internal/api/v2/remotes.go

@@ -12,18 +12,20 @@ import (
 )
 
 // Primer enqueues a background metadata prime for a newly created remote so the
-// create call never blocks on a derive. *rpm.Syncer satisfies it.
+// create call never blocks on a derive. *rpm.Syncer and *deb.Syncer satisfy it.
 type Primer interface {
 	EnqueuePrime(remote models.Remote)
 }
 
 type RemotesHandler struct {
-	db     *database.DB
-	primer Primer
+	db      *database.DB
+	primers map[models.PackageType]Primer
 }
 
-func NewRemotesHandler(db *database.DB, primer Primer) *RemotesHandler {
-	return &RemotesHandler{db: db, primer: primer}
+// NewRemotesHandler wires the handler to the per-type metadata primers. primers
+// may be nil; a package type with no registered primer simply skips priming.
+func NewRemotesHandler(db *database.DB, primers map[models.PackageType]Primer) *RemotesHandler {
+	return &RemotesHandler{db: db, primers: primers}
 }
 
 func (h *RemotesHandler) Routes() chi.Router {
@@ -84,10 +86,10 @@ func (h *RemotesHandler) create(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return
 	}
-	// Prime a github_rpm remote's metadata in the background so its first
-	// repodata request is served from cache instead of a cold on-demand derive.
-	if h.primer != nil && remote.PackageType == models.PackageGitHubRPM {
-		h.primer.EnqueuePrime(remote)
+	// Prime a metadata-only remote (github_rpm/github_deb) in the background so
+	// its first index request is served from cache instead of a cold derive.
+	if primer := h.primers[remote.PackageType]; primer != nil {
+		primer.EnqueuePrime(remote)
 	}
 	writeJSON(w, http.StatusCreated, remote)
 }

internal/database/deb_github_sync.go

@@ -0,0 +1,70 @@
+package database
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+// ListGitHubDebRemotes returns every github_deb remote so the syncer can sweep
+// them on each poll tick.
+func (db *DB) ListGitHubDebRemotes(ctx context.Context) ([]models.Remote, error) {
+	rows, err := db.Pool.Query(ctx, `SELECT `+remoteCols+` FROM remotes WHERE package_type = $1 ORDER BY name`, models.PackageGitHubDeb)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var remotes []models.Remote
+	for rows.Next() {
+		var r models.Remote
+		if err := scanRemote(rows, &r); err != nil {
+			return nil, err
+		}
+		remotes = append(remotes, r)
+	}
+	return remotes, rows.Err()
+}
+
+// ClaimGitHubDebSyncLease atomically claims the per-remote sync lease. It
+// succeeds only when the remote is due (never synced, or synced longer than
+// freshness ago) and no live lease is held by another replica. A zero freshness
+// (prime scans) ignores the recency gate. The returned etag is the stored
+// releases-list ETag, shared across replicas.
+func (db *DB) ClaimGitHubDebSyncLease(ctx context.Context, remoteName, owner string, freshness, lease time.Duration) (bool, string, error) {
+	row := db.Pool.QueryRow(ctx, `
+		INSERT INTO github_deb_sync_state AS s (remote_name, sync_lease_owner, sync_lease_expires)
+		VALUES ($1, $2, now() + make_interval(secs => $4))
+		ON CONFLICT (remote_name) DO UPDATE
+			SET sync_lease_owner   = $2,
+			    sync_lease_expires = now() + make_interval(secs => $4)
+			WHERE (s.last_synced_at IS NULL OR s.last_synced_at < now() - make_interval(secs => $3))
+			  AND (s.sync_lease_expires IS NULL OR s.sync_lease_expires < now())
+		RETURNING s.etag
+	`, remoteName, owner, freshness.Seconds(), lease.Seconds())
+
+	var etag string
+	if err := row.Scan(&etag); err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return false, "", nil
+		}
+		return false, "", err
+	}
+	return true, etag, nil
+}
+
+// ReleaseGitHubDebSyncLease records the completed scan and frees the lease. Only
+// the owning replica may release; last_synced_at advances so the next poll waits
+// a full freshness window, and etag is persisted for the next conditional request.
+func (db *DB) ReleaseGitHubDebSyncLease(ctx context.Context, remoteName, owner, etag string, syncedAt time.Time) error {
+	_, err := db.Pool.Exec(ctx, `
+		UPDATE github_deb_sync_state
+		   SET last_synced_at = $3, etag = $4, sync_lease_owner = '', sync_lease_expires = NULL
+		 WHERE remote_name = $1 AND sync_lease_owner = $2
+	`, remoteName, owner, syncedAt, etag)
+	return err
+}

internal/database/deb_github_sync_test.go

@@ -0,0 +1,90 @@
+package database
+
+import (
+	"testing"
+	"time"
+
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+func seedGitHubDebRemote(t *testing.T, name string) {
+	t.Helper()
+	if err := testDB.CreateRemote(ctx(), &models.Remote{
+		Name: name, PackageType: models.PackageGitHubDeb, RepoType: models.RepoTypeRemote,
+		BaseURL: "https://api.github.com/repos/acme/tools", ReleasesRemote: "github", MutableTTL: 3600,
+	}); err != nil {
+		t.Fatalf("seed github_deb remote: %v", err)
+	}
+}
+
+// TestGitHubDebSyncLease exercises the real SQL: exactly one replica may hold the
+// lease, the recency window blocks a too-soon periodic re-claim, and a prime
+// (freshness 0) bypasses recency but still respects a live lease.
+func TestGitHubDebSyncLease(t *testing.T) {
+	requireDB(t)
+	name := "ghdeb-lease-" + time.Now().Format("150405.000000")
+	seedGitHubDebRemote(t, name)
+
+	const lease = 15 * time.Minute
+	freshness := time.Hour
+
+	claimed, etag, err := testDB.ClaimGitHubDebSyncLease(ctx(), name, "replica-1", freshness, lease)
+	if err != nil || !claimed {
+		t.Fatalf("replica-1 first claim: claimed=%v err=%v", claimed, err)
+	}
+	if etag != "" {
+		t.Fatalf("initial etag should be empty, got %q", etag)
+	}
+
+	claimed2, _, err := testDB.ClaimGitHubDebSyncLease(ctx(), name, "replica-2", freshness, lease)
+	if err != nil {
+		t.Fatalf("replica-2 claim err: %v", err)
+	}
+	if claimed2 {
+		t.Fatal("replica-2 claimed while replica-1 holds the lease")
+	}
+
+	if err := testDB.ReleaseGitHubDebSyncLease(ctx(), name, "replica-1", `"etag-1"`, time.Now()); err != nil {
+		t.Fatalf("release: %v", err)
+	}
+
+	claimed3, _, err := testDB.ClaimGitHubDebSyncLease(ctx(), name, "replica-2", freshness, lease)
+	if err != nil {
+		t.Fatalf("replica-2 recency claim err: %v", err)
+	}
+	if claimed3 {
+		t.Fatal("periodic claim succeeded inside the freshness window")
+	}
+
+	claimed4, etag4, err := testDB.ClaimGitHubDebSyncLease(ctx(), name, "replica-2", 0, lease)
+	if err != nil || !claimed4 {
+		t.Fatalf("prime claim: claimed=%v err=%v", claimed4, err)
+	}
+	if etag4 != `"etag-1"` {
+		t.Fatalf("prime claim etag = %q, want persisted \"etag-1\"", etag4)
+	}
+}
+
+func TestListGitHubDebRemotes(t *testing.T) {
+	requireDB(t)
+	name := "ghdeb-list-" + time.Now().Format("150405.000000")
+	seedGitHubDebRemote(t, name)
+	seedRemote(t, "generic-"+time.Now().Format("150405.000000"))
+
+	remotes, err := testDB.ListGitHubDebRemotes(ctx())
+	if err != nil {
+		t.Fatalf("list: %v", err)
+	}
+	found := false
+	for _, r := range remotes {
+		if r.PackageType != models.PackageGitHubDeb {
+			t.Fatalf("non-github_deb remote returned: %s (%s)", r.Name, r.PackageType)
+		}
+		if r.Name == name {
+			found = true
+		}
+	}
+	if !found {
+		t.Fatalf("seeded remote %q not returned", name)
+	}
+}

internal/database/postgres.go

@@ -190,6 +190,14 @@ func (db *DB) migrate() error {
 			sync_lease_expires TIMESTAMPTZ
 		);
 
+		CREATE TABLE IF NOT EXISTS github_deb_sync_state (
+			remote_name        TEXT PRIMARY KEY,
+			etag               TEXT DEFAULT '',
+			last_synced_at     TIMESTAMPTZ,
+			sync_lease_owner   TEXT DEFAULT '',
+			sync_lease_expires TIMESTAMPTZ
+		);
+
 		CREATE TABLE IF NOT EXISTS signing_keys (
 			purpose             TEXT PRIMARY KEY,
 			private_key_armor   TEXT NOT NULL,

internal/provider/deb/deb.go

@@ -194,7 +194,14 @@ func extractControl(deb []byte) (string, error) {
 		return "", err
 	}
 
