Merge pull request #180 from Dash-Industry-Forum/add-expires-to-patch

fix: add Expires header to Patch response

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - MPD Patch functionality with new `/patch_ttl` URL configuration
 - nowDate query parameter as an alternative to nowMS for MPD and patch
+- MPD Patch has Expires header equal to publishTime + ttl + 10s
 
 ### Fixed
 

cmd/livesim2/app/handler_patch.go

@@ -50,7 +50,7 @@ func (s *Server) patchHandlerFunc(w http.ResponseWriter, r *http.Request) {
 	r.URL.RawQuery = newQuery
 	s.livesimHandlerFunc(new, r)
 
-	doc, err := patch.MPDDiff(old.body, new.body)
+	doc, expiration, err := patch.MPDDiff(old.body, new.body)
 	switch {
 	case errors.Is(err, patch.ErrPatchSamePublishTime):
 		http.Error(w, err.Error(), http.StatusTooEarly)
@@ -71,6 +71,7 @@ func (s *Server) patchHandlerFunc(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	w.Header().Set("Content-Type", "application/dash-patch+xml")
+	w.Header().Set("Expires", expiration.Format(http.TimeFormat))
 	w.Header().Set("Content-Length", strconv.Itoa(len(b)))
 	_, err = w.Write(b)
 	if err != nil {

cmd/livesim2/app/handler_patch_test.go

@@ -11,18 +11,22 @@ import (
 )
 
 var wantedPatchSegTimelineTime = `<?xml version="1.0" encoding="UTF-8"?>
-<Patch xmlns="urn:mpeg:dash:schema:mpd-patch:2020" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:mpeg:dash:schema:mpd-patch:2020 DASH-MPD-PATCH.xsd" mpdId="base" originalPublishTime="2024-04-02T15:50:56Z" publishTime="2024-04-02T15:52:40Z">
-  <replace sel="/MPD/@publishTime">2024-04-02T15:52:40Z</replace>
+<Patch xmlns="urn:mpeg:dash:schema:mpd-patch:2020" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:mpeg:dash:schema:mpd-patch:2020 DASH-MPD-PATCH.xsd" mpdId="base" originalPublishTime="2024-04-02T15:50:56Z" publishTime="2024-04-02T15:51:40Z">
+  <replace sel="/MPD/@publishTime">2024-04-02T15:51:40Z</replace>
   <replace sel="/MPD/PatchLocation[1]">
-    <PatchLocation ttl="60">/patch/livesim2/patch_60/segtimeline_1/testpic_2s/Manifest.mpp?publishTime=2024-04-02T15%3A52%3A40Z</PatchLocation>
+    <PatchLocation ttl="60">/patch/livesim2/patch_60/segtimeline_1/testpic_2s/Manifest.mpp?publishTime=2024-04-02T15%3A51%3A40Z</PatchLocation>
   </replace>
   <remove sel="/MPD/Period[@id=&apos;P0&apos;]/AdaptationSet[@id=&apos;1&apos;]/SegmentTemplate/SegmentTimeline/S[1]"/>
+  <remove sel="/MPD/Period[@id=&apos;P0&apos;]/AdaptationSet[@id=&apos;1&apos;]/SegmentTemplate/SegmentTimeline/S[1]"/>
   <add sel="/MPD/Period[@id=&apos;P0&apos;]/AdaptationSet[@id=&apos;1&apos;]/SegmentTemplate/SegmentTimeline" pos="prepend">
-    <S t="82179508704256" d="96256" r="1"/>
+    <S t="82179505824768" d="95232"/>
+  </add>
+  <add sel="/MPD/Period[@id=&apos;P0&apos;]/AdaptationSet[@id=&apos;1&apos;]/SegmentTemplate/SegmentTimeline/S[15]" pos="after">
+    <S d="96256" r="1"/>
   </add>
   <remove sel="/MPD/Period[@id=&apos;P0&apos;]/AdaptationSet[@id=&apos;2&apos;]/SegmentTemplate/SegmentTimeline/S[1]"/>
   <add sel="/MPD/Period[@id=&apos;P0&apos;]/AdaptationSet[@id=&apos;2&apos;]/SegmentTemplate/SegmentTimeline" pos="prepend">
-    <S t="154086578820000" d="180000" r="30"/>
+    <S t="154086573420000" d="180000" r="30"/>
   </add>
 </Patch>
 `
@@ -67,6 +71,7 @@ func TestPatchHandler(t *testing.T) {
 		wantedStatusCode  int
 		wantedContentType string
 		wantedBody        string
+		wantedExpires     string
 	}{
 		{
 			desc:              "segTimeline no update yet",
@@ -84,17 +89,19 @@ func TestPatchHandler(t *testing.T) {
 		},
 		{
 			desc:              "segTimeline",
-			url:               "/patch/livesim2/patch_60/segtimeline_1/testpic_2s/Manifest.mpp?publishTime=2024-04-02T15:50:56Z&nowMS=1712073160000",
+			url:               "/patch/livesim2/patch_60/segtimeline_1/testpic_2s/Manifest.mpp?publishTime=2024-04-02T15:50:56Z&nowDate=2024-04-02T15:51:40Z",
 			wantedStatusCode:  http.StatusOK,
 			wantedContentType: "application/dash-patch+xml",
 			wantedBody:        wantedPatchSegTimelineTime,
+			wantedExpires:     "Tue, 02 Apr 2024 15:52:06 GMT",
 		},
 		{
 			desc:              "segTimeline with Number",
 			url:               "/patch/livesim2/patch_60/segtimelinenr_1/testpic_2s/Manifest.mpp?publishTime=2024-04-16T07:34:38Z&nowDate=2024-04-16T07:34:57Z",
 			wantedStatusCode:  http.StatusOK,
 			wantedContentType: "application/dash-patch+xml",
 			wantedBody:        wantedPatchSegTimelineNumberWithAddAtEnd,
+			wantedExpires:     "Tue, 16 Apr 2024 07:35:48 GMT",
 		},
 	}
 
