Ensembia/nextcloud-ng_backup
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Backup step: write the run only if no other process wrote it since it was loaded

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Dillard Blom
2026-10-11 12:24:00 +02:00
parent 894258f836
commit 6385925845
3 changed files with 58 additions and 25 deletions
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CHANGELOG.md
+3 -3
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@@ -17,9 +17,9 @@ instead carried by the app description, the git tag, the release, and this file.
- A long first backup could end as failed although its snapshot was complete: when its final
step took longer than the step's lease (150 s with `occ backup:run`), the background job took
the run over, finished it a second time and failed on the snapshot it had already recorded,
overwriting the result. The lease now lasts at least 15 minutes, a step no longer overwrites a
run that another process wrote in the meantime, and recording a snapshot that is already
recorded is no longer an error.
overwriting the result. The lease now lasts at least 15 minutes, a step writes the run only if
no other process wrote it since the step loaded it (in one database statement), and recording
a snapshot that is already recorded is no longer an error.
## [0.9.4-beta.5] - 2026-10-09
lib/Db/RunMapper.php
+30
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@@ -17,6 +17,36 @@ final class RunMapper extends QBMapper {
parent::__construct($db, 'ngb_runs', Run::class);
}
/**
* Write $run only if it is still running and unchanged since it was loaded (updated_at
* $loadedAt), in one statement: two processes that loaded the same run cannot both write it.
* The new updated_at is always later than $loadedAt, so every write is seen as a change.
*
* @return Run|null the written run, or null when another process wrote it first
*/
public function updateIfUnchanged(Run $run, int $loadedAt): ?Run {
$run->setUpdatedAt(max(time(), $loadedAt + 1));
$types = $run->getFieldTypes();
$qb = $this->db->getQueryBuilder();
$qb->update($this->getTableName());
foreach (array_keys($run->getUpdatedFields()) as $field) {
if ($field === 'id') {
continue;
}
$value = $run->{'get' . ucfirst($field)}();
$type = ($types[$field] ?? 'string') === 'integer' ? IQueryBuilder::PARAM_INT : IQueryBuilder::PARAM_STR;
$qb->set($run->propertyToColumn($field), $qb->createNamedParameter($value, $value === null ? IQueryBuilder::PARAM_NULL : $type));
}
$qb->where($qb->expr()->eq('id', $qb->createNamedParameter($run->getId(), IQueryBuilder::PARAM_INT)))
->andWhere($qb->expr()->eq('status', $qb->createNamedParameter(Run::RUNNING)))
->andWhere($qb->expr()->eq('updated_at', $qb->createNamedParameter($loadedAt, IQueryBuilder::PARAM_INT)));
if ($qb->executeStatement() !== 1) {
return null;
}
$run->resetUpdatedFields();
return $run;
}
public function find(int $id): Run {
$qb = $this->db->getQueryBuilder();
$qb->select('*')->from($this->getTableName())->where($qb->expr()->eq('id', $qb->createNamedParameter($id, IQueryBuilder::PARAM_INT)));
lib/Service/BackupService.php
+25 -22
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@@ -122,6 +122,7 @@ final class BackupService {
$this->leases->release($runLease);
return $run;
}
$loadedAt = null;
try {
$run = $this->runs->find($run->getId()); // fresh state after acquiring the lock
if ($run->getStatus() !== Run::RUNNING || $run->getKind() !== self::KIND_FULL) {
@@ -183,23 +184,27 @@ final class BackupService {
}
$run->setState(json_encode($state, JSON_THROW_ON_ERROR));
$run->setStats(json_encode(['db' => $state['dbStats'] ?? null, 'files' => $state['files']['stats']], JSON_THROW_ON_ERROR));
$run->setUpdatedAt(time());
$current = $this->takenOver($run->getId(), $loadedAt);
return $current ?? $this->runs->update($run);
// Another process may have taken the run over after this step's lease expired: then its
// writes stand and this step's are dropped.
return $this->runs->updateIfUnchanged($run, $loadedAt) ?? $this->runs->find($run->getId());
} catch (\Throwable $e) {
// Another process that took the run over (after this step's lease expired) may have
// finished it in the meantime: its result stands, this step's error does not.
$current = isset($loadedAt) ? $this->takenOver($run->getId(), $loadedAt) : null;
if ($current !== null) {
$this->logger->warning('NG Backup run ' . $run->getId() . ': a step that another process had taken over ended with: ' . $e->getMessage());
return $current;
if ($loadedAt === null) {
// The run could not even be loaded: there is nothing fresh to mark as failed, and
// the caller's copy may be stale.
$this->logger->error('NG Backup run ' . $run->getId() . ': step could not load the run: ' . $e->getMessage(), ['exception' => $e]);
return $run;
}
$this->logger->error('NG Backup run ' . $run->getId() . ' failed: ' . $e->getMessage(), ['exception' => $e]);
$run->setStatus(Run::FAILED);
$run->setError($e->getMessage());
$run->setFinishedAt(time());
$run->setUpdatedAt(time());
$run = $this->runs->update($run);
$failed = $this->runs->updateIfUnchanged($run, $loadedAt);
if ($failed === null) {
// Another process that took the run over may have finished it: its result stands.
$this->logger->warning('NG Backup run ' . $run->getId() . ': a step that another process had taken over ended with: ' . $e->getMessage());
return $this->runs->find($run->getId());
}
$run = $failed;
$this->logger->error('NG Backup run ' . $run->getId() . ' failed: ' . $e->getMessage(), ['exception' => $e]);
try {
$this->alerts->runFailed($run, isset($target) ? $target->getName() : '#' . $run->getTargetId());
} catch (\Throwable) {
@@ -211,15 +216,6 @@ final class BackupService {
}
}
/**
* The run as stored, when another process has written it since this step loaded it (updated_at
* $loadedAt); null when it is still this step's to write.
*/
private function takenOver(int $runId, int $loadedAt): ?Run {
$current = $this->runs->find($runId);
return $current->getUpdatedAt() !== $loadedAt || $current->getStatus() !== Run::RUNNING ? $current : null;
}
/** Run to completion in this process (occ, system cron), reporting progress. */
public function runToCompletion(Run $run, ?callable $progress = null, float $stepSeconds = 30): Run {
while ($run->getStatus() === Run::RUNNING) {
@@ -259,7 +255,14 @@ final class BackupService {
$s->setCreatedAt(time());
$s->setFiles($files['stats']['files']);
$s->setBytes($files['stats']['bytes']);
$this->snapshots->insert($s);
try {
$this->snapshots->insert($s);
} catch (\OCP\DB\Exception $e) {
// Recorded by another process between the check above and this insert.
if ($e->getReason() !== \OCP\DB\Exception::REASON_UNIQUE_CONSTRAINT_VIOLATION) {
throw $e;
}
}
}
/** @return list<string> */