-	tr := tar.NewReader(bytes.NewReader(tarBytes))
+	return readControlParagraph(tarBytes)
+}
+
+// readControlParagraph scans a decompressed control.tar and returns the raw
+// ./control paragraph. Shared by the local upload path (extractControl) and the
+// github_deb ranged-prefix parser.
+func readControlParagraph(controlTar []byte) (string, error) {
+	tr := tar.NewReader(bytes.NewReader(controlTar))
 	for {
 		hdr, err := tr.Next()
 		if err == io.EOF {
@@ -370,8 +377,12 @@ func generatePackages(metas []provider.DebMetadata) []byte {
 		b.WriteString("\n")
 		fmt.Fprintf(&b, "Filename: %s\n", m.FilePath)
 		fmt.Fprintf(&b, "Size: %d\n", m.Size)
-		fmt.Fprintf(&b, "MD5sum: %s\n", m.MD5)
-		fmt.Fprintf(&b, "SHA256: %s\n", m.SHA256)
+		if m.MD5 != "" {
+			fmt.Fprintf(&b, "MD5sum: %s\n", m.MD5)
+		}
+		if m.SHA256 != "" {
+			fmt.Fprintf(&b, "SHA256: %s\n", m.SHA256)
+		}
 		b.WriteString("\n")
 	}
 	return b.Bytes()

