Bound serve_stale member copies by age, toggle and eviction

- drop a member's copy when serve_stale is off
- block on the member again once its copy is over an hour old
- skip storing a refresh whose entry was evicted or replaced
- show serve_stale in the UI and TUI

docs/common/caching.md

@@ -15,7 +15,9 @@ Every proxied request on a remote is classified as **denied**, **immutable** or
 | `mutable_ttl` | Seconds a mutable path stays fresh. `0` also means never expires. Omitted on create, it defaults to `3600`; omitted on update, the stored value is kept. |
 | `check_mutable` | When a mutable path's `mutable_ttl` expires, sends a conditional `HEAD` (`If-None-Match`) with the stored upstream ETag. A `304` re-arms the TTL and serves the stored copy; anything else refetches in full. The ETag is kept for `max(10 × mutable_ttl, 7 days)`, re-armed on each `304`, so idle paths age out. It is only stored when `check_mutable` is set and `mutable_ttl` is non-zero, and never for immutable paths. |
 | `stale_on_error` | On an upstream network error, serve the stored copy instead of failing. |
-| `serve_stale` | rpm/deb/alpine virtual members only. When a virtual re-merges, use this member's previous index at once and refresh it in the background; the next merge picks up the refresh. The first merge still waits. Default `false`. |
+| `serve_stale` | rpm/deb/alpine virtual members only. When a virtual re-merges, use this member's previous index at once and refresh it in the background; the next merge picks up the refresh. The first merge still waits, and so does any merge once the previous index is over an hour old, so a member that keeps failing surfaces its error. Default `false`. |
+
+`PUT` replaces the whole remote: any field omitted from the body, such as `stale_on_error` or `serve_stale`, resets to its default (`mutable_ttl` is the exception above).
 | `quarantine_enabled` / `quarantine_days` | Stored on the remote but not enforced by the proxy yet. |
 | `mirrorlist` / `mirror_strategy` | rpm/deb/alpine only. Upstream pool is `[base_url] + mirrorlist`; `round_robin` (default) rotates the starting mirror, `least_conn` starts at the one with the fewest in-flight requests. Network errors and 5xx fail over to the next mirror; other statuses return as-is. |
 

internal/server/server_test.go

@@ -416,6 +416,25 @@ func TestServerRemoteUpdateAndVirtualCRUD(t *testing.T) {
 	}
 }
 
+func TestServerRemoteServeStaleRoundTrip(t *testing.T) {
+	requireStack(t)
+	if resp, b := req(t, "POST", "/api/v2/remotes", `{"name":"srv-ss","package_type":"rpm","repo_type":"remote","base_url":"https://a.example.com","serve_stale":true}`); resp.StatusCode != 201 {
+		t.Fatalf("create remote: %d %s", resp.StatusCode, b)
+	}
+	defer req(t, "DELETE", "/api/v2/remotes/srv-ss", "")
+	get := func(want string) {
+		t.Helper()
+		if _, b := req(t, "GET", "/api/v2/remotes/srv-ss", ""); !strings.Contains(string(b), want) {
+			t.Errorf("get remote: want %s in %s", want, b)
+		}
+	}
+	get(`"serve_stale":true`)
+	if resp, b := req(t, "PUT", "/api/v2/remotes/srv-ss", `{"package_type":"rpm","base_url":"https://a.example.com"}`); resp.StatusCode != 200 {
+		t.Fatalf("update remote: %d %s", resp.StatusCode, b)
+	}
+	get(`"serve_stale":false`)
+}
+
 func TestServerLocalRemoveAndMissing(t *testing.T) {
 	requireStack(t)
 	req(t, "POST", "/api/v2/remotes", `{"name":"srv-rm","package_type":"generic","repo_type":"local"}`)

internal/tui/render.go

@@ -58,6 +58,7 @@ func (m *model) viewRemoteDetail() string {
 	sb.WriteString(fmt.Sprintf("  Mutable TTL:    %ds\n", r.MutableTTL))
 	sb.WriteString(fmt.Sprintf("  Revalidation:   %v\n", r.CheckMutable))
 	sb.WriteString(fmt.Sprintf("  Stale on Error: %v\n", r.StaleOnError))
+	fmt.Fprintf(&sb, "  Serve Stale:    %v\n", r.ServeStale)
 
