bsc/core/chain_indexer.go
gary rong 802074cba9 core: fix chain indexer (#19786)
This PR fixes an issue in chain indexer. Currently chain indexer will
validate whether the stored data is canonical by comparing section head
and canonical hash. But the header of the checkpoint may not exist in
the database. We should skip validation for sections below the
checkpoint.
2019-07-03 11:18:48 +03:00

513 lines
17 KiB
Go

// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package core
import (
"context"
"encoding/binary"
"fmt"
"sync"
"sync/atomic"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/rawdb"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/event"
"github.com/ethereum/go-ethereum/log"
)
// ChainIndexerBackend defines the methods needed to process chain segments in
// the background and write the segment results into the database. These can be
// used to create filter blooms or CHTs.
type ChainIndexerBackend interface {
// Reset initiates the processing of a new chain segment, potentially terminating
// any partially completed operations (in case of a reorg).
Reset(ctx context.Context, section uint64, prevHead common.Hash) error
// Process crunches through the next header in the chain segment. The caller
// will ensure a sequential order of headers.
Process(ctx context.Context, header *types.Header) error
// Commit finalizes the section metadata and stores it into the database.
Commit() error
}
// ChainIndexerChain interface is used for connecting the indexer to a blockchain
type ChainIndexerChain interface {
// CurrentHeader retrieves the latest locally known header.
CurrentHeader() *types.Header
// SubscribeChainHeadEvent subscribes to new head header notifications.
SubscribeChainHeadEvent(ch chan<- ChainHeadEvent) event.Subscription
}
// ChainIndexer does a post-processing job for equally sized sections of the
// canonical chain (like BlooomBits and CHT structures). A ChainIndexer is
// connected to the blockchain through the event system by starting a
// ChainHeadEventLoop in a goroutine.
//
// Further child ChainIndexers can be added which use the output of the parent
// section indexer. These child indexers receive new head notifications only
// after an entire section has been finished or in case of rollbacks that might
// affect already finished sections.
type ChainIndexer struct {
chainDb ethdb.Database // Chain database to index the data from
indexDb ethdb.Database // Prefixed table-view of the db to write index metadata into
backend ChainIndexerBackend // Background processor generating the index data content
children []*ChainIndexer // Child indexers to cascade chain updates to
active uint32 // Flag whether the event loop was started
update chan struct{} // Notification channel that headers should be processed
quit chan chan error // Quit channel to tear down running goroutines
ctx context.Context
ctxCancel func()
sectionSize uint64 // Number of blocks in a single chain segment to process
confirmsReq uint64 // Number of confirmations before processing a completed segment
storedSections uint64 // Number of sections successfully indexed into the database
knownSections uint64 // Number of sections known to be complete (block wise)
cascadedHead uint64 // Block number of the last completed section cascaded to subindexers
checkpointSections uint64 // Number of sections covered by the checkpoint
checkpointHead common.Hash // Section head belonging to the checkpoint
throttling time.Duration // Disk throttling to prevent a heavy upgrade from hogging resources
log log.Logger
lock sync.RWMutex
}
// NewChainIndexer creates a new chain indexer to do background processing on
// chain segments of a given size after certain number of confirmations passed.
// The throttling parameter might be used to prevent database thrashing.
func NewChainIndexer(chainDb ethdb.Database, indexDb ethdb.Database, backend ChainIndexerBackend, section, confirm uint64, throttling time.Duration, kind string) *ChainIndexer {
c := &ChainIndexer{
chainDb: chainDb,
indexDb: indexDb,
backend: backend,
update: make(chan struct{}, 1),
quit: make(chan chan error),
sectionSize: section,
confirmsReq: confirm,
throttling: throttling,
log: log.New("type", kind),
}
// Initialize database dependent fields and start the updater
c.loadValidSections()
c.ctx, c.ctxCancel = context.WithCancel(context.Background())
go c.updateLoop()
return c
}
// AddCheckpoint adds a checkpoint. Sections are never processed and the chain
// is not expected to be available before this point. The indexer assumes that
// the backend has sufficient information available to process subsequent sections.
