union: Implement multiple writable remotes

backend/union/policy/all.go

@@ -0,0 +1,44 @@
+package policy
+
+import (
+	"context"
+
+	"github.com/rclone/rclone/backend/union/upstream"
+	"github.com/rclone/rclone/fs"
+)
+
+func init() {
+	registerPolicy("all", &All{})
+}
+
+// All policy behaves the same as EpAll except for the CREATE category
+// Action category: same as epall.
+// Create category: apply to all branches.
+// Search category: same as epall.
+type All struct {
+	EpAll
+}
+
+// Create category policy, governing the creation of files and directories
+func (p *All) 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
+	}
+	return upstreams, nil
+}
+
+// CreateEntries is CREATE category policy but receving a set of candidate entries
+func (p *All) CreateEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	if len(entries) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	entries = filterNCEntries(entries)
+	if len(entries) == 0 {
+		return nil, fs.ErrorPermissionDenied
+	}
+	return entries, nil
+}

backend/union/policy/epall.go

@@ -0,0 +1,99 @@
+package policy
+
+import (
+	"context"
+	"path"
+	"sync"
+
+	"github.com/rclone/rclone/backend/union/upstream"
+	"github.com/rclone/rclone/fs"
+)
+
+func init() {
+	registerPolicy("epall", &EpAll{})
+}
+
+// EpAll stands for existing path, all
+// Action category: apply to all found.
+// Create category: apply to all found.
+// Search category: same as epff.
+type EpAll struct {
+	EpFF
+}
+
+func (p *EpAll) epall(ctx context.Context, upstreams []*upstream.Fs, filePath string) ([]*upstream.Fs, error) {
+	var wg sync.WaitGroup
+	ufs := make([]*upstream.Fs, len(upstreams))
+	for i, u := range upstreams {
+		wg.Add(1)
+		i, u := i, u // Closure
+		go func() {
+			rfs := u.RootFs
+			remote := path.Join(u.RootPath, filePath)
+			if findEntry(ctx, rfs, remote) != nil {
+				ufs[i] = u
+			}
+			wg.Done()
+		}()
+	}
+	wg.Wait()
+	var results []*upstream.Fs
+	for _, f := range ufs {
+		if f != nil {
+			results = append(results, f)
+		}
+	}
+	if len(results) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return results, nil
+}
+
+// Action category policy, governing the modification of files and directories
+func (p *EpAll) Action(ctx context.Context, upstreams []*upstream.Fs, path string) ([]*upstream.Fs, error) {
+	if len(upstreams) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	upstreams = filterRO(upstreams)
+	if len(upstreams) == 0 {
+		return nil, fs.ErrorPermissionDenied
+	}
+	return p.epall(ctx, upstreams, path)
+}
+
+// ActionEntries is ACTION category policy but receving a set of candidate entries
+func (p *EpAll) ActionEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	if len(entries) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	entries = filterROEntries(entries)
+	if len(entries) == 0 {
+		return nil, fs.ErrorPermissionDenied
+	}
+	return entries, nil
+}
+
+// Create category policy, governing the creation of files and directories
+func (p *EpAll) 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
+	}
+	upstreams, err := p.epall(ctx, upstreams, path+"/..")
+	return upstreams, err
+}
+
+// CreateEntries is CREATE category policy but receving a set of candidate entries
+func (p *EpAll) CreateEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	if len(entries) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	entries = filterNCEntries(entries)
+	if len(entries) == 0 {
+		return nil, fs.ErrorPermissionDenied
+	}
+	return entries, nil
+}