 	if len(r.Patterns) > 0 {
 		sb.WriteString(fmt.Sprintf("  Patterns:       %s\n", strings.Join(r.Patterns, ", ")))

internal/virtual/engine.go

@@ -57,9 +57,18 @@ type Engine struct {
 	gens map[string]*repoGen
 	// stale holds the last good fetch of each serve_stale member, keyed by
 	// merge key and member name.
-	stale map[string]any
+	stale map[string]*staleEntry
 }
 
+type staleEntry struct {
+	m  any
+	at time.Time
+}
+
+// maxStaleAge bounds how old a serve_stale member copy may be before merges
+// block on the member again and surface its error.
+const maxStaleAge = time.Hour
+
 // mergedRepo is a merged index document plus the files it references.
 type mergedRepo interface {
 	index() []byte
@@ -535,30 +544,41 @@ func (e *Engine) fetchAlpineMember(ctx context.Context, name, dir string) (*Alpi
 }
 
 // staleMember fetches member name for the merge under key. A serve_stale member
-// with a previous good fetch returns it at once and refreshes in the
-// background, one refresh per member at a time; the next merge picks it up.
+// with a good fetch younger than maxStaleAge returns it at once and refreshes in
+// the background, one refresh per member at a time; the next merge picks it up.
 func staleMember[T any](ctx context.Context, e *Engine, key, name string, fetch func(context.Context) (*T, error)) (*T, error) {
+	sk := key + "\x00" + name
 	remote, err := e.getRemote(ctx, name)
 	if err != nil || !remote.ServeStale {
+		e.mu.Lock()
+		delete(e.stale, sk)
+		e.mu.Unlock()
 		return fetch(ctx)
 	}
-	sk := key + "\x00" + name
+	e.mu.Lock()
+	for k, se := range e.stale {
+		if time.Since(se.at) >= maxStaleAge {
+			delete(e.stale, k)
+		}
+	}
+	prev := e.stale[sk]
+	e.mu.Unlock()
 	refresh := func() (any, error) {
 		m, err := fetch(ctx)
 		if err == nil {
 			e.mu.Lock()
-			if e.stale == nil {
-				e.stale = map[string]any{}
+			// An evicted or replaced entry means this refresh is no longer wanted.
+			if e.stale[sk] == prev {
+				if e.stale == nil {
+					e.stale = map[string]*staleEntry{}
+				}
+				e.stale[sk] = &staleEntry{m: m, at: time.Now()}
 			}
-			e.stale[sk] = m
 			e.mu.Unlock()
 		}
 		return m, err
 	}
-	e.mu.Lock()
-	prev, ok := e.stale[sk].(*T)
-	e.mu.Unlock()
-	if !ok {
+	if prev == nil {
 		m, err := refresh()
 		return m.(*T), err
 	}
@@ -568,7 +588,7 @@ func staleMember[T any](ctx context.Context, e *Engine, key, name string, fetch
 			slog.Warn("virtual member background refresh failed", "member", name, "error", r.Err)
 		}
 	}()
-	return prev, nil
+	return prev.m.(*T), nil
 }
 
 // evictLRU drops the least recently used merges under prefix beyond keep.

