Class: Kube::Cluster::Middleware::PodAntiAffinity

Inherits:
Kube::Cluster::Middleware show all
Defined in:
lib/kube/cluster/middleware/pod_anti_affinity.rb

Overview

Injects soft pod anti-affinity on pod-bearing resources so that pods prefer to spread across nodes.

The anti-affinity uses the resource’s own matchLabels from spec.selector.matchLabels as the label selector, and kubernetes.io/hostname as the topology key.

Resources that already have spec.template.spec.affinity set are left untouched.

stack do
  use Middleware::PodAntiAffinity
  use Middleware::PodAntiAffinity, topology_key: "topology.kubernetes.io/zone"
end

Constant Summary

Constants inherited from Kube::Cluster::Middleware

DEFAULT_FILTER

Instance Method Summary collapse

Methods inherited from Kube::Cluster::Middleware

build, #filter, #initialize

Constructor Details

This class inherits a constructor from Kube::Cluster::Middleware

Instance Method Details

#call(manifest) ⇒ Object 



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# File 'lib/kube/cluster/middleware/pod_anti_affinity.rb', line 25

def call(manifest)
  topology_key = @opts.fetch(:topology_key, "kubernetes.io/hostname")
  weight = @opts.fetch(:weight, 1)

  manifest.resources.map! do |resource|
    filter(resource) do
      next resource unless resource.pod_bearing?

      h = resource.to_h
      pod_spec = resource.pod_template(h)
      next resource unless pod_spec

      # Don't overwrite existing affinity configuration.
      next resource if pod_spec[:affinity]

      match_labels = h.dig(:spec, :selector, :matchLabels)
      next resource unless match_labels && !match_labels.empty?

      pod_spec[:affinity] = {
        podAntiAffinity: {
          preferredDuringSchedulingIgnoredDuringExecution: [
            {
              weight: weight,
              podAffinityTerm: {
                labelSelector: { matchLabels: match_labels },
                topologyKey: topology_key,
              },
            },
          ],
        },
      }

      resource.rebuild(h)
    end
  end
end