accounts: cache key addresses

In order to avoid disk thrashing for Accounts and HasAccount,
address->key file mappings are now cached in memory. This makes it no
longer necessary to keep the key address in the file name. The address
of each key is derived from file content instead.

There are minor user-visible changes:

- "geth account list" now reports key file paths alongside the address.
- If multiple keys are present for an address, unlocking by address is
  not possible. Users are directed to remove the duplicate files
  instead. Unlocking by index is still possible.
- Key files are overwritten written in place when updating the password.

1 files changed, 269 insertions, 0 deletions

diff --git a/accounts/addrcache.go b/accounts/addrcache.go
new file mode 100644
index 000000000..0a904f788
--- /dev/null
+++ b/accounts/addrcache.go
@@ -0,0 +1,269 @@
+// Copyright 2016 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 accounts
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
+)
+
+// Minimum amount of time between cache reloads. This limit applies if the platform does
+// not support change notifications. It also applies if the keystore directory does not
+// exist yet, the code will attempt to create a watcher at most this often.
+const minReloadInterval = 2 * time.Second
+
+type accountsByFile []Account
+
+func (s accountsByFile) Len() int           { return len(s) }
+func (s accountsByFile) Less(i, j int) bool { return s[i].File < s[j].File }
+func (s accountsByFile) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+
+// AmbiguousAddrError is returned when attempting to unlock
+// an address for which more than one file exists.
+type AmbiguousAddrError struct {
+	Addr    common.Address
+	Matches []Account
+}
+
+func (err *AmbiguousAddrError) Error() string {
+	files := ""
+	for i, a := range err.Matches {
+		files += a.File
+		if i < len(err.Matches)-1 {
+			files += ", "
+		}
+	}
+	return fmt.Sprintf("multiple keys match address (%s)", files)
+}
+
+// addrCache is a live index of all accounts in the keystore.
+type addrCache struct {
+	keydir   string
+	watcher  *watcher
+	mu       sync.Mutex
+	all      accountsByFile
+	byAddr   map[common.Address][]Account
+	throttle *time.Timer
+}
+
+func newAddrCache(keydir string) *addrCache {
+	ac := &addrCache{
+		keydir: keydir,
+		byAddr: make(map[common.Address][]Account),
+	}
+	ac.watcher = newWatcher(ac)
+	return ac
+}
+
+func (ac *addrCache) accounts() []Account {
+	ac.maybeReload()
+	ac.mu.Lock()
+	defer ac.mu.Unlock()
+	cpy := make([]Account, len(ac.all))
+	copy(cpy, ac.all)
+	return cpy
+}
+
+func (ac *addrCache) hasAddress(addr common.Address) bool {
+	ac.maybeReload()
+	ac.mu.Lock()
+	defer ac.mu.Unlock()
+	return len(ac.byAddr[addr]) > 0
+}
+
+func (ac *addrCache) add(newAccount Account) {
+	ac.mu.Lock()
+	defer ac.mu.Unlock()
+
+	i := sort.Search(len(ac.all), func(i int) bool { return ac.all[i].File >= newAccount.File })
+	if i < len(ac.all) && ac.all[i] == newAccount {
+		return
+	}
+	// newAccount is not in the cache.
+	ac.all = append(ac.all, Account{})
+	copy(ac.all[i+1:], ac.all[i:])
+	ac.all[i] = newAccount
+	ac.byAddr[newAccount.Address] = append(ac.byAddr[newAccount.Address], newAccount)
+}
+
+// note: removed needs to be unique here (i.e. both File and Address must be set).
+func (ac *addrCache) delete(removed Account) {
+	ac.mu.Lock()
+	defer ac.mu.Unlock()
+	ac.all = removeAccount(ac.all, removed)
+	if ba := removeAccount(ac.byAddr[removed.Address], removed); len(ba) == 0 {
