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|
package streamcache
import (
"context"
"crypto/rand"
"fmt"
"io"
"os"
"path/filepath"
"sync"
"time"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promauto"
"github.com/sirupsen/logrus"
"gitlab.com/gitlab-org/gitaly/v16/internal/dontpanic"
"gitlab.com/gitlab-org/gitaly/v16/internal/git/housekeeping"
"gitlab.com/gitlab-org/gitaly/v16/internal/helper/perm"
)
var (
fileRemoveCounter = promauto.NewCounterVec(
prometheus.CounterOpts{
Name: "gitaly_streamcache_filestore_removed_total",
Help: "Number of files removed from streamcache via file walks",
},
[]string{"dir"},
)
diskUsageGauge = promauto.NewGaugeVec(
prometheus.GaugeOpts{
Name: "gitaly_streamcache_filestore_disk_usage_bytes",
Help: "Disk usage per filestore",
},
[]string{"dir"},
)
)
// Filestore creates temporary files in dir. These files get deleted once
// they are older (by mtime) than maxAge via a goroutine that does
// periodic file walks. To make these file walks efficient, we spread the
// temporary files across a balanced directory tree in subdirectories
// aa/my-temp-file where aa is a hexadecimal number. This means
// we eventually create exactly 256 subdirectories.
//
// Each instance of filestore carries a random token which is used as a
// prefix in the tempfiles it creates. This ensures that it is safe to
// have multiple instances of filestore use the same directory on disk;
// their tempfiles will not collide. There is one caveat: if multiple
// filestores share the same directory but have different maximum ages,
// then lowest maximum age becomes the effective maximum age for all of
// them.
type filestore struct {
dir string
maxAge time.Duration
m sync.Mutex
id []byte
counter uint64
stop chan struct{}
sleepLoop *dontpanic.Forever
}
func newFilestore(dir string, maxAge time.Duration, sleep func(time.Duration) <-chan time.Time, logger logrus.FieldLogger) *filestore {
fs := &filestore{
dir: dir,
maxAge: maxAge,
stop: make(chan struct{}),
sleepLoop: dontpanic.NewForever(time.Minute),
}
fs.sleepLoop.Go(func() {
sleepLoop(fs.stop, fs.maxAge, sleep, func() {
diskUsageGauge.WithLabelValues(fs.dir).Set(fs.diskUsage())
if err := fs.cleanWalk(time.Now().Add(-fs.maxAge)); err != nil {
logger.WithError(err).Error("streamcache filestore cleanup")
}
})
})
return fs
}
type namedWriteCloser interface {
Name() string
io.WriteCloser
}
// Create creates a new tempfile. It does not use os.CreateTemp because
// the documentation of TempFile makes no promises about reusing tempfile
// names after a file has been deleted. By using a very large (uint64)
// counter, Create makes it clear / explicit how unlikely reuse is.
func (fs *filestore) Create() (namedWriteCloser, error) {
if err := fs.ensureCacheID(); err != nil {
return nil, err
}
fileID := fs.nextFileID()
name := fmt.Sprintf("%x-%d",
// fs.id ensures uniqueness among other *filestore instances
fs.id,
// fileID ensures uniqueness (modulo roll-over) among other files
// created by this *filestore instance
fileID,
)
path := filepath.Join(fs.dir, fmt.Sprintf("%02x", uint8(fileID)), name)
if err := os.MkdirAll(filepath.Dir(path), perm.PrivateDir); err != nil {
return nil, fmt.Errorf("Create: mkdir: %w", err)
}
f, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_EXCL, perm.SharedFile)
if err != nil {
return nil, fmt.Errorf("Create: %w", err)
}
return f, nil
}
func (fs *filestore) ensureCacheID() error {
fs.m.Lock()
defer fs.m.Unlock()
if len(fs.id) == 0 {
buf := make([]byte, 10)
if _, err := io.ReadFull(rand.Reader, buf); err != nil {
return err
}
fs.id = buf
}
return nil
}
func (fs *filestore) nextFileID() uint64 {
fs.m.Lock()
defer fs.m.Unlock()
fs.counter++
return fs.counter
}
func (fs *filestore) Stop() {
fs.m.Lock()
defer fs.m.Unlock()
select {
case <-fs.stop:
default:
close(fs.stop)
}
fs.sleepLoop.Cancel()
}
// cleanWalk removes files but not directories. This is to avoid races
// when a directory looks empty but another goroutine is about to create
// a new file in it with fs.Create(). Because the number of directories
// is bounded by the directory scheme to 256, there is no need to remove
// the directories anyway.
func (fs *filestore) cleanWalk(cutoff time.Time) error {
// If a server reset has left some directories in a bad state, this will
// fix it.
if err := housekeeping.FixDirectoryPermissions(context.Background(), fs.dir); err != nil {
return err
}
return filepath.Walk(fs.dir, func(path string, info os.FileInfo, err error) error {
if err == nil && !info.IsDir() && info.ModTime().Before(cutoff) {
err = os.Remove(path)
fileRemoveCounter.WithLabelValues(fs.dir).Inc()
}
if os.IsNotExist(err) {
err = nil
}
return err
})
}
func (fs *filestore) diskUsage() float64 {
var total float64
_ = filepath.Walk(fs.dir, func(_ string, info os.FileInfo, _ error) error {
if info != nil {
total += float64(info.Size())
}
return nil
})
return total
}
|
