Serve deb virtual indexes by hash and bound cached suites

internal/virtual/deb_merger.go

@@ -5,6 +5,7 @@ import (
 	"crypto/md5"
 	"encoding/hex"
 	"fmt"
+	"path"
 	"regexp"
 	"slices"
 	"strings"
@@ -15,6 +16,9 @@ import (
 // repo's root Packages and a suite's <component>/binary-<arch>/Packages.
 var debIndexRe = regexp.MustCompile(`^([^/]+/binary-[^/]+/)?Packages(\.[a-z0-9]+)?$`)
 
+// debByHashRe matches an index requested by its SHA256 (Acquire-By-Hash).
+var debByHashRe = regexp.MustCompile(`^([^/]+/binary-[^/]+/)?by-hash/SHA256/[0-9a-f]{64}$`)
+
 // debCompressions is the order a member's index variants are fetched in.
 var debCompressions = []string{".xz", ".gz", ".zst", ".bz2", ""}
 
@@ -127,9 +131,9 @@ func parseDebDate(s string) (time.Time, bool) {
 }
 
 // MergeDeb merges members into one apt repo. Members are in priority order: the
-// first member to carry a (Package, Version, Architecture) in an index wins.
-// Filename is prefixed with the owning member's name so the virtual can route
-// downloads back to it.
+// first member to carry a (Package, Version, Architecture) in an index wins;
+// stanzas missing any of those are always kept. Filename is prefixed with the
+// owning member's name so the virtual can route downloads back to it.
 func MergeDeb(members []DebMember) *DebRepo {
 	var suite, codename string
 	var arches, comps, dirs []string
@@ -158,20 +162,26 @@ func MergeDeb(members []DebMember) *DebRepo {
 		var b bytes.Buffer
 		for _, m := range members {
 			for _, s := range splitStanzas(m.Packages[d]) {
-				key := stanzaField(s, "Package") + "\x00" + stanzaField(s, "Version") + "\x00" + stanzaField(s, "Architecture")
-				if seen[key] {
-					continue
+				pkg, ver, arch := stanzaField(s, "Package"), stanzaField(s, "Version"), stanzaField(s, "Architecture")
+				if pkg != "" && ver != "" && arch != "" {
+					key := pkg + "\x00" + ver + "\x00" + arch
+					if seen[key] {
+						continue
+					}
+					seen[key] = true
 				}
-				seen[key] = true
 				if fn := stanzaField(s, "Filename"); fn != "" {
-					s = rewriteFilename(s, m.RemoteName+"/"+strings.TrimLeft(fn, "/"))
+					s = rewriteFilename(s, m.RemoteName+"/"+strings.TrimPrefix(path.Clean("/"+fn), "/"))
 				}
 				b.WriteString(s)
 				b.WriteString("\n\n")
 			}
 		}
+		gz := gzipDeterministic(b.Bytes())
 		repo.Files[d+"Packages"] = b.Bytes()
-		repo.Files[d+"Packages.gz"] = gzipDeterministic(b.Bytes())
+		repo.Files[d+"Packages.gz"] = gz
+		repo.Files[d+"by-hash/SHA256/"+sha256Hex(b.Bytes())] = b.Bytes()
+		repo.Files[d+"by-hash/SHA256/"+sha256Hex(gz)] = gz
 	}
 
 	var r bytes.Buffer
@@ -186,7 +196,7 @@ func MergeDeb(members []DebMember) *DebRepo {
 	if len(comps) > 0 {
 		fmt.Fprintf(&r, "Components: %s\n", strings.Join(comps, " "))
 	}
-	r.WriteString("Acquire-By-Hash: no\n")
+	r.WriteString("Acquire-By-Hash: yes\n")
 	for _, sec := range []struct {
 		name string
 		sum  func([]byte) string
@@ -223,7 +233,7 @@ func debIndexPath(p string) (base, name string, ok bool) {
 		}
 		base, p = "dists/"+suite+"/", n
 	}
-	if p != "Release" && !debIndexRe.MatchString(p) {
+	if p != "Release" && !debIndexRe.MatchString(p) && !debByHashRe.MatchString(p) {
 		return "", "", false
 	}
 	return base, p, true

