Try every event database file on delete and say which was left (closes #275)

DeleteDB stopped at the first file it could not remove, and the
webhook delete handler logged one message for every failure. Once
the database file itself is gone, its events are lost, and telling
the operator only that a file was left behind suggests otherwise.

DeleteDB now tries the database file and both sidecars, and its
error wraps ErrEventDBNotRemoved when the database file is still on
disk, or ErrSidecarNotRemoved when only a -wal or -shm sidecar is
left. The handler logs a different message for each.

Model: opus-5-5

internal/database/webhook_db_manager.go

@@ -33,6 +33,19 @@ var errInvalidCachedDBType = errors.New(
 	"invalid cached database type",
 )
 
+// ErrEventDBNotRemoved is in DeleteDB's error when the event
+// database file itself could not be removed: it is still on disk.
+var ErrEventDBNotRemoved = errors.New(
+	"event database file not removed",
+)
+
+// ErrSidecarNotRemoved is in DeleteDB's error when the event
+// database file was removed, so its events are gone, but its -wal
+// or -shm sidecar could not be.
+var ErrSidecarNotRemoved = errors.New(
+	"event database file removed, but a -wal or -shm sidecar was not",
+)
+
 // WebhookDBManager manages per-webhook SQLite database files
 // for event storage. Each webhook gets its own dedicated
 // database containing Events, Deliveries, DeliveryResults and the
@@ -151,7 +164,10 @@ func (m *WebhookDBManager) DBExists(
 }
 
 // DeleteDB closes the connection and deletes the database file
-// for a webhook. The file is permanently removed.
+// for a webhook, with its -wal and -shm sidecars. The files are
+// permanently removed. Each file is tried even when another could
+// not be removed, and the error wraps ErrEventDBNotRemoved or
+// ErrSidecarNotRemoved to say which was left, naming each file.
 func (m *WebhookDBManager) DeleteDB(
 	webhookID string,
 ) error {
@@ -170,16 +186,23 @@ func (m *WebhookDBManager) DeleteDB(
 		}
 	}
 
-	// Delete the main DB file and WAL/SHM files
 	path := m.dbPath(webhookID)
-	for _, suffix := range []string{"", "-wal", "-shm"} {
-		err := os.Remove(path + suffix)
-		if err != nil && !os.IsNotExist(err) {
-			return fmt.Errorf(
-				"deleting webhook database file %s%s: %w",
-				path, suffix, err,
-			)
-		}
+
+	dbErr := removeFile(path)
+	sidecarErr := errors.Join(
+		removeFile(path+"-wal"),
+		removeFile(path+"-shm"),
+	)
+
+	if dbErr != nil {
+		return fmt.Errorf(
+			"%w: %w",
+			ErrEventDBNotRemoved, errors.Join(dbErr, sidecarErr),
+		)
+	}
+
+	if sidecarErr != nil {
+		return fmt.Errorf("%w: %w", ErrSidecarNotRemoved, sidecarErr)
 	}
 
 	m.log.Info(
@@ -190,6 +213,17 @@ func (m *WebhookDBManager) DeleteDB(
 	return nil
 }
 
+// removeFile removes path. A file that is already gone counts as
+// removed; the error from any other failure names the file.
+func removeFile(path string) error {
+	err := os.Remove(path)
+	if errors.Is(err, os.ErrNotExist) {
+		return nil
+	}
+
+	return err
+}
+
 // CloseAll closes all open per-webhook database connections.
 // Called during application shutdown.
 func (m *WebhookDBManager) CloseAll() error {

internal/database/webhook_db_manager_test.go

@@ -182,17 +182,91 @@ func TestWebhookDBManager_DeleteDB(t *testing.T) {
 	}
 	require.NoError(t, db.Create(event).Error)
 
+	// Under WAL, an open database that has been written to has both
+	// sidecars beside it.
+	dbPath := mgr.DBPath(webhookID)
+	require.FileExists(t, dbPath+"-wal")
+	require.FileExists(t, dbPath+"-shm")
+
 	// Delete the DB
 	require.NoError(t, mgr.DeleteDB(webhookID))
 
 	// File should no longer exist
 	assert.False(t, mgr.DBExists(webhookID))
 
-	// Verify the file is actually gone from disk
+	// Verify the files are actually gone from disk
+	assert.NoFileExists(t, dbPath)
+	assert.NoFileExists(t, dbPath+"-wal")
+	assert.NoFileExists(t, dbPath+"-shm")
+}
+
+// blockRemoval puts a non-empty directory at path, which os.Remove
+// cannot remove whoever runs the test, root included.
+func blockRemoval(t *testing.T, path string) {
+	t.Helper()
+
+	require.NoError(t, os.MkdirAll(filepath.Join(path, "keep"), 0o700))
+}
+
+// TestWebhookDBManager_DeleteDBKeepsDatabaseFile proves that when the
+// event database file cannot be removed, the error says so, and both
+// sidecars are still removed.
+func TestWebhookDBManager_DeleteDBKeepsDatabaseFile(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()
 	dbPath := mgr.DBPath(webhookID)
 