backend/union/policy/epff.go

@@ -0,0 +1,115 @@
+package policy
+
+import (
+	"context"
+	"path"
+
+	"github.com/rclone/rclone/backend/union/upstream"
+	"github.com/rclone/rclone/fs"
+)
+
+func init() {
+	registerPolicy("epff", &EpFF{})
+}
+
+// EpFF stands for existing path, first found
+// Given the order of the candidates, act on the first one found where the relative path exists.
+type EpFF struct{}
+
+func (p *EpFF) epff(ctx context.Context, upstreams []*upstream.Fs, filePath string) (*upstream.Fs, error) {
+	ch := make(chan *upstream.Fs)
+	for _, u := range upstreams {
+		u := u // Closure
+		go func() {
+			rfs := u.RootFs
+			remote := path.Join(u.RootPath, filePath)
+			if findEntry(ctx, rfs, remote) == nil {
+				u = nil
+			}
+			ch <- u
+		}()
+	}
+	var u *upstream.Fs
+	for i := 0; i < len(upstreams); i++ {
+		u = <-ch
+		if u != nil {
+			// close remaining goroutines
+			go func(num int) {
+				defer close(ch)
+				for i := 0; i < num; i++ {
+					<-ch
+				}
+			}(len(upstreams) - 1 - i)
+		}
+	}
+	if u == nil {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return u, nil
+}
+
+// Action category policy, governing the modification of files and directories
+func (p *EpFF) Action(ctx context.Context, upstreams []*upstream.Fs, path string) ([]*upstream.Fs, error) {
+	if len(upstreams) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	upstreams = filterRO(upstreams)
+	if len(upstreams) == 0 {
+		return nil, fs.ErrorPermissionDenied
+	}
+	u, err := p.epff(ctx, upstreams, path)
+	return []*upstream.Fs{u}, err
+}
+
+// ActionEntries is ACTION category policy but receving a set of candidate entries
+func (p *EpFF) ActionEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	if len(entries) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	entries = filterROEntries(entries)
+	if len(entries) == 0 {
+		return nil, fs.ErrorPermissionDenied
+	}
+	return entries[:1], nil
+}
+
+// Create category policy, governing the creation of files and directories
+func (p *EpFF) 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.epff(ctx, upstreams, path+"/..")
+	return []*upstream.Fs{u}, err
+}
+
+// CreateEntries is CREATE category policy but receving a set of candidate entries
+func (p *EpFF) CreateEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	if len(entries) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	entries = filterNCEntries(entries)
+	if len(entries) == 0 {
+		return nil, fs.ErrorPermissionDenied
+	}
+	return entries[:1], nil
+}
+
+// Search category policy, governing the access to files and directories
+func (p *EpFF) Search(ctx context.Context, upstreams []*upstream.Fs, path string) (*upstream.Fs, error) {
+	if len(upstreams) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return p.epff(ctx, upstreams, path)
+}
+
+// SearchEntries is SEARCH category policy but receving a set of candidate entries
+func (p *EpFF) SearchEntries(entries ...upstream.Entry) (upstream.Entry, error) {
+	if len(entries) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return entries[0], nil
+}

