files: video previews are made on the Transcode device too

The setting's device makes every video preview: on the file's own machine
when it is there (the hub tells it by header), else on the device's machine,
which reads the file through the hub by a one-file token, and the preview is
kept in the file's machine's own cache (PUT /api/files/thumb, refused if the
file changed). Images and covers stay on the file's machine's CPU. If the
device's machine can't, the file's makes it as before.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/api/play.go

@@ -225,6 +225,9 @@ func (s *Server) playPiece(w http.ResponseWriter, r *http.Request) {
 // transcodeChoice is the setting; nil is the machine the file is on.
 func (s *Server) transcodeChoice() *store.Transcode {
 	var t *store.Transcode
+	if s.store == nil {
+		return nil
+	}
 	s.store.View(func(st *store.State) {
 		if st.Transcode != nil {
 			c := *st.Transcode

internal/api/play_test.go

@@ -1,7 +1,9 @@
 package api
 
 import (
+	"fmt"
 	"net/http/httptest"
+	"net/url"
 	"os"
 	"path/filepath"
 	"strings"
@@ -49,3 +51,43 @@ func TestPlaySrc(t *testing.T) {
 		t.Fatalf("unknown token: %d", w.Code)
 	}
 }
+
+// A preview made on another machine is kept by the file's own: only while the file is still
+// the one it was made of, and a failure is kept as a failure.
+func TestThumbPut(t *testing.T) {
+	dir := t.TempDir()
+	p := filepath.Join(dir, "film.mp4")
+	if err := os.WriteFile(p, []byte("0123456789"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	fi, _ := os.Stat(p)
+	s := &Server{fsLocal: files.Local{}, thumbs: newThumbSvc(dir, "")}
+	v := fmt.Sprintf("%d-%d", fi.ModTime().UnixMilli(), fi.Size())
+	put := func(v string, body string, hdr map[string]string) int {
+		r := httptest.NewRequest("PUT", "/api/files/thumb?path="+url.QueryEscape(p)+"&v="+v, strings.NewReader(body))
+		for k, x := range hdr {
+			r.Header.Set(k, x)
+		}
+		w := httptest.NewRecorder()
+		s.thumbPut(w, r)
+		return w.Code
+	}
+	get := func() *httptest.ResponseRecorder {
+		r := httptest.NewRequest("GET", "/api/files/thumb?cached=1&path="+url.QueryEscape(p)+"&v="+v, nil)
+		w := httptest.NewRecorder()
+		s.filesThumb(w, r)
+		return w
+	}
+	if w := get(); w.Code != 404 {
+		t.Fatalf("cached=1 before anything: %d", w.Code)
+	}
+	if c := put("1-10", "jpeg", nil); c != 409 {
+		t.Fatalf("a changed file: %d", c)
+	}
+	if c := put(v, "jpeg-bytes", map[string]string{"X-Hamlab-Thumb": "grid vaapi:/dev/dri/renderD129"}); c != 204 {
+		t.Fatalf("put: %d", c)
+	}
+	if w := get(); w.Code != 200 || w.Body.String() != "jpeg-bytes" || !strings.Contains(w.Header().Get("X-Hamlab-Thumb"), "grid") {
+		t.Fatalf("kept: %d %q %q", w.Code, w.Body, w.Header().Get("X-Hamlab-Thumb"))
+	}
+}

internal/api/server.go

@@ -276,6 +276,9 @@ func (s *Server) routes() *http.ServeMux {
 	m.HandleFunc("POST /api/files/delete", s.auth(s.filesDelete))
 	m.HandleFunc("POST /api/files/chmod", s.auth(s.filesChmod))
 	m.HandleFunc("GET /api/files/thumb", s.auth(s.filesThumb))
+	m.HandleFunc("PUT /api/files/thumb", s.auth(s.thumbPut))
+	m.HandleFunc("POST /api/files/thumb-from", s.auth(s.thumbFrom))
+	m.HandleFunc("GET /api/nodes/{name}/files/thumb", s.auth(s.hubThumb))
 	m.HandleFunc("GET /api/files/thumbs", s.auth(s.thumbsStatus))
 	m.HandleFunc("POST /api/files/thumbs/install", s.auth(s.thumbsInstall))
 	m.HandleFunc("POST /api/files/thumbs/gpu-access", s.auth(s.thumbsGPUAccess))

internal/api/thumbs.go

@@ -10,10 +10,16 @@ package api
 // opens every render node, whatever groups the daemon's user has.
 
