[rpc] add GetValidatorsStakeByBlockNumber (#4254)

GetValidatorsStakeByBlockNumber calculates each validator's total
delegation at the specified block.

hmy/hmy.go

@@ -35,6 +35,8 @@ const (
 	undelegationPayoutsCacheSize           = 500  // max number of epochs to store in cache
 	preStakingBlockRewardsCacheSize        = 1024 // max number of block rewards to store in cache
 	totalStakeCacheDuration                = 20   // number of blocks where the returned total stake will remain the same
+	// max number of blocks for which the map "validator address -> total delegation to validator" is stored
+	stakeByBlockNumberCacheSize = 250
 )
 
 var (
@@ -78,6 +80,8 @@ type Harmony struct {
 	preStakingBlockRewardsCache *lru.Cache
 	// totalStakeCache to save on recomputation for `totalStakeCacheDuration` blocks.
 	totalStakeCache *totalStakeCache
+	// stakeByBlockNumberCache to save on recomputation for `totalStakeCacheDuration` blocks
+	stakeByBlockNumberCache *lru.Cache
 }
 
 // NodeAPI is the list of functions from node used to call rpc apis.
@@ -125,6 +129,7 @@ func New(
 ) *Harmony {
 	leaderCache, _ := lru.New(leaderCacheSize)
 	undelegationPayoutsCache, _ := lru.New(undelegationPayoutsCacheSize)
+	stakeByBlockNumberCache, _ := lru.New(stakeByBlockNumberCacheSize)
 	preStakingBlockRewardsCache, _ := lru.New(preStakingBlockRewardsCacheSize)
 	totalStakeCache := newTotalStakeCache(totalStakeCacheDuration)
 	bloomIndexer := NewBloomIndexer(nodeAPI.Blockchain(), params.BloomBitsBlocks, params.BloomConfirms)
@@ -148,6 +153,7 @@ func New(
 		totalStakeCache:             totalStakeCache,
 		undelegationPayoutsCache:    undelegationPayoutsCache,
 		preStakingBlockRewardsCache: preStakingBlockRewardsCache,
+		stakeByBlockNumberCache:     stakeByBlockNumberCache,
 	}
 
 	// Setup gas price oracle

hmy/staking.go

@@ -10,6 +10,7 @@ import (
 	"github.com/harmony-one/harmony/block"
 	"github.com/harmony-one/harmony/consensus/quorum"
 	"github.com/harmony-one/harmony/core/rawdb"
+	"github.com/harmony-one/harmony/core/state"
 	"github.com/harmony-one/harmony/core/types"
 	"github.com/harmony-one/harmony/eth/rpc"
 	"github.com/harmony-one/harmony/internal/chain"
@@ -226,6 +227,35 @@ func (hmy *Harmony) GetAllValidatorAddresses() []common.Address {
 	return hmy.BlockChain.ValidatorCandidates()
 }
 
+func (hmy *Harmony) GetValidatorsStakeByBlockNumber(
+	block *types.Block,
+) (map[common.Address]*big.Int, error) {
+	if cachedReward, ok := hmy.stakeByBlockNumberCache.Get(block.Hash()); ok {
+		return cachedReward.(map[common.Address]*big.Int), nil
+	}
+	validatorAddresses := hmy.GetAllValidatorAddresses()
+	stakes := make(map[common.Address]*big.Int, len(validatorAddresses))
+	for _, validatorAddress := range validatorAddresses {
+		wrapper, err := hmy.BlockChain.ReadValidatorInformationAtRoot(validatorAddress, block.Root())
+		if err != nil {
+			if errors.Cause(err) != state.ErrAddressNotPresent {
+				return nil, errors.Errorf(
+					"cannot fetch information for validator %s at block %d due to %s",
+					validatorAddress.Hex(),
+					block.Number(),
+					err,
+				)
+			} else {
+				// `validatorAddress` was not a validator back then
+				continue
+			}
+		}
+		stakes[validatorAddress] = wrapper.TotalDelegation()
+	}
+	hmy.stakeByBlockNumberCache.Add(block.Hash(), stakes)
+	return stakes, nil
+}
+
 var (
 	epochBlocksMap = map[common.Address]map[uint64]staking.EpochSigningEntry{}
 	mapLock        = sync.Mutex{}

rpc/metrics.go

@@ -71,6 +71,7 @@ const (
 	GetAllValidatorInformationByBlockNumber = "GetAllValidatorInformationByBlockNumber"
 	GetValidatorInformation                 = "GetValidatorInformation"
 	GetValidatorInformationByBlockNumber    = "GetValidatorInformationByBlockNumber"
+	GetValidatorsStakeByBlockNumber         = "GetValidatorsStakeByBlockNumber"
 	GetValidatorSelfDelegation              = "GetValidatorSelfDelegation"
 	GetValidatorTotalDelegation             = "GetValidatorTotalDelegation"
 	GetAllDelegationInformation             = "GetAllDelegationInformation"

rpc/staking.go

@@ -458,6 +458,40 @@ func (s *PublicStakingService) GetValidatorInformationByBlockNumber(
 	return NewStructuredResponse(validatorInfo)
 }
 
+// GetValidatorsStakeByBlockNumber returns the stake per validator at the specified block
+func (s *PublicStakingService) GetValidatorsStakeByBlockNumber(
+	ctx context.Context, blockNumber BlockNumber,
+) (StructuredResponse, error) {
+	timer := DoMetricRPCRequest(GetValidatorsStakeByBlockNumber)
+	defer DoRPCRequestDuration(GetValidatorsStakeByBlockNumber, timer)
+
+	// Process number based on version
+	blockNum := blockNumber.EthBlockNumber()
+
+	// Fetch block
+	if !isBeaconShard(s.hmy) {
+		DoMetricRPCQueryInfo(GetValidatorsStakeByBlockNumber, FailedNumber)
+		return nil, ErrNotBeaconShard
+	}
+	if isBlockGreaterThanLatest(s.hmy, blockNum) {
+		DoMetricRPCQueryInfo(GetValidatorsStakeByBlockNumber, FailedNumber)
+		return nil, ErrRequestedBlockTooHigh
+	}
+	blk, err := s.hmy.BlockByNumber(ctx, blockNum)
+	if err != nil {
+		DoMetricRPCQueryInfo(GetValidatorsStakeByBlockNumber, FailedNumber)
+		return nil, errors.Wrapf(err, "could not retrieve the blk information for blk number: %d", blockNum)
+	}
+	response, err := s.hmy.GetValidatorsStakeByBlockNumber(blk)
+	if err != nil {
+		DoMetricRPCQueryInfo(GetValidatorsStakeByBlockNumber, FailedNumber)
+		return nil, err
+	}
+
+	// Response output is the same for all versions
+	return NewStructuredResponse(response)
+}
+
 // GetValidatorSelfDelegation returns validator stake.
 func (s *PublicStakingService) GetValidatorSelfDelegation(
 	ctx context.Context, address string,