package blockpool
import (
"sync"
"time"
"github.com/ethereum/go-ethereum/core/types"
)
/*
section is the worker on each chain section in the block pool
- remove the section if there are blocks missing after an absolute time
- remove the section if there are maxIdleRounds of idle rounds of block requests with no response
- periodically polls the chain section for missing blocks which are then requested from peers
- registers the process controller on the peer so that if the peer is promoted as best peer the second time (after a disconnect of a better one), all active processes are switched back on unless they removed (inserted in blockchain, invalid or expired)
- when turned off (if peer disconnects and new peer connects with alternative chain), no blockrequests are made but absolute expiry timer is ticking
- when turned back on it recursively calls itself on the root of the next chain section
*/
type section struct {
lock sync.RWMutex
parent *section // connecting section back in time towards blockchain
child *section // connecting section forward in time
top *node // the topmost node = head node = youngest node within the chain section
bottom *node // the bottom node = root node = oldest node within the chain section
nodes []*node
peer *peer
parentHash []byte
blockHashes [][]byte
poolRootIndex int
bp *BlockPool
controlC chan *peer // to (de)register the current best peer
poolRootC chan *peer // indicate connectedness to blockchain (well, known blocks)
offC chan bool // closed if process terminated
suicideC chan bool // initiate suicide on the section
quitInitC chan bool // to signal end of initialisation
forkC chan chan bool // freeze section process while splitting
switchC chan bool // switching
idleC chan bool // channel to indicate thai food
processC chan *node //
missingC chan *node //
blocksRequestTimer <-chan time.Time
blockHashesRequestTimer <-chan time.Time
suicideTimer <-chan time.Time
blocksRequests int
blockHashesRequests int
blocksRequestsComplete bool
blockHashesRequestsComplete bool
ready bool
same bool
initialised bool
active bool
step int
idle int
missing int
lastMissing int
depth int
invalid bool
poolRoot bool
}
//
func (self *BlockPool) newSection(nodes []*node) *section {
sec := §ion{
bottom: nodes[len(nodes)-1],
top: nodes[0],
nodes: nodes,
poolRootIndex: len(nodes),
bp: self,
controlC: make(chan *peer),
poolRootC: make(chan *peer),
offC: make(chan bool),
}
for i, node := range nodes {
entry := &entry{node: node, section: sec, index: &index{i}}
self.set(node.hash, entry)
}
plog.DebugDetailf("[%s] setup section process", sectionhex(sec))
go sec.run()
return sec
}
func (self *section) addSectionToBlockChain(p *peer) {
self.bp.wg.Add(1)
go func() {
self.lock.Lock()
defer self.lock.Unlock()
defer func() {
self.bp.wg.Done()
}()
var node *node
var keys []string
var blocks []*types.Block
for self.poolRootIndex > 0 {
node = self.nodes[self.poolRootIndex-1]
node.lock.RLock()
block := node.block
node.lock.RUnlock()
if block == nil {
break
}
self.poolRootIndex--
keys = append(keys, string(node.hash))
blocks = append(blocks, block)
}
if len(blocks) == 0 {
return
}
self.bp.lock.Lock()
for _, key := range keys {
delete(self.bp.pool, key)
}
self.bp.lock.Unlock()
plog.Infof("[%s] insert %v blocks [%v/%v] into blockchain", sectionhex(self), len(blocks), hex(blocks[0].Hash()), hex(blocks[len(blocks)-1].Hash()))
err := self.bp.insertChain(blocks)
if err != nil {
self.invalid = true
self.bp.peers.peerError(node.blockBy, ErrInvalidBlock, "%v", err)
plog.Warnf("invalid block %x", node.hash)
plog.Warnf("penalise peers %v (hash), %v (block)", node.hashBy, node.blockBy)
// or invalid block and the entire chain needs to be removed
self.removeInvalidChain()
} else {
// if all blocks inserted in this section
// then need to try to insert blocks in child section
