Full restore: say to run occ upgrade before rerunning a restore that stopped after the database; remove empty spool folders of a stopped restore

CHANGELOG.md

@@ -17,6 +17,9 @@ instead carried by the app description, the git tag, the release, and this file.
   cannot be read this way is read as before. Restores from other locations work as before.
 
 ### Fixed
+- After a full restore stopped halfway, running it again with `--force` was refused when the
+  database was already restored: Nextcloud then first wants `occ upgrade`. The guide and the
+  error message now say so.
 - A full restore of a backup made before 1.0.0-rc.2 with `--skip-missing-tables` failed on
   PostgreSQL with "relation ... does not exist": the left-out tables were still looked up to set
   their ID counters. It now skips them. A new test restores a backup made by 1.0.0-rc.1 on

docs/DISASTER-RECOVERY.md

@@ -95,6 +95,8 @@ out with `--skip-missing-tables`.
 
 **8. Let the restore run.** It restores the database, then the data directory, and takes hours for
 a large backup. If it stops halfway, fix the cause and run the same command again with `--force`.
+If occ then says that Nextcloud or one of the apps requires an upgrade, the database is already
+the old server's: run `occ upgrade` first, then the same command with `--force`.
 
 **9. After the restore.** These worked in our tests:
 

lib/Command/RestoreFull.php

@@ -92,6 +92,7 @@ HELP);
 		} catch (\Throwable $e) {
 			$output->writeln('<error>' . $e->getMessage() . '</error>');
 			$output->writeln('If this happened after the restore had started, the instance may be partly restored: fix the cause and run the same command again with --force.');
+			$output->writeln('If occ then says that Nextcloud needs an upgrade (the database is already the old server\'s), run occ upgrade first.');
 			return 1;
 		}
 		$output->writeln(sprintf(

lib/Repository/Repository.php

@@ -237,6 +237,11 @@ final class Repository {
 		if (!$this->backend instanceof IReadsAhead || !$this->backend->canReadAhead()) {
 			return null;
 		}
+		// what a restore that was stopped left behind: empty, its files were unlinked when opened
+		$stale = glob(rtrim($target, '/') . '/.ngb-restore-spool-*', GLOB_ONLYDIR);
+		foreach ($stale === false ? [] : $stale as $dir) {
+			@rmdir($dir);
+		}
 		$plan = new ReadAheadPlan(rtrim($target, '/') . '/.ngb-restore-spool-' . bin2hex(random_bytes(4)));
 		foreach ($this->streamEntries($snapshotId) as $entry) {
 			if ($prefix !== '' && !str_starts_with($entry['p'], $prefix)) {

tests/Unit/Repository/ReadAheadTest.php

@@ -41,8 +41,8 @@ class ReadAheadTest extends TestCase {
 		$this->snapshot = $repo->backupDirectory($this->src)['snapshot'];
 	}
 
-	private function restore(ReadAheadBackend $backend, string $prefix = ''): string {
-		$target = $this->tempDir();
+	private function restore(ReadAheadBackend $backend, string $prefix = '', ?string $target = null): string {
+		$target ??= $this->tempDir();
 		$repo = Repository::openWithKey($backend, $this->keys, null, null);
 		$repo->restore($this->snapshot, $target, $prefix);
 		return $target;
@@ -66,6 +66,13 @@ class ReadAheadTest extends TestCase {
 		$this->assertLessThanOrEqual(count($backend->inner->list('packs')) + 1, count($backend->asked));
 	}
 
+	public function testTheEmptySpoolOfAStoppedRestoreIsRemoved(): void {
+		$target = $this->tempDir();
+		mkdir("$target/.ngb-restore-spool-0badc0de", 0700); // a restore that was killed
+
+		$this->assertRestored($this->restore(new ReadAheadBackend(new LocalBackend($this->root)), '', $target));
+	}
+
 	public function testARangeThatCouldNotBeReadAheadIsReadTheUsualWay(): void {
 		$backend = new ReadAheadBackend(new LocalBackend($this->root), fail: [1]);