implement inter pod topological affinity and anti-affinity

pkg/api/types.go

@@ -1159,11 +1159,109 @@ const (
 	NodeSelectorOpLt           NodeSelectorOperator = "Lt"
 )
 
-// Affinity is a group of affinity scheduling rules, currently
-// only node affinity, but in the future also inter-pod affinity.
+// Affinity is a group of affinity scheduling rules.
 type Affinity struct {
 	// Describes node affinity scheduling rules for the pod.
 	NodeAffinity *NodeAffinity `json:"nodeAffinity,omitempty"`
+	// Describes pod affinity scheduling rules (e.g. co-locate this pod in the same node, zone, etc. as some other pod(s)).
+	PodAffinity *PodAffinity `json:"podAffinity,omitempty"`
+	// Describes pod anti-affinity scheduling rules (e.g. avoid putting this pod in the same node, zone, etc. as some other pod(s)).
+	PodAntiAffinity *PodAntiAffinity `json:"podAntiAffinity,omitempty"`
+}
+
+// Pod affinity is a group of inter pod affinity scheduling rules.
+type PodAffinity struct {
+	// NOT YET IMPLEMENTED. TODO: Uncomment field once it is implemented.
+	// If the affinity requirements specified by this field are not met at
+	// scheduling time, the pod will not be scheduled onto the node.
+	// If the affinity requirements specified by this field cease to be met
+	// at some point during pod execution (e.g. due to a pod label update), the
+	// system will try to eventually evict the pod from its node.
+	// When there are multiple elements, the lists of nodes corresponding to each
+	// podAffinityTerm are intersected, i.e. all terms must be satisfied.
+	// RequiredDuringSchedulingRequiredDuringExecution []PodAffinityTerm  `json:"requiredDuringSchedulingRequiredDuringExecution,omitempty"`
+	// If the affinity requirements specified by this field are not met at
+	// scheduling time, the pod will not be scheduled onto the node.
+	// If the affinity requirements specified by this field cease to be met
+	// at some point during pod execution (e.g. due to a pod label update), the
+	// system may or may not try to eventually evict the pod from its node.
+	// When there are multiple elements, the lists of nodes corresponding to each
+	// podAffinityTerm are intersected, i.e. all terms must be satisfied.
+	RequiredDuringSchedulingIgnoredDuringExecution []PodAffinityTerm `json:"requiredDuringSchedulingIgnoredDuringExecution,omitempty"`
+	// The scheduler will prefer to schedule pods to nodes that satisfy
+	// the affinity expressions specified by this field, but it may choose
+	// a node that violates one or more of the expressions. The node that is
+	// most preferred is the one with the greatest sum of weights, i.e.
+	// for each node that meets all of the scheduling requirements (resource
+	// request, requiredDuringScheduling affinity expressions, etc.),
+	// compute a sum by iterating through the elements of this field and adding
+	// "weight" to the sum if the node has pods which matches the corresponding podAffinityTerm; the
+	// node(s) with the highest sum are the most preferred.
+	PreferredDuringSchedulingIgnoredDuringExecution []WeightedPodAffinityTerm `json:"preferredDuringSchedulingIgnoredDuringExecution,omitempty"`
+}
+
+// Pod anti affinity is a group of inter pod anti affinity scheduling rules.
+type PodAntiAffinity struct {
+	// NOT YET IMPLEMENTED. TODO: Uncomment field once it is implemented.
+	// If the anti-affinity requirements specified by this field are not met at
+	// scheduling time, the pod will not be scheduled onto the node.
+	// If the anti-affinity requirements specified by this field cease to be met
+	// at some point during pod execution (e.g. due to a pod label update), the
+	// system will try to eventually evict the pod from its node.
+	// When there are multiple elements, the lists of nodes corresponding to each
+	// podAffinityTerm are intersected, i.e. all terms must be satisfied.
+	// RequiredDuringSchedulingRequiredDuringExecution []PodAffinityTerm  `json:"requiredDuringSchedulingRequiredDuringExecution,omitempty"`
+	// If the anti-affinity requirements specified by this field are not met at
+	// scheduling time, the pod will not be scheduled onto the node.
+	// If the anti-affinity requirements specified by this field cease to be met
+	// at some point during pod execution (e.g. due to a pod label update), the
