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chain.go
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// Copyright (c) 2013-2016 The btcsuite developers
// Copyright (c) 2015-2018 The Decred developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package blockchain
import (
"container/list"
"fmt"
"sync"
"time"
"github.com/decred/dcrd/blockchain/stake"
"github.com/decred/dcrd/chaincfg"
"github.com/decred/dcrd/chaincfg/chainhash"
"github.com/decred/dcrd/database"
"github.com/decred/dcrd/dcrutil"
"github.com/decred/dcrd/txscript"
"github.com/decred/dcrd/wire"
)
const (
// maxOrphanBlocks is the maximum number of orphan blocks that can be
// queued.
maxOrphanBlocks = 500
// minMemoryNodes is the minimum number of consecutive nodes needed
// in memory in order to perform all necessary validation. It is used
// to determine when it's safe to prune nodes from memory without
// causing constant dynamic reloading. This value should be larger than
// that for minMemoryStakeNodes.
minMemoryNodes = 2880
// minMemoryStakeNodes is the maximum height to keep stake nodes
// in memory for in their respective nodes. Beyond this height,
// they will need to be manually recalculated. This value should
// be at least the stake retarget interval.
minMemoryStakeNodes = 288
// mainchainBlockCacheSize is the number of mainchain blocks to
// keep in memory, by height from the tip of the mainchain.
mainchainBlockCacheSize = 12
// maxSearchDepth is the distance in block nodes to search down the
// blockchain to find some parent, loading block nodes from the
// database if necessary. Reorganizations longer than this disance may
// fail.
maxSearchDepth = 2880
)
// orphanBlock represents a block that we don't yet have the parent for. It
// is a normal block plus an expiration time to prevent caching the orphan
// forever.
type orphanBlock struct {
block *dcrutil.Block
expiration time.Time
}
// BestState houses information about the current best block and other info
// related to the state of the main chain as it exists from the point of view of
// the current best block.
//
// The BestSnapshot method can be used to obtain access to this information
// in a concurrent safe manner and the data will not be changed out from under
// the caller when chain state changes occur as the function name implies.
// However, the returned snapshot must be treated as immutable since it is
// shared by all callers.
type BestState struct {
Hash chainhash.Hash // The hash of the block.
Height int64 // The height of the block.
Bits uint32 // The difficulty bits of the block.
BlockSize uint64 // The size of the block.
NumTxns uint64 // The number of txns in the block.
TotalTxns uint64 // The total number of txns in the chain.
MedianTime time.Time // Median time as per CalcPastMedianTime.
TotalSubsidy int64 // The total subsidy for the chain.
}
// newBestState returns a new best stats instance for the given parameters.
func newBestState(node *blockNode, blockSize, numTxns, totalTxns uint64, medianTime time.Time, totalSubsidy int64) *BestState {
return &BestState{
Hash: node.hash,
Height: node.height,
Bits: node.bits,
BlockSize: blockSize,
NumTxns: numTxns,
TotalTxns: totalTxns,
MedianTime: medianTime,
TotalSubsidy: totalSubsidy,
}
}
// BlockChain provides functions for working with the Decred block chain.
// It includes functionality such as rejecting duplicate blocks, ensuring blocks
// follow all rules, orphan handling, checkpoint handling, and best chain
// selection with reorganization.
type BlockChain struct {
// The following fields are set when the instance is created and can't
// be changed afterwards, so there is no need to protect them with a
// separate mutex.
checkpointsByHeight map[int64]*chaincfg.Checkpoint
db database.DB
dbInfo *databaseInfo
chainParams *chaincfg.Params
timeSource MedianTimeSource
notifications NotificationCallback
sigCache *txscript.SigCache
indexManager IndexManager
// subsidyCache is the cache that provides quick lookup of subsidy
// values.
subsidyCache *SubsidyCache
// chainLock protects concurrent access to the vast majority of the
// fields in this struct below this point.
chainLock sync.RWMutex
// These fields are configuration parameters that can be toggled at
// runtime. They are protected by the chain lock.
