth1 follow distance makes such long-range reorgs extremely unlikely.
+		eth1DepositIndex := int64(finalizedState.Eth1Data().DepositCount - 1)
+		s.depositCache.InsertFinalizedDeposits(ctx, eth1DepositIndex)
+		if featureconfig.Get().EnablePruningDepositProofs {
+			// Deposit proofs are only used during state transition and can be safely removed to save space.
+			if err = s.depositCache.PruneProofs(ctx, eth1DepositIndex); err != nil {
+				return errors.Wrap(err, "could not prune deposit proofs")
+			}
+		}
 	}
 
 	defer reportAttestationInclusion(b)

beacon-chain/cache/depositcache/deposits_cache.go

@@ -258,3 +258,28 @@ func (dc *DepositCache) NonFinalizedDeposits(ctx context.Context, untilBlk *big.
 
 	return deposits
 }
+
+// PruneProofs removes proofs from all deposits whose index is equal or less than untilDepositIndex.
+func (dc *DepositCache) PruneProofs(ctx context.Context, untilDepositIndex int64) error {
+	ctx, span := trace.StartSpan(ctx, "DepositsCache.PruneProofs")
+	defer span.End()
+	dc.depositsLock.Lock()
+	defer dc.depositsLock.Unlock()
+
+	if untilDepositIndex > int64(len(dc.deposits)) {
+		untilDepositIndex = int64(len(dc.deposits) - 1)
+	}
+
+	for i := untilDepositIndex; i >= 0; i-- {
+		if ctx.Err() != nil {
+			return ctx.Err()
+		}
+		// Finding a nil proof means that all proofs up to this deposit have been already pruned.
+		if dc.deposits[i].Deposit.Proof == nil {
+			break
+		}
+		dc.deposits[i].Deposit.Proof = nil
+	}
+
+	return nil
+}

beacon-chain/cache/depositcache/deposits_cache_test.go

@@ -573,3 +573,137 @@ func TestNonFinalizedDeposits_ReturnsNonFinalizedDepositsUpToBlockNumber(t *test
 	deps := dc.NonFinalizedDeposits(context.Background(), big.NewInt(10))
 	assert.Equal(t, 1, len(deps))
 }
+
+func TestPruneProofs_Ok(t *testing.T) {
+	dc, err := New()
+	require.NoError(t, err)
+
+	deposits := []struct {
+		blkNum  uint64
+		deposit *ethpb.Deposit
+		index   int64
+	}{
+		{
+			blkNum:  0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
+			index:   0,
+		},
+		{
+			blkNum:  0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
+			index:   1,
+		},
+		{
+			blkNum:  0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
+			index:   2,
+		},
+		{
+			blkNum:  0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
+			index:   3,
+		},
+	}
+
+	for _, ins := range deposits {
+		dc.InsertDeposit(context.Background(), ins.deposit, ins.blkNum, ins.index, [32]byte{})
+	}
+
+	require.NoError(t, dc.PruneProofs(context.Background(), 1))
+
+	assert.DeepEqual(t, ([][]byte)(nil), dc.deposits[0].Deposit.Proof)
+	assert.DeepEqual(t, ([][]byte)(nil), dc.deposits[1].Deposit.Proof)
+	assert.NotNil(t, dc.deposits[2].Deposit.Proof)
+	assert.NotNil(t, dc.deposits[3].Deposit.Proof)
+}
+
+func TestPruneProofs_SomeAlreadyPruned(t *testing.T) {
+	dc, err := New()
+	require.NoError(t, err)
+
+	deposits := []struct {
+		blkNum  uint64
+		deposit *ethpb.Deposit
+		index   int64
+	}{
+		{
+			blkNum:  0,
+			deposit: &ethpb.Deposit{Proof: nil},
+			index:   0,
+		},
+		{
+			blkNum:  0,
+			deposit: &ethpb.Deposit{Proof: nil},
+			index:   1,
+		},
+		{
+			blkNum:  0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
+			index:   2,
+		},
+		{
+			blkNum:  0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
+			index:   3,
+		},
+	}
+
+	for _, ins := range deposits {
+		dc.InsertDeposit(context.Background(), ins.deposit, ins.blkNum, ins.index, [32]byte{})
+	}
+
+	require.NoError(t, dc.PruneProofs(context.Background(), 2))
+
+	assert.DeepEqual(t, ([][]byte)(nil), dc.deposits[2].Deposit.Proof)
+}
+
+func TestPruneProofs_PruneAllWhenDepositIndexTooBig(t *testing.T) {
+	dc, err := New()
+	require.NoError(t, err)
+
+	deposits := []struct {
+		blkNum  uint64
+		deposit *ethpb.Deposit
+		index   int64
+	}{
+		{
+			blkNum:  0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
+			index:   0,
+		},
+		{
+			blkNum:  0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
+			index:   1,
+		},
+		{
+			blkNum:  0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
+			index:   2,
+		},
+		{
+			blkNum:  0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
+			index:   3,
+		},
+	}
+
+	for _, ins := range deposits {
+		dc.InsertDeposit(context.Background(), ins.deposit, ins.blkNum, ins.index, [32]byte{})
+	}
+
+	require.NoError(t, dc.PruneProofs(context.Background(), 99))
+
+	assert.DeepEqual(t, ([][]byte)(nil), dc.deposits[0].Deposit.Proof)
+	assert.DeepEqual(t, ([][]byte)(nil), dc.deposits[1].Deposit.Proof)
+	assert.DeepEqual(t, ([][]byte)(nil), dc.deposits[2].Deposit.Proof)
+	assert.DeepEqual(t, ([][]byte)(nil), dc.deposits[3].Deposit.Proof)
+}
+
+func makeDepositProof() [][]byte {
+	proof := make([][]byte, int(params.BeaconConfig().DepositContractTreeDepth)+1)
+	for i := range proof {
+		proof[i] = make([]byte, 32)
+	}
+	return proof
+}