+	// system may or may not try to eventually evict the pod from its node.
+	// When there are multiple elements, the lists of nodes corresponding to each
+	// podAffinityTerm are intersected, i.e. all terms must be satisfied.
+	RequiredDuringSchedulingIgnoredDuringExecution []PodAffinityTerm `json:"requiredDuringSchedulingIgnoredDuringExecution,omitempty"`
+	// The scheduler will prefer to schedule pods to nodes that satisfy
+	// the anti-affinity expressions specified by this field, but it may choose
+	// a node that violates one or more of the expressions. The node that is
+	// most preferred is the one with the greatest sum of weights, i.e.
+	// for each node that meets all of the scheduling requirements (resource
+	// request, requiredDuringScheduling anti-affinity expressions, etc.),
+	// compute a sum by iterating through the elements of this field and adding
+	// "weight" to the sum if the node has pods which matches the corresponding podAffinityTerm; the
+	// node(s) with the highest sum are the most preferred.
+	PreferredDuringSchedulingIgnoredDuringExecution []WeightedPodAffinityTerm `json:"preferredDuringSchedulingIgnoredDuringExecution,omitempty"`
+}
+
+// The weights of all of the matched WeightedPodAffinityTerm fields are added per-node to find the most preferred node(s)
+type WeightedPodAffinityTerm struct {
+	// weight associated with matching the corresponding podAffinityTerm,
+	// in the range 1-100.
+	Weight int `json:"weight"`
+	// Required. A pod affinity term, associated with the corresponding weight.
+	PodAffinityTerm PodAffinityTerm `json:"podAffinityTerm"`
+}
+
+// Defines a set of pods (namely those matching the labelSelector
+// relative to the given namespace(s)) that this pod should be
+// co-located (affinity) or not co-located (anti-affinity) with,
+// where co-located is defined as running on a node whose value of
+// the label with key <topologyKey> matches that of any node on which
+// a pod of the set of pods is running.
+type PodAffinityTerm struct {
+	// A label query over a set of resources, in this case pods.
+	LabelSelector *unversioned.LabelSelector `json:"labelSelector,omitempty"`
+	// namespaces specifies which namespaces the labelSelector applies to (matches against);
+	// nil list means "this pod's namespace," empty list means "all namespaces"
+	// The json tag here is not "omitempty" since we need to distinguish nil and empty.
+	// See https://golang.org/pkg/encoding/json/#Marshal for more details.
+	Namespaces []string `json:"namespaces"`
+	// This pod should be co-located (affinity) or not co-located (anti-affinity) with the pods matching
+	// the labelSelector in the specified namespaces, where co-located is defined as running on a node
+	// whose value of the label with key topologyKey matches that of any node on which any of the
+	// selected pods is running.
+	// For PreferredDuringScheduling pod anti-affinity, empty topologyKey is interpreted as "all topologies"
+	// ("all topologies" here means all the topologyKeys indicated by scheduler command-line argument --failure-domains);
+	// for affinity and for RequiredDuringScheduling pod anti-affinity, empty topologyKey is not allowed.
+	TopologyKey string `json:"topologyKey,omitempty"`
 }
 
 // Node affinity is a group of node affinity scheduling rules.
@@ -2604,4 +2702,14 @@ type RangeAllocation struct {
 const (
 	// "default-scheduler" is the name of default scheduler.
 	DefaultSchedulerName = "default-scheduler"
+
+	// RequiredDuringScheduling affinity is not symmetric, but there is an implicit PreferredDuringScheduling affinity rule
+	// corresponding to every RequiredDuringScheduling affinity rule.
+	// When the --hard-pod-affinity-weight scheduler flag is not specified,
+	// DefaultHardPodAffinityWeight defines the weight of the implicit PreferredDuringScheduling affinity rule.
+	DefaultHardPodAffinitySymmetricWeight int = 1
+
+	// When the --failure-domains scheduler flag is not specified,
+	// DefaultFailureDomains defines the set of label keys used when TopologyKey is empty in PreferredDuringScheduling anti-affinity.
+	DefaultFailureDomains string = unversioned.LabelHostname + "," + unversioned.LabelZoneFailureDomain + "," + unversioned.LabelZoneRegion
 )