union: Implement policy by least number of object

backend/union/policy/eplno.go

@@ -0,0 +1,116 @@
+package policy
+
+import (
+	"context"
+	"math"
+
+	"github.com/rclone/rclone/backend/union/upstream"
+	"github.com/rclone/rclone/fs"
+)
+
+func init() {
+	registerPolicy("eplno", &EpLno{})
+}
+
+// EpLno stands for existing path, least number of objects
+// Of all the candidates on which the path exists choose the one with the least number of objects
+type EpLno struct {
+	EpAll
+}
+
+func (p *EpLno) lno(upstreams []*upstream.Fs) (*upstream.Fs, error) {
+	var minNumObj int64 = math.MaxInt64
+	var lnoUpstream *upstream.Fs
+	for _, u := range upstreams {
+		numObj, err := u.GetNumObjects()
+		if err != nil {
+			fs.LogPrintf(fs.LogLevelNotice, nil,
+				"Number of Objects is not supported for upstream %s, treating as 0", u.Name())
+		}
+		if minNumObj > numObj {
+			minNumObj = numObj
+			lnoUpstream = u
+		}
+	}
+	if lnoUpstream == nil {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return lnoUpstream, nil
+}
+
+func (p *EpLno) lnoEntries(entries []upstream.Entry) (upstream.Entry, error) {
+	var minNumObj int64 = math.MaxInt64
+	var lnoEntry upstream.Entry
+	for _, e := range entries {
+		numObj, err := e.UpstreamFs().GetNumObjects()
+		if err != nil {
+			fs.LogPrintf(fs.LogLevelNotice, nil,
+				"Number of Objects is not supported for upstream %s, treating as 0", e.UpstreamFs().Name())
+		}
+		if minNumObj > numObj {
+			minNumObj = numObj
+			lnoEntry = e
+		}
+	}
+	return lnoEntry, nil
+}
+
+// Action category policy, governing the modification of files and directories
+func (p *EpLno) Action(ctx context.Context, upstreams []*upstream.Fs, path string) ([]*upstream.Fs, error) {
+	upstreams, err := p.EpAll.Action(ctx, upstreams, path)
+	if err != nil {
+		return nil, err
+	}
+	u, err := p.lno(upstreams)
+	return []*upstream.Fs{u}, err
+}
+
+// ActionEntries is ACTION category policy but receving a set of candidate entries
+func (p *EpLno) ActionEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	entries, err := p.EpAll.ActionEntries(entries...)
+	if err != nil {
+		return nil, err
+	}
+	e, err := p.lnoEntries(entries)
+	return []upstream.Entry{e}, err
+}
+
+// Create category policy, governing the creation of files and directories
+func (p *EpLno) Create(ctx context.Context, upstreams []*upstream.Fs, path string) ([]*upstream.Fs, error) {
+	upstreams, err := p.EpAll.Create(ctx, upstreams, path)
+	if err != nil {
+		return nil, err
+	}
+	u, err := p.lno(upstreams)
+	return []*upstream.Fs{u}, err
+}
+
+// CreateEntries is CREATE category policy but receving a set of candidate entries
+func (p *EpLno) CreateEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	entries, err := p.EpAll.CreateEntries(entries...)
+	if err != nil {
+		return nil, err
+	}
+	e, err := p.lnoEntries(entries)
+	return []upstream.Entry{e}, err
+}
+
+// Search category policy, governing the access to files and directories
+func (p *EpLno) Search(ctx context.Context, upstreams []*upstream.Fs, path string) (*upstream.Fs, error) {
+	if len(upstreams) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	upstreams, err := p.epall(ctx, upstreams, path)
+	if err != nil {
+		return nil, err
+	}
+	return p.lno(upstreams)
+}
+
+// SearchEntries is SEARCH category policy but receving a set of candidate entries
+func (p *EpLno) SearchEntries(entries ...upstream.Entry) (upstream.Entry, error) {
+	if len(entries) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return p.lnoEntries(entries)
+}

