dillard
d96229f370
A killed restore left its leases for up to two hours, so the first backup of the recovered server was refused. A backup from before 1.0.3 records no empty folders: the test now expects that.
109 lines
3.7 KiB
PHP
109 lines
3.7 KiB
PHP
<?php
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declare(strict_types=1);
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// SPDX-FileCopyrightText: 2026 Dillard Blom
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// SPDX-License-Identifier: AGPL-3.0-or-later
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namespace OCA\NgBackup\Service;
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use OCP\IDBConnection;
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use OCP\Lock\ILockingProvider;
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use OCP\Lock\LockedException;
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/**
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* Shared/exclusive leases with an expiry, stored in ngb_leases.
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*
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* Nextcloud's locks live up to an hour; a PHP process killed while holding one (web cron time
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* limit, OOM, kill -9) would block a location that long. A lease expires on its own unless its
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* holder keeps refreshing it. Nextcloud's lock is only held for the few milliseconds in which a
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* lease is checked and written.
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*/
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final class LeaseService {
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public const SHARED = 's';
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public const EXCLUSIVE = 'x';
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public function __construct(
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private IDBConnection $db,
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private ILockingProvider $locking,
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) {
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}
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/** @return string lease id; throws LockedException when it conflicts with a live lease */
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public function acquire(string $name, string $mode, int $ttl): string {
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$guard = 'ng_backup/lease/' . $name;
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$this->locking->acquireLock($guard, ILockingProvider::LOCK_EXCLUSIVE);
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try {
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$now = time();
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$qb = $this->db->getQueryBuilder();
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$qb->delete('ngb_leases')
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->where($qb->expr()->eq('name', $qb->createNamedParameter($name)))
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->andWhere($qb->expr()->lt('expires_at', $qb->createNamedParameter($now)));
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$qb->executeStatement();
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$qb = $this->db->getQueryBuilder();
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$qb->select('mode')->from('ngb_leases')->where($qb->expr()->eq('name', $qb->createNamedParameter($name)));
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$modes = $qb->executeQuery()->fetchAll(\PDO::FETCH_COLUMN);
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if ($modes !== [] && ($mode === self::EXCLUSIVE || in_array(self::EXCLUSIVE, $modes, true))) {
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throw new LockedException($name);
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}
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$id = bin2hex(random_bytes(16));
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$qb = $this->db->getQueryBuilder();
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$qb->insert('ngb_leases')->values([
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'id' => $qb->createNamedParameter($id),
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'name' => $qb->createNamedParameter($name),
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'mode' => $qb->createNamedParameter($mode),
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'expires_at' => $qb->createNamedParameter($now + $ttl),
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]);
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$qb->executeStatement();
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return $id;
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} finally {
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$this->locking->releaseLock($guard, ILockingProvider::LOCK_EXCLUSIVE);
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}
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}
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/** Extend a lease while its holder is still working. */
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public function refresh(string $id, int $ttl): void {
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$qb = $this->db->getQueryBuilder();
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$qb->update('ngb_leases')->set('expires_at', $qb->createNamedParameter(time() + $ttl))
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->where($qb->expr()->eq('id', $qb->createNamedParameter($id)));
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$qb->executeStatement();
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}
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public function release(string $id): void {
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$qb = $this->db->getQueryBuilder();
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$qb->delete('ngb_leases')->where($qb->expr()->eq('id', $qb->createNamedParameter($id)));
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$qb->executeStatement();
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}
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/** Remove the shared leases on $name, for a caller that knows their holders were stopped. */
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public function dropShared(string $name): void {
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$qb = $this->db->getQueryBuilder();
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$qb->delete('ngb_leases')
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->where($qb->expr()->eq('name', $qb->createNamedParameter($name)))
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->andWhere($qb->expr()->eq('mode', $qb->createNamedParameter(self::SHARED)));
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$qb->executeStatement();
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}
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/** Wraps $refresh so calling it often (per file, per row batch) only touches the database every $seconds. */
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public static function throttled(callable $refresh, int $seconds = 60): \Closure {
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$last = time();
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return static function () use ($refresh, $seconds, &$last): void {
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if (time() - $last >= $seconds) {
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$refresh();
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$last = time();
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}
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};
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}
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/** Run $fn under a lease; $refresh() can be called during long work. */
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public function with(string $name, string $mode, int $ttl, callable $fn): mixed {
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$id = $this->acquire($name, $mode, $ttl);
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try {
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return $fn(fn () => $this->refresh($id, $ttl));
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} finally {
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$this->release($id);
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}
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}
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}
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