beacon-chain/cache/depositcache/pending_deposits_test.go

@@ -9,7 +9,6 @@ import (
 	ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
 	dbpb "github.com/prysmaticlabs/prysm/proto/beacon/db"
 	"github.com/prysmaticlabs/prysm/shared/bytesutil"
-	"github.com/prysmaticlabs/prysm/shared/params"
 	"github.com/prysmaticlabs/prysm/shared/testutil/assert"
 )
 
@@ -29,14 +28,6 @@ func TestInsertPendingDeposit_ignoresNilDeposit(t *testing.T) {
 	assert.Equal(t, 0, len(dc.pendingDeposits))
 }
 
-func makeDepositProof() [][]byte {
-	proof := make([][]byte, int(params.BeaconConfig().DepositContractTreeDepth)+1)
-	for i := range proof {
-		proof[i] = make([]byte, 32)
-	}
-	return proof
-}
-
 func TestRemovePendingDeposit_OK(t *testing.T) {
 	db := DepositCache{}
 	proof1 := makeDepositProof()

shared/featureconfig/config.go

@@ -68,6 +68,7 @@ type Flags struct {
 	EnableEth1DataMajorityVote                 bool // EnableEth1DataMajorityVote uses the Voting With The Majority algorithm to vote for eth1data.
 	EnableAttBroadcastDiscoveryAttempts        bool // EnableAttBroadcastDiscoveryAttempts allows the p2p service to attempt to ensure a subnet peer is present before broadcasting an attestation.
 	EnablePeerScorer                           bool // EnablePeerScorer enables experimental peer scoring in p2p.
+	EnablePruningDepositProofs                 bool // EnablePruningDepositProofs enables pruning deposit proofs which significantly reduces the size of a deposit
 
 	// DisableForkChoice disables using LMD-GHOST fork choice to update
 	// the head of the chain based on attestations and instead accepts any valid received block
@@ -297,6 +298,10 @@ func ConfigureBeaconChain(ctx *cli.Context) {
 		log.Warn("Enabling new BLS library blst")
 		cfg.EnableBlst = true
 	}
+	if ctx.Bool(enablePruningDepositProofs.Name) {
+		log.Warn("Enabling pruning deposit proofs")
+		cfg.EnablePruningDepositProofs = true
+	}
 	Init(cfg)
 }
 

shared/featureconfig/flags.go

@@ -184,6 +184,10 @@ var (
 		Name:  "use-check-point-cache",
 		Usage: "Enables check point info caching",
 	}
+	enablePruningDepositProofs = &cli.BoolFlag{
+		Name:  "enable-pruning-deposit-proofs",
+		Usage: "Enables pruning deposit proofs when they are no longer needed. This significantly reduces deposit size.",
+	}
 )
 
 // devModeFlags holds list of flags that are set when development mode is on.
@@ -192,6 +196,7 @@ var devModeFlags = []cli.Flag{
 	enableEth1DataMajorityVote,
 	enableAttBroadcastDiscoveryAttempts,
 	enablePeerScorer,
+	enablePruningDepositProofs,
 }
 
 // Deprecated flags list.
@@ -715,6 +720,7 @@ var BeaconChainFlags = append(deprecatedFlags, []cli.Flag{
 	enableAttBroadcastDiscoveryAttempts,
 	enablePeerScorer,
 	checkPtInfoCache,
+	enablePruningDepositProofs,
 }...)
 
 // E2EBeaconChainFlags contains a list of the beacon chain feature flags to be tested in E2E.
@@ -726,4 +732,5 @@ var E2EBeaconChainFlags = []string{
 	"--dev",
 	"--enable-eth1-data-majority-vote",
 	"--use-check-point-cache",
+	"--enable-pruning-deposit-proofs",
 }