Additive backup_target field, true for the drive backing the PRIMARY tier.
The controller cannot work this out itself: settings.StoragePath.BackupTarget is
customer INTENT, and on the two boxes migrated by hand in E-1 that intent was
never recorded -- intent is empty while the drive really IS the target. Without
this flag the absent-target alarm could not name the drive on exactly the boxes
that currently have one.
omitempty + false on an older agent, so an old controller degrades to the generic
disconnect alarm rather than a wrong one.
Test asserts the target IS flagged AND the non-target is NOT, as a pair -- a
blanket true would satisfy a naive one-sided check.
A regression guard on a configuration that is live right now. E-1 moved each
demo box's whole-guest vzdump target onto its secondary drive at that drive's
own mountpoint -- but RoleForStorage types a local-dir on a non-system device as
user-data, so the existing eject role gate PASSED it. POST /disks/eject on
/mnt/nvme-1tb (demo-hp) or /mnt/hdd_1 (demo-felhom) would have SUCCEEDED
silently, taking the only local whole-guest backup with it, with no alarm and
the box still reporting a configured tier. Found by E-2 Phase 0, not by a
failure.
handleDiskEject and handleDiskDecommission now call refuseIfBackupTarget AFTER
the role gate and refuse with 409, naming the storage and the remedy -- the op
is ordered, not forbidden: reassign the target first.
NOT a role reclassification, which is the obvious fix and the wrong one: making
RoleForStorage return RoleBackup would refuse every legitimate eject of the
customer's own data drive, because on both demo boxes that drive IS the target.
That trades a silent failure for a permanent obstruction.
backupTargetAt resolves through the agent's own storage view, never the caller's
claim, and fails OPEN -- safe because it sits behind the role gate, which fails
SAFE on the same error.
Red-proofed both ways, mutations verified to land first:
- removing the eject guard -> "eject of the backup-target drive SUCCEEDED (200)"
- the over-correction (any backup-content dir storage is the target)
-> the gate blocks /mnt/spare, failing TestEjectStillAllowedOnANonTargetDrive
Harness note: normalizeBackupTiers DROPS tiers with a nil Service and falls back
to the legacy empty-TargetID tier -- an earlier version of this test exercised
nothing and reported the production bug as if the fix had failed.
Green gate: build + vet + test rc=0 (29 packages), run separately from this commit.