noVerify bool
noCheckpoints bool
// These fields are related to the memory block index. They are
// protected by the chain lock.
bestNode *blockNode
index *blockIndex
// These fields are related to handling of orphan blocks. They are
// protected by a combination of the chain lock and the orphan lock.
orphanLock sync.RWMutex
orphans map[chainhash.Hash]*orphanBlock
prevOrphans map[chainhash.Hash][]*orphanBlock
oldestOrphan *orphanBlock
// The block cache for mainchain blocks, to facilitate faster
// reorganizations.
mainchainBlockCacheLock sync.RWMutex
mainchainBlockCache map[chainhash.Hash]*dcrutil.Block
mainchainBlockCacheSize int
// These fields are related to checkpoint handling. They are protected
// by the chain lock.
nextCheckpoint *chaincfg.Checkpoint
checkpointBlock *dcrutil.Block
// The state is used as a fairly efficient way to cache information
// about the current best chain state that is returned to callers when
// requested. It operates on the principle of MVCC such that any time a
// new block becomes the best block, the state pointer is replaced with
// a new struct and the old state is left untouched. In this way,
// multiple callers can be pointing to different best chain states.
// This is acceptable for most callers because the state is only being
// queried at a specific point in time.
//
// In addition, some of the fields are stored in the database so the
// chain state can be quickly reconstructed on load.
stateLock sync.RWMutex
stateSnapshot *BestState
// The following caches are used to efficiently keep track of the
// current deployment threshold state of each rule change deployment.
//
// This information is stored in the database so it can be quickly
// reconstructed on load.
//
// deploymentCaches caches the current deployment threshold state for
// blocks in each of the actively defined deployments.
deploymentCaches map[uint32][]thresholdStateCache
// pruner is the automatic pruner for block nodes and stake nodes,
// so that the memory may be restored by the garbage collector if
// it is unlikely to be referenced in the future.
pruner *chainPruner
// The following maps are various caches for the stake version/voting
// system. The goal of these is to reduce disk access to load blocks
// from disk. Measurements indicate that it is slightly more expensive
// so setup the cache (<10%) vs doing a straight chain walk. Every
// other subsequent call is >10x faster.
isVoterMajorityVersionCache map[[stakeMajorityCacheKeySize]byte]bool
isStakeMajorityVersionCache map[[stakeMajorityCacheKeySize]byte]bool
calcPriorStakeVersionCache map[[chainhash.HashSize]byte]uint32
calcVoterVersionIntervalCache map[[chainhash.HashSize]byte]uint32
calcStakeVersionCache map[[chainhash.HashSize]byte]uint32
}
const (
// stakeMajorityCacheKeySize is comprised of the stake version and the
// hash size. The stake version is a little endian uint32, hence we
// add 4 to the overall size.
stakeMajorityCacheKeySize = 4 + chainhash.HashSize
)
// StakeVersions is a condensed form of a dcrutil.Block that is used to prevent
// using gigabytes of memory.
type StakeVersions struct {
Hash chainhash.Hash
Height int64
BlockVersion int32
StakeVersion uint32
Votes []stake.VoteVersionTuple
}
// GetStakeVersions returns a cooked array of StakeVersions. We do this in
// order to not bloat memory by returning raw blocks.
func (b *BlockChain) GetStakeVersions(hash *chainhash.Hash, count int32) ([]StakeVersions, error) {
exists, err := b.HaveBlock(hash)
if err != nil {
return nil, err
}
if !exists {
return nil, fmt.Errorf("hash '%s' not found on chain", hash.String())
}
// Nothing to do if no count requested.
if count == 0 {
return nil, nil
}
if count < 0 {
return nil, fmt.Errorf("count must not be less than zero - "+
"got %d", count)
}
b.chainLock.Lock()
defer b.chainLock.Unlock()
startNode, err := b.findNode(hash, 0)
if err != nil {
return nil, err
}
// Limit the requested count to the max possible for the requested block.