//
// Note: knownSections == 0 and storedSections == checkpointSections until
// syncing reaches the checkpoint
func (c *ChainIndexer) AddCheckpoint(section uint64, shead common.Hash) {
c.lock.Lock()
defer c.lock.Unlock()
// Short circuit if the given checkpoint is below than local's.
if c.checkpointSections >= section+1 || section < c.storedSections {
return
}
c.checkpointSections = section + 1
c.checkpointHead = shead
c.setSectionHead(section, shead)
c.setValidSections(section + 1)
}
// Start creates a goroutine to feed chain head events into the indexer for
// cascading background processing. Children do not need to be started, they
// are notified about new events by their parents.
func (c *ChainIndexer) Start(chain ChainIndexerChain) {
events := make(chan ChainHeadEvent, 10)
sub := chain.SubscribeChainHeadEvent(events)
go c.eventLoop(chain.CurrentHeader(), events, sub)
}
// Close tears down all goroutines belonging to the indexer and returns any error
// that might have occurred internally.
func (c *ChainIndexer) Close() error {
var errs []error
c.ctxCancel()
// Tear down the primary update loop
errc := make(chan error)
c.quit <- errc
if err := <-errc; err != nil {
errs = append(errs, err)
}
// If needed, tear down the secondary event loop
if atomic.LoadUint32(&c.active) != 0 {
c.quit <- errc
if err := <-errc; err != nil {
errs = append(errs, err)
}
}
// Close all children
for _, child := range c.children {
if err := child.Close(); err != nil {
errs = append(errs, err)
}
}
// Return any failures
switch {
case len(errs) == 0:
return nil
case len(errs) == 1:
return errs[0]
default:
return fmt.Errorf("%v", errs)
}
}
// eventLoop is a secondary - optional - event loop of the indexer which is only
// started for the outermost indexer to push chain head events into a processing
// queue.
func (c *ChainIndexer) eventLoop(currentHeader *types.Header, events chan ChainHeadEvent, sub event.Subscription) {
// Mark the chain indexer as active, requiring an additional teardown
atomic.StoreUint32(&c.active, 1)
defer sub.Unsubscribe()
// Fire the initial new head event to start any outstanding processing
c.newHead(currentHeader.Number.Uint64(), false)
var (
prevHeader = currentHeader
prevHash = currentHeader.Hash()
)
for {
select {
case errc := <-c.quit:
// Chain indexer terminating, report no failure and abort
errc <- nil
return
case ev, ok := <-events:
// Received a new event, ensure it's not nil (closing) and update
if !ok {
errc := <-c.quit
errc <- nil
return
}
header := ev.Block.Header()
if header.ParentHash != prevHash {
// Reorg to the common ancestor if needed (might not exist in light sync mode, skip reorg then)
// TODO(karalabe, zsfelfoldi): This seems a bit brittle, can we detect this case explicitly?
if rawdb.ReadCanonicalHash(c.chainDb, prevHeader.Number.Uint64()) != prevHash {
if h := rawdb.FindCommonAncestor(c.chainDb, prevHeader, header); h != nil {
c.newHead(h.Number.Uint64(), true)
}
}
}
c.newHead(header.Number.Uint64(), false)
prevHeader, prevHash = header, header.Hash()
}
}
}
// newHead notifies the indexer about new chain heads and/or reorgs.
