fix(diskcache): make Close terminal

diskcache/README.md

@@ -10,6 +10,8 @@ diskcache 是一种类似 wal 的磁盘缓存，它有如下特性：
 限制：
 
 - 不支持随机读取，只支持按照 FIFO 的顺序来消费数据
+- `Close()` 是终止操作；关闭后的读写和 rotate 操作会返回 `ErrClosed`
+- `.lock` 是持久标记文件；`Close()` 只释放文件锁，不删除该文件
 
 ## 实现算法
 

diskcache/diskcache.go

@@ -51,6 +51,9 @@ var (
 	// Diskcache full, no data can be write now.
 	ErrCacheFull = errors.New("cache full")
 
+	// ErrClosed indicates an operation was attempted on a closed cache.
+	ErrClosed = errors.New("diskcache closed")
+
 	ErrInvalidStreamSize = errors.New("invalid stream size")
 
 	// Invalid cache filename.
@@ -72,6 +75,11 @@ type DiskCache struct {
 
 	dataFiles []string
 
+	// lifecycleMu excludes Close from in-flight I/O and protects closed and closeErr.
+	lifecycleMu sync.RWMutex
+	closed      bool
+	closeErr    error
+
 	// current writing/reading file.
 	curWriteFile,
 	curReadfile string

diskcache/flock_test.go

@@ -16,7 +16,7 @@ import (
 )
 
 func TestLockUnlock(t *T.T) {
-	t.Run("unlock-remove", func(t *T.T) {
+	t.Run("unlock-keeps-lock-file", func(t *T.T) {
 		p := t.TempDir()
 		fl := newFlock(p)
 
@@ -28,10 +28,10 @@ func TestLockUnlock(t *T.T) {
 		assert.NoError(t, err)
 		t.Logf("fi: %+#v", fi)
 
-		fl.unlock()
+		assert.NoError(t, fl.unlock())
 
 		_, err = os.Stat(filepath.Join(p, ".lock"))
-		assert.Error(t, err)
+		assert.NoError(t, err)
 	})
 
 	t.Run("lock", func(t *T.T) {
@@ -48,7 +48,9 @@ func TestLockUnlock(t *T.T) {
 
 			assert.True(t, ok)
 			assert.NoError(t, err)
-			defer fl.unlock()
+			defer func() {
+				assert.NoError(t, fl.unlock())
+			}()
 
 			time.Sleep(time.Second * 5)
 		}()

diskcache/flock_unix.go

@@ -40,18 +40,22 @@ func (wl *walLock) tryLock() (bool, error) {
 	return true, nil
 }
 
-func (wl *walLock) unlock() {
+func (wl *walLock) unlock() error {
 	if wl.f != nil {
-		if err := syscall.Flock(int(wl.f.Fd()), syscall.LOCK_UN); err != nil {
-			l.Errorf("Flock: %s", err.Error())
-		}
+		f := wl.f
+		wl.f = nil
+		var errs []error
 
-		if err := wl.f.Close(); err != nil {
-			l.Errorf("CLose: %s", err.Error())
+		if err := syscall.Flock(int(f.Fd()), syscall.LOCK_UN); err != nil {
+			errs = append(errs, fmt.Errorf("unlock lock file: %w", err))
 		}
 
-		if err := os.Remove(wl.file); err != nil { // Optional on Unix
-			l.Errorf("Remove: %s", err.Error())
+		if err := f.Close(); err != nil {
+			errs = append(errs, fmt.Errorf("close lock file: %w", err))
 		}
+
+		return errors.Join(errs...)
 	}
+
+	return nil
 }

diskcache/flock_windows.go

@@ -53,9 +53,12 @@ func (wl *walLock) tryLock() (bool, error) {
 	return true, nil
 }
 