if count > int32(startNode.height+1) {
count = int32(startNode.height + 1)
}
result := make([]StakeVersions, 0, count)
prevNode := startNode
for i := int32(0); prevNode != nil && i < count; i++ {
sv := StakeVersions{
Hash: prevNode.hash,
Height: prevNode.height,
BlockVersion: prevNode.blockVersion,
StakeVersion: prevNode.stakeVersion,
Votes: prevNode.votes,
}
result = append(result, sv)
prevNode, err = b.index.PrevNodeFromNode(prevNode)
if err != nil {
return nil, err
}
}
return result, nil
}
type VoteInfo struct {
Agendas []chaincfg.ConsensusDeployment
AgendaStatus []ThresholdStateTuple
}
// GetVoteInfo returns
func (b *BlockChain) GetVoteInfo(hash *chainhash.Hash, version uint32) (*VoteInfo, error) {
deployments, ok := b.chainParams.Deployments[version]
if !ok {
return nil, VoteVersionError(version)
}
if !ok {
return nil, HashError(hash.String())
}
vi := VoteInfo{
Agendas: make([]chaincfg.ConsensusDeployment,
0, len(deployments)),
AgendaStatus: make([]ThresholdStateTuple, 0, len(deployments)),
}
for _, deployment := range deployments {
vi.Agendas = append(vi.Agendas, deployment)
status, err := b.ThresholdState(hash, version, deployment.Vote.Id)
if err != nil {
return nil, err
}
vi.AgendaStatus = append(vi.AgendaStatus, status)
}
return &vi, nil
}
// DisableVerify provides a mechanism to disable transaction script validation
// which you DO NOT want to do in production as it could allow double spends
// and other undesirable things. It is provided only for debug purposes since
// script validation is extremely intensive and when debugging it is sometimes
// nice to quickly get the chain.
//
// This function is safe for concurrent access.
func (b *BlockChain) DisableVerify(disable bool) {
b.chainLock.Lock()
b.noVerify = disable
b.chainLock.Unlock()
}
// TotalSubsidy returns the total subsidy mined so far in the best chain.
//
// This function is safe for concurrent access.
func (b *BlockChain) TotalSubsidy() int64 {
b.chainLock.RLock()
ts := b.BestSnapshot().TotalSubsidy
b.chainLock.RUnlock()
return ts
}
// FetchSubsidyCache returns the current subsidy cache from the blockchain.
//
// This function is safe for concurrent access.
func (b *BlockChain) FetchSubsidyCache() *SubsidyCache {
return b.subsidyCache
}
// HaveBlock returns whether or not the chain instance has the block represented
// by the passed hash. This includes checking the various places a block can
// be like part of the main chain, on a side chain, or in the orphan pool.
//
// This function is safe for concurrent access.
func (b *BlockChain) HaveBlock(hash *chainhash.Hash) (bool, error) {
b.chainLock.RLock()
exists, err := b.blockExists(hash)
b.chainLock.RUnlock()
if err != nil {
return false, err
}
return exists || b.IsKnownOrphan(hash), nil
}
// IsKnownOrphan returns whether the passed hash is currently a known orphan.
// Keep in mind that only a limited number of orphans are held onto for a
// limited amount of time, so this function must not be used as an absolute
// way to test if a block is an orphan block. A full block (as opposed to just
// its hash) must be passed to ProcessBlock for that purpose. However, calling
// ProcessBlock with an orphan that already exists results in an error, so this
// function provides a mechanism for a caller to intelligently detect *recent*
// duplicate orphans and react accordingly.
//
// This function is safe for concurrent access.
func (b *BlockChain) IsKnownOrphan(hash *chainhash.Hash) bool {
// Protect concurrent access. Using a read lock only so multiple
// readers can query without blocking each other.
b.orphanLock.RLock()
_, exists := b.orphans[*hash]
b.orphanLock.RUnlock()
return exists
}
// GetOrphanRoot returns the head of the chain for the provided hash from the
// map of orphan blocks.
