feat(loadtest): sync add real 500-session capacity harness

internal/observability/metrics/registry_test.go

@@ -0,0 +1,83 @@
+package metrics
+
+import (
+	"errors"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+
+	"telesrv/internal/mtprotoedge"
+	"telesrv/internal/rpc"
+)
+
+var (
+	_ mtprotoedge.Metrics                 = (*Registry)(nil)
+	_ mtprotoedge.RPCResultMetrics        = (*Registry)(nil)
+	_ mtprotoedge.LogicalOutboxMetrics    = (*Registry)(nil)
+	_ mtprotoedge.ConnectionIntakeMetrics = (*Registry)(nil)
+	_ rpc.Metrics                         = (*Registry)(nil)
+)
+
+func TestRegistryExportsBoundedAggregateMetrics(t *testing.T) {
+	registry := New()
+	registry.maxSeries = 2
+	registry.RPCHandled("help.getConfig", 5*time.Millisecond, nil)
+	registry.RPCHandled("users.getUsers", time.Second, errors.New("secret auth_key_id=deadbeef session=123"))
+
+	recorder := httptest.NewRecorder()
+	registry.ServeHTTP(recorder, httptest.NewRequest("GET", "/metrics", nil))
+	body := recorder.Body.String()
+	if recorder.Code != 200 {
+		t.Fatalf("status = %d, want 200", recorder.Code)
+	}
+	if !strings.Contains(body, "telesrv_mtproto_rpc_handled_total") || !strings.Contains(body, "telesrv_mtproto_rpc_duration_seconds_bucket") {
+		t.Fatalf("expected RPC counter and histogram, got:\n%s", body)
+	}
+	if strings.Contains(body, "deadbeef") || strings.Contains(body, "session=123") {
+		t.Fatalf("raw error identity leaked into metrics:\n%s", body)
+	}
+	if got := registry.series.Load(); got != registry.maxSeries {
+		t.Fatalf("resident dynamic series = %d, want cap %d", got, registry.maxSeries)
+	}
+	if got := registry.dropped.Load(); got == 0 {
+		t.Fatal("series overflow was not reported")
+	}
+	if !strings.Contains(body, "telesrv_metrics_dropped_observations_total 2") {
+		t.Fatalf("overflow counter missing from:\n%s", body)
+	}
+}
+
+func TestRegistrySanitizesAndBoundsProviderSamples(t *testing.T) {
+	registry := New()
+	registry.AddGaugeProvider(func() []GaugeSample {
+		return []GaugeSample{{
+			Name:   "9 invalid metric",
+			Labels: []Label{{Name: "bad:label", Value: "quoted\"\nvalue"}},
+			Value:  3,
+		}}
+	})
+	recorder := httptest.NewRecorder()
+	registry.ServeHTTP(recorder, httptest.NewRequest("GET", "/metrics", nil))
+	body := recorder.Body.String()
+	if !strings.Contains(body, `__invalid_metric{bad_label="quoted\"\nvalue"} 3`) {
+		t.Fatalf("provider sample was not safely sanitized:\n%s", body)
+	}
+}
+
+func TestErrorOutcomeHasFixedCardinality(t *testing.T) {
+	tests := []struct {
+		err  error
+		want string
+	}{
+		{nil, "ok"},
+		{errors.New("FLOOD_WAIT_1 for phone 123"), "flood_wait"},
+		{errors.New("global capacity exceeded for auth key"), "edge_overload"},
+		{errors.New("arbitrary user-controlled failure"), "error"},
+	}
+	for _, test := range tests {
+		if got := errorOutcome(test.err); got != test.want {
+			t.Errorf("errorOutcome(%v) = %q, want %q", test.err, got, test.want)
+		}
+	}
+}