github.com/ava-labs/subnet-evm@v0.6.4/accounts/keystore/watch.go (about)

     1  // (c) 2019-2020, Ava Labs, Inc.
     2  //
     3  // This file is a derived work, based on the go-ethereum library whose original
     4  // notices appear below.
     5  //
     6  // It is distributed under a license compatible with the licensing terms of the
     7  // original code from which it is derived.
     8  //
     9  // Much love to the original authors for their work.
    10  // **********
    11  // Copyright 2016 The go-ethereum Authors
    12  // This file is part of the go-ethereum library.
    13  //
    14  // The go-ethereum library is free software: you can redistribute it and/or modify
    15  // it under the terms of the GNU Lesser General Public License as published by
    16  // the Free Software Foundation, either version 3 of the License, or
    17  // (at your option) any later version.
    18  //
    19  // The go-ethereum library is distributed in the hope that it will be useful,
    20  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    21  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    22  // GNU Lesser General Public License for more details.
    23  //
    24  // You should have received a copy of the GNU Lesser General Public License
    25  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    26  
    27  //go:build (darwin && !ios && cgo) || freebsd || (linux && !arm64) || netbsd || solaris
    28  // +build darwin,!ios,cgo freebsd linux,!arm64 netbsd solaris
    29  
    30  package keystore
    31  
    32  import (
    33  	"os"
    34  	"time"
    35  
    36  	"github.com/ethereum/go-ethereum/log"
    37  	"github.com/fsnotify/fsnotify"
    38  )
    39  
    40  type watcher struct {
    41  	ac       *accountCache
    42  	running  bool // set to true when runloop begins
    43  	runEnded bool // set to true when runloop ends
    44  	starting bool // set to true prior to runloop starting
    45  	quit     chan struct{}
    46  }
    47  
    48  func newWatcher(ac *accountCache) *watcher {
    49  	return &watcher{
    50  		ac:   ac,
    51  		quit: make(chan struct{}),
    52  	}
    53  }
    54  
    55  // enabled returns false on systems not supported.
    56  func (*watcher) enabled() bool { return true }
    57  
    58  // starts the watcher loop in the background.
    59  // Start a watcher in the background if that's not already in progress.
    60  // The caller must hold w.ac.mu.
    61  func (w *watcher) start() {
    62  	if w.starting || w.running {
    63  		return
    64  	}
    65  	w.starting = true
    66  	go w.loop()
    67  }
    68  
    69  func (w *watcher) close() {
    70  	close(w.quit)
    71  }
    72  
    73  func (w *watcher) loop() {
    74  	defer func() {
    75  		w.ac.mu.Lock()
    76  		w.running = false
    77  		w.starting = false
    78  		w.runEnded = true
    79  		w.ac.mu.Unlock()
    80  	}()
    81  	logger := log.New("path", w.ac.keydir)
    82  
    83  	// Create new watcher.
    84  	watcher, err := fsnotify.NewWatcher()
    85  	if err != nil {
    86  		log.Error("Failed to start filesystem watcher", "err", err)
    87  		return
    88  	}
    89  	defer watcher.Close()
    90  	if err := watcher.Add(w.ac.keydir); err != nil {
    91  		if !os.IsNotExist(err) {
    92  			logger.Warn("Failed to watch keystore folder", "err", err)
    93  		}
    94  		return
    95  	}
    96  
    97  	logger.Trace("Started watching keystore folder", "folder", w.ac.keydir)
    98  	defer logger.Trace("Stopped watching keystore folder")
    99  
   100  	w.ac.mu.Lock()
   101  	w.running = true
   102  	w.ac.mu.Unlock()
   103  
   104  	// Wait for file system events and reload.
   105  	// When an event occurs, the reload call is delayed a bit so that
   106  	// multiple events arriving quickly only cause a single reload.
   107  	var (
   108  		debounceDuration = 500 * time.Millisecond
   109  		rescanTriggered  = false
   110  		debounce         = time.NewTimer(0)
   111  	)
   112  	// Ignore initial trigger
   113  	if !debounce.Stop() {
   114  		<-debounce.C
   115  	}
   116  	defer debounce.Stop()
   117  	for {
   118  		select {
   119  		case <-w.quit:
   120  			return
   121  		case _, ok := <-watcher.Events:
   122  			if !ok {
   123  				return
   124  			}
   125  			// Trigger the scan (with delay), if not already triggered
   126  			if !rescanTriggered {
   127  				debounce.Reset(debounceDuration)
   128  				rescanTriggered = true
   129  			}
   130  			// The fsnotify library does provide more granular event-info, it
   131  			// would be possible to refresh individual affected files instead
   132  			// of scheduling a full rescan. For most cases though, the
   133  			// full rescan is quick and obviously simplest.
   134  		case err, ok := <-watcher.Errors:
   135  			if !ok {
   136  				return
   137  			}
   138  			log.Info("Filsystem watcher error", "err", err)
   139  		case <-debounce.C:
   140  			w.ac.scanAccounts()
   141  			rescanTriggered = false
   142  		}
   143  	}
   144  }