backend/union/policy/eplfs.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("eplfs", &EpLfs{})
+}
+
+// EpLfs stands for existing path, least free space
+// Of all the candidates on which the path exists choose the one with the least free space.
+type EpLfs struct {
+	EpAll
+}
+
+func (p *EpLfs) lfs(upstreams []*upstream.Fs) (*upstream.Fs, error) {
+	var minFreeSpace int64 = math.MaxInt64
+	var lfsupstream *upstream.Fs
+	for _, u := range upstreams {
+		space, err := u.GetFreeSpace()
+		if err != nil {
+			fs.LogPrintf(fs.LogLevelNotice, nil,
+				"Free Space is not supported for upstream %s, treating as infinite", u.Name())
+		}
+		if space < minFreeSpace {
+			minFreeSpace = space
+			lfsupstream = u
+		}
+	}
+	if lfsupstream == nil {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return lfsupstream, nil
+}
+
+func (p *EpLfs) lfsEntries(entries []upstream.Entry) (upstream.Entry, error) {
+	var minFreeSpace int64
+	var lfsEntry upstream.Entry
+	for _, e := range entries {
+		space, err := e.UpstreamFs().GetFreeSpace()
+		if err != nil {
+			fs.LogPrintf(fs.LogLevelNotice, nil,
+				"Free Space is not supported for upstream %s, treating as infinite", e.UpstreamFs().Name())
+		}
+		if space < minFreeSpace {
+			minFreeSpace = space
+			lfsEntry = e
+		}
+	}
+	return lfsEntry, nil
+}
+
+// Action category policy, governing the modification of files and directories
+func (p *EpLfs) 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.lfs(upstreams)
+	return []*upstream.Fs{u}, err
+}
+
+// ActionEntries is ACTION category policy but receving a set of candidate entries
+func (p *EpLfs) ActionEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	entries, err := p.EpAll.ActionEntries(entries...)
+	if err != nil {
+		return nil, err
+	}
+	e, err := p.lfsEntries(entries)
+	return []upstream.Entry{e}, err
+}
+
+// Create category policy, governing the creation of files and directories
+func (p *EpLfs) 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.lfs(upstreams)
+	return []*upstream.Fs{u}, err
+}
+
+// CreateEntries is CREATE category policy but receving a set of candidate entries
+func (p *EpLfs) CreateEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	entries, err := p.EpAll.CreateEntries(entries...)
+	if err != nil {
+		return nil, err
+	}
+	e, err := p.lfsEntries(entries)
+	return []upstream.Entry{e}, err
+}
+
+// Search category policy, governing the access to files and directories
+func (p *EpLfs) 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.lfs(upstreams)
+}
+
+// SearchEntries is SEARCH category policy but receving a set of candidate entries
+func (p *EpLfs) SearchEntries(entries ...upstream.Entry) (upstream.Entry, error) {
+	if len(entries) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return p.lfsEntries(entries)
+}

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/eplus.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("eplus", &EpLus{})
+}
+
+// EpLus stands for existing path, least used space
+// Of all the candidates on which the path exists choose the one with the least used space.
+type EpLus struct {
+	EpAll
+}
+
+func (p *EpLus) lus(upstreams []*upstream.Fs) (*upstream.Fs, error) {
+	var minUsedSpace int64 = math.MaxInt64
+	var lusupstream *upstream.Fs
+	for _, u := range upstreams {
+		space, err := u.GetUsedSpace()
+		if err != nil {
+			fs.LogPrintf(fs.LogLevelNotice, nil,
+				"Used Space is not supported for upstream %s, treating as 0", u.Name())
+		}
+		if space < minUsedSpace {
+			minUsedSpace = space
+			lusupstream = u
+		}
+	}
+	if lusupstream == nil {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return lusupstream, nil
+}
+
+func (p *EpLus) lusEntries(entries []upstream.Entry) (upstream.Entry, error) {
+	var minUsedSpace int64
+	var lusEntry upstream.Entry
+	for _, e := range entries {
+		space, err := e.UpstreamFs().GetFreeSpace()
+		if err != nil {
+			fs.LogPrintf(fs.LogLevelNotice, nil,
+				"Used Space is not supported for upstream %s, treating as 0", e.UpstreamFs().Name())
+		}
+		if space < minUsedSpace {
+			minUsedSpace = space
+			lusEntry = e
+		}
+	}
+	return lusEntry, nil
+}
+
+// Action category policy, governing the modification of files and directories
+func (p *EpLus) 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.lus(upstreams)
+	return []*upstream.Fs{u}, err
+}
+
+// ActionEntries is ACTION category policy but receving a set of candidate entries
+func (p *EpLus) ActionEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	entries, err := p.EpAll.ActionEntries(entries...)
+	if err != nil {
+		return nil, err
+	}
+	e, err := p.lusEntries(entries)
+	return []upstream.Entry{e}, err
+}
+
+// Create category policy, governing the creation of files and directories
+func (p *EpLus) 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.lus(upstreams)
+	return []*upstream.Fs{u}, err
+}
+
+// CreateEntries is CREATE category policy but receving a set of candidate entries
+func (p *EpLus) CreateEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	entries, err := p.EpAll.CreateEntries(entries...)
+	if err != nil {
+		return nil, err
+	}
+	e, err := p.lusEntries(entries)
+	return []upstream.Entry{e}, err
+}
+
+// Search category policy, governing the access to files and directories
+func (p *EpLus) 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.lus(upstreams)
+}
+
+// SearchEntries is SEARCH category policy but receving a set of candidate entries
+func (p *EpLus) SearchEntries(entries ...upstream.Entry) (upstream.Entry, error) {
+	if len(entries) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return p.lusEntries(entries)
+}