internal/virtual/engine_stale_test.go

@@ -2,6 +2,8 @@ package virtual
 
 import (
 	"context"
+	"errors"
+	"fmt"
 	"sync/atomic"
 	"testing"
 	"time"
@@ -16,18 +18,32 @@ func rpmPkgMember(name, ver string) *RPMMember {
 // staleEngine re-merges on every request; member "a" is fetched through fetch
 // and has serve_stale set to stale.
 func staleEngine(stale bool, fetch func() *RPMMember) (*Engine, *atomic.Int32) {
+	e, calls, _ := staleEngineErr(stale, func() (*RPMMember, error) { return fetch(), nil })
+	return e, calls
+}
+
+func staleEngineErr(stale bool, fetch func() (*RPMMember, error)) (*Engine, *atomic.Int32, *atomic.Bool) {
 	var calls atomic.Int32
+	var flag atomic.Bool
+	flag.Store(stale)
 	e := fakeEngine(nil)
 	e.getRemote = func(_ context.Context, name string) (*models.Remote, error) {
-		return &models.Remote{Name: name, RepoType: models.RepoTypeRemote, ServeStale: stale}, nil
+		return &models.Remote{Name: name, RepoType: models.RepoTypeRemote, ServeStale: flag.Load()}, nil
 	}
 	e.rpmMember = func(_ context.Context, name string) (*RPMMember, error) {
 		calls.Add(1)
-		return fetch(), nil
+		return fetch()
 	}
-	return e, &calls
+	return e, &calls, &flag
 }
 