+		delete(ac.byAddr, removed.Address)
+	} else {
+		ac.byAddr[removed.Address] = ba
+	}
+}
+
+func removeAccount(slice []Account, elem Account) []Account {
+	for i := range slice {
+		if slice[i] == elem {
+			return append(slice[:i], slice[i+1:]...)
+		}
+	}
+	return slice
+}
+
+// find returns the cached account for address if there is a unique match.
+// The exact matching rules are explained by the documentation of Account.
+// Callers must hold ac.mu.
+func (ac *addrCache) find(a Account) (Account, error) {
+	// Limit search to address candidates if possible.
+	matches := ac.all
+	if (a.Address != common.Address{}) {
+		matches = ac.byAddr[a.Address]
+	}
+	if a.File != "" {
+		// If only the basename is specified, complete the path.
+		if !strings.ContainsRune(a.File, filepath.Separator) {
+			a.File = filepath.Join(ac.keydir, a.File)
+		}
+		for i := range matches {
+			if matches[i].File == a.File {
+				return matches[i], nil
+			}
+		}
+		if (a.Address == common.Address{}) {
+			return Account{}, ErrNoMatch
+		}
+	}
+	switch len(matches) {
+	case 1:
+		return matches[0], nil
+	case 0:
+		return Account{}, ErrNoMatch
+	default:
+		err := &AmbiguousAddrError{Addr: a.Address, Matches: make([]Account, len(matches))}
+		copy(err.Matches, matches)
+		return Account{}, err
+	}
+}
+
+func (ac *addrCache) maybeReload() {
+	ac.mu.Lock()
+	defer ac.mu.Unlock()
+	if ac.watcher.running {
+		return // A watcher is running and will keep the cache up-to-date.
+	}
+	if ac.throttle == nil {
+		ac.throttle = time.NewTimer(0)
+	} else {
+		select {
+		case <-ac.throttle.C:
+		default:
+			return // The cache was reloaded recently.
+		}
+	}
+	ac.watcher.start()
+	ac.reload()
+	ac.throttle.Reset(minReloadInterval)
+}
+
+func (ac *addrCache) close() {
+	ac.mu.Lock()
+	ac.watcher.close()
+	if ac.throttle != nil {
+		ac.throttle.Stop()
+	}
+	ac.mu.Unlock()
+}
+
+// reload caches addresses of existing accounts.
+// Callers must hold ac.mu.
+func (ac *addrCache) reload() {
+	accounts, err := ac.scan()
+	if err != nil && glog.V(logger.Debug) {
+		glog.Errorf("can't load keys: %v", err)
+	}
+	ac.all = accounts
+	sort.Sort(ac.all)
+	for k := range ac.byAddr {
+		delete(ac.byAddr, k)
+	}
+	for _, a := range accounts {
+		ac.byAddr[a.Address] = append(ac.byAddr[a.Address], a)
+	}
+	glog.V(logger.Debug).Infof("reloaded keys, cache has %d accounts", len(ac.all))
+}
+
+func (ac *addrCache) scan() ([]Account, error) {
+	files, err := ioutil.ReadDir(ac.keydir)
+	if err != nil {
+		return nil, err
+	}
+
+	var (
+		buf     = new(bufio.Reader)
+		addrs   []Account
+		keyJSON struct {
+			Address common.Address `json:"address"`
+		}
+	)
+	for _, fi := range files {
+		path := filepath.Join(ac.keydir, fi.Name())
+		if skipKeyFile(fi) {
+			glog.V(logger.Detail).Infof("ignoring file %s", path)
+			continue
+		}
+		fd, err := os.Open(path)
+		if err != nil {
+			glog.V(logger.Detail).Infoln(err)
+			continue
+		}
+		buf.Reset(fd)
+		// Parse the address.
+		keyJSON.Address = common.Address{}
+		err = json.NewDecoder(buf).Decode(&keyJSON)
+		switch {
+		case err != nil:
+			glog.V(logger.Debug).Infof("can't decode key %s: %v", path, err)
+		case (keyJSON.Address == common.Address{}):
+			glog.V(logger.Debug).Infof("can't decode key %s: missing or zero address", path)
+		default:
+			addrs = append(addrs, Account{Address: keyJSON.Address, File: path})
+		}
+		fd.Close()
+	}
+	return addrs, err
+}
+
+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
+}