func (c *ChainIndexer) newHead(head uint64, reorg bool) {
c.lock.Lock()
defer c.lock.Unlock()
// If a reorg happened, invalidate all sections until that point
if reorg {
// Revert the known section number to the reorg point
known := (head + 1) / c.sectionSize
stored := known
if known < c.checkpointSections {
known = 0
}
if stored < c.checkpointSections {
stored = c.checkpointSections
}
if known < c.knownSections {
c.knownSections = known
}
// Revert the stored sections from the database to the reorg point
if stored < c.storedSections {
c.setValidSections(stored)
}
// Update the new head number to the finalized section end and notify children
head = known * c.sectionSize
if head < c.cascadedHead {
c.cascadedHead = head
for _, child := range c.children {
child.newHead(c.cascadedHead, true)
}
}
return
}
// No reorg, calculate the number of newly known sections and update if high enough
var sections uint64
if head >= c.confirmsReq {
sections = (head + 1 - c.confirmsReq) / c.sectionSize
if sections < c.checkpointSections {
sections = 0
}
if sections > c.knownSections {
if c.knownSections < c.checkpointSections {
// syncing reached the checkpoint, verify section head
syncedHead := rawdb.ReadCanonicalHash(c.chainDb, c.checkpointSections*c.sectionSize-1)
if syncedHead != c.checkpointHead {
c.log.Error("Synced chain does not match checkpoint", "number", c.checkpointSections*c.sectionSize-1, "expected", c.checkpointHead, "synced", syncedHead)
return
}
}
c.knownSections = sections
select {
case c.update <- struct{}{}:
default:
}
}
}
}
// updateLoop is the main event loop of the indexer which pushes chain segments
// down into the processing backend.
func (c *ChainIndexer) updateLoop() {
var (
updating bool
updated time.Time
)
for {
select {
case errc := <-c.quit:
// Chain indexer terminating, report no failure and abort
errc <- nil
return
case <-c.update:
// Section headers completed (or rolled back), update the index
c.lock.Lock()
if c.knownSections > c.storedSections {
// Periodically print an upgrade log message to the user
if time.Since(updated) > 8*time.Second {
if c.knownSections > c.storedSections+1 {
updating = true
c.log.Info("Upgrading chain index", "percentage", c.storedSections*100/c.knownSections)
}
updated = time.Now()
}
// Cache the current section count and head to allow unlocking the mutex
c.verifyLastHead()
section := c.storedSections
var oldHead common.Hash
if section > 0 {
oldHead = c.SectionHead(section - 1)
}
// Process the newly defined section in the background
c.lock.Unlock()
newHead, err := c.processSection(section, oldHead)
if err != nil {
select {
case <-c.ctx.Done():
<-c.quit <- nil
return
default:
}
c.log.Error("Section processing failed", "error", err)
}
c.lock.Lock()
// If processing succeeded and no reorgs occurred, mark the section completed
if err == nil && (section == 0 || oldHead == c.SectionHead(section-1)) {
c.setSectionHead(section, newHead)
c.setValidSections(section + 1)
if c.storedSections == c.knownSections && updating {
updating = false
c.log.Info("Finished upgrading chain index")
}
c.cascadedHead = c.storedSections*c.sectionSize - 1
for _, child := range c.children {
c.log.Trace("Cascading chain index update", "head", c.cascadedHead)
child.newHead(c.cascadedHead, false)
}
} else {
// If processing failed, don't retry until further notification
c.log.Debug("Chain index processing failed", "section", section, "err", err)
c.verifyLastHead()
c.knownSections = c.storedSections
}
}
// If there are still further sections to process, reschedule
if c.knownSections > c.storedSections {
time.AfterFunc(c.throttling, func() {
select {
case c.update <- struct{}{}:
default:
}
})
}
c.lock.Unlock()
}
}
}
// processSection processes an entire section by calling backend functions while
// ensuring the continuity of the passed headers. Since the chain mutex is not
// held while processing, the continuity can be broken by a long reorg, in which
// case the function returns with an error.