 import (
+	"bytes"
 	"context"
+	"encoding/json"
 	"errors"
+	"fmt"
+	"io"
 	"log"
 	"net/http"
+	"net/http/httptest"
+	"net/url"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -25,6 +31,7 @@ import (
 
 	"hamlab/internal/media"
 	"hamlab/internal/priv"
+	"hamlab/internal/store"
 )
 
 const thumbSize = 256
@@ -117,7 +124,9 @@ func describeCaps(c media.Caps) string {
 }
 
 // make produces a preview, sharing the work when the same file is asked for twice at once.
-func (t *thumbSvc) make(ctx context.Context, root bool, key, path string) (media.Result, error) {
+// in is a path, or a URL the hub serves another machine's file at (kind then says what it
+// is); device is the one to decode on ("" any, "cpu" none).
+func (t *thumbSvc) make(ctx context.Context, root bool, key, in, kind, device string) (media.Result, error) {
 	t.mu.Lock()
 	if c, ok := t.calls[key]; ok {
 		t.mu.Unlock()
@@ -153,19 +162,29 @@ func (t *thumbSvc) make(ctx context.Context, root bool, key, path string) (media
 		c.err = err
 		return c.res, c.err
 	}
-	o := media.Opts{Size: thumbSize, Timeout: thumbTimeout}
+	o := media.Opts{Size: thumbSize, Timeout: thumbTimeout, Kind: kind}
+	caps = caps.Only(device)
 	if root {
-		c.res, c.err = media.MakeRoot(wctx, t.self, caps, path, o)
+		c.res, c.err = media.MakeRoot(wctx, t.self, caps, in, o)
 	} else {
-		c.res, c.err = media.Make(wctx, caps, path, o)
+		c.res, c.err = media.Make(wctx, caps, in, o)
 	}
 	return c.res, c.err
 }
 
