feat(server): online session history with configurable stats window (#1243)

Add persisted online sessions, configurable retention and online history statistics with lifecycle, recovery, timezone and concurrency regression coverage.

Co-authored-by: naiba/CloudCode <hi+cloudcode@nai.ba>

service/singleton/online_history_restore_test.go

@@ -0,0 +1,73 @@
+package singleton
+
+import (
+	"testing"
+	"time"
+
+	"github.com/nezhahq/nezha/model"
+	"github.com/stretchr/testify/require"
+)
+
+func TestRestoreOngoingSessionsReconcilesRecentDuplicates(t *testing.T) {
+	for _, failClose := range []bool{false, true} {
+		name := "successful_close"
+		if failClose {
+			name = "retry_failed_close"
+		}
+		t.Run(name, func(t *testing.T) {
+			setupOnlineHistoryTestDB(t)
+			base := time.Now().Add(-10 * time.Second).Truncate(time.Second)
+			// Insert out of chronological order: choosing by ID alone would keep the wrong session.
+			newest := model.OnlineSession{ServerID: 1, StartedAt: base.Add(4 * time.Second), LastActiveAt: base.Add(5 * time.Second), Ongoing: true}
+			oldest := model.OnlineSession{ServerID: 1, StartedAt: base, LastActiveAt: base.Add(time.Second), Ongoing: true}
+			middle := model.OnlineSession{ServerID: 1, StartedAt: base.Add(2 * time.Second), LastActiveAt: base.Add(3 * time.Second), Ongoing: true}
+			for _, session := range []*model.OnlineSession{&newest, &oldest, &middle} {
+				require.NoError(t, DB.Create(session).Error)
+			}
+			if failClose {
+				injectCloseUpdateFailure(t)
+			}
+			r := NewOnlineHistoryRecorder()
+			require.Len(t, r.open, 1)
+			require.Equal(t, newest.ID, r.open[1].id)
+			if failClose {
+				require.Len(t, r.closing[1], 2)
+				require.Equal(t, int64(3), countOnlineSessions(t, "ongoing = ?", true))
+				dropCloseUpdateFailure(t)
+			}
+			r.SweepStale(base.Add(6*time.Second), func(uint64) (time.Time, bool) { return newest.LastActiveAt, true })
+			require.Empty(t, r.closing)
+			require.True(t, getOnlineSession(t, newest.ID).Ongoing)
+			for _, previous := range []model.OnlineSession{oldest, middle} {
+				stored := getOnlineSession(t, previous.ID)
+				require.False(t, stored.Ongoing)
+				require.True(t, stored.EndedAt.Equal(previous.LastActiveAt))
+			}
+			r.RecordOnline(1, base.Add(7*time.Second))
+			require.Equal(t, newest.ID, r.open[1].id)
+			require.Equal(t, int64(3), countOnlineSessions(t, "server_id = ?", 1))
+			r.SweepStale(base.Add(2*model.OnlineActiveWindow), func(uint64) (time.Time, bool) { return time.Time{}, false })
+			require.Empty(t, r.open)
+			require.Empty(t, r.closing)
+			require.Equal(t, int64(0), countOnlineSessions(t, "ongoing = ?", true))
+		})
+	}
+}
+
+func TestRestoreOngoingSessionsUsesIDToBreakStartTimeTies(t *testing.T) {
+	setupOnlineHistoryTestDB(t)
+	start := time.Now().Add(-5 * time.Second)
+	first := model.OnlineSession{ServerID: 1, StartedAt: start, LastActiveAt: start, Ongoing: true}
+	second := first
+	other := model.OnlineSession{ServerID: 2, StartedAt: start, LastActiveAt: start, Ongoing: true}
+	for _, session := range []*model.OnlineSession{&first, &second, &other} {
+		require.NoError(t, DB.Create(session).Error)
+	}
+	r := NewOnlineHistoryRecorder()
+	require.Len(t, r.open, 2)
+	require.Equal(t, second.ID, r.open[1].id)
+	require.Equal(t, other.ID, r.open[2].id)
+	require.False(t, getOnlineSession(t, first.ID).Ongoing)
+	require.True(t, getOnlineSession(t, first.ID).EndedAt.Equal(start))
+	require.Equal(t, int64(2), countOnlineSessions(t, "ongoing = ?", true))
+}