backend/union/policy/lno.go

@@ -0,0 +1,33 @@
+package policy
+
+import (
+	"context"
+
+	"github.com/rclone/rclone/backend/union/upstream"
+	"github.com/rclone/rclone/fs"
+)
+
+func init() {
+	registerPolicy("lno", &Lno{})
+}
+
+// Lno stands for least number of objects
+// Search category: same as eplno.
+// Action category: same as eplno.
+// Create category: Pick the drive with the least number of objects.
+type Lno struct {
+	EpLno
+}
+
+// Create category policy, governing the creation of files and directories
+func (p *Lno) Create(ctx context.Context, upstreams []*upstream.Fs, path string) ([]*upstream.Fs, error) {
+	if len(upstreams) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	upstreams = filterNC(upstreams)
+	if len(upstreams) == 0 {
+		return nil, fs.ErrorPermissionDenied
+	}
+	u, err := p.lno(upstreams)
+	return []*upstream.Fs{u}, err
+}

backend/union/policy/lus.go

@@ -11,7 +11,7 @@ func init() {
 	registerPolicy("lus", &Lus{})
 }
 
-// Lus stands for most free space
+// Lus stands for least free space
 // Search category: same as eplus.
 // Action category: same as eplus.
 // Create category: Pick the drive with the least used space.

backend/union/upstream/upstream.go

@@ -182,6 +182,9 @@ func (f *Fs) Put(ctx context.Context, in io.Reader, src fs.ObjectInfo, options .
 	if f.usage.Free != nil {
 		*f.usage.Free -= size
 	}
+	if f.usage.Objects != nil {
+		*f.usage.Objects++
+	}
 	return o, nil
 }
 
@@ -208,6 +211,9 @@ func (f *Fs) PutStream(ctx context.Context, in io.Reader, src fs.ObjectInfo, opt
 	if f.usage.Free != nil {
 		*f.usage.Free -= size
 	}
+	if f.usage.Objects != nil {
+		*f.usage.Objects++
+	}
 	return o, nil
 }
 
@@ -282,6 +288,22 @@ func (f *Fs) GetUsedSpace() (int64, error) {
 	return *f.usage.Used, nil
 }
 
+// GetNumObjects get the number of objects of the fs
+func (f *Fs) GetNumObjects() (int64, error) {
+	if atomic.LoadInt64(&f.cacheExpiry) <= time.Now().Unix() {
+		err := f.updateUsage()
+		if err != nil {
+			return 0, ErrUsageFieldNotSupported
+		}
+	}
+	f.cacheMutex.RLock()
+	defer f.cacheMutex.RUnlock()
+	if f.usage.Objects == nil {
+		return 0, ErrUsageFieldNotSupported
+	}
+	return *f.usage.Objects, nil
+}
+
 func (f *Fs) updateUsage() (err error) {
 	if do := f.RootFs.Features().About; do == nil {
 		return ErrUsageFieldNotSupported

docs/content/union.md

@@ -58,6 +58,7 @@ Some policies rely on quota information. These policies should be used only if y
 | lfs, eplfs | Free           |
 | mfs, epmfs | Free           |
 | lus, eplus | Used           |
+| lno, eplno | Objects        |
 
 To check if your upstream support the field, run `rclone about remote: [flags]` and see if the reuqired field exists.
 
@@ -82,11 +83,13 @@ THe policies definition are inspired by [trapexit/mergerfs](https://github.com/t
 | epff (existing path, first found) | Act on the first one found, by the time upstreams reply, where the relative path exists. |
 | eplfs (existing path, least free space) | Of all the remotes on which the relative path exists choose the one with the least free space. |
 | eplus (existing path, least used space) | Of all the remotes on which the relative path exists choose the one with the least used space. |
+| eplno (existing path, least number of objects) | Of all the remotes on which the relative path exists choose the one with the least number of objects. |
 | epmfs (existing path, most free space) | Of all the remotes on which the relative path exists choose the one with the most free space. |
 | eprand (existing path, random) | Calls **epall** and then randomizes. Returns only one remote. |
 | ff (first found) | Search category: same as **epff**. Action category: same as **epff**. Create category: Act on the first one found by the time upstreams reply. |
 | lfs (least free space) | Search category: same as **eplfs**. Action category: same as **eplfs**. Create category: Pick the remote with the least available free space. |
 | lus (least used space) | Search category: same as **eplus**. Action category: same as **eplus**. Create category: Pick the remote with the least used space. |
+| lno (least number of objects) | Search category: same as **eplno**. Action category: same as **eplno**. Create category: Pick the remote with the least number of objects. |
 | mfs (most free space) | Search category: same as **epmfs**. Action category: same as **epmfs**. Create category: Pick the remote with the most available free space. |
 | newest | Pick the file / directory with the largest mtime. |
 | rand (random) | Calls **all** and then randomizes. Returns only one remote. |