backend/union/policy/epmfs.go

@@ -0,0 +1,115 @@
+package policy
+
+import (
+	"context"
+
+	"github.com/rclone/rclone/backend/union/upstream"
+	"github.com/rclone/rclone/fs"
+)
+
+func init() {
+	registerPolicy("epmfs", &EpMfs{})
+}
+
+// EpMfs stands for existing path, most free space
+// Of all the candidates on which the path exists choose the one with the most free space.
+type EpMfs struct {
+	EpAll
+}
+
+func (p *EpMfs) mfs(upstreams []*upstream.Fs) (*upstream.Fs, error) {
+	var maxFreeSpace int64
+	var mfsupstream *upstream.Fs
+	for _, u := range upstreams {
+		space, err := u.GetFreeSpace()
+		if err != nil {
+			fs.LogPrintf(fs.LogLevelNotice, nil,
+				"Free Space is not supported for upstream %s, treating as infinite", u.Name())
+		}
+		if maxFreeSpace < space {
+			maxFreeSpace = space
+			mfsupstream = u
+		}
+	}
+	if mfsupstream == nil {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return mfsupstream, nil
+}
+
+func (p *EpMfs) mfsEntries(entries []upstream.Entry) (upstream.Entry, error) {
+	var maxFreeSpace int64
+	var mfsEntry upstream.Entry
+	for _, e := range entries {
+		space, err := e.UpstreamFs().GetFreeSpace()
+		if err != nil {
+			fs.LogPrintf(fs.LogLevelNotice, nil,
+				"Free Space is not supported for upstream %s, treating as infinite", e.UpstreamFs().Name())
+		}
+		if maxFreeSpace < space {
+			maxFreeSpace = space
+			mfsEntry = e
+		}
+	}
+	return mfsEntry, nil
+}
+
+// Action category policy, governing the modification of files and directories
+func (p *EpMfs) 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.mfs(upstreams)
+	return []*upstream.Fs{u}, err
+}
+
+// ActionEntries is ACTION category policy but receving a set of candidate entries
+func (p *EpMfs) ActionEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	entries, err := p.EpAll.ActionEntries(entries...)
+	if err != nil {
+		return nil, err
+	}
+	e, err := p.mfsEntries(entries)
+	return []upstream.Entry{e}, err
+}
+
+// Create category policy, governing the creation of files and directories
+func (p *EpMfs) 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.mfs(upstreams)
+	return []*upstream.Fs{u}, err
+}
+
+// CreateEntries is CREATE category policy but receving a set of candidate entries
+func (p *EpMfs) CreateEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	entries, err := p.EpAll.CreateEntries(entries...)
+	if err != nil {
+		return nil, err
+	}
+	e, err := p.mfsEntries(entries)
+	return []upstream.Entry{e}, err
+}
+
+// Search category policy, governing the access to files and directories
+func (p *EpMfs) 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.mfs(upstreams)
+}
+
+// SearchEntries is SEARCH category policy but receving a set of candidate entries
+func (p *EpMfs) SearchEntries(entries ...upstream.Entry) (upstream.Entry, error) {
+	if len(entries) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return p.mfsEntries(entries)
+}