 // ---- handlers ----
 
-// filesThumb: GET /api/files/thumb?path=…&v=<mtime>-<size>[&sudo=1]. v is the client's idea of
+// thumbDeviceHeader carries the device a hub wants a video preview made on: the Transcode
-// the file, from its listing; it makes a cache hit free of a stat, and a changed file a new URL.
+// device setting, when it is on the machine the file is on.
+const thumbDeviceHeader = "X-Hamlab-Device"
+
+// filesThumb: GET /api/files/thumb?path=…&v=<mtime>-<size>[&sudo=1][&cached=1]. v is the
+// client's idea of the file, from its listing; it makes a cache hit free of a stat, and a
+// changed file a new URL. cached=1 answers from the cache or 404, and makes nothing: the hub
+// asks that before having the preview made on another machine.
+//
+// A video preview is made on the Transcode device: on the hub, by the setting (another
+// machine's device reads the file through the hub); on a node, by the hub's header.
 func (s *Server) filesThumb(w http.ResponseWriter, r *http.Request) {
 	fsys, ok := s.fsFor(w, r)
 	if !ok {
@@ -203,7 +222,28 @@ func (s *Server) filesThumb(w http.ResponseWriter, r *http.Request) {
 	if s.serveCachedThumb(w, key) {
 		return
 	}
-	res, err := s.thumbs.make(r.Context(), root, key, p)
+	if r.URL.Query().Get("cached") == "1" {
+		jsonErr(w, 404, "not made yet")
+		return
+	}
+	device := r.Header.Get(thumbDeviceHeader)
+	if c := s.transcodeChoice(); c != nil && device == "" && media.Kind(p) == "video" {
+		if c.Node != "" {
+			// The hub's own file, previewed on another machine.
+			if res, ok := s.thumbElsewhere(r.Context(), c, "", p, root, key); ok {
+				if res.Failure != "" {
+					_ = s.thumbs.cache.Put(key, media.Entry{Path: p, Failure: res.Failure})
+					jsonErr(w, 422, res.Failure)
+					return
+				}
+				s.keepThumb(w, key, p, res)
+				return
+			}
+		} else {
+			device = c.Device
+		}
+	}
+	res, err := s.thumbs.make(r.Context(), root, key, p, "", device)
 	if err != nil {
 		var de *media.DecodeError
 		switch {
@@ -223,12 +263,204 @@ func (s *Server) filesThumb(w http.ResponseWriter, r *http.Request) {
 		}
 		return
 	}
+	s.keepThumb(w, key, p, res)
+}
+
+// keepThumb puts a preview in the cache and answers with it.
+func (s *Server) keepThumb(w http.ResponseWriter, key, p string, res media.Result) {
 	if err := s.thumbs.cache.Put(key, media.Entry{Path: p, Engine: res.Engine, Codec: res.Codec, Width: res.Width, Height: res.Height, JPEG: res.JPEG}); err != nil {
 		log.Printf("thumbs: cache: %v", err)
 	}
 	writeThumb(w, key, res.JPEG, res.Engine)
 }
 