if self.poolRootIndex == 0 {
// if there is a child section, then recursively call itself:
// also if section process is not terminated,
// then signal blockchain connectivity with poolRootC
if child := self.bp.getChild(self); child != nil {
select {
case <-child.offC:
plog.DebugDetailf("[%s] add complete child section [%s] to the blockchain", sectionhex(self), sectionhex(child))
case child.poolRootC <- p:
plog.DebugDetailf("[%s] add incomplete child section [%s] to the blockchain", sectionhex(self), sectionhex(child))
}
child.addSectionToBlockChain(p)
} else {
plog.DebugDetailf("[%s] no child section in pool", sectionhex(self))
}
plog.DebugDetailf("[%s] section completely inserted to blockchain - remove", sectionhex(self))
// complete sections are removed. if called from within section process,
// this must run in its own go routine to avoid deadlock
self.remove()
}
}
self.bp.status.lock.Lock()
if err == nil {
headKey := string(blocks[0].ParentHash())
height := self.bp.status.chain[headKey] + len(blocks)
self.bp.status.chain[string(blocks[len(blocks)-1].Hash())] = height
if height > self.bp.status.values.LongestChain {
self.bp.status.values.LongestChain = height
}
delete(self.bp.status.chain, headKey)
}
self.bp.status.values.BlocksInChain += len(blocks)
self.bp.status.values.BlocksInPool -= len(blocks)
if err != nil {
self.bp.status.badPeers[node.blockBy]++
}
self.bp.status.lock.Unlock()
}()
}
func (self *section) run() {
// absolute time after which sub-chain is killed if not complete (some blocks are missing)
self.suicideC = make(chan bool)
self.forkC = make(chan chan bool)
self.suicideTimer = time.After(self.bp.Config.BlocksTimeout)
// node channels for the section
// container for missing block hashes
var checking bool
var ping = time.NewTicker(5 * time.Second)
LOOP:
for !self.blockHashesRequestsComplete || !self.blocksRequestsComplete {
select {
case <-ping.C:
var name = "no peer"
if self.peer != nil {
name = self.peer.id
}
plog.DebugDetailf("[%s] peer <%s> active: %v", sectionhex(self), name, self.active)
// global quit from blockpool
case <-self.bp.quit:
break LOOP
// pause for peer switching
case <-self.switchC:
self.switchC = nil
case p := <-self.poolRootC:
// signal on pool root channel indicates that the blockpool is
// connected to the blockchain, insert the longest chain of blocks
// ignored in idle mode to avoid inserting chain sections of non-live peers
self.poolRoot = true
// switch off hash requests in case they were on
self.blockHashesRequestTimer = nil
self.blockHashesRequestsComplete = true
self.switchOn(p)
// peer quit or demoted, put section in idle mode
case <-self.idleC:
// peer quit or demoted, put section in idle mode
plog.Debugf("[%s] peer <%s> quit or demoted", sectionhex(self), self.peer.id)
self.switchOff()
self.idleC = nil
// timebomb - if section is not complete in time, nuke the entire chain
case <-self.suicideTimer:
self.suicide()
plog.Debugf("[%s] timeout. (%v total attempts): missing %v/%v/%v...suicide", sectionhex(self), self.blocksRequests, self.missing, self.lastMissing, self.depth)
self.suicideTimer = nil
// closing suicideC triggers section suicide: removes section nodes from pool and terminates section process
case <-self.suicideC:
plog.DebugDetailf("[%s] suicide", sectionhex(self))
self.unlink()
self.bp.remove(self)
plog.DebugDetailf("[%s] done", sectionhex(self))
break LOOP
// alarm for checking blocks in the section
case <-self.blocksRequestTimer:
plog.DebugDetailf("[%s] alarm: block request time", sectionhex(self))
self.processC = self.missingC
// alarm for checking parent of the section or sending out hash requests
case <-self.blockHashesRequestTimer:
plog.DebugDetailf("[%s] alarm: hash request time", sectionhex(self))
self.blockHashesRequest()
// activate this section process with a peer
case p := <-self.controlC:
if p == nil {
