accounts: fix two races in the account manager

accounts/keystore/account_cache.go

@@ -20,7 +20,6 @@ import (
 	"bufio"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"sort"
@@ -75,13 +74,6 @@ type accountCache struct {
 	fileC    fileCache
 }
 
-// fileCache is a cache of files seen during scan of keystore
-type fileCache struct {
-	all   *set.SetNonTS // list of all files
-	mtime time.Time     // latest mtime seen
-	mu    sync.RWMutex
-}
-
 func newAccountCache(keydir string) (*accountCache, chan struct{}) {
 	ac := &accountCache{
 		keydir: keydir,
@@ -236,66 +228,22 @@ func (ac *accountCache) close() {
 	ac.mu.Unlock()
 }
 
-// scanFiles performs a new scan on the given directory, compares against the already
-// cached filenames, and returns file sets: new, missing , modified
-func (fc *fileCache) scanFiles(keyDir string) (set.Interface, set.Interface, set.Interface, error) {
-	t0 := time.Now()
-	files, err := ioutil.ReadDir(keyDir)
-	t1 := time.Now()
-	if err != nil {
-		return nil, nil, nil, err
-	}
-	fc.mu.RLock()
-	prevMtime := fc.mtime
-	fc.mu.RUnlock()
-
-	filesNow := set.NewNonTS()
-	moddedFiles := set.NewNonTS()
-	var newMtime time.Time
-	for _, fi := range files {
-		modTime := fi.ModTime()
-		path := filepath.Join(keyDir, fi.Name())
-		if skipKeyFile(fi) {
-			log.Trace("Ignoring file on account scan", "path", path)
-			continue
-		}
-		filesNow.Add(path)
-		if modTime.After(prevMtime) {
-			moddedFiles.Add(path)
-		}
-		if modTime.After(newMtime) {
-			newMtime = modTime
-		}
-	}
-	t2 := time.Now()
-
-	fc.mu.Lock()
-	// Missing = previous - current
-	missing := set.Difference(fc.all, filesNow)
-	// New = current - previous
-	newFiles := set.Difference(filesNow, fc.all)
-	// Modified = modified - new
-	modified := set.Difference(moddedFiles, newFiles)
-	fc.all = filesNow
-	fc.mtime = newMtime
-	fc.mu.Unlock()
-	t3 := time.Now()
-	log.Debug("FS scan times", "list", t1.Sub(t0), "set", t2.Sub(t1), "diff", t3.Sub(t2))
-	return newFiles, missing, modified, nil
-}
-
 // scanAccounts checks if any changes have occurred on the filesystem, and
 // updates the account cache accordingly
 func (ac *accountCache) scanAccounts() error {
-	newFiles, missingFiles, modified, err := ac.fileC.scanFiles(ac.keydir)
-	t1 := time.Now()
+	// Scan the entire folder metadata for file changes
+	creates, deletes, updates, err := ac.fileC.scan(ac.keydir)
 	if err != nil {
 		log.Debug("Failed to reload keystore contents", "err", err)
 		return err
 	}
+	if creates.Size() == 0 && deletes.Size() == 0 && updates.Size() == 0 {
+		return nil
+	}
+	// Create a helper method to scan the contents of the key files
 	var (
-		buf     = new(bufio.Reader)
-		keyJSON struct {
+		buf = new(bufio.Reader)
+		key struct {
 			Address string `json:"address"`
 		}
 	)
@@ -308,9 +256,9 @@ func (ac *accountCache) scanAccounts() error {
 		defer fd.Close()
 		buf.Reset(fd)
 		// Parse the address.
-		keyJSON.Address = ""
-		err = json.NewDecoder(buf).Decode(&keyJSON)
-		addr := common.HexToAddress(keyJSON.Address)
+		key.Address = ""
+		err = json.NewDecoder(buf).Decode(&key)
+		addr := common.HexToAddress(key.Address)
 		switch {
 		case err != nil:
 			log.Debug("Failed to decode keystore key", "path", path, "err", err)
@@ -321,47 +269,30 @@ func (ac *accountCache) scanAccounts() error {
 		}
 		return nil
 	}
+	// Process all the file diffs
+	start := time.Now()
 