-	_, err = os.Stat(dbPath)
-	assert.True(t, os.IsNotExist(err))
+	blockRemoval(t, dbPath)
+	require.NoError(t, os.WriteFile(dbPath+"-wal", nil, 0o600))
+	require.NoError(t, os.WriteFile(dbPath+"-shm", nil, 0o600))
+
+	err := mgr.DeleteDB(webhookID)
+
+	require.ErrorIs(t, err, database.ErrEventDBNotRemoved)
+	require.NotErrorIs(t, err, database.ErrSidecarNotRemoved)
+	assert.Contains(t, err.Error(), dbPath)
+	assert.NoFileExists(t, dbPath+"-wal")
+	assert.NoFileExists(t, dbPath+"-shm")
+}
+
+// TestWebhookDBManager_DeleteDBKeepsSidecar proves that when the
+// event database file is removed but a sidecar is not, the error
+// says the database file is gone, and the other sidecar is still
+// removed.
+func TestWebhookDBManager_DeleteDBKeepsSidecar(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()
+	dbPath := mgr.DBPath(webhookID)
+
+	require.NoError(t, mgr.CreateDB(webhookID))
+	// Closing removes the sidecars, so the ones below are the only
+	// ones there.
+	require.NoError(t, mgr.CloseAll())
+
+	blockRemoval(t, dbPath+"-wal")
+	require.NoError(t, os.WriteFile(dbPath+"-shm", nil, 0o600))
+
+	err := mgr.DeleteDB(webhookID)
+
+	require.ErrorIs(t, err, database.ErrSidecarNotRemoved)
+	require.NotErrorIs(t, err, database.ErrEventDBNotRemoved)
+	assert.Contains(t, err.Error(), dbPath+"-wal")
+	assert.NoFileExists(t, dbPath)
+	assert.NoFileExists(t, dbPath+"-shm")
 }
 
 func TestWebhookDBManager_LazyCreation(t *testing.T) {

internal/handlers/export_test.go

@@ -36,6 +36,15 @@ const MaxRenderedAttemptsForTest = maxRenderedAttempts
 // the handlers enforce rather than a number copied beside it.
 const MaxTargetRetriesForTest = maxTargetRetries
 
+// EventDBLeftMsgForTest and SidecarLeftMsgForTest expose the two
+// messages the webhook delete handler logs when a file of the event
+// database is left on disk, so a test checking that one is absent
+// checks for the handler's own wording.
+const (
+	EventDBLeftMsgForTest = eventDBLeftMsg
+	SidecarLeftMsgForTest = sidecarLeftMsg
+)
+
 // PageOrFirstForTest exposes pageOrFirst for use in the handlers_test
 // package.
 func PageOrFirstForTest(s string) int {

internal/handlers/source_delete_test.go

@@ -1,8 +1,10 @@
 package handlers_test
 
 import (
+	"bytes"
 	"context"
 	"errors"
+	"log/slog"
 	"net/http"
 	"net/http/httptest"
 	"os"
@@ -466,6 +468,121 @@ func TestHandleSourceDelete_RemovesConfigAndEventDatabase(
 	)
 }
 