-func (wl *walLock) unlock() {
+func (wl *walLock) unlock() error {
 	if wl.f != nil {
-		wl.f.Close() // Closing the file handle automatically releases the lock in Windows
-		os.Remove(wl.file)
+		f := wl.f
+		wl.f = nil
+		return f.Close() // Closing the file handle automatically releases the lock in Windows
 	}
+
+	return nil
 }

diskcache/get.go

@@ -13,7 +13,8 @@ import (
 	"time"
 )
 
-// Fn is the handler to eat cache from diskcache.
+// Fn is the handler to consume data from diskcache.
+// A callback must not synchronously call methods on the same DiskCache.
 type Fn func([]byte) error
 
 func (c *DiskCache) switchNextFile() error {
@@ -51,6 +52,8 @@ func (c *DiskCache) Get(fn Fn) error {
 	return c.doGet(nil, fn, nil)
 }
 
+// BufFunc supplies a buffer for BufCallbackGet.
+// A callback must not synchronously call methods on the same DiskCache.
 type BufFunc func() []byte
 
 // BufCallbackGet fetch new data from disk cache, and read into buffer that returned by bfn.
@@ -70,6 +73,13 @@ func (c *DiskCache) doGet(buf []byte, fn Fn, bfn BufFunc) error {
 		err       error
 	)
 
+	c.lifecycleMu.RLock()
+	defer c.lifecycleMu.RUnlock()
+
+	if c.closed {
+		return WrapGetError(ErrClosed, c.path, "")
+	}
+
 	c.rlock.Lock()
 	defer c.rlock.Unlock()
 

diskcache/open.go

@@ -6,6 +6,7 @@
 package diskcache
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -186,42 +187,57 @@ func (c *DiskCache) doOpen() error {
 	return nil
 }
 
-// Close reclame fd resources.
-// Close is safe to call concurrently with other operations and will
-// block until all other operations finish.
+// Close permanently closes the cache and reclaims its file descriptors.
+// It waits for in-flight operations, is idempotent, and causes later I/O
+// operations to return ErrClosed.
 func (c *DiskCache) Close() error {
-	c.rwlock.Lock()
-	defer c.rwlock.Unlock()
+	c.lifecycleMu.Lock()
+	defer c.lifecycleMu.Unlock()
 
 	defer func() {
 		lastCloseTimeVec.WithLabelValues(c.path).Set(float64(time.Now().Unix()))
 	}()
 
-	if c.rfd != nil {
-		if err := c.rfd.Close(); err != nil {
-			return WrapCloseError(err, c.path, "read_fd")
-		}
-		c.rfd = nil
+	if c.closed {
+		return c.closeErr
 	}
+	c.closed = true
 
-	if !c.noLock {
-		if c.flock != nil {
-			c.flock.unlock()
+	c.rwlock.Lock()
+	defer c.rwlock.Unlock()
+
+	var errs []error
+
+	if c.rfd != nil {
+		fd := c.rfd
+		c.rfd = nil
+		if err := fd.Close(); err != nil {
+			errs = append(errs, WrapCloseError(err, c.path, "read_fd"))
 		}
 	}
 
 	if c.wfd != nil {
-		if err := c.wfd.Close(); err != nil {
-			return WrapCloseError(err, c.path, "write_fd")
-		}
+		fd := c.wfd
 		c.wfd = nil
+		if err := fd.Close(); err != nil {
+			errs = append(errs, WrapCloseError(err, c.path, "write_fd"))
+		}
 	}
 
 	if c.pos != nil {
 		if err := c.pos.close(); err != nil {
-			return WrapPosError(err, c.path, c.pos.Seek).WithDetails("failed_to_close_position_file")
+			errs = append(errs, WrapPosError(err, c.path, c.pos.Seek).WithDetails("failed_to_close_position_file"))
 		}
 	}
 
-	return nil
+	if !c.noLock && c.flock != nil {
+		flock := c.flock
+		c.flock = nil
+		if err := flock.unlock(); err != nil {
+			errs = append(errs, NewCacheError(OpUnlock, err, "failed_to_release_directory_lock").WithPath(c.path))
+		}
+	}
+
+	c.closeErr = errors.Join(errs...)
+	return c.closeErr
 }