internal/provider/deb/github.go

@@ -0,0 +1,724 @@
+package deb
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"net/url"
+	"regexp"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	"git.unkin.net/unkin/artifactapi/internal/githubauth"
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+// gitHubProvider is the process-wide singleton for github_deb. The background
+// Syncer binds its shared rate limiter and work queue onto this instance so the
+// request path and the syncer drive the same derive machinery.
+var gitHubProvider = newGitHubProvider()
+
+func init() {
+	provider.Register(gitHubProvider)
+}
+
+// Tuning knobs for the no-precache control fetch. A .deb is an ar archive whose
+// control.tar member sits right after the tiny debian-binary member, so a small
+// front prefix reliably covers it.
+const (
+	defaultHeaderRangeInitial = 32 << 10 // 32 KiB — covers control.tar of almost every .deb
+	defaultHeaderRangeMax     = 16 << 20 // 16 MiB — give up past this and skip the asset
+	defaultReleasePageCap     = 10       // 100 releases/page * 10 pages
+
+	defaultScanTimeout  = 10 * time.Minute
+	defaultServeTimeout = 30 * time.Second
+	defaultColdWait     = 8 * time.Second
+)
+
+// GitHubProvider is a metadata-only remote: it scans a GitHub repo's releases
+// for .deb assets, derives per-asset control metadata via a ranged prefix fetch
+// (never downloading whole packages), synthesizes a flat apt repository from that
+// cached metadata, and redirects package downloads to a backend "releases_remote"
+// (the generic github.com remote) that serves the actual bytes.
+type GitHubProvider struct {
+	client *http.Client
+
+	headerInitial int64
+	headerMax     int64
+	pageCap       int
+	scanTimeout   time.Duration
+	serveTimeout  time.Duration
+	coldWait      time.Duration
+
+	limiter *rate.Limiter
+	syncer  *Syncer
+
+	serverCred githubauth.Credential
+
+	mu       sync.Mutex
+	scanning map[string]bool
+	lastScan map[string]time.Time
+}
+
+func newGitHubProvider() *GitHubProvider {
+	return &GitHubProvider{
+		client:        &http.Client{},
+		headerInitial: defaultHeaderRangeInitial,
+		headerMax:     defaultHeaderRangeMax,
+		pageCap:       defaultReleasePageCap,
+		scanTimeout:   defaultScanTimeout,
+		serveTimeout:  defaultServeTimeout,
+		coldWait:      defaultColdWait,
+		scanning:      map[string]bool{},
+		lastScan:      map[string]time.Time{},
+	}
+}
+
+func (p *GitHubProvider) limiterWait(ctx context.Context) error {
+	if p.limiter == nil {
+		return nil
+	}
+	return p.limiter.Wait(ctx)
+}
+
+func (p *GitHubProvider) Type() models.PackageType { return models.PackageGitHubDeb }
+
+func (p *GitHubProvider) Classify(path string) provider.Mutability {
+	switch path {
+	case "Packages", "Packages.gz", "Release", "InRelease", "Release.gpg":
+		return provider.Mutable
+	}
+	return provider.Immutable
+}
+
+func (p *GitHubProvider) ContentType(path string) string {
+	switch {
+	case strings.HasSuffix(path, ".deb"):
+		return "application/vnd.debian.binary-package"
+	case strings.HasSuffix(path, ".gz"):
+		return "application/gzip"
+	case path == "Packages" || path == "Release" || path == "InRelease":
+		return "text/plain"
+	}
+	return "application/octet-stream"
+}
+
+func (p *GitHubProvider) UpstreamURL(remote models.Remote, path string) string {
+	return strings.TrimRight(remote.BaseURL, "/") + "/" + strings.TrimLeft(path, "/")
+}
+
+func (p *GitHubProvider) RewriteResponse(_ []byte, _ models.Remote, _ string) ([]byte, error) {
+	return nil, nil
+}
+
+func (p *GitHubProvider) AuthHeaders(ctx context.Context, remote models.Remote) (http.Header, error) {
+	return p.githubHeaders(ctx, remote, false)
+}
+
+// ServeRemote answers a request against a github_deb remote. It refreshes the
+// derived metadata (bounded by mutable_ttl), serves a synthesized flat apt repo
+// (Packages/Packages.gz/Release), 404s the signed index variants (the repo is
+// consumed via [trusted=yes]), and 302-redirects .deb downloads to the backend
+// releases_remote. Returns false only for paths it does not own.
+func (p *GitHubProvider) ServeRemote(w http.ResponseWriter, r *http.Request, remote models.Remote, reqPath, proxyBaseURL string, store provider.RemoteMetadataStore) bool {
+	p.onRequest(remote, store)
+
+	// apt appends the flat-repo dist "./" verbatim, so it asks for "./Packages"
+	// etc.; collapse the dot-segment before matching the synthesized index.
+	path := normalizeIndexPath(reqPath)
+
+	switch path {
+	case "Packages", "Packages.gz", "Release":
+		p.serveIndex(w, r, remote, path, store)
+		return true
+	case "InRelease", "Release.gpg":
+		// Unsigned flat repo: apt consumes it with [trusted=yes]. Signal absence
+		// so apt falls back to the plain Release without waiting on a signature.
+		http.Error(w, "not found", http.StatusNotFound)
+		return true
+	}
+
+	if strings.HasSuffix(path, ".deb") {
+		if remote.ReleasesRemote == "" {
+			http.Error(w, "github_deb remote has no releases_remote configured for downloads", http.StatusInternalServerError)
+			return true
+		}
+		loc := strings.TrimRight(proxyBaseURL, "/") + "/api/v1/remote/" + remote.ReleasesRemote + "/" + strings.TrimLeft(path, "/")
+		http.Redirect(w, r, loc, http.StatusFound)
+		return true
+	}
+
+	return false
+}
+
+func (p *GitHubProvider) serveIndex(w http.ResponseWriter, r *http.Request, remote models.Remote, path string, store provider.RemoteMetadataStore) {
+	// Serve on a context detached from the inbound request so a client disconnect
+	// never cancels the metadata DB read and surfaces as a 500.
+	sctx, cancel := context.WithTimeout(context.WithoutCancel(r.Context()), p.serveTimeout)
+	defer cancel()
+
+	if p.syncer != nil && !p.ensurePrimed(sctx, remote, store) {
+		w.Header().Set("Retry-After", "5")
+		http.Error(w, "metadata is being prepared, retry shortly", http.StatusServiceUnavailable)
+		return
+	}
+
+	reader, ok := store.(provider.DebMetadataReader)
+	if !ok {
+		http.Error(w, "deb metadata not available", http.StatusInternalServerError)
+		return
+	}
+	metas, err := reader.ListDebMetadataEntries(sctx, remote.Name)
+	if err != nil {
+		if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
+			http.Error(w, "metadata read canceled", http.StatusServiceUnavailable)
+			return
+		}
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	switch path {
+	case "Packages":
+		w.Header().Set("Content-Type", "text/plain")
+		w.WriteHeader(http.StatusOK)
+		w.Write(generatePackages(metas))
+	case "Packages.gz":
+		w.Header().Set("Content-Type", "application/gzip")
+		w.WriteHeader(http.StatusOK)
+		w.Write(gzipBytes(generatePackages(metas)))
+	case "Release":
+		w.Header().Set("Content-Type", "text/plain")
+		w.WriteHeader(http.StatusOK)
+		w.Write(generateRelease(metas))
+	}
+}
+
+// onRequest keeps a remote's derived metadata fresh off the request path.
+func (p *GitHubProvider) onRequest(remote models.Remote, store provider.RemoteMetadataStore) {
+	if p.syncer != nil {
+		p.syncer.enqueue(remote, false)
+		return
+	}
+	p.refresh(remote, store)
+}
+
+// ensurePrimed returns true once the remote has at least one cached row. On an
+// empty cache it enqueues a prime and polls briefly for it to land.
+func (p *GitHubProvider) ensurePrimed(ctx context.Context, remote models.Remote, store provider.RemoteMetadataStore) bool {
+	if !p.cacheEmpty(ctx, store, remote.Name) {
+		return true
+	}
+	if p.syncer != nil {
+		p.syncer.enqueue(remote, true)
+	}
+
+	deadline := time.Now().Add(p.coldWait)
+	for time.Now().Before(deadline) {
+		select {
+		case <-ctx.Done():
+			return false
+		case <-time.After(400 * time.Millisecond):
+		}
+		if !p.cacheEmpty(ctx, store, remote.Name) {
+			return true
+		}
+	}
+	return false
+}
+
+func (p *GitHubProvider) cacheEmpty(ctx context.Context, store provider.RemoteMetadataStore, name string) bool {
+	reader, ok := store.(provider.DebMetadataReader)
+	if !ok {
+		return false
+	}
+	rows, err := reader.ListDebMetadataEntries(ctx, name)
+	if err != nil {
+		return false
+	}
+	return len(rows) == 0
+}
+
+// refresh brings the derived metadata up to date without coupling the scan to
+// the inbound request (legacy inline path used without a syncer / in unit tests).
+func (p *GitHubProvider) refresh(remote models.Remote, store provider.RemoteMetadataStore) {
+	ttl := time.Duration(remote.MutableTTL) * time.Second
+	if ttl <= 0 {
+		ttl = 5 * time.Minute
+	}
+
+	p.mu.Lock()
+	last, ok := p.lastScan[remote.Name]
+	fresh := ok && time.Since(last) < ttl
+	if fresh || p.scanning[remote.Name] {
+		p.mu.Unlock()
+		return
+	}
+	p.scanning[remote.Name] = true
+	p.mu.Unlock()
+
+	if p.cacheEmpty(context.Background(), store, remote.Name) {
+		p.runScan(remote, store)
+		return
+	}
+	go p.runScan(remote, store)
+}
+
+func (p *GitHubProvider) runScan(remote models.Remote, store provider.RemoteMetadataStore) {
+	defer func() {
+		p.mu.Lock()
+		delete(p.scanning, remote.Name)
+		p.mu.Unlock()
+	}()
+
+	ctx, cancel := context.WithTimeout(context.Background(), p.scanTimeout)
+	defer cancel()
+
+	if err := p.scan(ctx, remote, store); err != nil {
+		slog.Error("github_deb: release scan failed", "remote", remote.Name, "error", err)
+		return
+	}
+
+	p.mu.Lock()
+	p.lastScan[remote.Name] = time.Now()
+	p.mu.Unlock()
+}
+
+// scan runs a full unconditional derive. Retained for the legacy inline refresh
+// path and existing tests; the syncer uses scanWithState.
+func (p *GitHubProvider) scan(ctx context.Context, remote models.Remote, store provider.RemoteMetadataStore) error {
+	_, _, err := p.scanWithState(ctx, remote, store, "")
+	return err
+}
+
+// scanWithState derives metadata incrementally. It sends the prior releases-list
+// ETag as a conditional request: a 304 means nothing changed. On a 200 it diffs
+// the release assets against the cache, derives only new/changed assets, prunes
+// assets that disappeared, and returns the new ETag.
+func (p *GitHubProvider) scanWithState(ctx context.Context, remote models.Remote, store provider.RemoteMetadataStore, etag string) (newEtag string, changed bool, err error) {
+	releases, newEtag, notModified, err := p.fetchReleases(ctx, remote, etag)
+	if err != nil {
+		return etag, false, err
+	}
+	if notModified {
+		return etag, false, nil
+	}
+
+	reader, ok := store.(provider.DebMetadataReader)
+	if !ok {
+		return newEtag, false, errors.New("store does not support deb metadata reads")
+	}
+	existing, err := reader.ListDebMetadataEntries(ctx, remote.Name)
+	if err != nil {
+		return newEtag, false, err
+	}
+	existingByPath := make(map[string]provider.DebMetadata, len(existing))
+	for _, m := range existing {
+		existingByPath[m.FilePath] = m
+	}
+
+	allow, err := compilePatterns(remote.Patterns)
+	if err != nil {
+		return newEtag, false, err
+	}
+
+	seen := map[string]bool{}
+	for _, rel := range releases {
+		if rel.Draft {
+			continue
+		}
+		for _, asset := range rel.Assets {
+			if !strings.HasSuffix(strings.ToLower(asset.Name), ".deb") {
+				continue
+			}
+			if !matchesAny(allow, asset.Name) {
+				continue
+			}
+			fp := assetPath(asset)
+			if fp == "" {
+				continue
+			}