@@ -106,6 +113,9 @@ func TestPatchHandler(t *testing.T) {
 			if tc.wantedStatusCode != http.StatusOK {
 				return
 			}
+			if tc.wantedExpires != "" {
+				require.Equal(t, tc.wantedExpires, resp.Header.Get("Expires"))
+			}
 			bodyStr := string(body)
 			require.Equal(t, tc.wantedBody, bodyStr)
 		})

pkg/patch/patch.go

@@ -9,6 +9,9 @@ import (
 	"github.com/beevik/etree"
 )
 
+// PatchExpirationMargin is added to the HTTP expiration beyond ttl.
+const PatchExpirationMargin = 10 * time.Second
+
 var ErrPatchSamePublishTime = fmt.Errorf("same publishTime in both MPDs")
 var ErrPatchTooLate = fmt.Errorf("patch TTL exceeded")
 
@@ -46,77 +49,77 @@ func newPatchDoc(oldRoot, newRoot *etree.Element) (*patchDoc, error) {
 }
 
 // MPDDiff compares two MPDs and returns a patch document or an error.
-func MPDDiff(mpdOld, mpdNew []byte) (*etree.Document, error) {
+func MPDDiff(mpdOld, mpdNew []byte) (doc *etree.Document, expiration time.Time, err error) {
 	dOld := etree.NewDocument()
-	err := dOld.ReadFromBytes(mpdOld)
+	err = dOld.ReadFromBytes(mpdOld)
 	if err != nil {
-		return nil, fmt.Errorf("failed to read old MPD: %w", err)
+		return nil, expiration, fmt.Errorf("failed to read old MPD: %w", err)
 	}
 	dNew := etree.NewDocument()
 	err = dNew.ReadFromBytes(mpdNew)
 	if err != nil {
-		return nil, fmt.Errorf("failed to read new MPD: %w", err)
+		return nil, expiration, fmt.Errorf("failed to read new MPD: %w", err)
 	}
 	oldRoot := dOld.Root()
 	newRoot := dNew.Root()
 
-	err = checkPatchConditions(oldRoot, newRoot)
+	expiration, err = checkPatchConditions(oldRoot, newRoot)
 	if err != nil {
-		return nil, err
+		return nil, expiration, err
 	}
 
 	pDoc, err := newPatchDoc(oldRoot, newRoot)
 	if err != nil {
-		return nil, fmt.Errorf("failed to create patch doc: %w", err)
+		return nil, expiration, fmt.Errorf("failed to create patch doc: %w", err)
 	}
 
 	elemPath := "/MPD"
 	root := pDoc.doc.Root()
 	err = addElemChanges(root, oldRoot, newRoot, elemPath)
 	if err != nil {
-		return nil, err
+		return nil, expiration, err
 	}
 