backend/union/policy/eprand.go

@@ -0,0 +1,86 @@
+package policy
+
+import (
+	"context"
+	"math/rand"
+	"time"
+
+	"github.com/rclone/rclone/backend/union/upstream"
+	"github.com/rclone/rclone/fs"
+)
+
+func init() {
+	registerPolicy("eprand", &EpRand{})
+}
+
+// EpRand stands for existing path, random
+// Calls epall and then randomizes. Returns one candidate.
+type EpRand struct {
+	EpAll
+}
+
+func (p *EpRand) rand(upstreams []*upstream.Fs) *upstream.Fs {
+	rand.Seed(time.Now().Unix())
+	return upstreams[rand.Intn(len(upstreams))]
+}
+
+func (p *EpRand) randEntries(entries []upstream.Entry) upstream.Entry {
+	rand.Seed(time.Now().Unix())
+	return entries[rand.Intn(len(entries))]
+}
+
+// Action category policy, governing the modification of files and directories
+func (p *EpRand) 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
+	}
+	return []*upstream.Fs{p.rand(upstreams)}, nil
+}
+
+// ActionEntries is ACTION category policy but receving a set of candidate entries
+func (p *EpRand) ActionEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	entries, err := p.EpAll.ActionEntries(entries...)
+	if err != nil {
+		return nil, err
+	}
+	return []upstream.Entry{p.randEntries(entries)}, nil
+}
+
+// Create category policy, governing the creation of files and directories
+func (p *EpRand) 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
+	}
+	return []*upstream.Fs{p.rand(upstreams)}, nil
+}
+
+// CreateEntries is CREATE category policy but receving a set of candidate entries
+func (p *EpRand) CreateEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	entries, err := p.EpAll.CreateEntries(entries...)
+	if err != nil {
+		return nil, err
+	}
+	return []upstream.Entry{p.randEntries(entries)}, nil
+}
+
+// Search category policy, governing the access to files and directories
+func (p *EpRand) 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.rand(upstreams), nil
+}
+
+// SearchEntries is SEARCH category policy but receving a set of candidate entries
+func (p *EpRand) SearchEntries(entries ...upstream.Entry) (upstream.Entry, error) {
+	if len(entries) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return p.randEntries(entries), nil
+}

backend/union/policy/ff.go

@@ -0,0 +1,32 @@
+package policy
+
+import (
+	"context"
+
+	"github.com/rclone/rclone/backend/union/upstream"
+	"github.com/rclone/rclone/fs"
+)
+
+func init() {
+	registerPolicy("ff", &FF{})
+}
+
+// FF stands for first found
+// Search category: same as epff.
+// Action category: same as epff.
+// Create category: Given the order of the candiates, act on the first one found.
+type FF struct {
+	EpFF
+}
+
+// Create category policy, governing the creation of files and directories
+func (p *FF) 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 upstreams, fs.ErrorPermissionDenied
+	}
+	return upstreams[:1], nil
+}

backend/union/policy/lfs.go

@@ -0,0 +1,33 @@
+package policy
+
+import (
+	"context"
+
+	"github.com/rclone/rclone/backend/union/upstream"
+	"github.com/rclone/rclone/fs"
+)
+
+func init() {
+	registerPolicy("lfs", &Lfs{})
+}
+
+// Lfs stands for least free space
+// Search category: same as eplfs.
+// Action category: same as eplfs.
+// Create category: Pick the drive with the least free space.
+type Lfs struct {
+	EpLfs
+}
+
+// Create category policy, governing the creation of files and directories
+func (p *Lfs) 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.lfs(upstreams)
+	return []*upstream.Fs{u}, err
+}