+			seen[fp] = true
+
+			if cur, ok := existingByPath[fp]; ok {
+				if asset.Digest == "" || cur.ContentHash == asset.Digest {
+					continue
+				}
+				_ = store.DeleteDebMetadata(ctx, remote.Name, fp)
+			}
+
+			meta, err := p.deriveAsset(ctx, remote, asset, fp)
+			if err != nil {
+				slog.Warn("github_deb: derive asset failed", "remote", remote.Name, "asset", asset.Name, "error", err)
+				continue
+			}
+			if err := store.InsertDebMetadata(ctx, meta); err != nil {
+				slog.Error("github_deb: insert metadata failed", "remote", remote.Name, "asset", asset.Name, "error", err)
+				continue
+			}
+			slog.Info("github_deb: derived asset", "remote", remote.Name, "name", meta.Name, "version", meta.Version, "arch", meta.Architecture)
+		}
+	}
+
+	for fp := range existingByPath {
+		if !seen[fp] {
+			_ = store.DeleteDebMetadata(ctx, remote.Name, fp)
+		}
+	}
+	return newEtag, true, nil
+}
+
+type ghRelease struct {
+	TagName string    `json:"tag_name"`
+	Draft   bool      `json:"draft"`
+	Assets  []ghAsset `json:"assets"`
+}
+
+type ghAsset struct {
+	Name               string `json:"name"`
+	Size               int64  `json:"size"`
+	BrowserDownloadURL string `json:"browser_download_url"`
+	Digest             string `json:"digest"`
+}
+
+// fetchReleases lists a repo's releases, sending the prior ETag as If-None-Match
+// on page 1 so an unchanged repo short-circuits to notModified. Every call waits
+// on the shared limiter first.
+func (p *GitHubProvider) fetchReleases(ctx context.Context, remote models.Remote, etag string) (all []ghRelease, newEtag string, notModified bool, err error) {
+	base := strings.TrimRight(remote.BaseURL, "/") + "/releases"
+	for page := 1; page <= p.pageCap; page++ {
+		u := fmt.Sprintf("%s?per_page=100&page=%d", base, page)
+		req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
+		if err != nil {
+			return nil, "", false, err
+		}
+		hdr, err := p.githubHeaders(ctx, remote, true)
+		if err != nil {
+			return nil, "", false, err
+		}
+		copyHeaders(req, hdr)
+		if page == 1 && etag != "" {
+			req.Header.Set("If-None-Match", etag)
+		}
+
+		if err := p.limiterWait(ctx); err != nil {
+			return nil, "", false, err
+		}
+		resp, err := p.client.Do(req)
+		if err != nil {
+			return nil, "", false, err
+		}
+		if page == 1 && resp.StatusCode == http.StatusNotModified {
+			io.Copy(io.Discard, resp.Body)
+			resp.Body.Close()
+			return nil, etag, true, nil
+		}
+		body, err := io.ReadAll(resp.Body)
+		respEtag := resp.Header.Get("ETag")
+		resp.Body.Close()
+		if err != nil {
+			return nil, "", false, err
+		}
+		if resp.StatusCode != http.StatusOK {
+			return nil, "", false, fmt.Errorf("github releases API %s: status %d", u, resp.StatusCode)
+		}
+		if page == 1 {
+			newEtag = respEtag
+		}
+		var releases []ghRelease
+		if err := json.Unmarshal(body, &releases); err != nil {
+			return nil, "", false, fmt.Errorf("decode releases: %w", err)
+		}
+		if len(releases) == 0 {
+			break
+		}
+		all = append(all, releases...)
+		if len(releases) < 100 {
+			break
+		}
+	}
+	return all, newEtag, false, nil
+}
+
+func (p *GitHubProvider) deriveAsset(ctx context.Context, remote models.Remote, asset ghAsset, fp string) (*provider.DebMetadata, error) {
+	control, err := p.fetchControl(ctx, remote, asset.BrowserDownloadURL)
+	if err != nil {
+		return nil, err
+	}
+	fields := parseControlFields(control)
+
+	meta := &provider.DebMetadata{
+		RepoName:     remote.Name,
+		FilePath:     fp,
+		Name:         fields["Package"],
+		Version:      fields["Version"],
+		Architecture: fields["Architecture"],
+		Control:      strings.TrimRight(control, "\n"),
+		Size:         asset.Size,
+	}
+	if meta.Name == "" {
+		return nil, errors.New("control missing Package field")
+	}
+
+	// The Packages SHA256 must be the sha256 of the whole .deb. Prefer GitHub's
+	// asset digest so we never download the body; only when it is absent (or not
+	// sha256) do we stream the asset once. MD5sum is left unset — apt verifies the
+	// download against SHA256 alone under [trusted=yes].
+	if h, ok := sha256FromDigest(asset.Digest); ok {
+		meta.ContentHash = "sha256:" + h
+		meta.SHA256 = h
+	} else {
+		h, err := p.computeSHA256(ctx, remote, asset.BrowserDownloadURL)
+		if err != nil {
+			return nil, fmt.Errorf("compute sha256: %w", err)
+		}
+		meta.ContentHash = "sha256:" + h
+		meta.SHA256 = h
+	}
+
+	return meta, nil
+}
+
+// fetchControl pulls only the front of the .deb with a ranged GET and extracts
+// the control paragraph from it. control.tar sits right after the tiny
+// debian-binary member, so a small prefix suffices; a prefix that truncates the
+// control member doubles the range and retries.
+func (p *GitHubProvider) fetchControl(ctx context.Context, remote models.Remote, downloadURL string) (string, error) {
+	n := p.headerInitial
+	for {
+		body, full, err := p.rangeGet(ctx, remote, downloadURL, n)
+		if err != nil {
+			return "", err
+		}
+		control, complete, perr := controlFromPrefix(body)
+		if perr != nil {
+			return "", fmt.Errorf("parse deb control: %w", perr)
+		}
+		if complete {
+			return control, nil
+		}
+		if full || n >= p.headerMax {
+			return "", fmt.Errorf("control.tar not found within %d bytes of %s", n, downloadURL)
+		}
+		n *= 2
+		if n > p.headerMax {
+			n = p.headerMax
+		}
+	}
+}
+
+// controlFromPrefix parses the ar members present in a front prefix of a .deb.
+// It returns the ./control paragraph once control.tar.* is fully covered
+// (complete=true); a prefix too short to cover it returns complete=false so the
+// caller can widen the range. Later members (data.tar.*) are ignored.
+func controlFromPrefix(prefix []byte) (control string, complete bool, err error) {
+	const magic = "!<arch>\n"
+	if len(prefix) < len(magic) {
+		return "", false, nil
+	}
+	if string(prefix[:len(magic)]) != magic {
+		return "", false, errors.New("not an ar archive")
+	}
+	off := len(magic)
+	for {
+		if off+60 > len(prefix) {
+			return "", false, nil
+		}
+		hdr := prefix[off : off+60]
+		off += 60
+		name := strings.TrimSuffix(strings.TrimRight(string(hdr[0:16]), " "), "/")
+		size, err := strconv.ParseInt(strings.TrimSpace(string(hdr[48:58])), 10, 64)
+		if err != nil {
+			return "", false, fmt.Errorf("bad ar size for %q: %w", name, err)
+		}
+		if strings.HasPrefix(name, "control.tar") {
+			if off+int(size) > len(prefix) {
+				return "", false, nil
+			}
+			tarBytes, err := decompress(name, prefix[off:off+int(size)])
+			if err != nil {
+				return "", false, err
+			}
+			c, err := readControlParagraph(tarBytes)
+			if err != nil {
+				return "", false, err
+			}
+			return c, true, nil
+		}
+		if off+int(size) > len(prefix) {
+			return "", false, nil
+		}
+		off += int(size)
+		if size%2 == 1 {
+			off++
+		}
+	}
+}
+
+// rangeGet returns the first n bytes of downloadURL. full is true when the
+// response body was shorter than n (i.e. we already have the whole object).
+func (p *GitHubProvider) rangeGet(ctx context.Context, remote models.Remote, downloadURL string, n int64) ([]byte, bool, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, downloadURL, nil)
+	if err != nil {
+		return nil, false, err
+	}
+	hdr, err := p.githubHeaders(ctx, remote, false)
+	if err != nil {
+		return nil, false, err
+	}
+	copyHeaders(req, hdr)
+	req.Header.Set("Range", fmt.Sprintf("bytes=0-%d", n-1))
+
+	if err := p.limiterWait(ctx); err != nil {
+		return nil, false, err
+	}
+	resp, err := p.client.Do(req)
+	if err != nil {
+		return nil, false, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusPartialContent {
+		return nil, false, fmt.Errorf("range GET %s: status %d", downloadURL, resp.StatusCode)
+	}
+
+	body, err := io.ReadAll(io.LimitReader(resp.Body, n))
+	if err != nil {
+		return nil, false, err
+	}
+	full := int64(len(body)) < n
+	return body, full, nil
+}
+
+func (p *GitHubProvider) computeSHA256(ctx context.Context, remote models.Remote, downloadURL string) (string, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, downloadURL, nil)
+	if err != nil {
+		return "", err
+	}
+	hdr, err := p.githubHeaders(ctx, remote, false)
+	if err != nil {
+		return "", err
+	}
+	copyHeaders(req, hdr)
+
+	if err := p.limiterWait(ctx); err != nil {
+		return "", err
+	}
+	resp, err := p.client.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("GET %s: status %d", downloadURL, resp.StatusCode)
+	}
+
+	h := sha256.New()
+	if _, err := io.Copy(h, resp.Body); err != nil {
+		return "", err
+	}
+	return hex.EncodeToString(h.Sum(nil)), nil
+}
+
+// assetPath is the package's location relative to github.com — the path the
+// backend releases_remote (base https://github.com) proxies. It doubles as the
+// deb_metadata key and the Filename field in the Packages index, so a .deb
+// download resolves back to this remote and redirects to the backend.
+func assetPath(asset ghAsset) string {
+	u, err := url.Parse(asset.BrowserDownloadURL)
+	if err != nil {
+		return ""
+	}
+	return strings.TrimPrefix(u.Path, "/")
+}
+
+func sha256FromDigest(digest string) (string, bool) {
+	if strings.HasPrefix(digest, "sha256:") {
+		return strings.TrimPrefix(digest, "sha256:"), true
+	}
+	return "", false
+}
+
+// githubHeaders builds the outbound headers for a GitHub request, attaching a
+// bearer credential when one is available. A per-remote credential wins; absent
+// that, the process-wide server credential is used; absent both, the request is
+// unauthenticated.
+func (p *GitHubProvider) githubHeaders(ctx context.Context, remote models.Remote, api bool) (http.Header, error) {
+	h := http.Header{}
+	if api {
+		h.Set("Accept", "application/vnd.github+json")
+		h.Set("X-GitHub-Api-Version", "2022-11-28")
+	}
+	tok, err := p.githubToken(ctx, remote)
+	if err != nil {
+		return nil, err
+	}
+	if tok != "" {
+		h.Set("Authorization", "Bearer "+tok)
+	}
+	return h, nil
+}
+
+// githubToken resolves the bearer token for a remote. Precedence: a per-remote
+// credential (password, then username) overrides the server credential.
+func (p *GitHubProvider) githubToken(ctx context.Context, remote models.Remote) (string, error) {
+	if remote.Password != "" {
+		return remote.Password, nil
+	}
+	if remote.Username != "" {
+		return remote.Username, nil
+	}
+	if c := p.serverCredential(); c != nil {
+		return c.Token(ctx)
+	}
+	return "", nil
+}
+
+func (p *GitHubProvider) serverCredential() githubauth.Credential {
+	if p.serverCred != nil {
+		return p.serverCred
+	}
+	return githubauth.Server()
+}
+
+func copyHeaders(req *http.Request, h http.Header) {
+	for k, vals := range h {
+		for _, v := range vals {
+			req.Header.Add(k, v)
+		}
+	}
+}
+
+func compilePatterns(patterns []string) ([]*regexp.Regexp, error) {
+	var out []*regexp.Regexp
+	for _, p := range patterns {
+		re, err := regexp.Compile(p)
+		if err != nil {
+			return nil, fmt.Errorf("invalid pattern %q: %w", p, err)
+		}
+		out = append(out, re)
+	}
+	return out, nil
+}
+
+func matchesAny(res []*regexp.Regexp, s string) bool {
+	if len(res) == 0 {
+		return true
+	}
+	for _, re := range res {
+		if re.MatchString(s) {
+			return true
+		}
+	}
+	return false
+}

