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| 1 | +/* |
| 2 | +Copyright 2025. |
| 3 | +
|
| 4 | +Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | +you may not use this file except in compliance with the License. |
| 6 | +You may obtain a copy of the License at |
| 7 | +
|
| 8 | + http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | +
|
| 10 | +Unless required by applicable law or agreed to in writing, software |
| 11 | +distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | +See the License for the specific language governing permissions and |
| 14 | +limitations under the License. |
| 15 | +*/ |
| 16 | +package scheduler |
| 17 | + |
| 18 | +import ( |
| 19 | + "context" |
| 20 | + "fmt" |
| 21 | + |
| 22 | + "github.com/samber/lo" |
| 23 | + corev1 "k8s.io/api/core/v1" |
| 24 | + metav1 "k8s.io/apimachinery/pkg/apis/meta/v1" |
| 25 | + "k8s.io/apimachinery/pkg/labels" |
| 26 | + v1helper "k8s.io/component-helpers/scheduling/corev1" |
| 27 | + "k8s.io/component-helpers/scheduling/corev1/nodeaffinity" |
| 28 | + "sigs.k8s.io/controller-runtime/pkg/client" |
| 29 | + "sigs.k8s.io/controller-runtime/pkg/log" |
| 30 | +) |
| 31 | + |
| 32 | +type SchedulerSimulator struct { |
| 33 | + client client.Client |
| 34 | + pendingPods []*corev1.Pod |
| 35 | + toBeDeletedPods map[string]*corev1.Pod |
| 36 | + nodes map[string]corev1.Node |
| 37 | +} |
| 38 | + |
| 39 | +func NewSchedulerSimulator(c client.Client, nodes []corev1.Node) *SchedulerSimulator { |
| 40 | + return &SchedulerSimulator{ |
| 41 | + client: c, |
| 42 | + pendingPods: make([]*corev1.Pod, 0), |
| 43 | + toBeDeletedPods: make(map[string]*corev1.Pod), |
| 44 | + nodes: lo.KeyBy(nodes, func(n corev1.Node) string { return n.Name }), |
| 45 | + } |
| 46 | +} |
| 47 | + |
| 48 | +// CanSchedulePodOnNode checks if a pod can be scheduled on a specific node |
| 49 | +// This is a lightweight simulation and does not cover all scheduling scenarios |
| 50 | +// It mainly checks node affinity, tolerations, pod affinity, and pod anti-affinity |
| 51 | +// It does not consider resource requests, limits, or other constraints |
| 52 | +// The returned result may be inaccurate, leading to scheduling failures and causing the Pod to remain in a Pending state. |
| 53 | +func (s *SchedulerSimulator) CanSchedulePodOnNode(ctx context.Context, pod *corev1.Pod, node *corev1.Node) (bool, error) { |
| 54 | + log := log.FromContext(ctx) |
| 55 | + if pod == nil || node == nil { |
| 56 | + return false, nil |
| 57 | + } |
| 58 | + log.WithValues("pod", pod.Name, "node", node.Name) |
| 59 | + if !s.checkNodeAffinity(pod, node) { |
| 60 | + log.V(1).Info("pod cannot be scheduled on node", "reason", "node affinity not match") |
| 61 | + return false, nil |
| 62 | + } |
| 63 | + |
| 64 | + if !s.checkTolerations(pod, node) { |
| 65 | + log.V(1).Info("pod cannot be scheduled on node", "reason", "tolerations not match") |
| 66 | + return false, nil |
| 67 | + } |
| 68 | + |
| 69 | + if v, err := s.checkPodAffinity(ctx, pod, node); err != nil || !v { |
| 70 | + log.V(1).Info("pod cannot be scheduled on node", "reason", "pod affinity not match") |
| 71 | + return false, err |
| 72 | + } |
| 73 | + |
| 74 | + if v, err := s.checkPodAntiAffinity(ctx, pod, node); err != nil || !v { |
| 75 | + log.V(1).Info("pod cannot be scheduled on node", "reason", "pod anti-affinity not match") |
| 76 | + return false, err |
| 77 | + } |
| 78 | + |
| 79 | + log.V(1).Info("pod can be scheduled on node") |
| 80 | + return true, nil |
| 81 | +} |
| 82 | + |
| 83 | +func (s *SchedulerSimulator) AppendPendingPod(pod *corev1.Pod) { |
| 84 | + s.pendingPods = append(s.pendingPods, pod) |
| 85 | +} |
| 86 | + |
| 87 | +func (s *SchedulerSimulator) AppendToBeDeletedPod(pod *corev1.Pod) { |
| 88 | + s.toBeDeletedPods[pod.Name] = pod |
| 89 | +} |
| 90 | + |
| 91 | +func (s *SchedulerSimulator) checkNodeAffinity(pod *corev1.Pod, node *corev1.Node) bool { |
| 92 | + if pod.Spec.Affinity == nil || pod.Spec.Affinity.NodeAffinity == nil { |
| 93 | + return true |
| 94 | + } |
| 95 | + fitsNodeAffinity, _ := nodeaffinity.GetRequiredNodeAffinity(pod).Match(node) |
| 96 | + return fitsNodeAffinity |
| 97 | +} |
| 98 | + |
| 99 | +func (s *SchedulerSimulator) checkTolerations(pod *corev1.Pod, node *corev1.Node) bool { |
| 100 | + _, hasUntoleratedTaint := v1helper.FindMatchingUntoleratedTaint(node.Spec.Taints, pod.Spec.Tolerations, func(t *corev1.Taint) bool { |