-	for _, p := range newFiles.List() {
-		path, _ := p.(string)
-		a := readAccount(path)
-		if a != nil {
+	for _, p := range creates.List() {
+		if a := readAccount(p.(string)); a != nil {
 			ac.add(*a)
 		}
 	}
-	for _, p := range missingFiles.List() {
-		path, _ := p.(string)
-		ac.deleteByFile(path)
+	for _, p := range deletes.List() {
+		ac.deleteByFile(p.(string))
 	}
-
-	for _, p := range modified.List() {
-		path, _ := p.(string)
-		a := readAccount(path)
+	for _, p := range updates.List() {
+		path := p.(string)
 		ac.deleteByFile(path)
-		if a != nil {
+		if a := readAccount(path); a != nil {
 			ac.add(*a)
 		}
 	}
-
-	t2 := time.Now()
+	end := time.Now()
 
 	select {
 	case ac.notify <- struct{}{}:
 	default:
 	}
-	log.Trace("Handled keystore changes", "time", t2.Sub(t1))
-
+	log.Trace("Handled keystore changes", "time", end.Sub(start))
 	return nil
 }
-
-func skipKeyFile(fi os.FileInfo) bool {
-	// Skip editor backups and UNIX-style hidden files.
-	if strings.HasSuffix(fi.Name(), "~") || strings.HasPrefix(fi.Name(), ".") {
-		return true
-	}
-	// Skip misc special files, directories (yes, symlinks too).
-	if fi.IsDir() || fi.Mode()&os.ModeType != 0 {
-		return true
-	}
-	return false
-}

accounts/keystore/file_cache.go

@@ -0,0 +1,102 @@
+// 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 keystore
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/log"
+	set "gopkg.in/fatih/set.v0"
+)
+
+// fileCache is a cache of files seen during scan of keystore.
+type fileCache struct {
+	all     *set.SetNonTS // Set of all files from the keystore folder
+	lastMod time.Time     // Last time instance when a file was modified
+	mu      sync.RWMutex
+}
+
+// scan performs a new scan on the given directory, compares against the already
+// cached filenames, and returns file sets: creates, deletes, updates.
+func (fc *fileCache) scan(keyDir string) (set.Interface, set.Interface, set.Interface, error) {
+	t0 := time.Now()
+
+	// List all the failes from the keystore folder
+	files, err := ioutil.ReadDir(keyDir)
+	if err != nil {
+		return nil, nil, nil, err
+	}
+	t1 := time.Now()
+
+	fc.mu.Lock()
+	defer fc.mu.Unlock()
+
+	// Iterate all the files and gather their metadata
+	all := set.NewNonTS()
+	mods := set.NewNonTS()
+
+	var newLastMod time.Time
+	for _, fi := range files {
+		// Skip any non-key files from the folder
+		path := filepath.Join(keyDir, fi.Name())
+		if skipKeyFile(fi) {
+			log.Trace("Ignoring file on account scan", "path", path)
+			continue
+		}
+		// Gather the set of all and fresly modified files
+		all.Add(path)
+
+		modified := fi.ModTime()
+		if modified.After(fc.lastMod) {
+			mods.Add(path)
+		}
+		if modified.After(newLastMod) {
+			newLastMod = modified
+		}
+	}
+	t2 := time.Now()
+
+	// Update the tracked files and return the three sets
+	deletes := set.Difference(fc.all, all)   // Deletes = previous - current
+	creates := set.Difference(all, fc.all)   // Creates = current - previous
+	updates := set.Difference(mods, creates) // Updates = modified - creates
+
+	fc.all, fc.lastMod = all, newLastMod
+	t3 := time.Now()
+
+	// Report on the scanning stats and return
+	log.Debug("FS scan times", "list", t1.Sub(t0), "set", t2.Sub(t1), "diff", t3.Sub(t2))
+	return creates, deletes, updates, nil
+}
+
+// skipKeyFile ignores editor backups, hidden files and folders/symlinks.
+func skipKeyFile(fi os.FileInfo) bool {
+	// Skip editor backups and UNIX-style hidden files.
+	if strings.HasSuffix(fi.Name(), "~") || strings.HasPrefix(fi.Name(), ".") {
+		return true
+	}
+	// Skip misc special files, directories (yes, symlinks too).
+	if fi.IsDir() || fi.Mode()&os.ModeType != 0 {
+		return true
+	}
+	return false
+}

accounts/manager.go

@@ -41,18 +41,18 @@ type Manager struct {
 // NewManager creates a generic account manager to sign transaction via various
 // supported backends.
 func NewManager(backends ...Backend) *Manager {
+	// Retrieve the initial list of wallets from the backends and sort by URL
+	var wallets []Wallet
+	for _, backend := range backends {
+		wallets = merge(wallets, backend.Wallets()...)
+	}
 	// Subscribe to wallet notifications from all backends
 	updates := make(chan WalletEvent, 4*len(backends))
 
 	subs := make([]event.Subscription, len(backends))
 	for i, backend := range backends {
 		subs[i] = backend.Subscribe(updates)
 	}
-	// Retrieve the initial list of wallets from the backends and sort by URL
-	var wallets []Wallet
-	for _, backend := range backends {
-		wallets = merge(wallets, backend.Wallets()...)
-	}
 	// Assemble the account manager and return
 	am := &Manager{
 		backends: make(map[reflect.Type][]Backend),