[override/podtemplatespec] Merge affinities (#1004) (#1052)

Co-authored-by: David Ortiz <david.ortiz@datadoghq.com>

controllers/datadogagent/override/podtemplatespec.go

@@ -10,6 +10,9 @@ import (
 	"sort"
 	"strings"
 
+	"github.com/go-logr/logr"
+	v1 "k8s.io/api/core/v1"
+
 	apicommon "github.com/DataDog/datadog-operator/apis/datadoghq/common"
 	"github.com/DataDog/datadog-operator/apis/datadoghq/common/v1"
 	"github.com/DataDog/datadog-operator/apis/datadoghq/v2alpha1"
@@ -18,8 +21,6 @@ import (
 	"github.com/DataDog/datadog-operator/controllers/datadogagent/object/volume"
 	"github.com/DataDog/datadog-operator/pkg/controller/utils/comparison"
 	"github.com/DataDog/datadog-operator/pkg/defaulting"
-
-	"github.com/go-logr/logr"
 )
 
 // PodTemplateSpec use to override a corev1.PodTemplateSpec with a 2alpha1.DatadogAgentPodTemplateOverride.
@@ -118,7 +119,7 @@ func PodTemplateSpec(logger logr.Logger, manager feature.PodTemplateManagers, ov
 	}
 
 	if override.Affinity != nil {
-		manager.PodTemplateSpec().Spec.Affinity = override.Affinity
+		manager.PodTemplateSpec().Spec.Affinity = mergeAffinities(manager.PodTemplateSpec().Spec.Affinity, override.Affinity)
 	}
 
 	for selectorKey, selectorVal := range override.NodeSelector {
@@ -214,6 +215,162 @@ func overrideImage(currentImg string, overrideImg *common.AgentImageConfig) stri
 	return apicommon.GetImage(&overrideImgCopy, &registry)
 }
 
