github.com/codysnider/go-ethereum@v1.10.18-0.20220420071915-14f4ae99222a/eth/downloader/statesync.go (about)

     1  // Copyright 2017 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package downloader
    18  
    19  import (
    20  	"sync"
    21  
    22  	"github.com/ethereum/go-ethereum/common"
    23  	"github.com/ethereum/go-ethereum/log"
    24  )
    25  
    26  // syncState starts downloading state with the given root hash.
    27  func (d *Downloader) syncState(root common.Hash) *stateSync {
    28  	// Create the state sync
    29  	s := newStateSync(d, root)
    30  	select {
    31  	case d.stateSyncStart <- s:
    32  		// If we tell the statesync to restart with a new root, we also need
    33  		// to wait for it to actually also start -- when old requests have timed
    34  		// out or been delivered
    35  		<-s.started
    36  	case <-d.quitCh:
    37  		s.err = errCancelStateFetch
    38  		close(s.done)
    39  	}
    40  	return s
    41  }
    42  
    43  // stateFetcher manages the active state sync and accepts requests
    44  // on its behalf.
    45  func (d *Downloader) stateFetcher() {
    46  	for {
    47  		select {
    48  		case s := <-d.stateSyncStart:
    49  			for next := s; next != nil; {
    50  				next = d.runStateSync(next)
    51  			}
    52  		case <-d.quitCh:
    53  			return
    54  		}
    55  	}
    56  }
    57  
    58  // runStateSync runs a state synchronisation until it completes or another root
    59  // hash is requested to be switched over to.
    60  func (d *Downloader) runStateSync(s *stateSync) *stateSync {
    61  	log.Trace("State sync starting", "root", s.root)
    62  
    63  	go s.run()
    64  	defer s.Cancel()
    65  
    66  	for {
    67  		select {
    68  		case next := <-d.stateSyncStart:
    69  			return next
    70  
    71  		case <-s.done:
    72  			return nil
    73  		}
    74  	}
    75  }
    76  
    77  // stateSync schedules requests for downloading a particular state trie defined
    78  // by a given state root.
    79  type stateSync struct {
    80  	d    *Downloader // Downloader instance to access and manage current peerset
    81  	root common.Hash // State root currently being synced
    82  
    83  	started    chan struct{} // Started is signalled once the sync loop starts
    84  	cancel     chan struct{} // Channel to signal a termination request
    85  	cancelOnce sync.Once     // Ensures cancel only ever gets called once
    86  	done       chan struct{} // Channel to signal termination completion
    87  	err        error         // Any error hit during sync (set before completion)
    88  }
    89  
    90  // newStateSync creates a new state trie download scheduler. This method does not
    91  // yet start the sync. The user needs to call run to initiate.
    92  func newStateSync(d *Downloader, root common.Hash) *stateSync {
    93  	return &stateSync{
    94  		d:       d,
    95  		root:    root,
    96  		cancel:  make(chan struct{}),
    97  		done:    make(chan struct{}),
    98  		started: make(chan struct{}),
    99  	}
   100  }
   101  
   102  // run starts the task assignment and response processing loop, blocking until
   103  // it finishes, and finally notifying any goroutines waiting for the loop to
   104  // finish.
   105  func (s *stateSync) run() {
   106  	close(s.started)
   107  	s.err = s.d.SnapSyncer.Sync(s.root, s.cancel)
   108  	close(s.done)
   109  }
   110  
   111  // Wait blocks until the sync is done or canceled.
   112  func (s *stateSync) Wait() error {
   113  	<-s.done
   114  	return s.err
   115  }
   116  
   117  // Cancel cancels the sync and waits until it has shut down.
   118  func (s *stateSync) Cancel() error {
   119  	s.cancelOnce.Do(func() {
   120  		close(s.cancel)
   121  	})
   122  	return s.Wait()
   123  }