internal/provider/deb/github_test.go

@@ -0,0 +1,462 @@
+package deb
+
+import (
+	"bytes"
+	"compress/gzip"
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strconv"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/internal/testsupport"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+// fakeStore is an in-memory provider.RemoteMetadataStore + DebMetadataReader
+// keyed by file_path, mirroring the (repo_name, file_path) uniqueness of the
+// real deb_metadata table.
+type fakeStore struct {
+	mu   sync.Mutex
+	rows map[string]provider.DebMetadata
+}
+
+func newFakeStore() *fakeStore { return &fakeStore{rows: map[string]provider.DebMetadata{}} }
+
+func (f *fakeStore) InsertDebMetadata(_ context.Context, m *provider.DebMetadata) error {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if _, ok := f.rows[m.FilePath]; ok {
+		return nil // ON CONFLICT DO NOTHING
+	}
+	f.rows[m.FilePath] = *m
+	return nil
+}
+
+func (f *fakeStore) DeleteDebMetadata(_ context.Context, _, filePath string) error {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	delete(f.rows, filePath)
+	return nil
+}
+
+func (f *fakeStore) InsertRPMMetadata(context.Context, *provider.RPMMetadata) error { return nil }
+func (f *fakeStore) DeleteRPMMetadata(context.Context, string, string) error        { return nil }
+func (f *fakeStore) ListRPMMetadataEntries(context.Context, string) ([]provider.RPMMetadata, error) {
+	return nil, nil
+}
+
+func (f *fakeStore) ListDebMetadataEntries(ctx context.Context, _ string) ([]provider.DebMetadata, error) {
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	out := make([]provider.DebMetadata, 0, len(f.rows))
+	for _, m := range f.rows {
+		out = append(out, m)
+	}
+	return out, nil
+}
+
+// githubFixture serves the releases API and the .deb asset downloads (with Range
+// support) for a set of packages. digest controls whether the asset carries a
+// sha256 digest (no-download path) or not (compute path).
+type githubFixture struct {
+	srv         *httptest.Server
+	debBytes    map[string][]byte
+	rangeHit    map[string]int
+	fullHit     map[string]int
+	etag        string
+	releasesHit int
+	notModHit   int
+	releaseAuth string
+	assetAuth   string
+	mu          sync.Mutex
+}
+
+func newGitHubFixture(t *testing.T, withDigest bool) *githubFixture {
+	t.Helper()
+	f := &githubFixture{
+		debBytes: map[string][]byte{},
+		rangeHit: map[string]int{},
+		fullHit:  map[string]int{},
+	}
+	f.debBytes["demo_1.2-3_amd64.deb"] = testsupport.MinimalDeb("demo", "1.2-3", "amd64")
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("/repos/acme/tools/releases", func(w http.ResponseWriter, r *http.Request) {
+		page := r.URL.Query().Get("page")
+		if page != "" && page != "1" {
+			w.Write([]byte("[]"))
+			return
+		}
+		f.mu.Lock()
+		f.releasesHit++
+		f.releaseAuth = r.Header.Get("Authorization")
+		etag := f.etag
+		if etag != "" && r.Header.Get("If-None-Match") == etag {
+			f.notModHit++
+			f.mu.Unlock()
+			w.WriteHeader(http.StatusNotModified)
+			return
+		}
+		f.mu.Unlock()
+		if etag != "" {
+			w.Header().Set("ETag", etag)
+		}
+		var assets []map[string]any
+		for name := range f.debBytes {
+			a := map[string]any{
+				"name":                 name,
+				"size":                 len(f.debBytes[name]),
+				"browser_download_url": f.srv.URL + "/acme/tools/releases/download/v1.2-3/" + name,
+			}
+			if withDigest {
+				sum := sha256.Sum256(f.debBytes[name])
+				a["digest"] = "sha256:" + hex.EncodeToString(sum[:])
+			}
+			assets = append(assets, a)
+		}
+		rel := []map[string]any{{"tag_name": "v1.2-3", "draft": false, "assets": assets}}
+		json.NewEncoder(w).Encode(rel)
+	})
+	mux.HandleFunc("/acme/tools/releases/download/", func(w http.ResponseWriter, r *http.Request) {
+		name := r.URL.Path[strings.LastIndex(r.URL.Path, "/")+1:]
+		body, ok := f.debBytes[name]
+		if !ok {
+			http.Error(w, "not found", 404)
+			return
+		}
+		rng := r.Header.Get("Range")
+		f.mu.Lock()
+		f.assetAuth = r.Header.Get("Authorization")
+		if rng != "" {
+			f.rangeHit[name]++
+		} else {
+			f.fullHit[name]++
+		}
+		f.mu.Unlock()
+
+		if rng == "" {
+			w.WriteHeader(200)
+			w.Write(body)
+			return
+		}
+		var end int
+		fmt.Sscanf(rng, "bytes=0-%d", &end)
+		if end >= len(body)-1 {
+			end = len(body) - 1
+		}
+		w.Header().Set("Content-Range", fmt.Sprintf("bytes 0-%d/%d", end, len(body)))
+		w.Header().Set("Content-Length", strconv.Itoa(end+1))
+		w.WriteHeader(http.StatusPartialContent)
+		w.Write(body[:end+1])
+	})
+	f.srv = httptest.NewServer(mux)
+	t.Cleanup(f.srv.Close)
+	return f
+}
+
+func (f *githubFixture) remote() models.Remote {
+	return models.Remote{
+		Name:           "acme-deb",
+		PackageType:    models.PackageGitHubDeb,
+		BaseURL:        f.srv.URL + "/repos/acme/tools",
+		ReleasesRemote: "github",
+		MutableTTL:     3600,
+	}
+}
+
+func newTestProvider() *GitHubProvider {
+	p := newGitHubProvider()
+	p.headerInitial = 32 // force the ranged-fetch retry loop against the tiny fixture
+	p.headerMax = 1 << 20
+	return p
+}
+
+const demoPath = "acme/tools/releases/download/v1.2-3/demo_1.2-3_amd64.deb"
+
+func TestGitHubScanDerivesControlFromPrefixAndDigest(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	store := newFakeStore()
+
+	if err := p.scan(context.Background(), fx.remote(), store); err != nil {
+		t.Fatalf("scan: %v", err)
+	}
+
+	metas, _ := store.ListDebMetadataEntries(context.Background(), "acme-deb")
+	if len(metas) != 1 {
+		t.Fatalf("want 1 metadata row, got %d", len(metas))
+	}
+	m := metas[0]
+	if m.Name != "demo" || m.Version != "1.2-3" || m.Architecture != "amd64" {
+		t.Fatalf("bad control fields: %+v", m)
+	}
+	if m.FilePath != demoPath {
+		t.Fatalf("FilePath = %q, want %q", m.FilePath, demoPath)
+	}
+	if int(m.Size) != len(fx.debBytes["demo_1.2-3_amd64.deb"]) {
+		t.Fatalf("Size = %d, want %d", m.Size, len(fx.debBytes["demo_1.2-3_amd64.deb"]))
+	}
+	sum := sha256.Sum256(fx.debBytes["demo_1.2-3_amd64.deb"])
+	if m.SHA256 != hex.EncodeToString(sum[:]) {
+		t.Fatalf("SHA256 = %q, want digest", m.SHA256)
+	}
+	if m.ContentHash != "sha256:"+hex.EncodeToString(sum[:]) {
+		t.Fatalf("ContentHash = %q", m.ContentHash)
+	}
+	if m.MD5 != "" {
+		t.Fatalf("MD5 should be unset for metadata-only derive, got %q", m.MD5)
+	}
+	if fx.fullHit["demo_1.2-3_amd64.deb"] != 0 {
+		t.Fatalf("expected no full download when digest present, got %d", fx.fullHit["demo_1.2-3_amd64.deb"])
+	}
+	if fx.rangeHit["demo_1.2-3_amd64.deb"] == 0 {
+		t.Fatalf("expected ranged control fetch")
+	}
+	if !strings.Contains(m.Control, "Package: demo") {
+		t.Fatalf("raw control not captured: %q", m.Control)
+	}
+}
+
+func TestGitHubChecksumComputedWhenDigestAbsent(t *testing.T) {
+	fx := newGitHubFixture(t, false)
+	p := newTestProvider()
+	store := newFakeStore()
+
+	if err := p.scan(context.Background(), fx.remote(), store); err != nil {
+		t.Fatalf("scan: %v", err)
+	}
+	metas, _ := store.ListDebMetadataEntries(context.Background(), "acme-deb")
+	if len(metas) != 1 {
+		t.Fatalf("want 1 row, got %d", len(metas))
+	}
+	sum := sha256.Sum256(fx.debBytes["demo_1.2-3_amd64.deb"])
+	if metas[0].SHA256 != hex.EncodeToString(sum[:]) {
+		t.Fatalf("computed checksum mismatch: %q", metas[0].SHA256)
+	}
+	if fx.fullHit["demo_1.2-3_amd64.deb"] == 0 {
+		t.Fatalf("expected a full download to compute sha256 when digest absent")
+	}
+}
+
+func TestGitHubServeRemoteIndexAndRedirect(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	store := newFakeStore()
+	remote := fx.remote()
+	const proxyBase = "https://artifactapi.example"
+
+	// Release is served and triggers the initial scan.
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/remote/acme-deb/Release", nil)
+	if !p.ServeRemote(rec, req, remote, "Release", proxyBase, store) {
+		t.Fatal("ServeRemote did not handle Release")
+	}
+	if rec.Code != 200 || !strings.Contains(rec.Body.String(), "Architectures:") {
+		t.Fatalf("Release bad: code=%d body=%s", rec.Code, rec.Body.String())
+	}
+	if !strings.Contains(rec.Body.String(), "amd64") {
+		t.Fatalf("Release missing arch: %s", rec.Body.String())
+	}
+
+	// Packages carries the package with a Filename that is the github-relative
+	// download path (so it resolves back to this remote and redirects).
+	rec = httptest.NewRecorder()
+	req = httptest.NewRequest(http.MethodGet, "/x", nil)
+	if !p.ServeRemote(rec, req, remote, "Packages", proxyBase, store) {
+		t.Fatal("ServeRemote did not handle Packages")
+	}
+	pkgs := rec.Body.String()
+	if !strings.Contains(pkgs, "Package: demo") {
+		t.Fatalf("Packages missing package: %s", pkgs)
+	}
+	if !strings.Contains(pkgs, "Filename: "+demoPath) {
+		t.Fatalf("Packages missing/incorrect Filename: %s", pkgs)
+	}
+	if !strings.Contains(pkgs, "SHA256: ") {
+		t.Fatalf("Packages missing SHA256: %s", pkgs)
+	}
+	if strings.Contains(pkgs, "MD5sum:") {
+		t.Fatalf("Packages should omit empty MD5sum: %s", pkgs)
+	}
+
+	// Packages.gz decompresses to the same content.
+	rec = httptest.NewRecorder()
+	req = httptest.NewRequest(http.MethodGet, "/x", nil)
+	if !p.ServeRemote(rec, req, remote, "Packages.gz", proxyBase, store) {
+		t.Fatal("ServeRemote did not handle Packages.gz")
+	}
+	gz, err := gzip.NewReader(rec.Body)
+	if err != nil {
+		t.Fatalf("gzip: %v", err)
+	}
+	unz, _ := io.ReadAll(gz)
+	if !strings.Contains(string(unz), "Package: demo") {
+		t.Fatalf("Packages.gz missing package: %s", unz)
+	}
+
+	// InRelease/Release.gpg 404 (unsigned, consumed via [trusted=yes]).
+	for _, sp := range []string{"InRelease", "Release.gpg"} {
+		rec = httptest.NewRecorder()
+		req = httptest.NewRequest(http.MethodGet, "/x", nil)
+		if !p.ServeRemote(rec, req, remote, sp, proxyBase, store) {
+			t.Fatalf("ServeRemote did not handle %s", sp)
+		}
+		if rec.Code != http.StatusNotFound {
+			t.Fatalf("%s want 404, got %d", sp, rec.Code)
+		}
+	}
+
+	// A .deb request redirects to the backend releases_remote.
+	rec = httptest.NewRecorder()
+	req = httptest.NewRequest(http.MethodGet, "/api/v1/remote/acme-deb/"+demoPath, nil)
+	if !p.ServeRemote(rec, req, remote, demoPath, proxyBase, store) {
+		t.Fatal("ServeRemote did not handle .deb")
+	}
+	if rec.Code != http.StatusFound {
+		t.Fatalf("want 302, got %d", rec.Code)
+	}
+	wantLoc := proxyBase + "/api/v1/remote/github/" + demoPath
+	if got := rec.Header().Get("Location"); got != wantLoc {
+		t.Fatalf("Location = %q, want %q", got, wantLoc)
+	}
+}
+
+// Real apt appends the flat-repo dist "./" verbatim, so the metadata-only remote
+// receives "./Packages" / "./Release"; ServeRemote must collapse the dot-segment
+// and synthesize the same index as the un-prefixed request.
+func TestGitHubServeRemoteAptDotSegment(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	store := newFakeStore()
+	remote := fx.remote()
+	const proxyBase = "https://artifactapi.example"
+
+	serve := func(path string) *httptest.ResponseRecorder {
+		rec := httptest.NewRecorder()
+		req := httptest.NewRequest(http.MethodGet, "/api/v1/remote/acme-deb/"+path, nil)
+		if !p.ServeRemote(rec, req, remote, path, proxyBase, store) {
+			t.Fatalf("ServeRemote did not handle %q", path)
+		}
+		return rec
+	}
+
+	// Packages is deterministic: byte-identical to the un-prefixed request.
+	plain, dotted := serve("Packages"), serve("./Packages")
+	if plain.Code != 200 || dotted.Code != 200 {
+		t.Fatalf("Packages: plain=%d dotted=%d, want 200/200", plain.Code, dotted.Code)
+	}
+	if !strings.Contains(dotted.Body.String(), "Package: demo") {
+		t.Fatalf("./Packages missing synthesized body: %s", dotted.Body.String())
+	}
+	if !bytes.Equal(plain.Body.Bytes(), dotted.Body.Bytes()) {
+		t.Error("./Packages body differs from Packages body")
+	}
+
+	// Release carries a time.Now() Date: header; compare the rest.
+	rPlain, rDotted := serve("Release"), serve("./Release")
+	if rPlain.Code != 200 || rDotted.Code != 200 {
+		t.Fatalf("Release: plain=%d dotted=%d, want 200/200", rPlain.Code, rDotted.Code)
+	}
+	if stripDate(rPlain.Body.String()) != stripDate(rDotted.Body.String()) {
+		t.Error("./Release body differs from Release body (ignoring Date)")
+	}
+}
+
+// A canceled inbound request must still serve the warm cache (detached context),
+// not turn the metadata read into a 500.
+func TestGitHubServeRemoteCanceledRequestServesCache(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	store := newFakeStore()
+	remote := fx.remote()
+
+	if err := p.scan(context.Background(), remote, store); err != nil {
+		t.Fatalf("warm scan: %v", err)
+	}
+	p.mu.Lock()
+	p.lastScan[remote.Name] = time.Now()
+	p.mu.Unlock()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/remote/acme-deb/Packages", nil).WithContext(ctx)
+
+	if !p.ServeRemote(rec, req, remote, "Packages", "https://x", store) {
+		t.Fatal("ServeRemote did not handle Packages")
+	}
+	if rec.Code != http.StatusOK {
+		t.Fatalf("canceled request must serve cache, not error; got code=%d body=%s", rec.Code, rec.Body.String())
+	}
+	if !strings.Contains(rec.Body.String(), "Package: demo") {
+		t.Fatalf("expected Packages served from cache, got %s", rec.Body.String())
+	}
+}
+
+func TestGitHubServeRemoteRedirectRequiresReleasesRemote(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	store := newFakeStore()
+	remote := fx.remote()
+	remote.ReleasesRemote = ""
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/x", nil)
+	if !p.ServeRemote(rec, req, remote, demoPath, "https://x", store) {
+		t.Fatal("expected handled")
+	}
+	if rec.Code != http.StatusInternalServerError {
+		t.Fatalf("want 500 when releases_remote unset, got %d", rec.Code)
+	}
+}
+
+func TestGitHubScanPrunesRemovedAssets(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	store := newFakeStore()
+
+	if err := p.scan(context.Background(), fx.remote(), store); err != nil {
+		t.Fatalf("scan: %v", err)
+	}
+	if rows, _ := store.ListDebMetadataEntries(context.Background(), "acme-deb"); len(rows) != 1 {
+		t.Fatalf("want 1 row after first scan, got %d", len(rows))
+	}
+
+	delete(fx.debBytes, "demo_1.2-3_amd64.deb")
+	if err := p.scan(context.Background(), fx.remote(), store); err != nil {
+		t.Fatalf("rescan: %v", err)
+	}
+	if rows, _ := store.ListDebMetadataEntries(context.Background(), "acme-deb"); len(rows) != 0 {
+		t.Fatalf("want 0 rows after prune, got %d", len(rows))
+	}
+}
+
+func TestGitHubAssetPatternFilter(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	fx.debBytes["other_9_arm64.deb"] = testsupport.MinimalDeb("other", "9", "arm64")
+	p := newTestProvider()
+	store := newFakeStore()
+	remote := fx.remote()
+	remote.Patterns = []string{`^demo_.*_amd64\.deb$`}
+
+	if err := p.scan(context.Background(), remote, store); err != nil {
+		t.Fatalf("scan: %v", err)
+	}
+	rows, _ := store.ListDebMetadataEntries(context.Background(), "acme-deb")
+	if len(rows) != 1 || rows[0].Name != "demo" {
+		t.Fatalf("pattern filter failed, rows=%+v", rows)
+	}
+}