-	return pDoc.doc, nil
+	return pDoc.doc, expiration, nil
 }
 
-func checkPatchConditions(oldRoot, newRoot *etree.Element) error {
+func checkPatchConditions(oldRoot, newRoot *etree.Element) (expiration time.Time, err error) {
 	if oldRoot.Tag != "MPD" || newRoot.Tag != "MPD" {
-		return fmt.Errorf("not MPD root element in both MPDs")
+		return expiration, fmt.Errorf("not MPD root element in both MPDs")
 	}
 	newPublishTime := getAttrValue(newRoot, "publishTime")
 	oldPublishTime := getAttrValue(oldRoot, "publishTime")
 	if newPublishTime == "" || oldPublishTime == "" {
-		return fmt.Errorf("lacking publishTime attribute in MPD")
+		return expiration, fmt.Errorf("lacking publishTime attribute in MPD")
 	}
 	if newPublishTime == oldPublishTime {
-		return ErrPatchSamePublishTime
+		return expiration, ErrPatchSamePublishTime
 	}
 	oldPatchLocation := oldRoot.SelectElement("PatchLocation")
 	if oldPatchLocation == nil {
-		return fmt.Errorf("no PatchLocation element in old MPD")
+		return expiration, fmt.Errorf("no PatchLocation element in old MPD")
 	}
 	oldTTL := oldPatchLocation.SelectAttr("ttl")
 	if oldTTL == nil {
-		return fmt.Errorf("no ttl attribute in PatchLocation element in old MPD")
+		return expiration, fmt.Errorf("no ttl attribute in PatchLocation element in old MPD")
 	}
 	ttl, err := strconv.Atoi(oldTTL.Value)
 	if err != nil {
-		return fmt.Errorf("failed to convert ttl attribute in PatchLocation element in old MPD: %w", err)
+		return expiration, fmt.Errorf("failed to convert ttl attribute in PatchLocation element in old MPD: %w", err)
 	}
 	oldPT, err := time.Parse(time.RFC3339, oldPublishTime)
 	if err != nil {
-		return fmt.Errorf("failed to parse old publishTime: %w", err)
+		return expiration, fmt.Errorf("failed to parse old publishTime: %w", err)
 	}
 	newPT, err := time.Parse(time.RFC3339, newPublishTime)
 	if err != nil {
-		return fmt.Errorf("failed to parse new publishTime: %w", err)
+		return expiration, fmt.Errorf("failed to parse new publishTime: %w", err)
 	}
-	endTime := oldPT.Add(2 * time.Duration(ttl) * time.Second)
-	if newPT.After(endTime) {
-		return ErrPatchTooLate
+	expiration = oldPT.Add(time.Duration(ttl)*time.Second + PatchExpirationMargin)
+	if newPT.After(expiration) {
+		return expiration, ErrPatchTooLate
 	}
-	return nil
+	return expiration, nil
 }
 
 // getAttrValue returns value if key exists, of empty string

pkg/patch/patch_test.go

@@ -4,6 +4,7 @@ import (
 	"os"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/google/go-cmp/cmp"
 
@@ -64,18 +65,20 @@ const wantedPatchSegmentTimelineNumber = (`<?xml version="1.0" encoding="UTF-8"?
 
 func TestDiff(t *testing.T) {
 	cases := []struct {
-		desc           string
-		oldMPD         string
-		newMPD         string
-		wantedDiff     string
-		wantedDiffFile string
-		wantedErr      string
+		desc             string
+		oldMPD           string
+		newMPD           string
+		wantedDiff       string
+		wantedDiffFile   string
+		wantedExpiration time.Time
+		wantedErr        string
 	}{
 		{
-			desc:           "multiPeriodPatch",
-			oldMPD:         "testdata/multiperiod_1.mpd",
-			newMPD:         "testdata/multiperiod_2.mpd",
-			wantedDiffFile: "testdata/multiperiod_patch.mpp",
+			desc:             "multiPeriodPatch",
+			oldMPD:           "testdata/multiperiod_1.mpd",
+			newMPD:           "testdata/multiperiod_2.mpd",
+			wantedDiffFile:   "testdata/multiperiod_patch.mpp",
+			wantedExpiration: time.Date(2024, 4, 21, 6, 12, 8, 0, time.UTC),
 		},
 		{
 			desc:      "too big publishTime diff vs ttl",
@@ -84,15 +87,17 @@ func TestDiff(t *testing.T) {
 			wantedErr: ErrPatchTooLate.Error(),
 		},
 		{
-			desc:       "segmentTimelineTime",
-			oldMPD:     "testdata/testpic_2s_1.mpd",
-			newMPD:     "testdata/testpic_2s_2.mpd",
-			wantedDiff: wantedPatchSegmentTimelineTime,
+			desc:             "segmentTimelineTime",
+			oldMPD:           "testdata/testpic_2s_1.mpd",
+			newMPD:           "testdata/testpic_2s_2.mpd",
+			wantedDiff:       wantedPatchSegmentTimelineTime,
+			wantedExpiration: time.Date(2024, 3, 28, 15, 44, 20, 0, time.UTC),
 		}, {
-			desc:       "segmentTimelineNumber",
-			oldMPD:     "testdata/testpic_2s_snr_1.mpd",
-			newMPD:     "testdata/testpic_2s_snr_2.mpd",
-			wantedDiff: wantedPatchSegmentTimelineNumber,
+			desc:             "segmentTimelineNumber",
+			oldMPD:           "testdata/testpic_2s_snr_1.mpd",
+			newMPD:           "testdata/testpic_2s_snr_2.mpd",
+			wantedDiff:       wantedPatchSegmentTimelineNumber,
+			wantedExpiration: time.Date(2024, 3, 28, 15, 44, 20, 0, time.UTC),
 		},
 		{
 			desc:       "no diff",
@@ -108,12 +113,14 @@ func TestDiff(t *testing.T) {
 			require.NoError(t, err)
 			in2, err := os.ReadFile(c.newMPD)
 			require.NoError(t, err)
-			patch, err := MPDDiff(in1, in2)
+			patch, expiration, err := MPDDiff(in1, in2)
 			if c.wantedErr != "" {
 				require.Error(t, err, c.wantedErr)
 				return
 			}
 			require.NoError(t, err)
+			expirationDiff := c.wantedExpiration.Sub(expiration)
+			require.Equal(t, time.Duration(0), expirationDiff)
 			patch.Indent(2)
 			out, err := patch.WriteToString()
 			wantedDiff := c.wantedDiff