internal/virtual/deb_merger_test.go

@@ -6,6 +6,7 @@ import (
 	"encoding/hex"
 	"fmt"
 	"maps"
+	"path"
 	"slices"
 	"strings"
 	"testing"
@@ -24,7 +25,10 @@ func TestMergeDebDedupesByMemberOrder(t *testing.T) {
 	repo := MergeDeb([]DebMember{
 		flatDebMember("a", "Mon, 05 Oct 2026 10:00:00 +0000",
 			debStanza("foo", "1.0", "amd64", "pool/foo_1.0_amd64.deb"),
-			debStanza("bar", "2.0", "amd64", "/pool/bar.deb")),
+			debStanza("bar", "2.0", "amd64", "/pool/bar.deb"),
+			debStanza("dot", "1.0", "amd64", "./dot.deb"),
+			"Package: noversion\nFilename: nv1.deb\n",
+			"Package: noversion\nFilename: nv2.deb\n"),
 		flatDebMember("b", "Tue, 06 Oct 2026 10:00:00 UTC",
 			debStanza("foo", "1.0", "amd64", "pool/foo-from-b.deb"),
 			debStanza("foo", "1.0", "arm64", "pool/foo_arm64.deb"),
@@ -32,12 +36,15 @@ func TestMergeDebDedupesByMemberOrder(t *testing.T) {
 	})
 	pk := string(repo.Files["Packages"])
 	stanzas := splitStanzas(repo.Files["Packages"])
-	if len(stanzas) != 4 {
-		t.Fatalf("want 4 stanzas (one duplicate dropped), got %d:\n%s", len(stanzas), pk)
+	if len(stanzas) != 7 {
+		t.Fatalf("want 7 stanzas (one duplicate dropped), got %d:\n%s", len(stanzas), pk)
 	}
 	for _, want := range []string{
 		"Filename: a/pool/foo_1.0_amd64.deb",
 		"Filename: a/pool/bar.deb",
+		"Filename: a/dot.deb",
+		"Filename: a/nv1.deb",
+		"Filename: a/nv2.deb",
 		"Filename: b/pool/foo_arm64.deb",
 		"Filename: b/o/r/releases/download/v1/foo.deb",
 		" multi-line body",
@@ -111,8 +118,20 @@ func TestMergeDebSuiteLayout(t *testing.T) {
 		}
 	}
 	want := []string{"contrib/binary-amd64/Packages", "contrib/binary-amd64/Packages.gz", "main/binary-amd64/Packages", "main/binary-amd64/Packages.gz"}
-	if got := slices.Sorted(maps.Keys(repo.Files)); !slices.Equal(got, want) {
-		t.Fatalf("files %v, want %v", got, want)
+	if got := slices.Sorted(slices.Values(parseDebRelease(repo.Release).files)); !slices.Equal(got, want) {
+		t.Fatalf("Release lists %v, want %v", got, want)
+	}
+	if !strings.Contains(string(repo.Release), "Acquire-By-Hash: yes\n") {
+		t.Fatalf("Release must advertise by-hash:\n%s", repo.Release)
+	}
+	for _, n := range want {
+		byHash := path.Dir(n) + "/by-hash/SHA256/" + sha256Hex(repo.Files[n])
+		if !bytes.Equal(repo.Files[byHash], repo.Files[n]) {
+			t.Errorf("%s not served at %s", n, byHash)
+		}
+	}
+	if len(repo.Files) != 2*len(want) {
+		t.Fatalf("files %v, want each index plus its by-hash copy", slices.Sorted(maps.Keys(repo.Files)))
 	}
 	if n := len(splitStanzas(repo.Files["main/binary-amd64/Packages"])); n != 2 {
 		t.Fatalf("main/binary-amd64 should merge both members, got %d stanzas", n)
@@ -142,6 +161,9 @@ func TestDebIndexPath(t *testing.T) {
 		{"Packages.gz", "", "Packages.gz", true},
 		{"dists/trixie/Release", "dists/trixie/", "Release", true},
 		{"dists/trixie/main/binary-amd64/Packages", "dists/trixie/", "main/binary-amd64/Packages", true},
+		{"by-hash/SHA256/abababababababababababababababababababababababababababababababab", "", "by-hash/SHA256/abababababababababababababababababababababababababababababababab", true},
+		{"dists/trixie/main/binary-amd64/by-hash/SHA256/abababababababababababababababababababababababababababababababab", "dists/trixie/", "main/binary-amd64/by-hash/SHA256/abababababababababababababababababababababababababababababababab", true},
+		{"dists/trixie/main/binary-amd64/by-hash/MD5Sum/abababababababababababababababab", "", "", false},
 		{"InRelease", "", "", false},
 		{"Release.gpg", "", "", false},
 		{"dists/trixie/InRelease", "", "", false},

