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Use maxUnavailable for the critical-op PDB to stop idle alert noise (#3141)

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* Use maxUnavailable for the critical-op PDB to stop idle alert noise

The critical-op PDB is created with minAvailable equal to
numberOfInstances while its selector (critical-operation=true) matches
no pods during normal operation. This leaves status.desiredHealthy at N
and currentHealthy at 0 permanently, so monitoring stacks fire alerts
like kube-prometheus-stack's KubePdbNotEnoughHealthyPods for every idle
cluster (#3020).

maxUnavailable: 0 provides the same protection while a critical
operation is running - no voluntary evictions of labeled pods - but
keeps the budget satisfied (desiredHealthy 0) when nothing matches.
When PDBs are disabled or there are no instances, the budget relaxes to
maxUnavailable 100% instead of minAvailable 0.

Fixes #3020

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Update PDB docs for critical-op maxUnavailable semantics

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Clarify why the two PDBs use different budget fields

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
Co-authored-by: Felix Kunde <felix-kunde@gmx.de>
This commit is contained in:
Juhani Pelli
2026-07-27 17:36:42 +02:00
committed by GitHub
co-authored by Claude Fable 5 Felix Kunde
parent d268c589c2
commit 4c1bb1c0ea
3 changed files with 38 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files
pkg/cluster/k8sres.go
+10 -4
View File
@@ -2315,12 +2315,18 @@ func (c *Cluster) generatePrimaryPodDisruptionBudget() *policyv1.PodDisruptionBu
}
func (c *Cluster) generateCriticalOpPodDisruptionBudget() *policyv1.PodDisruptionBudget {
minAvailable := intstr.FromInt32(c.Spec.NumberOfInstances)
// MaxUnavailable: 0 blocks voluntary disruption of any pod carrying the
// critical-operation label, while keeping the budget satisfied when no
// pod matches (status.desiredHealthy stays 0 outside critical
// operations). The previous MinAvailable: N spec left desiredHealthy at
// N with zero matching pods during normal operation, permanently firing
// alerts like kube-prometheus-stack's KubePdbNotEnoughHealthyPods (#3020).
maxUnavailable := intstr.FromInt32(0)
pdbEnabled := c.OpConfig.EnablePodDisruptionBudget
// if PodDisruptionBudget is disabled or if there are no DB pods, set the budget to 0.
// if PodDisruptionBudget is disabled or if there are no DB pods, allow all disruptions.
if (pdbEnabled != nil && !(*pdbEnabled)) || c.Spec.NumberOfInstances <= 0 {
minAvailable = intstr.FromInt(0)
maxUnavailable = intstr.FromString("100%")
}
labels := c.labelsSet(false)
@@ -2335,7 +2341,7 @@ func (c *Cluster) generateCriticalOpPodDisruptionBudget() *policyv1.PodDisruptio
OwnerReferences: c.ownerReferences(),
},
Spec: policyv1.PodDisruptionBudgetSpec{
MinAvailable: &minAvailable,
MaxUnavailable: &maxUnavailable,
Selector: &metav1.LabelSelector{
MatchLabels: labels,
},
pkg/cluster/k8sres_test.go
+15 -4
View File
@@ -2556,6 +2556,17 @@ func TestGeneratePodDisruptionBudget(t *testing.T) {
}
}
hasMaxUnavailable := func(expected string) func(cluster *Cluster, podDisruptionBudget *policyv1.PodDisruptionBudget) error {
return func(cluster *Cluster, podDisruptionBudget *policyv1.PodDisruptionBudget) error {
actual := podDisruptionBudget.Spec.MaxUnavailable.String()
if actual != expected {
return fmt.Errorf("PodDisruptionBudget MaxUnavailable is incorrect, got %s, expected %s",
actual, expected)
}
return nil
}
}
hasMinAvailable := func(expectedMinAvailable int) func(cluster *Cluster, podDisruptionBudget *policyv1.PodDisruptionBudget) error {
return func(cluster *Cluster, podDisruptionBudget *policyv1.PodDisruptionBudget) error {
actual := podDisruptionBudget.Spec.MinAvailable.IntVal
@@ -2749,7 +2760,7 @@ func TestGeneratePodDisruptionBudget(t *testing.T) {
check: []func(cluster *Cluster, podDisruptionBudget *policyv1.PodDisruptionBudget) error{
testPodDisruptionBudgetOwnerReference,
hasName("postgres-myapp-database-critical-op-pdb"),
hasMinAvailable(3),
hasMaxUnavailable("0"),
testLabelsAndSelectors(false),
},
},
@@ -2766,7 +2777,7 @@ func TestGeneratePodDisruptionBudget(t *testing.T) {
check: []func(cluster *Cluster, podDisruptionBudget *policyv1.PodDisruptionBudget) error{
testPodDisruptionBudgetOwnerReference,
hasName("postgres-myapp-database-critical-op-pdb"),
hasMinAvailable(0),
hasMaxUnavailable("100%"),
testLabelsAndSelectors(false),
},
},
@@ -2783,7 +2794,7 @@ func TestGeneratePodDisruptionBudget(t *testing.T) {
check: []func(cluster *Cluster, podDisruptionBudget *policyv1.PodDisruptionBudget) error{
testPodDisruptionBudgetOwnerReference,
hasName("postgres-myapp-database-critical-op-pdb"),
hasMinAvailable(0),
hasMaxUnavailable("100%"),
testLabelsAndSelectors(false),
},
},
@@ -2800,7 +2811,7 @@ func TestGeneratePodDisruptionBudget(t *testing.T) {
check: []func(cluster *Cluster, podDisruptionBudget *policyv1.PodDisruptionBudget) error{
testPodDisruptionBudgetOwnerReference,
hasName("postgres-myapp-database-critical-op-pdb"),
hasMinAvailable(3),
hasMaxUnavailable("0"),
testLabelsAndSelectors(false),
},
},