internal/provider/deb/syncer.go

@@ -0,0 +1,238 @@
+package deb
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/hex"
+	"log/slog"
+	"os"
+	"sync"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+const (
+	syncLeaseDuration    = 15 * time.Minute
+	defaultSyncFreshness = 5 * time.Minute
+	jobQueueDepth        = 256
+)
+
+// SyncStore is the persistence surface the deb syncer needs: the metadata cache
+// it primes plus the shared sync-state coordination (remote enumeration and the
+// per-remote lease). *database.DB satisfies it.
+type SyncStore interface {
+	provider.RemoteMetadataStore
+	ListGitHubDebRemotes(ctx context.Context) ([]models.Remote, error)
+	ClaimGitHubDebSyncLease(ctx context.Context, remoteName, owner string, freshness, lease time.Duration) (claimed bool, etag string, err error)
+	ReleaseGitHubDebSyncLease(ctx context.Context, remoteName, owner, etag string, syncedAt time.Time) error
+}
+
+// SyncConfig tunes the shared syncer. Zero values fall back to safe defaults.
+type SyncConfig struct {
+	RatePerSec   float64
+	Burst        int
+	Workers      int
+	PollInterval time.Duration
+}
+
+type syncJob struct {
+	remote models.Remote
+	prime  bool
+}
+
+// Syncer is the single per-process background worker that keeps every github_deb
+// remote's derived metadata fresh. It owns a deduped work queue, a pool of
+// workers, and a global token-bucket rate limiter shared across all remotes and
+// bound onto the github_deb provider. Periodic checks are gated by a shared DB
+// lease so, across replicas, only one performs each scan.
+type Syncer struct {
+	store   SyncStore
+	prov    *GitHubProvider
+	limiter *rate.Limiter
+	cfg     SyncConfig
+	owner   string
+
+	jobs   chan syncJob
+	mu     sync.Mutex
+	active map[string]bool
+}
+
+// NewSyncer builds the syncer bound to the process-wide github_deb provider
+// singleton. Call Run to start it.
+func NewSyncer(store SyncStore, cfg SyncConfig) *Syncer {
+	return newSyncer(store, gitHubProvider, cfg)
+}
+
+func newSyncer(store SyncStore, prov *GitHubProvider, cfg SyncConfig) *Syncer {
+	if cfg.RatePerSec <= 0 {
+		cfg.RatePerSec = 1
+	}
+	if cfg.Burst <= 0 {
+		cfg.Burst = 5
+	}
+	if cfg.Workers <= 0 {
+		cfg.Workers = 3
+	}
+	if cfg.PollInterval <= 0 {
+		cfg.PollInterval = 60 * time.Second
+	}
+
+	lim := rate.NewLimiter(rate.Limit(cfg.RatePerSec), cfg.Burst)
+	s := &Syncer{
+		store:   store,
+		prov:    prov,
+		limiter: lim,
+		cfg:     cfg,
+		owner:   leaseOwner(),
+		jobs:    make(chan syncJob, jobQueueDepth),
+		active:  map[string]bool{},
+	}
+	prov.limiter = lim
+	prov.syncer = s
+	return s
+}
+
+// Run starts the worker pool and the periodic scheduler and blocks until ctx is
+// canceled, at which point it drains in-flight scans and returns.
+func (s *Syncer) Run(ctx context.Context) {
+	slog.Info("github_deb syncer started",
+		"rate_per_sec", s.cfg.RatePerSec, "burst", s.cfg.Burst,
+		"workers", s.cfg.Workers, "poll_interval", s.cfg.PollInterval, "owner", s.owner)
+
+	var wg sync.WaitGroup
+	for i := 0; i < s.cfg.Workers; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			s.worker(ctx)
+		}()
+	}
+
+	ticker := time.NewTicker(s.cfg.PollInterval)
+	defer ticker.Stop()
+
+	s.schedule(ctx)
+	for {
+		select {
+		case <-ctx.Done():
+			wg.Wait()
+			slog.Info("github_deb syncer stopped")
+			return
+		case <-ticker.C:
+			s.schedule(ctx)
+		}
+	}
+}
+
+// schedule enqueues a periodic check for every github_deb remote. The DB lease
+// enforces the per-remote mutable_ttl cadence and cross-replica coordination.
+func (s *Syncer) schedule(ctx context.Context) {
+	remotes, err := s.store.ListGitHubDebRemotes(ctx)
+	if err != nil {
+		slog.Error("github_deb syncer: list remotes", "error", err)
+		return
+	}
+	for _, r := range remotes {
+		s.enqueue(r, false)
+	}
+}
+
+// EnqueuePrime queues an immediate background prime for a freshly created remote.
+func (s *Syncer) EnqueuePrime(remote models.Remote) {
+	if s == nil {
+		return
+	}
+	s.enqueue(remote, true)
+}
+
+// enqueue adds a job unless the remote is already queued or in-flight, coalescing
+// duplicate requests down to one scan. It never blocks.
+func (s *Syncer) enqueue(remote models.Remote, prime bool) {
+	s.mu.Lock()
+	if s.active[remote.Name] {
+		s.mu.Unlock()
+		return
+	}
+	s.active[remote.Name] = true
+	s.mu.Unlock()
+
+	select {
+	case s.jobs <- syncJob{remote: remote, prime: prime}:
+	default:
+		s.mu.Lock()
+		delete(s.active, remote.Name)
+		s.mu.Unlock()
+	}
+}
+
+func (s *Syncer) worker(ctx context.Context) {
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case job := <-s.jobs:
+			s.process(ctx, job)
+		}
+	}
+}
+
+// process claims the shared lease and, if won, runs an incremental scan. Losing
+// the claim (another replica scanning, or not yet due) is a no-op.
+func (s *Syncer) process(ctx context.Context, job syncJob) {
+	defer func() {
+		s.mu.Lock()
+		delete(s.active, job.remote.Name)
+		s.mu.Unlock()
+	}()
+
+	freshness := time.Duration(job.remote.MutableTTL) * time.Second
+	if freshness <= 0 {
+		freshness = defaultSyncFreshness
+	}
+	if job.prime {
+		freshness = 0
+	}
+
+	claimed, etag, err := s.store.ClaimGitHubDebSyncLease(ctx, job.remote.Name, s.owner, freshness, syncLeaseDuration)
+	if err != nil {
+		slog.Error("github_deb syncer: claim lease", "remote", job.remote.Name, "error", err)
+		return
+	}
+	if !claimed {
+		return
+	}
+
+	scanCtx, cancel := context.WithTimeout(ctx, s.prov.scanTimeout)
+	defer cancel()
+
+	newEtag, changed, scanErr := s.prov.scanWithState(scanCtx, job.remote, s.store, etag)
+	releaseEtag := etag
+	if scanErr == nil {
+		releaseEtag = newEtag
+	} else {
+		slog.Error("github_deb syncer: scan failed", "remote", job.remote.Name, "error", scanErr)
+	}
+
+	relCtx, relCancel := context.WithTimeout(context.WithoutCancel(ctx), 10*time.Second)
+	defer relCancel()
+	if err := s.store.ReleaseGitHubDebSyncLease(relCtx, job.remote.Name, s.owner, releaseEtag, time.Now()); err != nil {
+		slog.Warn("github_deb syncer: release lease", "remote", job.remote.Name, "error", err)
+	}
+
+	if scanErr == nil && changed {
+		slog.Info("github_deb syncer: refreshed", "remote", job.remote.Name, "prime", job.prime)
+	}
+}
+
+// leaseOwner is a per-replica identity for the lease: hostname plus a random
+// suffix so restarts and colocated replicas never collide.
+func leaseOwner() string {
+	host, _ := os.Hostname()
+	var b [6]byte
+	_, _ = rand.Read(b[:])
+	return host + "-" + hex.EncodeToString(b[:])
+}

