Backrest

Keep a Backrest server's snapshot index current for restic repositories it does not itself back up, and report how fresh each one is. Backrest indexes snapshots only for repositories it runs backups for; one that is merely configured — the normal shape when restic runs from systemd timers on each host and Backrest is only the console — is never indexed at all, and reports no error while doing so. The repository simply stays empty in the UI, which reads as no backups for a host whose backups are in fact current. sync reads the operation log and reports each repository's newest indexed snapshot. reindex triggers Backrest's own TASK_INDEX_SNAPSHOTS for every configured repository, waits for them to appear, and reports the same shape; it reads repositories and never creates, forgets or prunes a snapshot, so it is safe to schedule. Four server behaviours shape the implementation because each one silently produces a wrong answer if ignored. GetOperations' repoId selector does not filter — a selector matching nothing returns the ENTIRE operation log rather than an empty set, so a per-repository query makes every repository report the whole fleet's totals; operations are therefore fetched once and grouped on each operation's own repoId. A failed index task leaves no trace in the operation log, only successes being recorded, so a repository the server cannot read is indistinguishable through the API from one whose task has not run yet — both are reported as unindexed with the reason named as the server log rather than invented. The task queue is serial, so triggering N repositories enqueues N tasks behind each other and one whose credentials were revoked does not fail fast but retries with exponential backoff for six minutes or more while everything behind it waits, which is why the wait is a deadline over the whole set rather than a per-task timeout. And a repository with no indexed snapshot at all is a different failure from one whose snapshots have stopped advancing — the first is a credential this server holds that no longer exists, the second is a backup that has stopped running — so they are counted separately as unindexed and stale instead of being folded into one unhelpful total. Because it reaches repositories through the server's own stored credentials rather than the ones the backup hosts use, disagreement with a host-side view is informative: it means exactly one of the two credential sets has gone bad.

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