self.switchOff()
} else {
self.switchOn(p)
}
self.bp.wg.Done()
// blocks the process until section is split at the fork
case waiter := <-self.forkC:
<-waiter
self.initialised = false
self.quitInitC = nil
//
case n, ok := <-self.processC:
// channel closed, first iteration finished
if !ok && !self.initialised {
plog.DebugDetailf("[%s] section initalised: missing %v/%v/%v", sectionhex(self), self.missing, self.lastMissing, self.depth)
self.initialised = true
self.processC = nil
// self.processC = make(chan *node, self.missing)
self.checkRound()
checking = false
break
}
plog.DebugDetailf("[%s] section proc step %v: missing %v/%v/%v", sectionhex(self), self.step, self.missing, self.lastMissing, self.depth)
if !checking {
self.step = 0
self.missing = 0
checking = true
}
self.step++
n.lock.RLock()
block := n.block
n.lock.RUnlock()
// if node has no block, request it (buffer it for batch request)
// feed it to missingC channel for the next round
if block == nil {
pos := self.missing % self.bp.Config.BlockBatchSize
if pos == 0 {
if self.missing != 0 {
self.bp.requestBlocks(self.blocksRequests, self.blockHashes[:])
}
self.blockHashes = self.bp.getHashSlice()
}
self.blockHashes[pos] = n.hash
self.missing++
self.missingC <- n
} else {
// checking for parent block
if self.poolRoot {
// if node has got block (received via async AddBlock call from protocol)
if self.step == self.lastMissing {
// current root of the pool
plog.DebugDetailf("[%s] received block for current pool root %s", sectionhex(self), hex(n.hash))
self.addSectionToBlockChain(self.peer)
}
} else {
if self.parentHash == nil && n == self.bottom {
self.parentHash = block.ParentHash()
plog.DebugDetailf("[%s] got parent head block hash %s...checking", sectionhex(self), hex(self.parentHash))
self.blockHashesRequest()
}
}
}
if self.initialised && self.step == self.lastMissing {
plog.DebugDetailf("[%s] check if new blocks arrived (attempt %v): missing %v/%v/%v", sectionhex(self), self.blocksRequests, self.missing, self.lastMissing, self.depth)
self.checkRound()
checking = false
}
} // select
} // for
close(self.offC)
if self.peer != nil {
self.active = false
self.bp.wg.Done()
}
plog.DebugDetailf("[%s] section process terminated: %v blocks retrieved (%v attempts), hash requests complete on root (%v attempts).", sectionhex(self), self.depth, self.blocksRequests, self.blockHashesRequests)
}
func (self *section) switchOn(newpeer *peer) {
oldpeer := self.peer
// reset switchC/switchC to current best peer
self.idleC = newpeer.idleC
self.switchC = newpeer.switchC
self.peer = newpeer
if oldpeer != newpeer {
oldp := "no peer"
newp := "no peer"
if oldpeer != nil {
oldp = oldpeer.id
}
if newpeer != nil {
newp = newpeer.id
}
plog.DebugDetailf("[%s] active mode <%s> -> <%s>", sectionhex(self), oldp, newp)
}
// activate section with current peer
if oldpeer == nil {
self.bp.wg.Add(1)
self.active = true
if !self.blockHashesRequestsComplete {
self.blockHashesRequestTimer = time.After(0)
}
if !self.blocksRequestsComplete {
if !self.initialised {
if self.quitInitC != nil {
<-self.quitInitC
}
self.missingC = make(chan *node, self.bp.Config.BlockHashesBatchSize)
self.processC = make(chan *node, self.bp.Config.BlockHashesBatchSize)
self.quitInitC = make(chan bool)
self.step = 0
self.missing = 0
self.depth = len(self.nodes)
self.lastMissing = self.depth
self.feedNodes()
} else {
self.blocksRequestTimer = time.After(0)
}
}
}
}
// put the section to idle mode
func (self *section) switchOff() {
// active -> idle
if self.peer != nil {
oldp := "no peer"
oldpeer := self.peer
if oldpeer != nil {
oldp = oldpeer.id
}
plog.DebugDetailf("[%s] idle mode peer <%s> -> <> (%v total attempts): missing %v/%v/%v", sectionhex(self), oldp, self.blocksRequests, self.missing, self.lastMissing, self.depth)
self.active = false
self.peer = nil
// turn off timers