//
// This function is safe for concurrent access.
func (b *BlockChain) GetOrphanRoot(hash *chainhash.Hash) *chainhash.Hash {
// Protect concurrent access. Using a read lock only so multiple
// readers can query without blocking each other.
b.orphanLock.RLock()
defer b.orphanLock.RUnlock()
// Keep looping while the parent of each orphaned block is
// known and is an orphan itself.
orphanRoot := hash
prevHash := hash
for {
orphan, exists := b.orphans[*prevHash]
if !exists {
break
}
orphanRoot = prevHash
prevHash = &orphan.block.MsgBlock().Header.PrevBlock
}
return orphanRoot
}
// removeOrphanBlock removes the passed orphan block from the orphan pool and
// previous orphan index.
func (b *BlockChain) removeOrphanBlock(orphan *orphanBlock) {
// Protect concurrent access.
b.orphanLock.Lock()
defer b.orphanLock.Unlock()
// Remove the orphan block from the orphan pool.
orphanHash := orphan.block.Hash()
delete(b.orphans, *orphanHash)
// Remove the reference from the previous orphan index too. An indexing
// for loop is intentionally used over a range here as range does not
// reevaluate the slice on each iteration nor does it adjust the index
// for the modified slice.
prevHash := &orphan.block.MsgBlock().Header.PrevBlock
orphans := b.prevOrphans[*prevHash]
for i := 0; i < len(orphans); i++ {
hash := orphans[i].block.Hash()
if hash.IsEqual(orphanHash) {
copy(orphans[i:], orphans[i+1:])
orphans[len(orphans)-1] = nil
orphans = orphans[:len(orphans)-1]
i--
}
}
b.prevOrphans[*prevHash] = orphans
// Remove the map entry altogether if there are no longer any orphans
// which depend on the parent hash.
if len(b.prevOrphans[*prevHash]) == 0 {
delete(b.prevOrphans, *prevHash)
}
}
// addOrphanBlock adds the passed block (which is already determined to be
// an orphan prior calling this function) to the orphan pool. It lazily cleans
// up any expired blocks so a separate cleanup poller doesn't need to be run.
// It also imposes a maximum limit on the number of outstanding orphan
// blocks and will remove the oldest received orphan block if the limit is
// exceeded.
func (b *BlockChain) addOrphanBlock(block *dcrutil.Block) {
// Remove expired orphan blocks.
for _, oBlock := range b.orphans {
if time.Now().After(oBlock.expiration) {
b.removeOrphanBlock(oBlock)
continue
}
// Update the oldest orphan block pointer so it can be discarded
// in case the orphan pool fills up.
if b.oldestOrphan == nil ||
oBlock.expiration.Before(b.oldestOrphan.expiration) {
b.oldestOrphan = oBlock
}
}
// Limit orphan blocks to prevent memory exhaustion.
if len(b.orphans)+1 > maxOrphanBlocks {
// Remove the oldest orphan to make room for the new one.
b.removeOrphanBlock(b.oldestOrphan)
b.oldestOrphan = nil
}
// Protect concurrent access. This is intentionally done here instead
// of near the top since removeOrphanBlock does its own locking and
// the range iterator is not invalidated by removing map entries.
b.orphanLock.Lock()
defer b.orphanLock.Unlock()
// Insert the block into the orphan map with an expiration time
// 1 hour from now.
expiration := time.Now().Add(time.Hour)
oBlock := &orphanBlock{
block: block,
expiration: expiration,
}
b.orphans[*block.Hash()] = oBlock
// Add to previous hash lookup index for faster dependency lookups.
prevHash := &block.MsgBlock().Header.PrevBlock
b.prevOrphans[*prevHash] = append(b.prevOrphans[*prevHash], oBlock)
}
// TipGeneration returns the entire generation of blocks stemming from the
// parent of the current tip.