+// ---- previews made on another machine (the Transcode device) ----
+
+// thumbFrom: POST /api/files/thumb-from {url, kind, key, device} — a preview of a file on
+// another machine, read through the hub at url, made here on device. Answers the JPEG (the
+// engine in X-Hamlab-Thumb), or 422 with why the file can't be previewed.
+func (s *Server) thumbFrom(w http.ResponseWriter, r *http.Request) {
+	var body struct{ URL, Kind, Key, Device string }
+	if err := json.NewDecoder(io.LimitReader(r.Body, 8192)).Decode(&body); err != nil || !strings.HasPrefix(body.URL, "http") || body.Key == "" {
+		jsonErr(w, 400, "expected {url, kind, key, device}")
+		return
+	}
+	res, err := s.thumbs.make(r.Context(), false, "from:"+body.Key, body.URL, body.Kind, body.Device)
+	if err != nil {
+		var de *media.DecodeError
+		if errors.As(err, &de) {
+			jsonErr(w, 422, de.Msg)
+		} else {
+			jsonErr(w, 503, err.Error())
+		}
+		return
+	}
+	w.Header().Set("X-Hamlab-Thumb-Codec", res.Codec)
+	w.Header().Set("X-Hamlab-Thumb-Size", fmt.Sprintf("%dx%d", res.Width, res.Height))
+	writeThumb(w, body.Key, res.JPEG, res.Engine)
+}
+
+// thumbPut: PUT /api/files/thumb?path=…&v=<mtime>-<size>[&sudo=1] — a preview another machine
+// made of this file, kept here as if made here. The body is the JPEG, or nothing with
+// X-Hamlab-Thumb-Failure saying why the file can't be previewed. Refused if the file has
+// changed since v.
+func (s *Server) thumbPut(w http.ResponseWriter, r *http.Request) {
+	fsys, ok := s.fsFor(w, r)
+	if !ok {
+		return
+	}
+	p, ok := cleanQuery(w, r, "path")
+	if !ok {
+		return
+	}
+	mt, sz, ok := parseV(r.URL.Query().Get("v"))
+	if !ok {
+		jsonErr(w, 400, "v=<mtime>-<size> is required")
+		return
+	}
+	in, err := fsys.Stat(r.Context(), p)
+	if err != nil {
+		fsErr(w, err)
+		return
+	}
+	if in.Size != sz || in.Mtime != mt {
+		jsonErr(w, 409, "the file has changed")
+		return
+	}
+	key := media.Key(p, sz, mt)
+	e := media.Entry{Path: p, Engine: r.Header.Get("X-Hamlab-Thumb"), Codec: r.Header.Get("X-Hamlab-Thumb-Codec"), Failure: r.Header.Get("X-Hamlab-Thumb-Failure")}
+	fmt.Sscanf(r.Header.Get("X-Hamlab-Thumb-Size"), "%dx%d", &e.Width, &e.Height)
+	if e.Failure == "" {
+		if e.JPEG, err = io.ReadAll(io.LimitReader(r.Body, 4<<20)); err != nil || len(e.JPEG) == 0 {
+			jsonErr(w, 400, "no picture")
+			return
+		}
+	}
+	if err := s.thumbs.cache.Put(key, e); err != nil {
+		jsonErr(w, 500, err.Error())
+		return
+	}
+	w.WriteHeader(204)
+}
+
+// thumbElsewhere has a video preview made on the Transcode device's machine c.Node, of a
+// file on machine node ("" the hub), and answers it. ok is false when that machine can't
+// (unreachable, an older Ham Lab): the caller makes it where the file is instead. A file
+// that can't be previewed is a result too, with the failure in it.
+func (s *Server) thumbElsewhere(ctx context.Context, c *store.Transcode, node, p string, root bool, key string) (media.Result, bool) {
+	src, err := s.srcURL(c.Node, node, p, root)
+	if err != nil {
+		return media.Result{}, false
+	}
+	body, _ := json.Marshal(map[string]string{"url": src, "kind": "video", "key": key, "device": c.Device})
+	ctx, cancel := context.WithTimeout(ctx, thumbTimeout+10*time.Second)
+	defer cancel()
+	var code int
+	var b []byte
+	var hdr http.Header
+	if c.Node == "" {
+		rec := httptest.NewRecorder()
+		req := httptest.NewRequest("POST", "/api/files/thumb-from", bytes.NewReader(body)).WithContext(ctx)
+		s.thumbFrom(rec, req)
+		code, b, hdr = rec.Code, rec.Body.Bytes(), rec.Header()
+	} else {