self.blocksRequestTimer = nil
self.blockHashesRequestTimer = nil
if self.quitInitC != nil {
<-self.quitInitC
self.quitInitC = nil
}
self.processC = nil
self.bp.wg.Done()
}
}
// iterates through nodes of a section to feed processC
// used to initialise chain section
func (self *section) feedNodes() {
// if not run at least once fully, launch iterator
self.bp.wg.Add(1)
go func() {
self.lock.Lock()
defer self.lock.Unlock()
defer func() {
self.bp.wg.Done()
}()
var n *node
INIT:
for _, n = range self.nodes {
select {
case self.processC <- n:
case <-self.bp.quit:
break INIT
}
}
close(self.processC)
close(self.quitInitC)
}()
}
func (self *section) blockHashesRequest() {
if self.switchC != nil {
self.bp.chainLock.Lock()
parentSection := self.parent
if parentSection == nil {
// only link to new parent if not switching peers
// this protects against synchronisation issue where during switching
// a demoted peer's fork will be chosen over the best peer's chain
// because relinking the correct chain (activateChain) is overwritten here in
// demoted peer's section process just before the section is put to idle mode
if self.parentHash != nil {
if parent := self.bp.get(self.parentHash); parent != nil {
parentSection = parent.section
plog.DebugDetailf("[%s] blockHashesRequest: parent section [%s] linked\n", sectionhex(self), sectionhex(parentSection))
link(parentSection, self)
} else {
if self.bp.hasBlock(self.parentHash) {
self.poolRoot = true
plog.DebugDetailf("[%s] blockHashesRequest: parentHash known ... inserting section in blockchain", sectionhex(self))
self.addSectionToBlockChain(self.peer)
self.blockHashesRequestTimer = nil
self.blockHashesRequestsComplete = true
}
}
}
}
self.bp.chainLock.Unlock()
if !self.poolRoot {
if parentSection != nil {
// activate parent section with this peer
// but only if not during switch mode
plog.DebugDetailf("[%s] parent section [%s] activated\n", sectionhex(self), sectionhex(parentSection))
self.bp.activateChain(parentSection, self.peer, nil)
// if not root of chain, switch off
plog.DebugDetailf("[%s] parent found, hash requests deactivated (after %v total attempts)\n", sectionhex(self), self.blockHashesRequests)
self.blockHashesRequestTimer = nil
self.blockHashesRequestsComplete = true
} else {
self.blockHashesRequests++
plog.DebugDetailf("[%s] hash request on root (%v total attempts)\n", sectionhex(self), self.blockHashesRequests)
self.peer.requestBlockHashes(self.bottom.hash)
self.blockHashesRequestTimer = time.After(self.bp.Config.BlockHashesRequestInterval)
}
}
}
}
// checks number of missing blocks after each round of request and acts accordingly
func (self *section) checkRound() {
if self.missing == 0 {
// no missing blocks
plog.DebugDetailf("[%s] section checked: got all blocks. process complete (%v total blocksRequests): missing %v/%v/%v", sectionhex(self), self.blocksRequests, self.missing, self.lastMissing, self.depth)
self.blocksRequestsComplete = true
self.blocksRequestTimer = nil
} else {
// some missing blocks
plog.DebugDetailf("[%s] section checked: missing %v/%v/%v", sectionhex(self), self.missing, self.lastMissing, self.depth)
self.blocksRequests++
pos := self.missing % self.bp.Config.BlockBatchSize
if pos == 0 {
pos = self.bp.Config.BlockBatchSize
}
self.bp.requestBlocks(self.blocksRequests, self.blockHashes[:pos])
// handle idle rounds
if self.missing == self.lastMissing {
// idle round
if self.same {
// more than once
self.idle++
// too many idle rounds
if self.idle >= self.bp.Config.BlocksRequestMaxIdleRounds {
plog.DebugDetailf("[%s] block requests had %v idle rounds (%v total attempts): missing %v/%v/%v\ngiving up...", sectionhex(self), self.idle, self.blocksRequests, self.missing, self.lastMissing, self.depth)
self.suicide()
}
} else {
self.idle = 0
}
self.same = true
} else {
self.same = false
}
self.lastMissing = self.missing
