Reject bare * and unknown remotes on evict, serialise with fetch lock

- return 400 for a bare * and 404 for an unknown remote
- take the per-path fetch lock for single-path evicts
- pass the evictor to Routes so local routes no longer carry it
- test If-None-Match revalidation, ForgetPath/ForgetPrefix glob escaping

internal/proxy/engine.go

@@ -16,6 +16,8 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/jackc/pgx/v5"
+
 	"git.unkin.net/unkin/artifactapi/internal/cache"
 	"git.unkin.net/unkin/artifactapi/internal/database"
 	"git.unkin.net/unkin/artifactapi/internal/provider"
@@ -210,10 +212,21 @@ func (e *Engine) Fetch(ctx context.Context, remote models.Remote, path string, p
 
 // Evict drops path from every cache layer (artifact row, index object, Redis
 // freshness and ETag keys) so the next request refetches from upstream. A
-// trailing "*" evicts every path under that prefix.
+// trailing "*" evicts every path under that prefix; a bare "*" is rejected.
 func (e *Engine) Evict(ctx context.Context, remoteName, path string) error {
 	prefix, wildcard := strings.CutSuffix(path, "*")
+	if wildcard && prefix == "" {
+		return &ProxyError{Status: http.StatusBadRequest, Message: "refusing to evict an entire remote"}
+	}
+	if _, err := e.db.GetRemote(ctx, remoteName); errors.Is(err, pgx.ErrNoRows) {
+		return &ProxyError{Status: http.StatusNotFound, Message: fmt.Sprintf("remote %q not found", remoteName)}
+	} else if err != nil {
+		return fmt.Errorf("get remote: %w", err)
+	}
 	if !wildcard {
+		if e.waitForLock(ctx, remoteName, path) {
+			defer e.cache.ReleaseLock(ctx, remoteName, path)
+		}
 		if err := e.db.DeleteArtifact(ctx, remoteName, path); err != nil {
 			return fmt.Errorf("delete artifact: %w", err)
 		}
@@ -231,6 +244,23 @@ func (e *Engine) Evict(ctx context.Context, remoteName, path string) error {
 	return e.cache.ForgetPrefix(ctx, remoteName, prefix)
 }
 
+// waitForLock takes the per-path fetch lock so an in-flight Fetch cannot
+// re-set TTL/ETag keys after an evict. It gives up once the lock would have
+// expired anyway, or when ctx ends.
+func (e *Engine) waitForLock(ctx context.Context, remoteName, path string) bool {
+	deadline := time.Now().Add(fetchLockTTL)
+	for {
+		if ok, err := e.cache.AcquireLock(ctx, remoteName, path, fetchLockTTL); ok || err != nil || time.Now().After(deadline) {
+			return ok
+		}
+		select {
+		case <-ctx.Done():
+			return false
+		case <-time.After(50 * time.Millisecond):
+		}
+	}
+}
+
 // HeadResult carries artifact metadata for a HEAD request. There is no body.
 type HeadResult struct {
 	ContentType string

internal/proxy/evict_test.go

@@ -2,28 +2,40 @@ package proxy
 
 import (
 	"context"
+	"errors"
 	"net/http"
 	"net/http/httptest"
 	"sync/atomic"
 	"testing"
+	"time"
 
 	_ "git.unkin.net/unkin/artifactapi/internal/provider/rpm"
 	"git.unkin.net/unkin/artifactapi/pkg/models"
 )
 
 // changingUpstream serves every path with the current revision, as a mirror
-// does after a sync replaces its repodata.
-func changingUpstream(t *testing.T) (*httptest.Server, *atomic.Value) {
+// does after a sync replaces its repodata. It answers 304 to a matching
+// If-None-Match and counts conditional requests.
+func changingUpstream(t *testing.T) (*httptest.Server, *atomic.Value, *atomic.Int32) {
 	t.Helper()
 	var rev atomic.Value
+	var conditional atomic.Int32
 	rev.Store("rev1")
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		v := rev.Load().(string)
-		w.Header().Set("ETag", `"`+v+`"`)
+		etag := `"` + v + `"`
+		w.Header().Set("ETag", etag)
+		if inm := r.Header.Get("If-None-Match"); inm != "" {
+			conditional.Add(1)
+			if inm == etag {
+				w.WriteHeader(http.StatusNotModified)
+				return
+			}
+		}
 		_, _ = w.Write([]byte(v + ":" + r.URL.Path))
 	}))
 	t.Cleanup(srv.Close)
-	return srv, &rev
+	return srv, &rev, &conditional
 }
 