+		code, b, hdr, err = s.nodes.DoHeaders(ctx, c.Node, "POST", "/api/files/thumb-from", body, http.Header{"Content-Type": []string{"application/json"}})
+		if err != nil {
+			log.Printf("thumbs: %s on %s: %v; made where it is", p, c.Node, err)
+			return media.Result{}, false
+		}
+	}
+	switch code {
+	case 200:
+		res := media.Result{JPEG: b, Engine: c.Node + " " + hdr.Get("X-Hamlab-Thumb"), Codec: hdr.Get("X-Hamlab-Thumb-Codec")}
+		fmt.Sscanf(hdr.Get("X-Hamlab-Thumb-Size"), "%dx%d", &res.Width, &res.Height)
+		if c.Node == "" {
+			res.Engine = s.hostName() + " " + hdr.Get("X-Hamlab-Thumb")
+		}
+		return res, true
+	case 422:
+		var e struct{ Error string }
+		_ = json.Unmarshal(b, &e)
+		return media.Result{Failure: e.Error}, true
+	}
+	log.Printf("thumbs: %s on %s answered %d; made where it is", p, nodeLabel(c.Node), code)
+	return media.Result{}, false
+}
+
+// hubThumb: GET /api/nodes/{name}/files/thumb — a node's preview, through the hub. Without a
+// Transcode device setting, or for an image or a sound file's cover, it goes to the node as
+// any request does. A video is made on the setting's device: the node's own (told by header),
+// or another machine's, which reads the file through the hub; the node keeps the result in
+// its own cache either way.
+func (s *Server) hubThumb(w http.ResponseWriter, r *http.Request) {
+	node := r.PathValue("name")
+	proxy, ok := s.nodes.Proxy(node)
+	if !ok {
+		jsonErr(w, 404, "no such machine")
+		return
+	}
+	c := s.transcodeChoice()
+	q := r.URL.Query()
+	p := q.Get("path")
+	if c == nil || media.Kind(p) != "video" {
+		proxy.ServeHTTP(w, r)
+		return
+	}
+	if c.Node == node {
+		r.Header.Set(thumbDeviceHeader, c.Device)
+		proxy.ServeHTTP(w, r)
+		return
+	}
+	mt, sz, okV := parseV(q.Get("v"))
+	if !okV {
+		proxy.ServeHTTP(w, r)
+		return
+	}
+	// The node's own cache first.
+	cq := url.Values{"path": {p}, "v": {q.Get("v")}, "cached": {"1"}}
+	if q.Get("sudo") == "1" {
+		cq.Set("sudo", "1")
+	}
+	hdr := http.Header{}
+	if inm := r.Header.Get("If-None-Match"); inm != "" {
+		hdr.Set("If-None-Match", inm)
+	}
+	code, b, rh, err := s.nodes.DoHeaders(r.Context(), node, "GET", "/api/files/thumb?"+cq.Encode(), nil, hdr)
+	if err == nil && code != 404 {
+		for _, k := range []string{"Content-Type", "Cache-Control", "ETag", "X-Hamlab-Thumb"} {
+			if v := rh.Get(k); v != "" {
+				w.Header().Set(k, v)
+			}
+		}
+		w.WriteHeader(code)
+		_, _ = w.Write(b)
+		return
+	}
+	key := media.Key(p, sz, mt)
+	res, made := s.thumbElsewhere(r.Context(), c, node, p, q.Get("sudo") == "1", key)
+	if !made {
+		proxy.ServeHTTP(w, r) // the node makes it itself
+		return
+	}
+	// Kept where the file is, so it is made once.
+	ph := http.Header{"X-Hamlab-Thumb": {res.Engine}, "X-Hamlab-Thumb-Codec": {res.Codec}, "X-Hamlab-Thumb-Size": {fmt.Sprintf("%dx%d", res.Width, res.Height)}}
+	if res.Failure != "" {
+		ph.Set("X-Hamlab-Thumb-Failure", res.Failure)
+	}
+	pq := url.Values{"path": {p}, "v": {q.Get("v")}}
+	if q.Get("sudo") == "1" {
+		pq.Set("sudo", "1")
+	}
+	if code, _, _, err := s.nodes.DoHeaders(r.Context(), node, "PUT", "/api/files/thumb?"+pq.Encode(), res.JPEG, ph); err != nil || code != 204 {
+		log.Printf("thumbs: keeping %s's preview of %s: %d %v", node, p, code, err)
+	}
+	if res.Failure != "" {
+		jsonErr(w, 422, res.Failure)
+		return
+	}
+	writeThumb(w, key, res.JPEG, res.Engine)
+}
+
 // serveCachedThumb answers from the cache when it can. A cache that cannot be read is a
 // miss: the preview is made again rather than refused.
 func (s *Server) serveCachedThumb(w http.ResponseWriter, key string) bool {

