Add a statistics pane to the webhook page (closes #368)

Each webhook's event database keeps one row of running totals: events,
deliveries and failures, and how many of each retention removed.
Storing an event, creating a delivery, a delivery becoming failed and
the retention sweep each update it in the transaction that writes or
deletes the rows it counts. Deliveries get a finished_at column, the
last column of the status index, so the last-10-minutes and
last-24-hours figures are index-range counts. The pane is its own
template, included at the top of the page.

The schema changes in place with nothing back-filled, so an existing
database must be recreated.

Model: opus-5-5

internal/database/totals_test.go

@@ -0,0 +1,126 @@
+package database_test
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gorm.io/gorm"
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// readTotals reads a webhook database's row of running totals,
+// asserting that it has exactly one.
+func readTotals(t *testing.T, db *gorm.DB) database.Totals {
+	t.Helper()
+
+	var rows []database.Totals
+
+	require.NoError(t, db.Find(&rows).Error)
+	require.Len(t, rows, 1)
+
+	return rows[0]
+}
+
+// TestWebhookDBManager_TotalsRowSurvivesReopen verifies that a new
+// event database starts with one row of zero totals, and that opening
+// it again keeps that row and what was added to it.
+func TestWebhookDBManager_TotalsRowSurvivesReopen(t *testing.T) {
+	t.Parallel()
+
+	mgr, lc := setupTestWebhookDBManager(t)
+	ctx := context.Background()
+	require.NoError(t, lc.Start(ctx))
+
+	defer func() { require.NoError(t, lc.Stop(ctx)) }()
+
+	webhookID := uuid.New().String()
+
+	db, err := mgr.GetDB(webhookID)
+	require.NoError(t, err)
+
+	fresh := readTotals(t, db)
+	assert.Equal(t, database.Totals{ID: fresh.ID}, fresh)
+
+	require.NoError(t, database.AddTotals(db, database.Totals{
+		Events: 2, Deliveries: 3, Failures: 1,
+	}))
+
+	// Drop the cached connection so the next open reopens the file,
+	// as a restart would.
+	require.NoError(t, mgr.CloseAll())
+
+	db, err = mgr.GetDB(webhookID)
+	require.NoError(t, err)
+
+	assert.Equal(t, database.Totals{
+		ID: fresh.ID, Events: 2, Deliveries: 3, Failures: 1,
+	}, readTotals(t, db))
+}
+
+// TestRetentionReaper_AddsWhatItRemovesToTotals verifies that a sweep
+// leaves the lifetime totals alone and adds the events, deliveries and
+// failed deliveries it deletes to the removed totals, so the totals
+// within retention match the rows still stored.
+func TestRetentionReaper_AddsWhatItRemovesToTotals(t *testing.T) {
+	t.Parallel()
+
+	env := setupRetentionTest(t)
+
+	webhookID := createWebhook(t, env.mainDB.DB(), 30)
+
+	db, err := env.mgr.GetDB(webhookID)
+	require.NoError(t, err)
+
+	now := time.Now()
+	expired := now.Add(-40 * 24 * time.Hour)
+
+	seedEventChain(t, db, webhookID, expired)
+	expiredFailure := seedEventChain(t, db, webhookID, expired)
+	recentFailure := seedEventChain(
+		t, db, webhookID, now.Add(-24*time.Hour),
+	)
+
+	for _, id := range []string{
+		expiredFailure.deliveryID, recentFailure.deliveryID,
+	} {
+		require.NoError(t, db.Model(&database.Delivery{}).
+			Where("id = ?", id).
+			Update("status", database.DeliveryStatusFailed).Error)
+	}
+
+	// The totals storing those rows would have left.
+	require.NoError(t, database.AddTotals(db, database.Totals{
+		Events: 3, Deliveries: 3, Failures: 2,
+	}))
+
+	env.reaper.ExportSweep(context.Background())
+
+	totals := readTotals(t, db)
+	assert.Equal(t, database.Totals{
+		ID:     totals.ID,
+		Events: 3, Deliveries: 3, Failures: 2,
+		EventsRemoved: 2, DeliveriesRemoved: 2, FailuresRemoved: 1,
+	}, totals)
+
+	var events, deliveries, failures int64
+
+	require.NoError(t, db.Model(&database.Event{}).Count(&events).Error)
+	require.NoError(t, db.Model(&database.Delivery{}).
+		Count(&deliveries).Error)
+	require.NoError(t, db.Model(&database.Delivery{}).
+		Where("status = ?", database.DeliveryStatusFailed).
+		Count(&failures).Error)
+
+	assert.Equal(t, events, totals.EventsWithinRetention())
+	assert.Equal(t, deliveries, totals.DeliveriesWithinRetention())
+	assert.Equal(t, failures, totals.FailuresWithinRetention())
+
+	// A sweep with nothing left to remove changes nothing.
+	env.reaper.ExportSweep(context.Background())
+
+	assert.Equal(t, totals, readTotals(t, db))
+}