//
// The function is safe for concurrent access.
func (b *BlockChain) TipGeneration() ([]chainhash.Hash, error) {
b.chainLock.Lock()
b.index.RLock()
nodes := b.index.chainTips[b.bestNode.height]
nodeHashes := make([]chainhash.Hash, len(nodes))
for i, n := range nodes {
nodeHashes[i] = n.hash
}
b.index.RUnlock()
b.chainLock.Unlock()
return nodeHashes, nil
}
// findNode finds the node scaling backwards from best chain or return an
// error. If searchDepth equal zero there is no searchDepth.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) findNode(nodeHash *chainhash.Hash, searchDepth int) (*blockNode, error) {
var node *blockNode
err := b.db.View(func(dbTx database.Tx) error {
// Most common case; we're checking a block that wants to be connected
// on top of the current main chain.
distance := 0
if *nodeHash == b.bestNode.hash {
node = b.bestNode
} else {
// Look backwards in our blockchain and try to find it in the
// parents of blocks.
foundPrev := b.bestNode
notFound := true
for !foundPrev.hash.IsEqual(b.chainParams.GenesisHash) {
if searchDepth != 0 && distance >= searchDepth {
break
}
if foundPrev.hash.IsEqual(nodeHash) {
notFound = false
break
}
last := foundPrev.parentHash
foundPrev = foundPrev.parent
if foundPrev == nil {
parent, err := b.index.loadBlockNode(dbTx, &last)
if err != nil {
return err
}
foundPrev = parent
}
distance++
}
if notFound {
return fmt.Errorf("couldn't find node %v in best chain",
nodeHash)
}
node = foundPrev
}
return nil
})
return node, err
}
// fetchMainChainBlockByHash returns the block from the main chain with the
// given hash. It first attempts to use cache and then falls back to loading it
// from the database.
//
// An error is returned if the block is either not found or not in the main
// chain.
//
// This function is safe for concurrent access.
func (b *BlockChain) fetchMainChainBlockByHash(hash *chainhash.Hash) (*dcrutil.Block, error) {
b.mainchainBlockCacheLock.RLock()
block, ok := b.mainchainBlockCache[*hash]
b.mainchainBlockCacheLock.RUnlock()
if ok {
return block, nil
}
// Load the block from the database.
err := b.db.View(func(dbTx database.Tx) error {
var err error
block, err = dbFetchBlockByHash(dbTx, hash)
return err
})
return block, err
}
// fetchBlockByHash returns the block with the given hash from all known sources
// such as the internal caches and the database.
//
// This function is safe for concurrent access.
func (b *BlockChain) fetchBlockByHash(hash *chainhash.Hash) (*dcrutil.Block, error) {
// Check orphan cache.
b.orphanLock.RLock()
orphan, existsOrphans := b.orphans[*hash]
b.orphanLock.RUnlock()
if existsOrphans {
return orphan.block, nil
}
// Check main chain cache.
b.mainchainBlockCacheLock.RLock()
block, ok := b.mainchainBlockCache[*hash]
b.mainchainBlockCacheLock.RUnlock()
if ok {
return block, nil
}
// Attempt to load the block from the database.
err := b.db.View(func(dbTx database.Tx) error {
// NOTE: This does not use the dbFetchBlockByHash function since that
// function only works with main chain blocks.
blockBytes, err := dbTx.FetchBlock(hash)
if err != nil {
return err
}
block, err = dcrutil.NewBlockFromBytes(blockBytes)
return err
})
if err == nil && block != nil {
return block, nil
}
return nil, fmt.Errorf("unable to find block %v in cache or db", hash)
}
// FetchBlockByHash searches the internal chain block stores and the database
// in an attempt to find the requested block.
//
// This function differs from BlockByHash in that this one also returns blocks
// that are not part of the main chain (if they are known).
//
// This function is safe for concurrent access.
func (b *BlockChain) FetchBlockByHash(hash *chainhash.Hash) (*dcrutil.Block, error) {
return b.fetchBlockByHash(hash)
}
// pruneStakeNodes removes references to old stake nodes which should no
// longer be held in memory so as to keep the maximum memory usage down.