internal/provider/deb/syncer_test.go

@@ -0,0 +1,300 @@
+package deb
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"sync"
+	"testing"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/internal/testsupport"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+// fakeSyncStore is an in-memory SyncStore: the metadata cache (via the embedded
+// fakeStore) plus the shared sync-state lease, whose claim mirrors the atomic
+// semantics of the real SQL (recency gate AND no live lease).
+type fakeSyncStore struct {
+	*fakeStore
+
+	mu         sync.Mutex
+	remotes    []models.Remote
+	leaseOwner map[string]string
+	leaseExp   map[string]time.Time
+	lastSynced map[string]time.Time
+	etags      map[string]string
+}
+
+func newFakeSyncStore() *fakeSyncStore {
+	return &fakeSyncStore{
+		fakeStore:  newFakeStore(),
+		leaseOwner: map[string]string{},
+		leaseExp:   map[string]time.Time{},
+		lastSynced: map[string]time.Time{},
+		etags:      map[string]string{},
+	}
+}
+
+func (f *fakeSyncStore) ListGitHubDebRemotes(_ context.Context) ([]models.Remote, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	return append([]models.Remote(nil), f.remotes...), nil
+}
+
+func (f *fakeSyncStore) ClaimGitHubDebSyncLease(_ context.Context, name, owner string, freshness, lease time.Duration) (bool, string, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	now := time.Now()
+	ls, hasLS := f.lastSynced[name]
+	exp, hasExp := f.leaseExp[name]
+	freshOK := !hasLS || now.Sub(ls) >= freshness
+	leaseOK := !hasExp || exp.Before(now)
+	if freshOK && leaseOK {
+		f.leaseOwner[name] = owner
+		f.leaseExp[name] = now.Add(lease)
+		return true, f.etags[name], nil
+	}
+	return false, "", nil
+}
+
+func (f *fakeSyncStore) ReleaseGitHubDebSyncLease(_ context.Context, name, owner, etag string, syncedAt time.Time) error {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if f.leaseOwner[name] != owner {
+		return nil
+	}
+	f.lastSynced[name] = syncedAt
+	f.etags[name] = etag
+	delete(f.leaseOwner, name)
+	delete(f.leaseExp, name)
+	return nil
+}
+
+func testSyncConfig() SyncConfig {
+	return SyncConfig{RatePerSec: 1000, Burst: 100, Workers: 1, PollInterval: time.Hour}
+}
+
+// (a) A 304 conditional response must derive nothing: no asset fetches and
+// changed=false, so an unchanged repo is nearly free.
+func TestSyncerConditionalNotModifiedSkipsDerive(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	fx.etag = `"v1"`
+	p := newTestProvider()
+	store := newFakeStore()
+	remote := fx.remote()
+
+	etag1, changed, err := p.scanWithState(context.Background(), remote, store, "")
+	if err != nil {
+		t.Fatalf("first scan: %v", err)
+	}
+	if !changed || etag1 != `"v1"` {
+		t.Fatalf("first scan changed=%v etag=%q, want true and \"v1\"", changed, etag1)
+	}
+	priorRange := fx.rangeHit["demo_1.2-3_amd64.deb"]
+	if priorRange == 0 {
+		t.Fatal("first scan should have fetched the asset control")
+	}
+
+	etag2, changed2, err := p.scanWithState(context.Background(), remote, store, etag1)
+	if err != nil {
+		t.Fatalf("second scan: %v", err)
+	}
+	if changed2 {
+		t.Fatal("304 scan must report changed=false")
+	}
+	if etag2 != etag1 {
+		t.Fatalf("etag changed across 304: %q -> %q", etag1, etag2)
+	}
+	if fx.notModHit != 1 {
+		t.Fatalf("want exactly one 304 releases response, got %d", fx.notModHit)
+	}
+	if got := fx.rangeHit["demo_1.2-3_amd64.deb"]; got != priorRange {
+		t.Fatalf("304 scan re-fetched asset control: %d -> %d", priorRange, got)
+	}
+}
+
+// (b) On a real change, only the newly added asset is derived.
+func TestSyncerIncrementalDerivesOnlyNewAsset(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	fx.etag = `"v1"`
+	p := newTestProvider()
+	store := newFakeStore()
+	remote := fx.remote()
+
+	if _, _, err := p.scanWithState(context.Background(), remote, store, ""); err != nil {
+		t.Fatalf("first scan: %v", err)
+	}
+	demoRange := fx.rangeHit["demo_1.2-3_amd64.deb"]
+
+	fx.debBytes["other_9_arm64.deb"] = testsupport.MinimalDeb("other", "9", "arm64")
+	fx.etag = `"v2"`
+
+	if _, changed, err := p.scanWithState(context.Background(), remote, store, `"v1"`); err != nil || !changed {
+		t.Fatalf("second scan changed=%v err=%v", changed, err)
+	}
+
+	rows, _ := store.ListDebMetadataEntries(context.Background(), remote.Name)
+	if len(rows) != 2 {
+		t.Fatalf("want 2 cached rows after incremental derive, got %d", len(rows))
+	}
+	if got := fx.rangeHit["demo_1.2-3_amd64.deb"]; got != demoRange {
+		t.Fatalf("already-cached asset was re-fetched: %d -> %d", demoRange, got)
+	}
+	if fx.rangeHit["other_9_arm64.deb"] == 0 {
+		t.Fatal("newly added asset was not derived")
+	}
+}
+
+// (c) The shared limiter caps the request rate.
+func TestRateLimiterCapsRequestRate(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	p.limiter = rate.NewLimiter(rate.Every(120*time.Millisecond), 1)
+	remote := fx.remote()
+
+	start := time.Now()
+	for i := 0; i < 3; i++ {
+		if _, _, _, err := p.fetchReleases(context.Background(), remote, ""); err != nil {
+			t.Fatalf("fetchReleases %d: %v", i, err)
+		}
+	}
+	if elapsed := time.Since(start); elapsed < 200*time.Millisecond {
+		t.Fatalf("rate limiter did not throttle: 3 calls took %v, want >= 200ms", elapsed)
+	}
+}
+
+// (d) Concurrent enqueues for the same remote coalesce to a single queued job.
+func TestSyncerEnqueueDedup(t *testing.T) {
+	store := newFakeSyncStore()
+	p := newTestProvider()
+	s := newSyncer(store, p, testSyncConfig())
+	remote := models.Remote{Name: "acme-deb", PackageType: models.PackageGitHubDeb, MutableTTL: 3600}
+
+	var wg sync.WaitGroup
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+		go func() { defer wg.Done(); s.enqueue(remote, false) }()
+	}
+	wg.Wait()
+
+	if got := len(s.jobs); got != 1 {
+		t.Fatalf("want exactly 1 coalesced job, got %d", got)
+	}
+}
+
+// (e) Prime-on-create enqueues a prime job.
+func TestSyncerEnqueuePrime(t *testing.T) {
+	store := newFakeSyncStore()
+	p := newTestProvider()
+	s := newSyncer(store, p, testSyncConfig())
+	remote := models.Remote{Name: "acme-deb", PackageType: models.PackageGitHubDeb, MutableTTL: 3600}
+
+	s.EnqueuePrime(remote)
+	select {
+	case job := <-s.jobs:
+		if !job.prime || job.remote.Name != "acme-deb" {
+			t.Fatalf("bad prime job: %+v", job)
+		}
+	default:
+		t.Fatal("EnqueuePrime did not enqueue a job")
+	}
+}
+
+// (f) A held lease prevents a second replica from scanning.
+func TestSyncerLeasePreventsSecondReplica(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	fx.etag = `"v1"`
+	store := newFakeSyncStore()
+	p := newTestProvider()
+	s := newSyncer(store, p, testSyncConfig())
+	remote := fx.remote()
+
+	claimed, _, err := store.ClaimGitHubDebSyncLease(context.Background(), remote.Name, "replica-1", time.Duration(remote.MutableTTL)*time.Second, syncLeaseDuration)
+	if err != nil || !claimed {
+		t.Fatalf("replica-1 claim: claimed=%v err=%v", claimed, err)
+	}
+
+	s.process(context.Background(), syncJob{remote: remote})
+
+	if fx.releasesHit != 0 {
+		t.Fatalf("second replica scanned while lease held: %d releases calls", fx.releasesHit)
+	}
+	if rows, _ := store.ListDebMetadataEntries(context.Background(), remote.Name); len(rows) != 0 {
+		t.Fatalf("second replica derived metadata while lease held: %d rows", len(rows))
+	}
+}
+
+// With the syncer wired and the cache empty, an index request enqueues a prime
+// and returns a retryable 503 when it has not landed within the cold wait.
+func TestServeRemoteColdStartReturns503(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	store := newFakeSyncStore()
+	p := newTestProvider()
+	p.coldWait = 300 * time.Millisecond
+	_ = newSyncer(store, p, testSyncConfig()) // binds p.syncer, but no workers running
+	remote := fx.remote()
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/remote/acme-deb/Packages", nil)
+	if !p.ServeRemote(rec, req, remote, "Packages", "https://x", store) {
+		t.Fatal("ServeRemote did not handle Packages")
+	}
+	if rec.Code != http.StatusServiceUnavailable {
+		t.Fatalf("cold empty cache must return 503, got %d", rec.Code)
+	}
+	if rec.Header().Get("Retry-After") == "" {
+		t.Fatal("503 should carry Retry-After")
+	}
+	if got := len(p.syncer.jobs); got != 1 {
+		t.Fatalf("cold start did not enqueue a prime, jobs=%d", got)
+	}
+}
+
+// With the cache warm, the same request serves the index immediately (no 503).
+func TestServeRemoteWarmCacheServesImmediately(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	store := newFakeSyncStore()
+	p := newTestProvider()
+	_ = newSyncer(store, p, testSyncConfig())
+	remote := fx.remote()
+
+	if err := p.scan(context.Background(), remote, store); err != nil {
+		t.Fatalf("warm scan: %v", err)
+	}
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/remote/acme-deb/Packages", nil)
+	if !p.ServeRemote(rec, req, remote, "Packages", "https://x", store) {
+		t.Fatal("ServeRemote did not handle Packages")
+	}
+	if rec.Code != http.StatusOK {
+		t.Fatalf("warm cache must serve 200, got %d body=%s", rec.Code, rec.Body.String())
+	}
+}
+
+// A prime job (freshness 0) runs even right after a sync; a periodic job at the
+// same moment is gated by the recency window.
+func TestSyncerPrimeBypassesRecencyPeriodicDoesNot(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	fx.etag = `"v1"`
+	store := newFakeSyncStore()
+	p := newTestProvider()
+	s := newSyncer(store, p, testSyncConfig())
+	remote := fx.remote()
+
+	var _ provider.RemoteMetadataStore = store
+
+	s.process(context.Background(), syncJob{remote: remote, prime: true})
+	if rows, _ := store.ListDebMetadataEntries(context.Background(), remote.Name); len(rows) != 1 {
+		t.Fatalf("prime did not derive: %d rows", len(rows))
+	}
+	releasesAfterPrime := fx.releasesHit
+
+	s.process(context.Background(), syncJob{remote: remote, prime: false})
+	if fx.releasesHit != releasesAfterPrime {
+		t.Fatalf("periodic scan ran inside recency window: %d -> %d releases calls", releasesAfterPrime, fx.releasesHit)
+	}
+}

