Official Go implementation of the Ethereum protocol
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go-ethereum/eth/downloader/statesync.go

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// 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 downloader
import (
"sync"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/log"
)
// syncState starts downloading state with the given root hash.
func (d *Downloader) syncState(root common.Hash) *stateSync {
// Create the state sync
s := newStateSync(d, root)
select {
case d.stateSyncStart <- s:
// If we tell the statesync to restart with a new root, we also need
// to wait for it to actually also start -- when old requests have timed
// out or been delivered
<-s.started
case <-d.quitCh:
s.err = errCancelStateFetch
close(s.done)
}
return s
}
// stateFetcher manages the active state sync and accepts requests
// on its behalf.
func (d *Downloader) stateFetcher() {
for {
select {
case s := <-d.stateSyncStart:
for next := s; next != nil; {
next = d.runStateSync(next)
}
case <-d.quitCh:
return
}
}
}
// runStateSync runs a state synchronisation until it completes or another root
// hash is requested to be switched over to.
func (d *Downloader) runStateSync(s *stateSync) *stateSync {
log.Trace("State sync starting", "root", s.root)
go s.run()
defer s.Cancel()
for {
select {
case next := <-d.stateSyncStart:
return next
case <-s.done:
return nil
}
}
}
// stateSync schedules requests for downloading a particular state trie defined
// by a given state root.
type stateSync struct {
d *Downloader // Downloader instance to access and manage current peerset
root common.Hash // State root currently being synced
started chan struct{} // Started is signalled once the sync loop starts
cancel chan struct{} // Channel to signal a termination request
cancelOnce sync.Once // Ensures cancel only ever gets called once
done chan struct{} // Channel to signal termination completion
err error // Any error hit during sync (set before completion)
}
// newStateSync creates a new state trie download scheduler. This method does not
// yet start the sync. The user needs to call run to initiate.
func newStateSync(d *Downloader, root common.Hash) *stateSync {
return &stateSync{
d: d,
root: root,
cancel: make(chan struct{}),
done: make(chan struct{}),
started: make(chan struct{}),
}
}
// run starts the task assignment and response processing loop, blocking until
// it finishes, and finally notifying any goroutines waiting for the loop to
// finish.
func (s *stateSync) run() {
close(s.started)
s.err = s.d.SnapSyncer.Sync(s.root, s.cancel)
close(s.done)
}
// Wait blocks until the sync is done or canceled.
func (s *stateSync) Wait() error {
<-s.done
return s.err
}
// Cancel cancels the sync and waits until it has shut down.
func (s *stateSync) Cancel() error {
s.cancelOnce.Do(func() {
close(s.cancel)
})
return s.Wait()
}