// It proceeds from the bestNode back to the determined minimum height node,
// finds all the relevant children, and then drops the the stake nodes from
// them by assigning nil and allowing the memory to be recovered by GC.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) pruneStakeNodes() {
// Find the height to prune to.
pruneToNode := b.bestNode
for i := int64(0); i < minMemoryStakeNodes-1 && pruneToNode != nil; i++ {
pruneToNode = pruneToNode.parent
}
// Nothing to do if there are not enough nodes.
if pruneToNode == nil || pruneToNode.parent == nil {
return
}
// Push the nodes to delete on a list in reverse order since it's easier
// to prune them going forwards than it is backwards. This will
// typically end up being a single node since pruning is currently done
// just before each new node is created. However, that might be tuned
// later to only prune at intervals, so the code needs to account for
// the possibility of multiple nodes.
deleteNodes := list.New()
for node := pruneToNode.parent; node != nil; node = node.parent {
deleteNodes.PushFront(node)
}
// Loop through each node to prune, unlink its children, remove it from
// the dependency index, and remove it from the node index.
for e := deleteNodes.Front(); e != nil; e = e.Next() {
node := e.Value.(*blockNode)
// Do not attempt to prune if the node should already have been pruned,
// for example if you're adding an old side chain block.
if node.height > b.bestNode.height-minMemoryNodes {
node.stakeNode = nil
node.stakeUndoData = nil
node.newTickets = nil
node.ticketsVoted = nil
node.ticketsRevoked = nil
}
}
}
// BestPrevHash returns the hash of the previous block of the block at HEAD.
//
// This function is safe for concurrent access.
func (b *BlockChain) BestPrevHash() chainhash.Hash {
b.chainLock.Lock()
defer b.chainLock.Unlock()
return b.bestNode.parentHash
}
// isMajorityVersion determines if a previous number of blocks in the chain
// starting with startNode are at least the minimum passed version.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) isMajorityVersion(minVer int32, startNode *blockNode, numRequired uint64) bool {
numFound := uint64(0)
iterNode := startNode
for i := uint64(0); i < b.chainParams.BlockUpgradeNumToCheck &&
numFound < numRequired && iterNode != nil; i++ {
// This node has a version that is at least the minimum version.
if iterNode.blockVersion >= minVer {
numFound++
}
// Get the previous block node. This function is used over
// simply accessing iterNode.parent directly as it will
// dynamically create previous block nodes as needed. This
// helps allow only the pieces of the chain that are needed
// to remain in memory.
var err error
iterNode, err = b.index.PrevNodeFromNode(iterNode)
if err != nil {
break
}
}
return numFound >= numRequired
}
// getReorganizeNodes finds the fork point between the main chain and the passed
// node and returns a list of block nodes that would need to be detached from
// the main chain and a list of block nodes that would need to be attached to
// the fork point (which will be the end of the main chain after detaching the
// returned list of block nodes) in order to reorganize the chain such that the
// passed node is the new end of the main chain. The lists will be empty if the
// passed node is not on a side chain.
//
// This function MUST be called with the chain state lock held (for reads).
func (b *BlockChain) getReorganizeNodes(node *blockNode) (*list.List, *list.List, error) {
// Nothing to detach or attach if there is no node.
attachNodes := list.New()
detachNodes := list.New()
if node == nil {
return detachNodes, attachNodes, nil
}
// Don't allow a reorganize to a descendant of a known invalid block.
if b.index.NodeStatus(node.parent).KnownInvalid() {
b.index.SetStatusFlags(node, statusInvalidAncestor)
return detachNodes, attachNodes, nil
}
// Find the fork point (if any) adding each block to the list of nodes
// to attach to the main tree. Push them onto the list in reverse order
// so they are attached in the appropriate order when iterating the list
// later.
ancestor := node
for ; ancestor.parent != nil; ancestor = ancestor.parent {
if ancestor.inMainChain {
break
}
attachNodes.PushFront(ancestor)
}
// TODO(davec): Use prevNodeFromNode function in case the requested
// node is further back than the what is in memory. This shouldn't
// happen in the normal course of operation, but the ability to fetch
// input transactions of arbitrary blocks will likely to be exposed at
// some point and that could lead to an issue here.