// put processC offline
self.processC = nil
self.blocksRequestTimer = time.After(self.bp.Config.BlocksRequestInterval)
}
}
/*
link connects two sections via parent/child fields
creating a doubly linked list
caller must hold BlockPool chainLock
*/
func link(parent *section, child *section) {
if parent != nil {
exChild := parent.child
parent.child = child
if exChild != nil && exChild != child {
if child != nil {
// if child is nil it is not a real fork
plog.DebugDetailf("[%s] chain fork [%s] -> [%s]", sectionhex(parent), sectionhex(exChild), sectionhex(child))
}
exChild.parent = nil
}
}
if child != nil {
exParent := child.parent
if exParent != nil && exParent != parent {
if parent != nil {
// if parent is nil it is not a real fork, but suicide delinking section
plog.DebugDetailf("[%s] chain reverse fork [%s] -> [%s]", sectionhex(child), sectionhex(exParent), sectionhex(parent))
}
exParent.child = nil
}
child.parent = parent
}
}
/*
handle forks where connecting node is mid-section
by splitting section at fork
no splitting needed if connecting node is head of a section
caller must hold chain lock
*/
func (self *BlockPool) splitSection(parent *section, entry *entry) {
plog.DebugDetailf("[%s] split section at fork", sectionhex(parent))
parent.deactivate()
waiter := make(chan bool)
parent.wait(waiter)
chain := parent.nodes
parent.nodes = chain[entry.index.int:]
parent.top = parent.nodes[0]
parent.poolRootIndex -= entry.index.int
orphan := self.newSection(chain[0:entry.index.int])
link(orphan, parent.child)
close(waiter)
orphan.deactivate()
}
func (self *section) wait(waiter chan bool) {
self.forkC <- waiter
}
func (self *BlockPool) linkSections(nodes []*node, parent, child *section) (sec *section) {
// if new section is created, link it to parent/child sections
// and launch section process fetching block and further hashes
if len(nodes) > 0 {
sec = self.newSection(nodes)
plog.Debugf("[%s]->[%s](%v)->[%s] new chain section", sectionhex(parent), sectionhex(sec), len(nodes), sectionhex(child))
link(parent, sec)
link(sec, child)
} else {
// now this can only happen if we allow response to hash request to include <from> hash
// in this case we just link parent and child (without needing root block of child section)
plog.Debugf("[%s]->[%s] connecting known sections", sectionhex(parent), sectionhex(child))
link(parent, child)
}
return
}
func (self *section) activate(p *peer) {
self.bp.wg.Add(1)
select {
case <-self.offC:
self.bp.wg.Done()
case self.controlC <- p:
plog.DebugDetailf("[%s] activate section process for peer <%s>", sectionhex(self), p.id)
}
}
func (self *section) deactivate() {
self.bp.wg.Add(1)
self.controlC <- nil
}
func (self *section) suicide() {
select {
case <-self.suicideC:
return
default:
}
close(self.suicideC)
}
// removes this section exacly
func (self *section) remove() {
select {
case <-self.offC:
// section is complete, no process
self.unlink()
self.bp.remove(self)
close(self.suicideC)
plog.DebugDetailf("[%s] remove: suicide", sectionhex(self))
case <-self.suicideC:
plog.DebugDetailf("[%s] remove: suicided already", sectionhex(self))
default:
plog.DebugDetailf("[%s] remove: suicide", sectionhex(self))
close(self.suicideC)
}
plog.DebugDetailf("[%s] removed section.", sectionhex(self))
}
// remove a section and all its descendents from the pool
func (self *section) removeInvalidChain() {
// need to get the child before removeSection delinks the section
self.bp.chainLock.RLock()
child := self.child
self.bp.chainLock.RUnlock()
plog.DebugDetailf("[%s] remove invalid chain", sectionhex(self))
self.remove()
if child != nil {
child.removeInvalidChain()
}
}
// unlink a section from its parent/child
func (self *section) unlink() {
// first delink from child and parent under chainlock
self.bp.chainLock.Lock()
link(nil, self)
link(self, nil)
self.bp.chainLock.Unlock()
}
