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v0.98.0 — R-82 Slice A fix: per-tier vzdump wait bound (the 30-minute false failure)

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Found by live validation on demo-felhom, not by review.

The first real PBS-targeted backup ran past the runner's hard-coded 30-minute
WaitTask bound. The agent stopped waiting and recorded success=false WHILE THE
VZDUMP KEPT RUNNING (still running 72 min later, 2.4 GB uploaded). Consequences:
the tier stays permanently due, the next attempt collides with the guest lock
the live vzdump holds, and the hub sees a DR tier that never succeeds — R-82's
'applied and empty' fault re-created by a timeout.

Measured: ~33 MB/min over wg to Hetzner, so a first FULL ~10 GB snapshot
projects to ~5h.

- BackupTargetConfig.WaitTimeoutSeconds: per-tier bound. Primary 30m UNCHANGED
  (a local vzdump hanging 30m IS a real fault); additional tier 6h, sized from
  the measurement.
- backup.NewBackupRunnerWithWait: per-instance (per-tier) bound.
  NewBackupRunner keeps its signature, so restore-test/selftest are untouched.
- localapi.BackupTier.WaitTimeout: the fire-and-forget context is sized from the
  tier, not a fixed 2h. BOTH bounds had to move — a 6h runner bound under a 2h
  outer context reproduces the same false failure four hours later.

Same direction as restore_test_pbs_restore_timeout_seconds: when in doubt wait
LONGER. A slow backup is a slow backup; a false timeout is a corrupt status
plus lock contention.

Red-proof observed and restored; full suite green.
This commit is contained in:
Claude Code
2026-07-26 14:53:24 +02:00
parent 68bcebe493
commit a667c269c7
7 changed files with 155 additions and 21 deletions
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internal/config/config.go
+43 -7
View File
@@ -391,13 +391,43 @@ type BackupTargetConfig struct {
// (the fail-safe default, and the current behaviour for every PBS target). A PBS tier is never
// pruned by the per-run flag regardless — see BackupRunner.localPruneSpec.
KeepLast int `json:"keep_last"`
// WaitTimeoutSeconds bounds how long the agent WAITS for this tier's vzdump task. 0/unset →
// defaultExtraTierWaitTimeout.
//
// THIS FIELD EXISTS BECAUSE OF A LIVE FAILURE (2026-07-26, R-82 Slice A validation). The runner
// hard-coded a 30-minute wait, which is right for a local vzdump (minutes) and badly wrong for
// an offsite PBS backup over a home uplink: the first full ~10 GB snapshot ran past 30 min, the
// agent gave up waiting and recorded success=false — WHILE THE BACKUP WAS STILL RUNNING. That
// false failure is worse than a slow pass: the tier stays "due", a retry collides with the
// guest lock vzdump still holds, and the hub sees a DR tier that never succeeds.
//
// Same reasoning as RestoreTestPBSRestoreTimeoutSeconds on the restore side, and the same
// direction: when in doubt wait LONGER. A slow backup is a slow backup; a false timeout is a
// corrupt status plus lock contention.
WaitTimeoutSeconds int `json:"wait_timeout_seconds"`
}
// Per-tier vzdump wait bounds.
//
// The PRIMARY keeps the historical 30 minutes: it is the local tier, a local vzdump takes minutes,
// and one hanging 30 minutes is a genuine fault worth surfacing. Unchanged behaviour.
//
// An ADDITIONAL tier is by construction the offsite/WAN one in this design, where the binding
// constraint is uplink speed, not health. 6h covers a first FULL snapshot of a ~10 GB guest at the
// ~30 Mbit/s measured on demo-felhom (that first backup alone projects to ~5.5h); later
// incrementals are far quicker. Sized from the measurement, not guessed.
const (
defaultPrimaryTierWaitTimeout = 30 * time.Minute
defaultExtraTierWaitTimeout = 6 * time.Hour
)
// BackupTier is a RESOLVED backup tier: one target, its own cadence, its own retention. The agent
// builds one runner per tier from these.
type BackupTier struct {
TargetID string
Cadence time.Duration
// WaitTimeout bounds the wait on this tier's vzdump task (see WaitTimeoutSeconds).
WaitTimeout time.Duration
// KeepLast is the per-run prune keep-last; 0 means DO NOT PRUNE this tier.
KeepLast int
// Primary marks the tier that the UNTARGETED local-API endpoints act on — the pre-R-82 tier.
@@ -421,10 +451,11 @@ type BackupTier struct {
// - Duplicate extras are rejected after the first.
func (b BackupConfig) BackupTiers() ([]BackupTier, []string) {
primary := BackupTier{
TargetID: b.BackupTarget(),
Cadence: b.BackupCadence(),
KeepLast: b.KeepLast(),
Primary: true,
TargetID: b.BackupTarget(),
Cadence: b.BackupCadence(),
KeepLast: b.KeepLast(),
WaitTimeout: defaultPrimaryTierWaitTimeout,
Primary: true,
}
tiers := []BackupTier{primary}
var warnings []string
@@ -448,10 +479,15 @@ func (b BackupConfig) BackupTiers() ([]BackupTier, []string) {
if keep < 0 {
keep = 0
}
wait := defaultExtraTierWaitTimeout
if t.WaitTimeoutSeconds > 0 {
wait = time.Duration(t.WaitTimeoutSeconds) * time.Second
}
tiers = append(tiers, BackupTier{
TargetID: id,
Cadence: time.Duration(t.CadenceSeconds) * time.Second,
KeepLast: keep,
TargetID: id,
Cadence: time.Duration(t.CadenceSeconds) * time.Second,
KeepLast: keep,
WaitTimeout: wait,
})
}
return tiers, warnings