| 101 | + return t.Effect == corev1.TaintEffectNoExecute || t.Effect == corev1.TaintEffectNoSchedule |
| 102 | + }) |
| 103 | + return !hasUntoleratedTaint |
| 104 | +} |
| 105 | + |
| 106 | +func (s *SchedulerSimulator) checkPodAffinity(ctx context.Context, pod *corev1.Pod, node *corev1.Node) (bool, error) { |
| 107 | + if pod.Spec.Affinity == nil || pod.Spec.Affinity.PodAffinity == nil { |
| 108 | + return true, nil |
| 109 | + } |
| 110 | + terms := pod.Spec.Affinity.PodAffinity.RequiredDuringSchedulingIgnoredDuringExecution |
| 111 | + if len(terms) == 0 { |
| 112 | + return true, nil |
| 113 | + } |
| 114 | + for _, term := range terms { |
| 115 | + topologyValue, exists := node.Labels[term.TopologyKey] |
| 116 | + if !exists { |
| 117 | + return false, nil |
| 118 | + } |
| 119 | + pods, err := s.ListPodAffinityTermPods(ctx, pod.Name, term, topologyValue) |
| 120 | + if err != nil { |
| 121 | + return false, err |
| 122 | + } |
| 123 | + if len(pods) == 0 { |
| 124 | + return false, nil |
| 125 | + } |
| 126 | + } |
| 127 | + return true, nil |
| 128 | +} |
| 129 | + |
| 130 | +func (s *SchedulerSimulator) checkPodAntiAffinity(ctx context.Context, pod *corev1.Pod, node *corev1.Node) (bool, error) { |
| 131 | + if pod.Spec.Affinity == nil || pod.Spec.Affinity.PodAntiAffinity == nil { |
| 132 | + return true, nil |
| 133 | + } |
| 134 | + terms := pod.Spec.Affinity.PodAntiAffinity.RequiredDuringSchedulingIgnoredDuringExecution |
| 135 | + if len(terms) == 0 { |
| 136 | + return true, nil |
| 137 | + } |
| 138 | + for _, term := range terms { |
| 139 | + topologyValue, exists := node.Labels[term.TopologyKey] |
| 140 | + if !exists { |
| 141 | + // If the topology key doesn't exist, the anti-affinity constraint is considered satisfied. |
| 142 | + continue |
| 143 | + } |
| 144 | + pods, err := s.ListPodAffinityTermPods(ctx, pod.Name, term, topologyValue) |
| 145 | + if err != nil { |
| 146 | + return false, err |
| 147 | + } |
| 148 | + if len(pods) > 0 { |
| 149 | + return false, nil |
| 150 | + } |
| 151 | + } |
| 152 | + return true, nil |
| 153 | +} |
| 154 | + |
| 155 | +// ListPodAffinityTermPods lists pods that match the given PodAffinityTerms |
| 156 | +func (s *SchedulerSimulator) ListPodAffinityTermPods(ctx context.Context, currentPod string, term corev1.PodAffinityTerm, topologyValue string) ([]corev1.Pod, error) { |
| 157 | + var matchedPods []corev1.Pod |
| 158 | + selector, err := metav1.LabelSelectorAsSelector(term.LabelSelector) |
| 159 | + if err != nil { |
| 160 | + return nil, fmt.Errorf("failed to convert label selector: %w", err) |
| 161 | + } |
| 162 | + listOpts := []client.ListOption{ |
| 163 | + client.MatchingLabelsSelector{Selector: selector}, |
| 164 | + } |
| 165 | + |
| 166 | + var podLists []corev1.PodList |
| 167 | + if len(term.Namespaces) > 0 { |
| 168 | + for _, ns := range term.Namespaces { |
| 169 | + var podList corev1.PodList |
| 170 | + nsListOpts := append([]client.ListOption{client.InNamespace(ns)}, listOpts...) |
| 171 | + if err := s.client.List(ctx, &podList, nsListOpts...); err != nil { |
| 172 | + return nil, fmt.Errorf("failed to list pods in namespace %s: %w", ns, err) |
| 173 | + } |
| 174 | + podLists = append(podLists, podList) |
| 175 | + } |
| 176 | + } else { |
| 177 | + var podList corev1.PodList |
| 178 | + if err := s.client.List(ctx, &podList, listOpts...); err != nil { |
| 179 | + return nil, fmt.Errorf("failed to list pods: %w", err) |
| 180 | + } |
| 181 | + podLists = append(podLists, podList) |
| 182 | + } |
| 183 | + |
| 184 | + for _, podList := range podLists { |
| 185 | + for _, pod := range podList.Items { |
| 186 | + node, exists := s.nodes[pod.Spec.NodeName] |
| 187 | + if !exists { |
| 188 | + continue |
| 189 | + } |
| 190 | + if node.Labels[term.TopologyKey] == topologyValue && pod.Name != currentPod && s.toBeDeletedPods[pod.Name] == nil { |
| 191 | + matchedPods = append(matchedPods, pod) |
| 192 | + } |
| 193 | + } |
| 194 | + } |
| 195 | + // check pending pods as well |
| 196 | + for _, pod := range s.pendingPods { |
| 197 | + node, exists := s.nodes[pod.Spec.NodeName] |
| 198 | + if !exists { |
| 199 | + continue |
| 200 | + } |
| 201 | + if node.Labels[term.TopologyKey] == topologyValue && selector.Matches(labels.Set(pod.Labels)) && pod.Name != currentPod { |
| 202 | + matchedPods = append(matchedPods, *pod) |
| 203 | + } |
| 204 | + } |
| 205 | + return matchedPods, nil |
| 206 | +} |
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