TODO.md

@@ -19,6 +19,8 @@ trial run of the finished image: https://git.eeqj.de/sneak/dnswatcher/issues/149
 
 # Completed Steps
 
+- 2026-10-01: a certificate within the expiry warning period is warned about on
+  every TLS check, where some checks used to skip it at random (closes #204).
 - 2026-10-01: a domain's NS set is its delegation from the parent zone's
   servers, not whichever of its own servers answered first (closes #200).
 - 2026-10-01: README has Getting Started, Rationale and TODO sections, and its

internal/watcher/export_test.go

@@ -28,7 +28,6 @@ func NewForTest(
 		tlsCheck:  tc,
 		notify:    n,
 		firstRun:  true,
-		expiryNotified: make(map[string]time.Time),
 	}
 }
 
@@ -72,6 +71,11 @@ func (w *Watcher) CheckAllPorts(ctx context.Context) {
 	w.checkAllPorts(ctx)
 }
 
+// RunTLSChecks exports runTLSChecks for testing.
+func (w *Watcher) RunTLSChecks(ctx context.Context) {
+	w.runTLSChecks(ctx)
+}
+
 // BuildHostnameState exports buildHostnameState for testing.
 func BuildHostnameState(
 	results map[string]*resolver.NameserverResponse,

internal/watcher/watcher.go

@@ -7,7 +7,6 @@ import (
 	"slices"
 	"sort"
 	"strings"
-	"sync"
 	"time"
 
 	"go.uber.org/fx"
@@ -59,8 +58,6 @@ type Watcher struct {
 	cancel    context.CancelFunc
 	done      chan struct{} // closed when Run returns
 	firstRun  bool
-	expiryNotifiedMu sync.Mutex
-	expiryNotified   map[string]time.Time
 }
 
 // New creates a new Watcher instance wired into the fx lifecycle.
@@ -77,7 +74,6 @@ func New(
 		tlsCheck:  params.TLSCheck,
 		notify:    params.Notify,
 		firstRun:  true,
-		expiryNotified: make(map[string]time.Time),
 	}
 
 	lifecycle.Append(fx.Hook{
@@ -1028,22 +1024,6 @@ func (w *Watcher) checkTLSExpiry(
 		return
 	}
 
-	// Deduplicate expiry warnings: don't re-notify for the same
-	// hostname within the TLS check interval.
-	dedupKey := fmt.Sprintf("expiry:%s:%s", hostname, ip)
-
-	w.expiryNotifiedMu.Lock()
-
-	lastNotified, seen := w.expiryNotified[dedupKey]
-	if seen && time.Since(lastNotified) < w.config.TLSInterval {
-		w.expiryNotifiedMu.Unlock()
-
-		return
-	}
-
-	w.expiryNotified[dedupKey] = time.Now()
-	w.expiryNotifiedMu.Unlock()
-
 	msg := fmt.Sprintf(
 		"Host: %s\nIP: %s\nCN: %s\n"+
 			"Expires: %s (%.0f days)",

internal/watcher/watcher_test.go

@@ -615,35 +615,56 @@ func TestTLSExpiryWarning(t *testing.T) {
 	assertNotified(t, deps, "TLS Expiry Warning: "+testHost, "warning")
 }
 
-func TestTLSExpiryWarningDedup(t *testing.T) {
+// TestTLSExpiryWarningEachCheck runs the TLS checks three times in a
+// row on hostname and port state built here, for a certificate that
+// expires within the warning period. Each check warns once, whether the
+// TLS interval is a nanosecond, shorter than the time between two
+// checks, or a day, longer than it.
+func TestTLSExpiryWarningEachCheck(t *testing.T) {
+	t.Parallel()
+
+	title := "TLS Expiry Warning: " + host
+
+	for _, interval := range []time.Duration{time.Nanosecond, 24 * time.Hour} {
+		t.Run(interval.String(), func(t *testing.T) {
 			t.Parallel()
 
 			cfg := defaultTestConfig(t)
-	cfg.Hostnames = []string{testHost}
-	cfg.TLSInterval = 24 * time.Hour
+			cfg.Hostnames = []string{host}
+			cfg.TLSInterval = interval
 
-	title := "TLS Expiry Warning: " + testHost
+			// The TLS checks read the saved hostname and port state and
+			// look nothing up, so the watcher has no resolver.
+			deps := newTestDeps(t, cfg)
+			w := watcher.NewForTest(
+				cfg, deps.state, nil,
+				deps.portChecker, deps.tlsChecker, deps.notifier,
+			)
 
-	// The second check comes within the TLS interval of the first,
-	// so it must not warn again.
-	var warnings int
-
-	deps := runChecks(t, cfg, expiresInThreeDays, func(deps *testDeps) {
-		warnings = countNotifications(deps, title)
+			expiresInThreeDays(deps)
+			deps.state.SetHostnameState(host, saved(
+				map[string]*state.NameserverRecordState{
+					nsA: answered(map[string][]string{"A": {ip1}}),
+				},
+			))
+			deps.state.SetPortState(ip1+":443", &state.PortState{
+				Open: true, Hostnames: []string{host},
 			})
 
-	if warnings == 0 {
-		t.Fatal("expected expiry warnings from the first check")
-	}
+			for check := 1; check <= 3; check++ {
+				w.RunTLSChecks(t.Context())
 
 				got := countNotifications(deps, title)
-	if got != warnings {
-		t.Errorf(
-			"expected %d expiry warnings (dedup), got %d",
-			warnings, got,
+				if got != check {
+					t.Fatalf(
+						"after check %d: %d expiry warnings, want %d",
+						check, got, check,
 					)
 				}
 			}
+		})
+	}
+}
 
 func TestGracefulShutdown(t *testing.T) {
 	t.Parallel()