fix: gc was being stupid allowing another thread to take the space it made before it could not anymore

vfs/gc/gc.go

@@ -13,59 +13,48 @@ import (
 	"time"
 )
 
-// LRUGC deletes files in LRU order until enough space is reclaimed.
-func LRUGC(vfss vfs.VFS, size uint) {
-	attempts := 0
-	deletions := 0
-	var reclaimed uint
+var (
+	// ErrInsufficientSpace is returned when there are no files to delete in the VFS.
+	ErrInsufficientSpace = fmt.Errorf("no files to delete")
+)
 
-	for reclaimed < size {
-		if attempts > 10 {
-			logger.Logger.Debug().
-				Int("attempts", attempts).
-				Msg("GC: Too many attempts to reclaim space, giving up")
-			return
-		}
-		attempts++
+// LRUGC deletes files in LRU order until enough space is reclaimed.
+func LRUGC(vfss vfs.VFS, size uint) error {
+	logger.Logger.Debug().Uint("target", size).Msg("Attempting to reclaim space using LRU GC")
+
+	var reclaimed uint // reclaimed space in bytes
+
+	for {
 		switch fs := vfss.(type) {
 		case *disk.DiskFS:
 			fi := fs.LRU.Back()
 			if fi == nil {
-				break
+				return ErrInsufficientSpace // No files to delete
 			}
 			sz := uint(fi.Size())
 			err := fs.Delete(fi.Name())
 			if err != nil {
-				continue
+				continue // If delete fails, try the next file
 			}
 			reclaimed += sz
-			deletions++
 		case *memory.MemoryFS:
 			fi := fs.LRU.Back()
 			if fi == nil {
-				break
+				return ErrInsufficientSpace // No files to delete
 			}
 			sz := uint(fi.Size())
 			err := fs.Delete(fi.Name())
 			if err != nil {
-				continue
+				continue // If delete fails, try the next file
 			}
 			reclaimed += sz
-			deletions++
 		default:
-			// Fallback to old method if not supported
-			stats := vfss.StatAll()
-			if len(stats) == 0 {
-				break
-			}
-			fi := stats[0] // Assume sorted or pick first
-			sz := uint(fi.Size())
-			err := vfss.Delete(fi.Name())
-			if err != nil {
-				continue
-			}
-			reclaimed += sz
-			deletions++
+			panic("unreachable: unsupported VFS type for LRU GC") // panic if the VFS is not disk or memory
+		}
+
+		if reclaimed >= size {
+			logger.Logger.Debug().Uint("target", size).Uint("achieved", reclaimed).Msg("Reclaimed enough space using LRU GC")
+			return nil // stop if enough space is reclaimed
 		}
 	}
 }
@@ -80,36 +69,39 @@ var _ vfs.VFS = (*GCFS)(nil)
 // GCFS is a virtual file system that calls a GC handler when the disk is full. The GC handler is responsible for freeing up space on the disk. The GCFS is a wrapper around another VFS.
 type GCFS struct {
 	vfs.VFS
-	multiplier int
 
-	// protected by mu
 	gcHanderFunc GCHandlerFunc
 }
 
 // GCHandlerFunc is a function that is called when the disk is full and the GCFS needs to free up space. It is passed the VFS and the size of the file that needs to be written. Its up to the implementation to free up space. How much space is freed is also up to the implementation.
-type GCHandlerFunc func(vfs vfs.VFS, size uint)
+type GCHandlerFunc func(vfs vfs.VFS, size uint) error
 
-func New(vfs vfs.VFS, multiplier int, gcHandlerFunc GCHandlerFunc) *GCFS {
-	if multiplier <= 0 {
-		multiplier = 1 // if the multiplier is less than or equal to 0 set it to 1 will be slow but the user can set it to a higher value if they want
-	}
+func New(vfs vfs.VFS, gcHandlerFunc GCHandlerFunc) *GCFS {
 	return &GCFS{
 		VFS:          vfs,
-		multiplier:   multiplier,
 		gcHanderFunc: gcHandlerFunc,
 	}
 }
 
 // Create overrides the Create method of the VFS interface. It tries to create the key, if it fails due to disk full error, it calls the GC handler and tries again. If it still fails it returns the error.
 func (g *GCFS) Create(key string, size int64) (io.WriteCloser, error) {
-	w, err := g.VFS.Create(key, size) // try to create the key
-
-	// if it fails due to disk full error, call the GC handler and try again in a loop that will continue until it succeeds or the error is not disk full
-	if err == vfserror.ErrDiskFull && g.gcHanderFunc != nil { // if the error is disk full and there is a GC handler
-		g.gcHanderFunc(g.VFS, uint(size*int64(g.multiplier))) // call the GC handler
+	w, err := g.VFS.Create(key, size)                          // try to create the key
+	for err == vfserror.ErrDiskFull && g.gcHanderFunc != nil { // if the error is disk full and there is a GC handler
+		errr := g.gcHanderFunc(g.VFS, uint(size)) // call the GC handler
+		if errr == ErrInsufficientSpace {
+			return nil, errr // if the GC handler returns no files to delete, return the error
+		}
 		w, err = g.VFS.Create(key, size)
 	}
 
+	if err != nil {
+		if err == vfserror.ErrDiskFull {
+			logger.Logger.Error().Str("key", key).Int64("size", size).Msg("Failed to create file due to disk full, even after GC")
+		} else {
+			logger.Logger.Error().Str("key", key).Int64("size", size).Err(err).Msg("Failed to create file")
+		}
+	}
+
 	return w, err
 }