+// waitRefresh blocks until the background refresh of sk, if any, has finished.
+func waitRefresh(e *Engine, sk string) {
+	_, _, _ = e.sf.Do("stale\x00"+sk, func() (any, error) { return nil, nil })
+}
+
+const rpmStaleKey = "rpm\x00v\x00a"
+
 func fetchRepomd(t *testing.T, e *Engine) string {
 	t.Helper()
 	b, _, err := e.Fetch(context.Background(), rpmVirt("a"), "repodata/repomd.xml", "")
@@ -111,3 +127,147 @@ func TestServeStaleColdStartBlocksMerge(t *testing.T) {
 	})
 	assertMergeBlocks(t, e, release)
 }
+
+func TestServeStaleRefreshErrorKeepsCopy(t *testing.T) {
+	var down atomic.Bool
+	e, _, _ := staleEngineErr(true, func() (*RPMMember, error) {
+		if down.Load() {
+			return nil, errors.New("upstream down")
+		}
+		return rpmPkgMember("a", "1"), nil
+	})
+	v1 := fetchRepomd(t, e)
+	down.Store(true)
+	for range 3 {
+		if got := fetchRepomd(t, e); got != v1 {
+			t.Fatal("a failed refresh should keep serving the previous copy")
+		}
+		waitRefresh(e, rpmStaleKey)
+	}
+}
+
+func TestServeStaleMaxAgeFallsBackToFetch(t *testing.T) {
+	var down atomic.Bool
+	e, _, _ := staleEngineErr(true, func() (*RPMMember, error) {
+		if down.Load() {
+			return nil, errors.New("upstream down")
+		}
+		return rpmPkgMember("a", "1"), nil
+	})
+	fetchRepomd(t, e)
+	down.Store(true)
+	e.mu.Lock()
+	e.stale[rpmStaleKey].at = time.Now().Add(-maxStaleAge)
+	e.mu.Unlock()
+	if _, _, err := e.Fetch(context.Background(), rpmVirt("a"), "repodata/repomd.xml", ""); err == nil {
+		t.Fatal("a copy past maxStaleAge should not be served")
+	}
+	if len(e.stale) != 0 {
+		t.Fatal("an expired copy should be dropped")
+	}
+}
+
+func TestServeStaleToggleOffClearsCopy(t *testing.T) {
+	var down atomic.Bool
+	e, _, flag := staleEngineErr(true, func() (*RPMMember, error) {
+		if down.Load() {
+			return nil, errors.New("upstream down")
+		}
+		return rpmPkgMember("a", "1"), nil
+	})
+	fetchRepomd(t, e)
+	flag.Store(false)
+	fetchRepomd(t, e)
+	if len(e.stale) != 0 {
+		t.Fatal("turning serve_stale off should drop the copy")
+	}
+	flag.Store(true)
+	down.Store(true)
+	if _, _, err := e.Fetch(context.Background(), rpmVirt("a"), "repodata/repomd.xml", ""); err == nil {
+		t.Fatal("re-enabling serve_stale must not resurrect the old copy")
+	}
+}
+
+func staleRemote(_ context.Context, name string) (*models.Remote, error) {
+	return &models.Remote{Name: name, RepoType: models.RepoTypeRemote, ServeStale: true}, nil
+}
+
+func TestServeStaleDebAndAlpine(t *testing.T) {
+	var down atomic.Bool
+	e := fakeEngine(nil)
+	e.getRemote = staleRemote
+	e.debMember = func(_ context.Context, name, _ string) (*DebMember, error) {
+		if down.Load() {
+			return nil, errors.New("upstream down")
+		}
+		return suiteDebMember(name, "1"), nil
+	}
+	e.apkMember = func(_ context.Context, name, _ string) (*AlpineMember, error) {
+		if down.Load() {
+			return nil, errors.New("upstream down")
+		}
+		return &AlpineMember{RemoteName: name, Index: []byte(apkRec("foo", "1-r0", "x86_64"))}, nil
+	}
+	for _, tc := range []struct {
+		virt models.Virtual
+		path string
+	}{
+		{debVirt("a"), "dists/s/Release"},
+		{alpineVirt("a"), "x86_64/APKINDEX.tar.gz"},
+	} {
+		down.Store(false)
+		first, _, err := e.Fetch(context.Background(), tc.virt, tc.path, "")
+		if err != nil {
+			t.Fatal(err)
+		}
+		down.Store(true)
+		got, _, err := e.Fetch(context.Background(), tc.virt, tc.path, "")
+		if err != nil || string(got) != string(first) {
+			t.Fatalf("%s: want the previous copy while the member is down, got err %v", tc.virt.PackageType, err)
+		}
+	}
+}
+
+func TestServeStaleEvictionDropsLateRefresh(t *testing.T) {
+	release := make(chan struct{})
+	var slow atomic.Bool
+	e := fakeEngine(nil)
+	e.mergeTTL = time.Minute
+	e.getRemote = staleRemote
+	e.debMember = func(_ context.Context, name, base string) (*DebMember, error) {
+		if base == "dists/s0/" && slow.Load() {
+			<-release
+		}
+		return suiteDebMember(name, "1"), nil
+	}
+	fetch := func(suite string) {
+		t.Helper()
+		if _, _, err := e.Fetch(context.Background(), debVirt("a"), "dists/"+suite+"/Release", ""); err != nil {
+			t.Fatal(err)
+		}
+	}
+	fetch("s0")
+	slow.Store(true)
+	e.mu.Lock()
+	e.gens["deb\x00v\x00dists/s0/"].at = time.Time{}
+	e.mu.Unlock()
+	fetch("s0")
+	for i := range maxDebSuites {
+		time.Sleep(time.Microsecond)
+		fetch(fmt.Sprintf("s%d", i+1))
+	}
+	close(release)
+	sk := "deb\x00v\x00dists/s0/\x00a"
+	waitRefresh(e, sk)
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	if e.gens["deb\x00v\x00dists/s0/"] != nil {
+		t.Fatal("suite s0 should be evicted")
+	}
+	if e.stale[sk] != nil {
+		t.Fatal("a refresh finishing after eviction must not re-insert its copy")
+	}
+	if len(e.stale) != maxDebSuites {
+		t.Fatalf("stale holds %d copies, want %d", len(e.stale), maxDebSuites)
+	}
+}

ui/src/api/types.ts

@@ -17,6 +17,7 @@ export interface Remote {
   quarantine_enabled: boolean;
   quarantine_days: number;
   stale_on_error: boolean;
+  serve_stale: boolean;
   releases_remote: string;
   managed_by: string;
   created_at: string;

ui/src/pages/RemoteDetail.tsx

@@ -50,6 +50,8 @@ export function RemoteDetail() {
             <dd>{remote.check_mutable ? 'enabled' : 'disabled'}</dd>
             <dt>Stale on Error</dt>
             <dd>{remote.stale_on_error ? 'enabled' : 'disabled'}</dd>
+            <dt>Serve Stale</dt>
+            <dd>{remote.serve_stale ? 'enabled' : 'disabled'}</dd>
             {remote.releases_remote && (
               <>
                 <dt>Releases Remote</dt>