// Start from the end of the main chain and work backwards until the
// common ancestor adding each block to the list of nodes to detach from
// the main chain.
for n := b.bestNode; n != nil; n = n.parent {
if n.hash == ancestor.hash {
break
}
detachNodes.PushBack(n)
if n.parent == nil {
var err error
n.parent, err = b.findNode(&n.parentHash, maxSearchDepth)
if err != nil {
return nil, nil, err
}
}
}
return detachNodes, attachNodes, nil
}
// pushMainChainBlockCache pushes a block onto the main chain block cache,
// and removes any old blocks from the cache that might be present.
func (b *BlockChain) pushMainChainBlockCache(block *dcrutil.Block) {
curHeight := block.Height()
curHash := block.Hash()
b.mainchainBlockCacheLock.Lock()
b.mainchainBlockCache[*curHash] = block
for hash, bl := range b.mainchainBlockCache {
if bl.Height() <= curHeight-int64(b.mainchainBlockCacheSize) {
delete(b.mainchainBlockCache, hash)
}
}
b.mainchainBlockCacheLock.Unlock()
}
// connectBlock handles connecting the passed node/block to the end of the main
// (best) chain.
//
// This passed utxo view must have all referenced txos the block spends marked
// as spent and all of the new txos the block creates added to it. In addition,
// the passed stxos slice must be populated with all of the information for the
// spent txos. This approach is used because the connection validation that
// must happen prior to calling this function requires the same details, so
// it would be inefficient to repeat it.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) connectBlock(node *blockNode, block, parent *dcrutil.Block, view *UtxoViewpoint, stxos []spentTxOut) error {
// Make sure it's extending the end of the best chain.
prevHash := block.MsgBlock().Header.PrevBlock
if prevHash != b.bestNode.hash {
return AssertError("connectBlock must be called with a block " +
"that extends the main chain")
}
// Sanity check the correct number of stxos are provided.
if len(stxos) != countSpentOutputs(block, parent) {
return AssertError("connectBlock called with inconsistent " +
"spent transaction out information")
}
// Calculate the median time for the block.
medianTime, err := b.index.CalcPastMedianTime(node)
if err != nil {
return err
}
// Generate a new best state snapshot that will be used to update the
// database and later memory if all database updates are successful.
b.stateLock.RLock()
curTotalTxns := b.stateSnapshot.TotalTxns
curTotalSubsidy := b.stateSnapshot.TotalSubsidy
b.stateLock.RUnlock()
// Calculate the number of transactions that would be added by adding
// this block.
numTxns := countNumberOfTransactions(block, parent)
// Calculate the exact subsidy produced by adding the block.
subsidy := CalculateAddedSubsidy(block, parent)
blockSize := uint64(block.MsgBlock().Header.Size)
state := newBestState(node, blockSize, numTxns, curTotalTxns+numTxns,
medianTime, curTotalSubsidy+subsidy)
// Get the stake node for this node, filling in any data that
// may have yet to have been filled in. In all cases this
// should simply give a pointer to data already prepared, but
// run this anyway to be safe.
stakeNode, err := b.fetchStakeNode(node)
if err != nil {
return err
}
// Atomically insert info into the database.
err = b.db.Update(func(dbTx database.Tx) error {
// Update best block state.
err := dbPutBestState(dbTx, state, node.workSum)
if err != nil {
return err
}
// Add the block to the block index. Ultimately the block index
// should track modified nodes and persist all of them prior
// this point as opposed to unconditionally peristing the node
// again. However, this is needed for now in lieu of that to
// ensure the updated status is written to the database.
err = dbPutBlockNode(dbTx, node)
if err != nil {
return err
}
// Add the block hash and height to the main chain index.
err = dbPutMainChainIndex(dbTx, block.Hash(), node.height)
if err != nil {
return err
}
// Update the utxo set using the state of the utxo view. This
// entails removing all of the utxos spent and adding the new
// ones created by the block.