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

@@ -0,0 +1,33 @@
+package policy
+
+import (
+	"context"
+
+	"github.com/rclone/rclone/backend/union/upstream"
+	"github.com/rclone/rclone/fs"
+)
+
+func init() {
+	registerPolicy("lus", &Lus{})
+}
+
+// Lus stands for least used space
+// Search category: same as eplus.
+// Action category: same as eplus.
+// Create category: Pick the drive with the least used space.
+type Lus struct {
+	EpLus
+}
+
+// Create category policy, governing the creation of files and directories
+func (p *Lus) 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.lus(upstreams)
+	return []*upstream.Fs{u}, err
+}

backend/union/policy/mfs.go

@@ -0,0 +1,33 @@
+package policy
+
+import (
+	"context"
+
+	"github.com/rclone/rclone/backend/union/upstream"
+	"github.com/rclone/rclone/fs"
+)
+
+func init() {
+	registerPolicy("mfs", &Mfs{})
+}
+
+// Mfs stands for most free space
+// Search category: same as epmfs.
+// Action category: same as epmfs.
+// Create category: Pick the drive with the most free space.
+type Mfs struct {
+	EpMfs
+}
+
+// Create category policy, governing the creation of files and directories
+func (p *Mfs) 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.mfs(upstreams)
+	return []*upstream.Fs{u}, err
+}

backend/union/policy/newest.go

@@ -0,0 +1,149 @@
+package policy
+
+import (
+	"context"
+	"path"
+	"sync"
+	"time"
+
+	"github.com/rclone/rclone/backend/union/upstream"
+	"github.com/rclone/rclone/fs"
+)
+
+func init() {
+	registerPolicy("newest", &Newest{})
+}
+
+// Newest policy picks the file / directory with the largest mtime
+// It implies the existance of a path
+type Newest struct {
+	EpAll
+}
+
+func (p *Newest) newest(ctx context.Context, upstreams []*upstream.Fs, filePath string) (*upstream.Fs, error) {
+	var wg sync.WaitGroup
+	ufs := make([]*upstream.Fs, len(upstreams))
+	mtimes := make([]time.Time, len(upstreams))
+	for i, u := range upstreams {
+		wg.Add(1)
+		i, u := i, u // Closure
+		go func() {
+			defer wg.Done()
+			rfs := u.RootFs
+			remote := path.Join(u.RootPath, filePath)
+			if e := findEntry(ctx, rfs, remote); e != nil {
+				ufs[i] = u
+				mtimes[i] = e.ModTime(ctx)
+			}
+		}()
+	}
+	wg.Wait()
+	maxMtime := time.Time{}
+	var newestFs *upstream.Fs
+	for i, u := range ufs {
+		if u != nil && mtimes[i].After(maxMtime) {
+			maxMtime = mtimes[i]
+			newestFs = u
+		}
+	}
+	if newestFs == nil {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return newestFs, nil
+}
+
+func (p *Newest) newestEntries(entries []upstream.Entry) (upstream.Entry, error) {
+	var wg sync.WaitGroup
+	mtimes := make([]time.Time, len(entries))
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	for i, e := range entries {
+		wg.Add(1)
+		i, e := i, e // Closure
+		go func() {
+			defer wg.Done()
+			mtimes[i] = e.ModTime(ctx)
+		}()
+	}
+	wg.Wait()
+	maxMtime := time.Time{}
+	var newestEntry upstream.Entry
+	for i, t := range mtimes {
+		if t.After(maxMtime) {
+			maxMtime = t
+			newestEntry = entries[i]
+		}
+	}
+	if newestEntry == nil {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return newestEntry, nil
+}
+
+// Action category policy, governing the modification of files and directories
+func (p *Newest) Action(ctx context.Context, upstreams []*upstream.Fs, path string) ([]*upstream.Fs, error) {
+	if len(upstreams) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	upstreams = filterRO(upstreams)
+	if len(upstreams) == 0 {
+		return nil, fs.ErrorPermissionDenied
+	}
+	u, err := p.newest(ctx, upstreams, path)
+	return []*upstream.Fs{u}, err
+}
+
+// ActionEntries is ACTION category policy but receving a set of candidate entries
+func (p *Newest) ActionEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	if len(entries) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	entries = filterROEntries(entries)
+	if len(entries) == 0 {
+		return nil, fs.ErrorPermissionDenied
+	}
+	e, err := p.newestEntries(entries)
+	return []upstream.Entry{e}, err
+}
+
+// Create category policy, governing the creation of files and directories
+func (p *Newest) 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.newest(ctx, upstreams, path+"/..")
+	return []*upstream.Fs{u}, err
+}
+
+// CreateEntries is CREATE category policy but receving a set of candidate entries
+func (p *Newest) CreateEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	if len(entries) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	entries = filterNCEntries(entries)
+	if len(entries) == 0 {
+		return nil, fs.ErrorPermissionDenied
+	}
+	e, err := p.newestEntries(entries)
+	return []upstream.Entry{e}, err
+}
+
+// Search category policy, governing the access to files and directories
+func (p *Newest) Search(ctx context.Context, upstreams []*upstream.Fs, path string) (*upstream.Fs, error) {
+	if len(upstreams) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return p.newest(ctx, upstreams, path)
+}
+
+// SearchEntries is SEARCH category policy but receving a set of candidate entries
+func (p *Newest) SearchEntries(entries ...upstream.Entry) (upstream.Entry, error) {
+	if len(entries) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return p.newestEntries(entries)
+}

