Add per-webhook event retention reaper (closes #63) (#78)

Enforces each webhook's `RetentionDays` so per-webhook SQLite files no longer grow without bound.

## Reaper

New `RetentionReaper` in `internal/database/retention.go`. A background ticker runs each sweep: it lists all webhooks from the main DB and, for each webhook with a positive `RetentionDays`, opens its per-webhook DB via `WebhookDBManager.GetDB` and deletes every `Event` (and its dependent `Delivery` and `DeliveryResult` rows) whose `CreatedAt` is older than `RetentionDays` days.

- Deletions run in foreign-key-safe order: delivery results, then deliveries, then events.
- Deletes are unscoped (hard deletes) so rows are physically removed and disk is reclaimed, rather than GORM soft-deleting them.
- `RetentionDays <= 0` means retain forever; those webhooks are skipped.
- Webhooks whose per-webhook DB does not yet exist are skipped.

## Config

`internal/config/config.go` gains `RetentionSweepInterval` (env `RETENTION_SWEEP_INTERVAL`, parsed as a Go duration, default `1h`) via a new `envDuration` helper, following the existing env-helper conventions.

## Wiring

`cmd/webhooker/main.go` registers `database.NewRetentionReaper` as an fx provider and forces its construction in `fx.Invoke`. The reaper starts its sweep loop on an fx `OnStart` hook and stops cleanly on `OnStop` via context cancellation, matching the existing lifecycle components.

## Test

`internal/database/retention_test.go` seeds an old event chain (event + delivery + result, 40 days old) and a recent one (1 day old) in a real per-webhook DB and asserts a single sweep removes only the expired chain while keeping the recent one. A second test forces a non-positive `RetentionDays` and asserts an ancient event is retained.

Note: the `Webhook.RetentionDays` column carries `gorm:"default:30"`, so a `0` passed to a GORM `Create` is replaced by the default; the test forces the value with an explicit column update to exercise the retain-forever path. No model changes were made.

Validated with `docker build .` (fmt-check, lint, test, build) exit 0.

Closes #63

Co-authored-by: sneak <sneak@sneak.berlin>
Reviewed-on: #78
Co-authored-by: clawbot <clawbot@noreply.example.org>
Co-committed-by: clawbot <clawbot@noreply.example.org>