+// TestHandleSourceDelete_LeftoverSidecar proves that when the event
+// database file is removed but a sidecar beside it is not, the
+// operator is told the events are gone, never that the event
+// database file is still there.
+func TestHandleSourceDelete_LeftoverSidecar(t *testing.T) {
+	t.Parallel()
+
+	var (
+		h    *handlers.Handlers
+		sess *session.Session
+		db   *database.Database
+		mgr  *database.WebhookDBManager
+	)
+
+	app := newTestApp(t, &h, &sess, &db, &mgr)
+	app.RequireStart()
+
+	t.Cleanup(app.RequireStop)
+
+	logs := new(bytes.Buffer)
+	h.SetLogForTest(slog.New(slog.NewTextHandler(logs, nil)))
+
+	wh := seedWebhook(t, db)
+
+	require.NoError(t, mgr.CreateDB(wh.ID))
+	// Closing removes the sidecars, so the -wal below is the only
+	// one there.
+	require.NoError(t, mgr.CloseAll())
+
+	// A non-empty directory in the -wal file's place, which
+	// os.Remove cannot remove whoever runs the test.
+	eventDBPath := mgr.DBPath(wh.ID)
+	require.NoError(t, os.MkdirAll(
+		filepath.Join(eventDBPath+"-wal", "keep"), 0o700,
+	))
+
+	cookies := authenticatedCookies(
+		t, sess, deleteTestUserID, deleteTestUsername,
+	)
+
+	req := postRequest(
+		"/hook/"+wh.ID+"/delete",
+		cookies,
+		map[string]string{paramSourceID: wh.ID},
+	)
+	w := httptest.NewRecorder()
+
+	h.HandleSourceDelete().ServeHTTP(w, req)
+
+	assert.Equal(t, http.StatusInternalServerError, w.Code)
+	assert.NoFileExists(t, eventDBPath)
+	assert.Contains(t, logs.String(), "its events are gone")
+	assert.Contains(t, logs.String(), eventDBPath+"-wal")
+	assert.NotContains(
+		t, logs.String(), handlers.EventDBLeftMsgForTest,
+		"the events are gone, so the operator must not be told "+
+			"the event database file survived",
+	)
+}
+
+// TestHandleSourceDelete_LeftoverDatabaseFile proves that when the
+// event database file itself cannot be removed, the operator is told
+// it is still on disk, never that its events are gone.
+func TestHandleSourceDelete_LeftoverDatabaseFile(t *testing.T) {
+	t.Parallel()
+
+	var (
+		h    *handlers.Handlers
+		sess *session.Session
+		db   *database.Database
+		mgr  *database.WebhookDBManager
+	)
+
+	app := newTestApp(t, &h, &sess, &db, &mgr)
+	app.RequireStart()
+
+	t.Cleanup(app.RequireStop)
+
+	logs := new(bytes.Buffer)
+	h.SetLogForTest(slog.New(slog.NewTextHandler(logs, nil)))
+
+	wh := seedWebhook(t, db)
+
+	// A non-empty directory in the database file's place, which
+	// os.Remove cannot remove whoever runs the test.
+	eventDBPath := mgr.DBPath(wh.ID)
+	require.NoError(t, os.MkdirAll(
+		filepath.Join(eventDBPath, "keep"), 0o700,
+	))
+
+	cookies := authenticatedCookies(
+		t, sess, deleteTestUserID, deleteTestUsername,
+	)
+
+	req := postRequest(
+		"/hook/"+wh.ID+"/delete",
+		cookies,
+		map[string]string{paramSourceID: wh.ID},
+	)
+	w := httptest.NewRecorder()
+
+	h.HandleSourceDelete().ServeHTTP(w, req)
+
+	assert.Equal(t, http.StatusInternalServerError, w.Code)
+	assert.Contains(
+		t, logs.String(), "event database file is still on disk",
+	)
+	assert.Contains(t, logs.String(), eventDBPath)
+	assert.NotContains(
+		t, logs.String(), handlers.SidecarLeftMsgForTest,
+		"the database file is still on disk, so the operator must "+
+			"not be told its events are gone",
+	)
+}
+
 // TestHandleTargetDelete_EvictsThatTarget proves that deleting a
 // database target releases that target's archive writer and no
 // other: the webhook's other database target keeps its own.

internal/handlers/source_management.go

@@ -723,6 +723,17 @@ func (h *Handlers) HandleSourceDelete() http.HandlerFunc {
 	}
 }
 
+// The messages deleteWebhookResources logs when a file of the event
+// database cannot be removed: the database file itself, or only a
+// sidecar once the database file is gone.
+const (
+	eventDBLeftMsg = "webhook deleted, but its event database file is " +
+		"still on disk; remove it by hand"
+	sidecarLeftMsg = "webhook deleted and its events are gone, but a " +
+		"-wal or -shm sidecar of its event database is " +
+		"still on disk; remove it by hand"
+)
+
 // deleteWebhookResources soft-deletes config and hard-deletes
 // the per-webhook event database.
 func (h *Handlers) deleteWebhookResources(
@@ -762,13 +773,18 @@ func (h *Handlers) deleteWebhookResources(
 	err = h.dbMgr.DeleteDB(webhook.ID)
 	if err != nil {
 		// The configuration is committed, so the webhook is gone,
-		// but its event database file is still on disk with
+		// but a file of its event database is still on disk with
 		// nothing referencing it. Report the failure rather than
 		// redirecting as though everything succeeded: the file
 		// needs removing by hand, and the logged error names it.
-		h.serverError(
-			w, r, "failed to delete webhook event database", err,
-		)
+		// When only a sidecar is left, the events are already
+		// gone, and the message must not suggest they survive.
+		msg := eventDBLeftMsg
+		if errors.Is(err, database.ErrSidecarNotRemoved) {
+			msg = sidecarLeftMsg
+		}
+
+		h.serverError(w, r, msg, err)
 
 		return
 	}