core: implement ChainIndexer
This commit is contained in:
Zsolt Felfoldi
committed by
Péter Szilágyi
Péter Szilágyi
parent
67439c1dba
commit
bd74882d83
294
core/chain_indexer.go
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294
core/chain_indexer.go
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// Copyright 2017 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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// Package core implements the Ethereum consensus protocol.
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package core
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import (
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"encoding/binary"
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"sync"
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"time"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/core/types"
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"github.com/ethereum/go-ethereum/ethdb"
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"github.com/ethereum/go-ethereum/event"
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)
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// ChainIndexer does a post-processing job for equally sized sections of the canonical
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// chain (like BlooomBits and CHT structures). A ChainIndexer is connected to the blockchain
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// through the event system by starting a ChainEventLoop in a goroutine.
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// Further child ChainIndexers can be added which use the output of the parent section
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// indexer. These child indexers receive new head notifications only after an entire section
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// has been finished or in case of rollbacks that might affect already finished sections.
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type ChainIndexer struct {
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chainDb, indexDb ethdb.Database
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backend ChainIndexerBackend
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sectionSize, confirmReq uint64
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stop chan struct{}
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lock sync.Mutex
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procWait time.Duration
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tryUpdate chan struct{}
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stored, targetCount, calcIdx, lastForwarded uint64
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updating bool
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children []*ChainIndexer
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}
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// ChainIndexerBackend interface is a backend for the indexer doing the actual post-processing job
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type ChainIndexerBackend interface {
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Reset(section uint64) // start processing a new section
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Process(header *types.Header) // process a single block (called for each block in the section)
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Commit(db ethdb.Database) error // do some more processing if necessary and store the results in the database
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UpdateMsg(done, all uint64) // print a progress update message if necessary (only called when multiple sections need to be processed)
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}
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// NewChainIndexer creates a new ChainIndexer
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// db: database where the index of available processed sections is stored (the index is stored by the
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// indexer, the actual processed chain data is stored by the backend)
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// dbKey: key prefix where the index is stored
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// backend: an implementation of ChainIndexerBackend
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// sectionSize: the size of processable sections
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// confirmReq: required number of confirmation blocks before a new section is being processed
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// procWait: waiting time between processing sections (simple way of limiting the resource usage of a db upgrade)
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// stop: quit channel
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func NewChainIndexer(chainDb, indexDb ethdb.Database, backend ChainIndexerBackend, sectionSize, confirmReq uint64, procWait time.Duration, stop chan struct{}) *ChainIndexer {
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c := &ChainIndexer{
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chainDb: chainDb,
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indexDb: indexDb,
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backend: backend,
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sectionSize: sectionSize,
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confirmReq: confirmReq,
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tryUpdate: make(chan struct{}, 1),
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stop: stop,
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procWait: procWait,
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}
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c.stored = c.getValidSections()
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go c.updateLoop()
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return c
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}
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// updateLoop is the main event loop of the indexer
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func (c *ChainIndexer) updateLoop() {
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updateMsg := false
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for {
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select {
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case <-c.stop:
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return
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case <-c.tryUpdate:
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c.lock.Lock()
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if c.targetCount > c.stored {
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if !updateMsg && c.targetCount > c.stored+1 {
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updateMsg = true
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c.backend.UpdateMsg(c.stored, c.targetCount)
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}
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c.calcIdx = c.stored
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var lastSectionHead common.Hash
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if c.calcIdx > 0 {
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lastSectionHead = c.getSectionHead(c.calcIdx - 1)
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}
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c.lock.Unlock()
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sectionHead, ok := c.processSection(c.calcIdx, lastSectionHead)
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c.lock.Lock()
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if ok && lastSectionHead == c.getSectionHead(c.calcIdx-1) {
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c.stored = c.calcIdx + 1
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c.setSectionHead(c.calcIdx, sectionHead)
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c.setValidSections(c.stored)
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if updateMsg {
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c.backend.UpdateMsg(c.stored, c.targetCount)
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if c.stored >= c.targetCount {
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updateMsg = false
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}
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}
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c.lastForwarded = c.stored*c.sectionSize - 1
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for _, cp := range c.children {
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cp.newHead(c.lastForwarded, false)
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}
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} else {
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// if processing has failed, do not retry until further notification
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c.targetCount = c.stored
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}
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}
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if c.targetCount > c.stored {
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go func() {
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time.Sleep(c.procWait)
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c.tryUpdate <- struct{}{}
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}()
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} else {
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c.updating = false
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}
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c.lock.Unlock()
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}
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}
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}
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// ChainEventLoop runs in a goroutine and feeds blockchain events to the indexer by calling newHead
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// (not needed for child indexers where the parent calls newHead)
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func (c *ChainIndexer) ChainEventLoop(currentHeader *types.Header, eventMux *event.TypeMux) {
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sub := eventMux.Subscribe(ChainEvent{})
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c.newHead(currentHeader.Number.Uint64(), false)
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lastHead := currentHeader.Hash()