func (c *ChainIndexer) processSection(section uint64, lastHead common.Hash) (common.Hash, error) {
c.log.Trace("Processing new chain section", "section", section)
// Reset and partial processing
if err := c.backend.Reset(c.ctx, section, lastHead); err != nil {
c.setValidSections(0)
return common.Hash{}, err
}
for number := section * c.sectionSize; number < (section+1)*c.sectionSize; number++ {
hash := rawdb.ReadCanonicalHash(c.chainDb, number)
if hash == (common.Hash{}) {
return common.Hash{}, fmt.Errorf("canonical block #%d unknown", number)
}
header := rawdb.ReadHeader(c.chainDb, hash, number)
if header == nil {
return common.Hash{}, fmt.Errorf("block #%d [%x…] not found", number, hash[:4])
} else if header.ParentHash != lastHead {
return common.Hash{}, fmt.Errorf("chain reorged during section processing")
}
if err := c.backend.Process(c.ctx, header); err != nil {
return common.Hash{}, err
}
lastHead = header.Hash()
}
if err := c.backend.Commit(); err != nil {
return common.Hash{}, err
}
return lastHead, nil
}
// verifyLastHead compares last stored section head with the corresponding block hash in the
// actual canonical chain and rolls back reorged sections if necessary to ensure that stored
// sections are all valid
func (c *ChainIndexer) verifyLastHead() {
for c.storedSections > 0 && c.storedSections > c.checkpointSections {
if c.SectionHead(c.storedSections-1) == rawdb.ReadCanonicalHash(c.chainDb, c.storedSections*c.sectionSize-1) {
return
}
c.setValidSections(c.storedSections - 1)
}
}
// Sections returns the number of processed sections maintained by the indexer
// and also the information about the last header indexed for potential canonical
// verifications.
func (c *ChainIndexer) Sections() (uint64, uint64, common.Hash) {
c.lock.Lock()
defer c.lock.Unlock()
c.verifyLastHead()
return c.storedSections, c.storedSections*c.sectionSize - 1, c.SectionHead(c.storedSections - 1)
}
// AddChildIndexer adds a child ChainIndexer that can use the output of this one
func (c *ChainIndexer) AddChildIndexer(indexer *ChainIndexer) {
c.lock.Lock()
defer c.lock.Unlock()
c.children = append(c.children, indexer)
// Cascade any pending updates to new children too
sections := c.storedSections
if c.knownSections < sections {
// if a section is "stored" but not "known" then it is a checkpoint without
// available chain data so we should not cascade it yet
sections = c.knownSections
}
if sections > 0 {
indexer.newHead(sections*c.sectionSize-1, false)
}
}
// loadValidSections reads the number of valid sections from the index database
// and caches is into the local state.
func (c *ChainIndexer) loadValidSections() {
data, _ := c.indexDb.Get([]byte("count"))
if len(data) == 8 {
c.storedSections = binary.BigEndian.Uint64(data)
}
}
// setValidSections writes the number of valid sections to the index database
func (c *ChainIndexer) setValidSections(sections uint64) {
// Set the current number of valid sections in the database
var data [8]byte
binary.BigEndian.PutUint64(data[:], sections)
c.indexDb.Put([]byte("count"), data[:])
// Remove any reorged sections, caching the valids in the mean time
for c.storedSections > sections {
c.storedSections--
c.removeSectionHead(c.storedSections)
}
c.storedSections = sections // needed if new > old
}
// SectionHead retrieves the last block hash of a processed section from the
// index database.
func (c *ChainIndexer) SectionHead(section uint64) common.Hash {
var data [8]byte
binary.BigEndian.PutUint64(data[:], section)
hash, _ := c.indexDb.Get(append([]byte("shead"), data[:]...))
if len(hash) == len(common.Hash{}) {
return common.BytesToHash(hash)
}
return common.Hash{}
}
// setSectionHead writes the last block hash of a processed section to the index
// database.
func (c *ChainIndexer) setSectionHead(section uint64, hash common.Hash) {
var data [8]byte
binary.BigEndian.PutUint64(data[:], section)
c.indexDb.Put(append([]byte("shead"), data[:]...), hash.Bytes())
}
// removeSectionHead removes the reference to a processed section from the index
// database.
func (c *ChainIndexer) removeSectionHead(section uint64) {
var data [8]byte
binary.BigEndian.PutUint64(data[:], section)
c.indexDb.Delete(append([]byte("shead"), data[:]...))
}