 func fetchBody(t *testing.T, r models.Remote, path string) string {
@@ -41,7 +53,7 @@ func rpmRemote(t *testing.T, name, baseURL string) models.Remote {
 
 func TestEvictMutableIndexRefetches(t *testing.T) {
 	requireStack(t)
-	srv, rev := changingUpstream(t)
+	srv, rev, conditional := changingUpstream(t)
 	r := rpmRemote(t, "evict-idx", srv.URL)
 	const path = "8/Everything/x86_64/repodata/repomd.xml"
 
@@ -55,14 +67,64 @@ func TestEvictMutableIndexRefetches(t *testing.T) {
 	if err := testEngine.Evict(context.Background(), r.Name, path); err != nil {
 		t.Fatalf("evict: %v", err)
 	}
+	conditional.Store(0)
 	if got := fetchBody(t, r, path); got != "rev2:/"+path {
 		t.Fatalf("after evict = %q, want rev2", got)
 	}
+	if n := conditional.Load(); n != 0 {
+		t.Errorf("post-evict fetch revalidated with the evicted ETag (%d conditional requests)", n)
+	}
+}
+
+func TestEvictRejectsBareWildcard(t *testing.T) {
+	requireStack(t)
+	srv, _, _ := changingUpstream(t)
+	r := rpmRemote(t, "evict-bare", srv.URL)
+	const path = "8/Everything/x86_64/repodata/repomd.xml"
+	fetchBody(t, r, path)
+
+	var pe *ProxyError
+	if err := testEngine.Evict(context.Background(), r.Name, "*"); !errors.As(err, &pe) || pe.Status != http.StatusBadRequest {
+		t.Fatalf("evict * = %v, want 400", err)
+	}
+	if fresh, _ := testEngine.cache.CheckTTL(context.Background(), r.Name, path); !fresh {
+		t.Error("bare * evicted cached keys")
+	}
+}
+
+func TestEvictUnknownRemote(t *testing.T) {
+	requireStack(t)
+	var pe *ProxyError
+	if err := testEngine.Evict(context.Background(), "evict-no-such-remote", "a/b"); !errors.As(err, &pe) || pe.Status != http.StatusNotFound {
+		t.Fatalf("evict unknown remote = %v, want 404", err)
+	}
+}
+
+func TestEvictWaitsForFetchLock(t *testing.T) {
+	requireStack(t)
+	srv, _, _ := changingUpstream(t)
+	r := rpmRemote(t, "evict-lock", srv.URL)
+	ctx := context.Background()
+	const path = "8/Everything/x86_64/repodata/repomd.xml"
+	if ok, err := testEngine.cache.AcquireLock(ctx, r.Name, path, time.Minute); !ok || err != nil {
+		t.Fatalf("acquire: %v %v", ok, err)
+	}
+	done := make(chan error, 1)
+	go func() { done <- testEngine.Evict(ctx, r.Name, path) }()
+	select {
+	case err := <-done:
+		t.Fatalf("evict returned while fetch lock held: %v", err)
+	case <-time.After(200 * time.Millisecond):
+	}
+	_ = testEngine.cache.ReleaseLock(ctx, r.Name, path)
+	if err := <-done; err != nil {
+		t.Fatalf("evict: %v", err)
+	}
 }
 
 func TestEvictWildcardClearsPrefixOnly(t *testing.T) {
 	requireStack(t)
-	srv, rev := changingUpstream(t)
+	srv, rev, _ := changingUpstream(t)
 	r := rpmRemote(t, "evict-wild", srv.URL)
 	const (
 		repomd = "8/Everything/x86_64/repodata/repomd.xml"