internal/server/server.go

@@ -21,7 +21,7 @@ import (
 	"git.unkin.net/unkin/artifactapi/internal/gc"
 	"git.unkin.net/unkin/artifactapi/internal/githubauth"
 	_ "git.unkin.net/unkin/artifactapi/internal/provider/alpine"
-	_ "git.unkin.net/unkin/artifactapi/internal/provider/deb"
+	"git.unkin.net/unkin/artifactapi/internal/provider/deb"
 	_ "git.unkin.net/unkin/artifactapi/internal/provider/docker"
 	_ "git.unkin.net/unkin/artifactapi/internal/provider/generic"
 	_ "git.unkin.net/unkin/artifactapi/internal/provider/goproxy"
@@ -35,6 +35,7 @@ import (
 	"git.unkin.net/unkin/artifactapi/internal/storage"
 	"git.unkin.net/unkin/artifactapi/internal/tfsign"
 	"git.unkin.net/unkin/artifactapi/internal/virtual"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
 )
 
 type Server struct {
@@ -50,6 +51,7 @@ type Server struct {
 	tfRegistry   *tfregistry.Handler
 	gc           *gc.Collector
 	syncer       *rpm.Syncer
+	debSyncer    *deb.Syncer
 }
 
 func New(cfg *config.Config, version string) (*Server, error) {
@@ -97,6 +99,12 @@ func New(cfg *config.Config, version string) (*Server, error) {
 		Workers:      cfg.GitHubSyncWorkers,
 		PollInterval: time.Duration(cfg.GitHubSyncPollInterval) * time.Second,
 	})
+	debSyncer := deb.NewSyncer(db, deb.SyncConfig{
+		RatePerSec:   cfg.GitHubSyncRatePerSec,
+		Burst:        cfg.GitHubSyncBurst,
+		Workers:      cfg.GitHubSyncWorkers,
+		PollInterval: time.Duration(cfg.GitHubSyncPollInterval) * time.Second,
+	})
 
 	// The terraform registry signs with a GPG key. A configured file wins (BYO
 	// key); otherwise artifactapi generates one on first start and persists it in
@@ -129,6 +137,7 @@ func New(cfg *config.Config, version string) (*Server, error) {
 		tfRegistry:   tfRegistry,
 		gc:           collector,
 		syncer:       syncer,
+		debSyncer:    debSyncer,
 	}
 
 	s.router = s.routes()
@@ -158,7 +167,10 @@ func (s *Server) routes() chi.Router {
 	r.Mount("/api/v1", proxyHandler.Routes())
 	r.Mount("/v2", proxyHandler.DockerV2Routes())
 
-	remotesHandler := v2.NewRemotesHandler(s.db, s.syncer)
+	remotesHandler := v2.NewRemotesHandler(s.db, map[models.PackageType]v2.Primer{
+		models.PackageGitHubRPM: s.syncer,
+		models.PackageGitHubDeb: s.debSyncer,
+	})
 	virtualsHandler := v2.NewVirtualsHandler(s.db)
 	healthHandler := v2.NewHealthHandler(s.db, s.cache, s.store)
 	statsHandler := v2.NewStatsHandler(s.db)
@@ -226,6 +238,7 @@ func (s *Server) newHTTPServer() *http.Server {
 func (s *Server) Run(ctx context.Context) error {
 	go s.gc.Run(ctx)
 	go s.syncer.Run(ctx)
+	go s.debSyncer.Run(ctx)
 
 	httpServer := s.newHTTPServer()
 
@@ -247,6 +260,7 @@ func (s *Server) Run(ctx context.Context) error {
 func (s *Server) RunOnListener(ctx context.Context, ln net.Listener) error {
 	go s.gc.Run(ctx)
 	go s.syncer.Run(ctx)
+	go s.debSyncer.Run(ctx)
 
 	httpServer := s.newHTTPServer()
 

pkg/models/package_type.go

@@ -17,6 +17,7 @@ const (
 	PackageTerraform PackageType = "terraform"
 	PackageGoProxy   PackageType = "goproxy"
 	PackageGitHubRPM PackageType = "github_rpm"
+	PackageGitHubDeb PackageType = "github_deb"
 )
 
 var validPackageTypes = map[PackageType]bool{
@@ -32,6 +33,7 @@ var validPackageTypes = map[PackageType]bool{
 	PackageTerraform: true,
 	PackageGoProxy:   true,
 	PackageGitHubRPM: true,
+	PackageGitHubDeb: true,
 }
 
 func (p PackageType) Valid() bool {