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for {
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select {
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case <-c.stop:
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return
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case ev := <-sub.Chan():
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header := ev.Data.(ChainEvent).Block.Header()
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c.newHead(header.Number.Uint64(), header.ParentHash != lastHead)
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lastHead = header.Hash()
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}
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}
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}
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// AddChildIndexer adds a child ChainIndexer that can use the output of this one
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func (c *ChainIndexer) AddChildIndexer(ci *ChainIndexer) {
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c.children = append(c.children, ci)
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}
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// newHead notifies the indexer about new chain heads or rollbacks
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func (c *ChainIndexer) newHead(headNum uint64, rollback bool) {
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c.lock.Lock()
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defer c.lock.Unlock()
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if rollback {
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firstChanged := headNum / c.sectionSize
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if firstChanged < c.targetCount {
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c.targetCount = firstChanged
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}
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if firstChanged < c.stored {
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c.stored = firstChanged
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c.setValidSections(c.stored)
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}
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headNum = firstChanged * c.sectionSize
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if headNum < c.lastForwarded {
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c.lastForwarded = headNum
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for _, cp := range c.children {
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cp.newHead(c.lastForwarded, true)
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}
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}
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} else {
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var newCount uint64
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if headNum >= c.confirmReq {
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newCount = (headNum + 1 - c.confirmReq) / c.sectionSize
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if newCount > c.targetCount {
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c.targetCount = newCount
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if !c.updating {
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c.updating = true
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c.tryUpdate <- struct{}{}
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}
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}
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}
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}
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}
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// processSection processes an entire section by calling backend functions while ensuring
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// the continuity of the passed headers. Since the chain mutex is not held while processing,
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// the continuity can be broken by a long reorg, in which case the function returns with ok == false.
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func (c *ChainIndexer) processSection(section uint64, lastSectionHead common.Hash) (sectionHead common.Hash, ok bool) {
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c.backend.Reset(section)
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head := lastSectionHead
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for i := section * c.sectionSize; i < (section+1)*c.sectionSize; i++ {
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hash := GetCanonicalHash(c.chainDb, i)
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if hash == (common.Hash{}) {
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return common.Hash{}, false
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}
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header := GetHeader(c.chainDb, hash, i)
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if header == nil || header.ParentHash != head {
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return common.Hash{}, false
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}
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c.backend.Process(header)
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head = header.Hash()
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}
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if err := c.backend.Commit(c.chainDb); err != nil {
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return common.Hash{}, false
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}
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return head, true
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}
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// CanonicalSections returns the number of processed sections that are consistent with
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// the current canonical chain
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func (c *ChainIndexer) CanonicalSections() uint64 {
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c.lock.Lock()
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defer c.lock.Unlock()
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cnt := c.getValidSections()
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for cnt > 0 {
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if c.getSectionHead(cnt-1) == GetCanonicalHash(c.chainDb, cnt*c.sectionSize-1) {
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break
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}
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cnt--
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c.setValidSections(cnt)
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}
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return cnt
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}
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// getValidSections reads the number of valid sections from the index database
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func (c *ChainIndexer) getValidSections() uint64 {
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data, _ := c.indexDb.Get([]byte("count"))
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if len(data) == 8 {
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return binary.BigEndian.Uint64(data[:])
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}
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return 0
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}
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// setValidSections writes the number of valid sections to the index database
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func (c *ChainIndexer) setValidSections(cnt uint64) {
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oldCnt := c.getValidSections()
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if cnt < oldCnt {
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for i := cnt; i < oldCnt; i++ {
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c.removeSectionHead(i)
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}
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}
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var data [8]byte
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binary.BigEndian.PutUint64(data[:], cnt)
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c.indexDb.Put([]byte("count"), data[:])
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}
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// getSectionHead reads the last block hash of a processed section from the index database
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func (c *ChainIndexer) getSectionHead(idx uint64) common.Hash {
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var data [8]byte
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binary.BigEndian.PutUint64(data[:], idx)
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hash, _ := c.indexDb.Get(append([]byte("shead"), data[:]...))
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if len(hash) == len(common.Hash{}) {
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return common.BytesToHash(hash)
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}
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return common.Hash{}
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}
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// setSectionHead writes the last block hash of a processed section to the index database
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func (c *ChainIndexer) setSectionHead(idx uint64, shead common.Hash) {
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var data [8]byte
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binary.BigEndian.PutUint64(data[:], idx)
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c.indexDb.Put(append([]byte("shead"), data[:]...), shead.Bytes())
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}
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// removeSectionHead removes the reference to a processed section from the index database
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func (c *ChainIndexer) removeSectionHead(idx uint64) {
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var data [8]byte
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binary.BigEndian.PutUint64(data[:], idx)
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c.indexDb.Delete(append([]byte("shead"), data[:]...))
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}
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