backend/union/policy/policy.go

@@ -0,0 +1,129 @@
+package policy
+
+import (
+	"context"
+	"math/rand"
+	"path"
+	"strings"
+	"time"
+
+	"github.com/pkg/errors"
+	"github.com/rclone/rclone/backend/union/upstream"
+	"github.com/rclone/rclone/fs"
+)
+
+var policies = make(map[string]Policy)
+
+// Policy is the interface of a set of defined behavior choosing
+// the upstream Fs to operate on
+type Policy interface {
+	// Action category policy, governing the modification of files and directories
+	Action(ctx context.Context, upstreams []*upstream.Fs, path string) ([]*upstream.Fs, error)
+
+	// Create category policy, governing the creation of files and directories
+	Create(ctx context.Context, upstreams []*upstream.Fs, path string) ([]*upstream.Fs, error)
+
+	// Search category policy, governing the access to files and directories
+	Search(ctx context.Context, upstreams []*upstream.Fs, path string) (*upstream.Fs, error)
+
+	// ActionEntries is ACTION category policy but receving a set of candidate entries
+	ActionEntries(entries ...upstream.Entry) ([]upstream.Entry, error)
+
+	// CreateEntries is CREATE category policy but receving a set of candidate entries
+	CreateEntries(entries ...upstream.Entry) ([]upstream.Entry, error)
+
+	// SearchEntries is SEARCH category policy but receving a set of candidate entries
+	SearchEntries(entries ...upstream.Entry) (upstream.Entry, error)
+}
+
+func registerPolicy(name string, p Policy) {
+	policies[strings.ToLower(name)] = p
+}
+
+// Get a Policy from the list
+func Get(name string) (Policy, error) {
+	p, ok := policies[strings.ToLower(name)]
+	if !ok {
+		return nil, errors.Errorf("didn't find policy called %q", name)
+	}
+	return p, nil
+}
+
+func filterRO(ufs []*upstream.Fs) (wufs []*upstream.Fs) {
+	for _, u := range ufs {
+		if u.IsWritable() {
+			wufs = append(wufs, u)
+		}
+	}
+	return wufs
+}
+
+func filterROEntries(ue []upstream.Entry) (wue []upstream.Entry) {
+	for _, e := range ue {
+		if e.UpstreamFs().IsWritable() {
+			wue = append(wue, e)
+		}
+	}
+	return wue
+}
+
+func filterNC(ufs []*upstream.Fs) (wufs []*upstream.Fs) {
+	for _, u := range ufs {
+		if u.IsCreatable() {
+			wufs = append(wufs, u)
+		}
+	}
+	return wufs
+}
+
+func filterNCEntries(ue []upstream.Entry) (wue []upstream.Entry) {
+	for _, e := range ue {
+		if e.UpstreamFs().IsCreatable() {
+			wue = append(wue, e)
+		}
+	}
+	return wue
+}
+
+func parentDir(absPath string) string {
+	parent := path.Dir(strings.TrimRight(absPath, "/"))
+	if parent == "." {
+		parent = ""
+	}
+	return parent
+}
+
+func clean(absPath string) string {
+	cleanPath := path.Clean(absPath)
+	if cleanPath == "." {
+		cleanPath = ""
+	}
+	return cleanPath
+}
+
+func findEntry(ctx context.Context, f fs.Fs, remote string) fs.DirEntry {
+	remote = clean(remote)
+	dir := parentDir(remote)
+	entries, err := f.List(ctx, dir)
+	if remote == dir {
+		if err != nil {
+			return nil
+		}
+		// random modtime for root
+		randomNow := time.Unix(time.Now().Unix()-rand.Int63n(10000), 0)
+		return fs.NewDir("", randomNow)
+	}
+	found := false
+	for _, e := range entries {
+		eRemote := e.Remote()
+		if f.Features().CaseInsensitive {
+			found = strings.EqualFold(remote, eRemote)
+		} else {
+			found = (remote == eRemote)
+		}
+		if found {
+			return e
+		}
+	}
+	return nil
+}

