// 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/ava-labs/coreth/core/rawdb"
"github.com/ava-labs/coreth/core/types"
"github.com/ethereum/go-ethereum/common"
"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
// Prune deletes the chain index older than the given threshold.
Prune(threshold uint64) 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