err = dbPutUtxoView(dbTx, view)
if err != nil {
return err
}
// Update the transaction spend journal by adding a record for
// the block that contains all txos spent by it.
err = dbPutSpendJournalEntry(dbTx, block.Hash(), stxos)
if err != nil {
return err
}
// Insert the block into the stake database.
err = stake.WriteConnectedBestNode(dbTx, stakeNode, node.hash)
if err != nil {
return err
}
// Allow the index manager to call each of the currently active
// optional indexes with the block being connected so they can
// update themselves accordingly.
if b.indexManager != nil {
err := b.indexManager.ConnectBlock(dbTx, block, parent, view)
if err != nil {
return err
}
}
return nil
})
if err != nil {
return err
}
// Prune fully spent entries and mark all entries in the view unmodified
// now that the modifications have been committed to the database.
view.commit()
// Mark block as being in the main chain.
node.inMainChain = true
// This node is now the end of the best chain.
b.bestNode = node
// Update the state for the best block. Notice how this replaces the
// entire struct instead of updating the existing one. This effectively
// allows the old version to act as a snapshot which callers can use
// freely without needing to hold a lock for the duration. See the
// comments on the state variable for more details.
b.stateLock.Lock()
b.stateSnapshot = state
b.stateLock.Unlock()
// Send stake notifications about the new block.
if node.height >= b.chainParams.StakeEnabledHeight {
nextStakeDiff, err := b.calcNextRequiredStakeDifficulty(node)
if err != nil {
return err
}
// Notify of spent and missed tickets
b.sendNotification(NTSpentAndMissedTickets,
&TicketNotificationsData{
Hash: node.hash,
Height: node.height,
StakeDifficulty: nextStakeDiff,
TicketsSpent: node.stakeNode.SpentByBlock(),
TicketsMissed: node.stakeNode.MissedByBlock(),
TicketsNew: []chainhash.Hash{},
})
// Notify of new tickets
b.sendNotification(NTNewTickets,
&TicketNotificationsData{
Hash: node.hash,
Height: node.height,
StakeDifficulty: nextStakeDiff,
TicketsSpent: []chainhash.Hash{},
TicketsMissed: []chainhash.Hash{},
TicketsNew: node.stakeNode.NewTickets(),
})
}
// Assemble the current block and the parent into a slice.
blockAndParent := []*dcrutil.Block{block, parent}
// Notify the caller that the block was connected to the main chain.
// The caller would typically want to react with actions such as
// updating wallets.
b.chainLock.Unlock()
b.sendNotification(NTBlockConnected, blockAndParent)
b.chainLock.Lock()
// Optimization: Before checkpoints, immediately dump the parent's stake
// node because we no longer need it.
if node.height < b.chainParams.LatestCheckpointHeight() {
b.bestNode.parent.stakeNode = nil
b.bestNode.parent.stakeUndoData = nil
b.bestNode.parent.newTickets = nil
b.bestNode.parent.ticketsVoted = nil
b.bestNode.parent.ticketsRevoked = nil
}
b.pushMainChainBlockCache(block)
return nil
}
// dropMainChainBlockCache drops a block from the main chain block cache.
func (b *BlockChain) dropMainChainBlockCache(block *dcrutil.Block) {
curHash := block.Hash()
b.mainchainBlockCacheLock.Lock()
delete(b.mainchainBlockCache, *curHash)
b.mainchainBlockCacheLock.Unlock()
}
// disconnectBlock handles disconnecting the passed node/block from the end of
// the main (best) chain.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) disconnectBlock(node *blockNode, block, parent *dcrutil.Block, view *UtxoViewpoint) error {
// Make sure the node being disconnected is the end of the best chain.
if node.hash != b.bestNode.hash {
return AssertError("disconnectBlock must be called with the " +
"block at the end of the main chain")
}
// Get the previous block node. This function is used over simply
// accessing node.parent directly as it will dynamically create previous
// block nodes as needed. This helps allow only the pieces of the chain
// that are needed to remain in memory.
prevNode, err := b.index.PrevNodeFromNode(node)
if err != nil {
return err
}