backend/union/policy/rand.go

@@ -0,0 +1,83 @@
+package policy
+
+import (
+	"context"
+	"math/rand"
+
+	"github.com/rclone/rclone/backend/union/upstream"
+	"github.com/rclone/rclone/fs"
+)
+
+func init() {
+	registerPolicy("rand", &Rand{})
+}
+
+// Rand stands for random
+// Calls all and then randomizes. Returns one candidate.
+type Rand struct {
+	All
+}
+
+func (p *Rand) rand(upstreams []*upstream.Fs) *upstream.Fs {
+	return upstreams[rand.Intn(len(upstreams))]
+}
+
+func (p *Rand) randEntries(entries []upstream.Entry) upstream.Entry {
+	return entries[rand.Intn(len(entries))]
+}
+
+// Action category policy, governing the modification of files and directories
+func (p *Rand) Action(ctx context.Context, upstreams []*upstream.Fs, path string) ([]*upstream.Fs, error) {
+	upstreams, err := p.All.Action(ctx, upstreams, path)
+	if err != nil {
+		return nil, err
+	}
+	return []*upstream.Fs{p.rand(upstreams)}, nil
+}
+
+// ActionEntries is ACTION category policy but receving a set of candidate entries
+func (p *Rand) ActionEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	entries, err := p.All.ActionEntries(entries...)
+	if err != nil {
+		return nil, err
+	}
+	return []upstream.Entry{p.randEntries(entries)}, nil
+}
+
+// Create category policy, governing the creation of files and directories
+func (p *Rand) Create(ctx context.Context, upstreams []*upstream.Fs, path string) ([]*upstream.Fs, error) {
+	upstreams, err := p.All.Create(ctx, upstreams, path)
+	if err != nil {
+		return nil, err
+	}
+	return []*upstream.Fs{p.rand(upstreams)}, nil
+}
+
+// CreateEntries is CREATE category policy but receving a set of candidate entries
+func (p *Rand) CreateEntries(entries ...upstream.Entry) ([]upstream.Entry, error) {
+	entries, err := p.All.CreateEntries(entries...)
+	if err != nil {
+		return nil, err
+	}
+	return []upstream.Entry{p.randEntries(entries)}, nil
+}
+
+// Search category policy, governing the access to files and directories
+func (p *Rand) 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.rand(upstreams), nil
+}
+
+// SearchEntries is SEARCH category policy but receving a set of candidate entries
+func (p *Rand) SearchEntries(entries ...upstream.Entry) (upstream.Entry, error) {
+	if len(entries) == 0 {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return p.randEntries(entries), nil
+}