internal/database/retention_test.go

@@ -0,0 +1,277 @@
+package database_test
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/fx/fxtest"
+	"gorm.io/gorm"
+	"gorm.io/gorm/clause"
+	"sneak.berlin/go/webhooker/internal/config"
+	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/globals"
+	"sneak.berlin/go/webhooker/internal/logger"
+)
+
+// retentionTestEnv bundles the pieces a retention test drives.
+type retentionTestEnv struct {
+	reaper *database.RetentionReaper
+	mainDB *database.Database
+	mgr    *database.WebhookDBManager
+}
+
+func setupRetentionTest(t *testing.T) *retentionTestEnv {
+	t.Helper()
+
+	lc := fxtest.NewLifecycle(t)
+
+	g := &globals.Globals{
+		Appname: "webhooker-test",
+		Version: "test",
+	}
+
+	l, err := logger.New(lc, logger.LoggerParams{Globals: g})
+	require.NoError(t, err)
+
+	cfg := &config.Config{
+		DataDir:     t.TempDir(),
+		Environment: "dev",
+	}
+
+	mainDB, err := database.New(lc, database.DatabaseParams{
+		Config: cfg,
+		Logger: l,
+	})
+	require.NoError(t, err)
+
+	mgr, err := database.NewWebhookDBManager(
+		lc,
+		database.WebhookDBManagerParams{Config: cfg, Logger: l},
+	)
+	require.NoError(t, err)
+
+	ctx := context.Background()
+	require.NoError(t, lc.Start(ctx))
+	t.Cleanup(func() { require.NoError(t, lc.Stop(ctx)) })
+
+	return &retentionTestEnv{
+		reaper: database.NewTestRetentionReaper(mainDB, mgr),
+		mainDB: mainDB,
+		mgr:    mgr,
+	}
+}
+
+// createWebhook inserts a webhook row into the main database with the
+// given retention policy and returns its ID.
+func createWebhook(
+	t *testing.T,
+	db *gorm.DB,
+	retentionDays int,
+) string {
+	t.Helper()
+
+	wh := &database.Webhook{
+		UserID:        uuid.New().String(),
+		Name:          "test-webhook",
+		RetentionDays: retentionDays,
+	}
+	require.NoError(
+		t,
+		db.Omit(clause.Associations).Create(wh).Error,
+	)
+
+	// The RetentionDays column carries a GORM default of 30, so a
+	// zero (or negative) value passed to Create is replaced by that
+	// default. Force the requested value explicitly so the
+	// retain-forever (<= 0) path can be exercised.
+	require.NoError(
+		t,
+		db.Model(wh).
+			Update("retention_days", retentionDays).Error,
+	)
+
+	return wh.ID
+}
+
+// eventChain is the set of row IDs seeded for a single event.
+type eventChain struct {
+	eventID    string
+	deliveryID string
+	resultID   string
+}
+
+// seedEventChain creates an event with one delivery and one delivery
+// result, all stamped with createdAt, and returns their IDs.
+func seedEventChain(
+	t *testing.T,
+	db *gorm.DB,
+	webhookID string,
+	createdAt time.Time,
+) eventChain {
+	t.Helper()
+
+	event := &database.Event{
+		WebhookID:    webhookID,
+		EntrypointID: uuid.New().String(),
+		Method:       "POST",
+		Body:         `{"seed": true}`,
+		ContentType:  "application/json",
+	}
+	event.CreatedAt = createdAt
+	require.NoError(t, db.Create(event).Error)
+
+	delivery := &database.Delivery{
+		EventID:  event.ID,
+		TargetID: uuid.New().String(),
+		Status:   database.DeliveryStatusDelivered,
+	}
+	delivery.CreatedAt = createdAt
+	require.NoError(t, db.Create(delivery).Error)
+
+	result := &database.DeliveryResult{
+		DeliveryID: delivery.ID,
+		AttemptNum: 1,
+		Success:    true,
+		StatusCode: 200,
+		Duration:   10,
+	}
+	result.CreatedAt = createdAt
+	require.NoError(t, db.Create(result).Error)
+
+	return eventChain{
+		eventID:    event.ID,
+		deliveryID: delivery.ID,
+		resultID:   result.ID,
+	}
+}
+
+// countByID returns how many rows of model match the given id,
+// counting even hard-deletable rows via Unscoped.
+func countByID(
+	t *testing.T,
+	db *gorm.DB,
+	model any,
+	id string,
+) int64 {
+	t.Helper()
+
+	var n int64
+
+	require.NoError(
+		t,
+		db.Unscoped().Model(model).
+			Where("id = ?", id).Count(&n).Error,
+	)
+
+	return n
+}
+
+func assertChainGone(
+	t *testing.T,
+	db *gorm.DB,
+	chain eventChain,
+) {
+	t.Helper()
+
+	assert.Zero(
+		t,
+		countByID(t, db, &database.Event{}, chain.eventID),
+		"expired event should be removed",
+	)
+	assert.Zero(
+		t,
+		countByID(t, db, &database.Delivery{}, chain.deliveryID),
+		"expired delivery should be removed",
+	)
+	assert.Zero(
+		t,
+		countByID(
+			t, db, &database.DeliveryResult{}, chain.resultID,
+		),
+		"expired delivery result should be removed",
+	)
+}
+
+func assertChainPresent(
+	t *testing.T,
+	db *gorm.DB,
+	chain eventChain,
+) {
+	t.Helper()
+
+	assert.Equal(
+		t,
+		int64(1),
+		countByID(t, db, &database.Event{}, chain.eventID),
+		"recent event should be retained",
+	)
+	assert.Equal(
+		t,
+		int64(1),
+		countByID(t, db, &database.Delivery{}, chain.deliveryID),
+		"recent delivery should be retained",
+	)
+	assert.Equal(
+		t,
+		int64(1),
+		countByID(
+			t, db, &database.DeliveryResult{}, chain.resultID,
+		),
+		"recent delivery result should be retained",
+	)
+}
+
+func TestRetentionReaper_ReapsExpiredKeepsRecent(t *testing.T) {
+	t.Parallel()
+
+	env := setupRetentionTest(t)
+
+	const retentionDays = 30
+
+	webhookID := createWebhook(
+		t, env.mainDB.DB(), retentionDays,
+	)
+
+	db, err := env.mgr.GetDB(webhookID)
+	require.NoError(t, err)
+
+	now := time.Now()
+	old := seedEventChain(
+		t, db, webhookID,
+		now.Add(-40*24*time.Hour),
+	)
+	recent := seedEventChain(
+		t, db, webhookID,
+		now.Add(-1*24*time.Hour),
+	)
+
+	env.reaper.ExportSweep(context.Background())
+
+	assertChainGone(t, db, old)
+	assertChainPresent(t, db, recent)
+}
+
+func TestRetentionReaper_RetainsForeverWhenNonPositive(t *testing.T) {
+	t.Parallel()
+
+	env := setupRetentionTest(t)
+
+	// RetentionDays of zero means retain forever.
+	webhookID := createWebhook(t, env.mainDB.DB(), 0)
+
+	db, err := env.mgr.GetDB(webhookID)
+	require.NoError(t, err)
+
+	ancient := seedEventChain(
+		t, db, webhookID,
+		time.Now().Add(-365*24*time.Hour),
+	)
+
+	env.reaper.ExportSweep(context.Background())
+
+	assertChainPresent(t, db, ancient)
+}