internal/media/encode_test.go

@@ -155,3 +155,17 @@ func TestPieceArgs(t *testing.T) {
 		t.Error("no sound means -an")
 	}
 }
+
+func TestCapsOnly(t *testing.T) {
+	c := gridCaps()
+	if got := c.Only("/dev/dri/renderD129"); len(got.GPUs) != 1 || got.GPUs[0].Name != "Intel Arc A380" || len(c.GPUs) != 2 {
+		t.Fatalf("one card: %+v", got.GPUs)
+	}
+	if len(c.Only(CPU).GPUs) != 0 || len(c.Only("/dev/dri/renderD200").GPUs) != 0 || len(c.Only("").GPUs) != 2 {
+		t.Fatal("cpu, a device not here, any")
+	}
+	// previews then go to that card, or the CPU
+	if g := c.Only("/dev/dri/renderD129").pick("hevc"); g == nil || g.Device != "/dev/dri/renderD129" {
+		t.Fatalf("pick: %+v", g)
+	}
+}

internal/media/thumbs.go

@@ -62,6 +62,24 @@ type Caps struct {
 type Opts struct {
 	Size    int           // the long edge in pixels; 256 when zero
 	Timeout time.Duration // for the whole job, ffprobe and every ffmpeg attempt; 30 s when zero
+	Kind    string        // image | video | audio; from the name when empty (a URL has none)
+}
+
+// Only is the caps with one device left to decode on: a render node, CPU for none, or ""
+// for all of them — the Transcode device setting, which previews follow too. A device this
+// machine doesn't have leaves the CPU.
+func (c Caps) Only(device string) Caps {
+	if device == "" {
+		return c
+	}
+	out := c
+	out.GPUs = nil
+	for _, g := range c.GPUs {
+		if g.Device == device {
+			out.GPUs = append(out.GPUs, g)
+		}
+	}
+	return out
 }
 
 func (o Opts) defaults() Opts {
@@ -81,6 +99,8 @@ type Result struct {
 	Codec  string `json:"codec"`
 	Width  int    `json:"width"`
 	Height int    `json:"height"`
+	// Failure is why the file can't be previewed, when another machine tried (no JPEG then).
+	Failure string `json:"-"`
 }
 
 // ErrUnsupported: not an image or a video by its name.
@@ -356,7 +376,10 @@ func (a attempt) engine() string {
 
 // Make produces the preview of one file.
 func Make(ctx context.Context, c Caps, path string, o Opts) (Result, error) {
-	kind := Kind(path)
+	kind := o.Kind
+	if kind == "" {
+		kind = Kind(path)
+	}
 	if kind == "" {
 		return Result{}, ErrUnsupported
 	}

internal/nodes/nodes.go

@@ -383,13 +383,19 @@ func (m *Manager) PushAll(ctx context.Context, binPath, ourArch string, force bo
 // WebSocket origin check (meant for browsers) doesn't reject the hub.
 // Do makes one request to a managed machine as this hub and returns the whole response.
 func (m *Manager) Do(ctx context.Context, name, method, path string, body []byte, hdr http.Header) (int, []byte, error) {
+	code, b, _, err := m.DoHeaders(ctx, name, method, path, body, hdr)
+	return code, b, err
+}
+
+// DoHeaders is Do that also answers the response's headers.
+func (m *Manager) DoHeaders(ctx context.Context, name, method, path string, body []byte, hdr http.Header) (int, []byte, http.Header, error) {
 	n, ok := m.node(name)
 	if !ok {
-		return 0, nil, errors.New("no such machine")
+		return 0, nil, nil, errors.New("no such machine")
 	}
 	req, err := http.NewRequestWithContext(ctx, method, strings.TrimRight(n.URL, "/")+path, bytes.NewReader(body))
 	if err != nil {
-		return 0, nil, err
+		return 0, nil, nil, err
 	}
 	for k, v := range hdr {
 		req.Header[k] = v
@@ -397,11 +403,11 @@ func (m *Manager) Do(ctx context.Context, name, method, path string, body []byte
 	req.Header.Set("Authorization", "Bearer "+n.Token)
 	resp, err := m.client(n).Do(req)
 	if err != nil {
-		return 0, nil, errors.New(shortErr(err))
+		return 0, nil, nil, errors.New(shortErr(err))
 	}
 	defer resp.Body.Close()
 	b, err := io.ReadAll(io.LimitReader(resp.Body, 8<<20))
-	return resp.StatusCode, b, err
+	return resp.StatusCode, b, resp.Header, err
 }
 
 // URL is a managed machine's address, "" for one not managed here.