+func mergeAffinities(affinity1 *v1.Affinity, affinity2 *v1.Affinity) *v1.Affinity {
+	if affinity1 == nil && affinity2 == nil {
+		return nil
+	}
+
+	if affinity1 == nil {
+		return affinity2
+	}
+
+	if affinity2 == nil {
+		return affinity1
+	}
+
+	merged := &v1.Affinity{}
+
+	merged.NodeAffinity = mergeNodeAffinities(affinity1.NodeAffinity, affinity2.NodeAffinity)
+	merged.PodAffinity = mergePodAffinities(affinity1.PodAffinity, affinity2.PodAffinity)
+	merged.PodAntiAffinity = mergePodAntiAffinities(affinity1.PodAntiAffinity, affinity2.PodAntiAffinity)
+
+	return merged
+}
+
+func mergeNodeAffinities(affinity1 *v1.NodeAffinity, affinity2 *v1.NodeAffinity) *v1.NodeAffinity {
+	if affinity1 == nil && affinity2 == nil {
+		return nil
+	}
+
+	if affinity1 == nil {
+		return affinity2
+	}
+
+	if affinity2 == nil {
+		return affinity1
+	}
+
+	merged := &v1.NodeAffinity{}
+
+	merged.RequiredDuringSchedulingIgnoredDuringExecution = mergeNodeSelectors(
+		affinity1.RequiredDuringSchedulingIgnoredDuringExecution,
+		affinity2.RequiredDuringSchedulingIgnoredDuringExecution,
+	)
+
+	merged.PreferredDuringSchedulingIgnoredDuringExecution = append(
+		merged.PreferredDuringSchedulingIgnoredDuringExecution,
+		affinity1.PreferredDuringSchedulingIgnoredDuringExecution...,
+	)
+	merged.PreferredDuringSchedulingIgnoredDuringExecution = append(
+		merged.PreferredDuringSchedulingIgnoredDuringExecution,
+		affinity2.PreferredDuringSchedulingIgnoredDuringExecution...,
+	)
+
+	return merged
+}
+
+func mergeNodeSelectors(selector1 *v1.NodeSelector, selector2 *v1.NodeSelector) *v1.NodeSelector {
+	if selector1 == nil && selector2 == nil {
+		return nil
+	}
+
+	if selector1 == nil {
+		return selector2
+	}
+
+	if selector2 == nil {
+		return selector1
+	}
+
+	merged := &v1.NodeSelector{}
+
+	// Note that the NodeSelectorTerms are ORed together.
+	for _, term1 := range selector1.NodeSelectorTerms {
+		for _, term2 := range selector2.NodeSelectorTerms {
+			mergedTerm := v1.NodeSelectorTerm{
+				// These are ANDed together.
+				MatchExpressions: append(term1.MatchExpressions, term2.MatchExpressions...),
+				MatchFields:      append(term1.MatchFields, term2.MatchFields...),
+			}
+			merged.NodeSelectorTerms = append(merged.NodeSelectorTerms, mergedTerm)
+		}
+	}
+
+	return merged
+}
+
+func mergePodAffinities(affinity1 *v1.PodAffinity, affinity2 *v1.PodAffinity) *v1.PodAffinity {
+	if affinity1 == nil && affinity2 == nil {
+		return nil
+	}
+
+	if affinity1 == nil {
+		return affinity2
+	}
+
+	if affinity2 == nil {
+		return affinity1
+	}
+
+	merged := &v1.PodAffinity{}
+
+	merged.RequiredDuringSchedulingIgnoredDuringExecution = append(
+		merged.RequiredDuringSchedulingIgnoredDuringExecution,
+		affinity1.RequiredDuringSchedulingIgnoredDuringExecution...,
+	)
+	merged.RequiredDuringSchedulingIgnoredDuringExecution = append(
+		merged.RequiredDuringSchedulingIgnoredDuringExecution,
+		affinity2.RequiredDuringSchedulingIgnoredDuringExecution...,
+	)
+
+	merged.PreferredDuringSchedulingIgnoredDuringExecution = append(
+		merged.PreferredDuringSchedulingIgnoredDuringExecution,
+		affinity1.PreferredDuringSchedulingIgnoredDuringExecution...,
+	)
+	merged.PreferredDuringSchedulingIgnoredDuringExecution = append(
+		merged.PreferredDuringSchedulingIgnoredDuringExecution,
+		affinity2.PreferredDuringSchedulingIgnoredDuringExecution...,
+	)
+
+	return merged
+}
+
+func mergePodAntiAffinities(affinity1 *v1.PodAntiAffinity, affinity2 *v1.PodAntiAffinity) *v1.PodAntiAffinity {
+	if affinity1 == nil && affinity2 == nil {
+		return nil
+	}
+
+	if affinity1 == nil {
+		return affinity2
+	}
+
+	if affinity2 == nil {
+		return affinity1
+	}
+
+	merged := &v1.PodAntiAffinity{}
+
+	merged.RequiredDuringSchedulingIgnoredDuringExecution = append(
+		merged.RequiredDuringSchedulingIgnoredDuringExecution,
+		affinity1.RequiredDuringSchedulingIgnoredDuringExecution...,
+	)
+	merged.RequiredDuringSchedulingIgnoredDuringExecution = append(
+		merged.RequiredDuringSchedulingIgnoredDuringExecution,
+		affinity2.RequiredDuringSchedulingIgnoredDuringExecution...,
+	)
+
+	merged.PreferredDuringSchedulingIgnoredDuringExecution = append(
+		merged.PreferredDuringSchedulingIgnoredDuringExecution,
+		affinity1.PreferredDuringSchedulingIgnoredDuringExecution...,
+	)
+	merged.PreferredDuringSchedulingIgnoredDuringExecution = append(
+		merged.PreferredDuringSchedulingIgnoredDuringExecution,
+		affinity2.PreferredDuringSchedulingIgnoredDuringExecution...,
+	)
+
+	return merged
+}
+
 func sortKeys(keysMap map[v2alpha1.AgentConfigFileName]v2alpha1.CustomConfig) []v2alpha1.AgentConfigFileName {
 	sortedKeys := make([]v2alpha1.AgentConfigFileName, 0, len(keysMap))
 	for key := range keysMap {