internal/virtual/engine.go

@@ -51,11 +51,14 @@ func (r *DebRepo) files() map[string][]byte { return r.Files }
 // holding the previous index can still fetch the files it references.
 type repoGen struct {
 	cur, prev mergedRepo
-	at        time.Time
+	at, used  time.Time
 }
 
 const rpmMergeTTL = 60 * time.Second
 
+// maxDebSuites bounds the client-chosen suites cached per deb virtual.
+const maxDebSuites = 32
+
 func NewEngine(db *database.DB, proxyEngine *proxy.Engine) *Engine {
 	e := &Engine{db: db, proxyEngine: proxyEngine, getRemote: db.GetRemote, mergeTTL: rpmMergeTTL}
 	e.rpmMember = e.fetchRPMMember
@@ -276,6 +279,7 @@ func (e *Engine) merged(ctx context.Context, key string, merge func(context.Cont
 	e.mu.Lock()
 	g := e.gens[key]
 	if g != nil && time.Since(g.at) < e.mergeTTL {
+		g.used = time.Now()
 		e.mu.Unlock()
 		return g.cur, nil
 	}
@@ -294,12 +298,12 @@ func (e *Engine) merged(ctx context.Context, key string, merge func(context.Cont
 		g := e.gens[key]
 		switch {
 		case g == nil:
-			e.gens[key] = &repoGen{cur: repo, at: time.Now()}
+			e.gens[key] = &repoGen{cur: repo, at: time.Now(), used: time.Now()}
 		case string(g.cur.index()) == string(repo.index()):
-			g.at = time.Now()
+			g.at, g.used = time.Now(), time.Now()
 			repo = g.cur
 		default:
-			g.prev, g.cur, g.at = g.cur, repo, time.Now()
+			g.prev, g.cur, g.at, g.used = g.cur, repo, time.Now(), time.Now()
 		}
 		return repo, nil
 	})
@@ -368,6 +372,7 @@ func (e *Engine) fetchDeb(ctx context.Context, virt models.Virtual, reqPath stri
 	if err != nil {
 		return nil, "", err
 	}
+	e.evictLRU("deb\x00"+virt.Name+"\x00", maxDebSuites)
 	if name == "Release" {
 		return repo.index(), "text/plain", nil
 	}
@@ -408,6 +413,22 @@ func (e *Engine) fetchDebMember(ctx context.Context, name, base string) (*DebMem
 	return m, nil
 }
 
+// evictLRU drops the least recently used merges under prefix beyond keep.
+func (e *Engine) evictLRU(prefix string, keep int) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	var keys []string
+	for k := range e.gens {
+		if strings.HasPrefix(k, prefix) {
+			keys = append(keys, k)
+		}
+	}
+	slices.SortFunc(keys, func(a, b string) int { return e.gens[b].used.Compare(e.gens[a].used) })
+	for _, k := range keys[min(len(keys), keep):] {
+		delete(e.gens, k)
+	}
+}
+
 func (e *Engine) cachedFile(key, path string) ([]byte, bool) {
 	e.mu.Lock()
 	defer e.mu.Unlock()
@@ -420,6 +441,7 @@ func (e *Engine) cachedFile(key, path string) ([]byte, bool) {
 			continue
 		}
 		if body, ok := r.files()[path]; ok {
+			g.used = time.Now()
 			return body, true
 		}
 	}

