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Myasnikov Daniil
546d8e6a54
The Talos userspace OOM handler (v1.12+) picks its victim by ranking
cgroups with `memory_max.hasValue() ? 0.0 : {Besteffort: 1.0, Burstable:
0.5, ...}[class] * memory_current`, discarding every cgroup that scores
zero. Only a memory limit sets memory.max on the pod cgroup, so only a
limit takes a pod out of the candidate set: a request merely demotes
BestEffort to Burstable, which under the v1.13.6 default
strictCgroupClassOrdering still means "killed second". PriorityClass has
no effect at all, because the handler walks cgroupfs and never talks to
the API server.
Victim selection is decoupled from the trigger, so the cgroup that
caused the pressure and the cgroup that gets SIGKILLed are unrelated by
design. Tenant workloads generally carry limits and system components
generally did not, which inverted the intended order: a tenant workload
thrashing against its own limit drives node-wide memory PSI, and
metallb-speaker or linstor-satellite is killed for it while the workload
responsible is never touched.
An audit found roughly 70 workloads across ~30 packages with at least
one container missing a memory limit, so per-chart resources would
neither cover the current set nor keep covering it. Maintain a
LimitRange in every system namespace instead, at the single choke point
that already creates them and already distinguishes system from tenant
(reconcileNamespaces). Tenant namespaces are left alone because
packages/apps/tenant owns LimitRange policy there.
The limit is a ceiling, not a reservation: it defaults well above real
usage (4Gi against a largest observed system request of 512Mi).
defaultRequest is set explicitly and small, because Kubernetes otherwise
defaults each request to the limit and reserves that much at schedule
time. Setting the limit to 0 disables the LimitRange and removes any the
operator previously created.
Two things keep the feature from being able to hurt more than it helps.
A LimitRange default only reaches a container that declares no memory
limit of its own, and the API server then rejects a request above its
limit. So before applying, scan the namespace for a container that
requests more than the configured limit and sets none, and where one
exists skip the namespace, retract any LimitRange applied earlier, and
log the pod, container, request and limit. This is not hypothetical:
packages/system/monitoring and packages/system/monitoring-agents ship
VPAs for cozy-monitoring with maxAllowed.memory of 8Gi and 6G under
updateMode: Initial, so the VPA admission webhook -- which runs after
the in-tree LimitRanger -- can write a request past 4Gi that no chart in
the tree declares. That is why the check runs against live pods rather
than rendered templates, and why it reads through APIReader rather than
starting a cluster-wide Pod informer.
And no failure inside the feature propagates: a LimitRange error, or a
pod list that cannot be read, is logged and stepped over instead of
failing the Package reconcile. A namespace without a LimitRange is back
to the behaviour of every earlier release, while a namespace that never
reconciles leaves its components uninstalled.
Assisted-By: LLM
Signed-off-by: Myasnikov Daniil <myasnikovdaniil2001@gmail.com>