internal/virtual/engine_test.go

@@ -298,3 +298,72 @@ func TestMergedReusesWithinTTLAndIsolatesKeys(t *testing.T) {
 		t.Error("unknown key served a file")
 	}
 }
+
+func suiteDebMember(name, version string) *DebMember {
+	return &DebMember{RemoteName: name, Release: []byte("Suite: s\nSHA256:\n x 1 main/binary-amd64/Packages.gz\n"),
+		Packages: map[string][]byte{"main/binary-amd64/": []byte(debStanza("foo", version, "amd64", "pool/foo_"+version+".deb"))}}
+}
+
+func TestFetchDebByHashSurvivesRemerge(t *testing.T) {
+	version := "1"
+	e := fakeEngine(nil)
+	e.debMember = func(_ context.Context, name, _ string) (*DebMember, error) { return suiteDebMember(name, version), nil }
+	virt := debVirt("a")
+	fetch := func(p string) []byte {
+		body, _, err := e.Fetch(context.Background(), virt, p, "")
+		if err != nil {
+			t.Fatalf("%s: %v", p, err)
+		}
+		return body
+	}
+	byHash := func(rel []byte) string {
+		m := regexp.MustCompile(`(?m)^SHA256:\n(?: .*\n)*? ([0-9a-f]{64}) \d+ main/binary-amd64/Packages.gz$`).FindSubmatch(rel)
+		if m == nil {
+			t.Fatalf("no Packages.gz SHA256 in Release:\n%s", rel)
+		}
+		return "dists/trixie/main/binary-amd64/by-hash/SHA256/" + string(m[1])
+	}
+
+	oldRel := fetch("dists/trixie/Release")
+	version, e.mergeTTL = "2", 0
+	if newRel := fetch("dists/trixie/Release"); string(newRel) == string(oldRel) {
+		t.Fatal("Release should reflect the member change")
+	}
+	if got := string(gunzip(t, fetch(byHash(oldRel)))); !strings.Contains(got, "Version: 1\n") {
+		t.Fatalf("by-hash from the previous Release served the wrong index:\n%s", got)
+	}
+	if got := string(fetch("dists/trixie/main/binary-amd64/Packages")); !strings.Contains(got, "Version: 2\n") {
+		t.Fatalf("fixed-name Packages should be the current merge:\n%s", got)
+	}
+}
+
+func TestFetchDebBoundsSuitesPerVirtual(t *testing.T) {
+	e := fakeEngine(nil)
+	e.mergeTTL = time.Minute
+	e.debMember = func(_ context.Context, name, _ string) (*DebMember, error) { return suiteDebMember(name, "1"), nil }
+	other := models.Virtual{Name: "other", PackageType: models.PackageDeb, Members: []string{"a"}}
+	if _, _, err := e.Fetch(context.Background(), other, "dists/keep/Release", ""); err != nil {
+		t.Fatal(err)
+	}
+	for i := range maxDebSuites + 5 {
+		if _, _, err := e.Fetch(context.Background(), debVirt("a"), fmt.Sprintf("dists/s%d/Release", i), ""); err != nil {
+			t.Fatal(err)
+		}
+		time.Sleep(time.Microsecond)
+	}
+	n := 0
+	for k := range e.gens {
+		if strings.HasPrefix(k, "deb\x00v\x00") {
+			n++
+		}
+	}
+	if n != maxDebSuites {
+		t.Fatalf("virtual v caches %d suites, want %d", n, maxDebSuites)
+	}
+	if e.gens["deb\x00v\x00dists/s0/"] != nil || e.gens["deb\x00v\x00dists/s4/"] != nil {
+		t.Fatal("least recently used suites should be evicted first")
+	}
+	if e.gens["deb\x00other\x00dists/keep/"] == nil {
+		t.Fatal("another virtual's suites must not be evicted")
+	}
+}