Compare Postgres pod priority on Sync (zalando#1144)

* compare Postgres pod priority on Sync

Co-authored-by: Sergey Dudoladov <sergey.dudoladov@zalando.de>

.travis.yml

@@ -20,4 +20,4 @@ script:
   - hack/verify-codegen.sh
   - travis_wait 20 go test -race -covermode atomic -coverprofile=profile.cov ./pkg/... -v
   - goveralls -coverprofile=profile.cov -service=travis-ci -v
-  - make e2e
+  - travis_wait 20 make e2e

delivery.yaml

@@ -2,6 +2,10 @@ version: "2017-09-20"
 pipeline:
     - id: build-postgres-operator
       type: script
+      vm: large
+      cache:
+        paths:
+          - /go/pkg/mod
       commands:
         - desc: 'Update'
           cmd: |

manifests/configmap.yaml

@@ -85,6 +85,7 @@ data:
   pod_service_account_name: "postgres-pod"
   # pod_service_account_role_binding_definition: ""
   pod_terminate_grace_period: 5m
+  # pod_priority_class_name: "postgres-pod-priority"
   # postgres_superuser_teams: "postgres_superusers"
   # protected_role_names: "admin"
   ready_wait_interval: 3s

manifests/postgres-pod-priority-class.yaml

@@ -0,0 +1,11 @@
+apiVersion: scheduling.k8s.io/v1
+description: 'This priority class must be used only for databases controlled by the
+  Postgres operator'
+kind: PriorityClass
+metadata:
+  labels:
+    application: postgres-operator
+  name: postgres-pod-priority
+preemptionPolicy: PreemptLowerPriority
+globalDefault: false
+value: 1000000

pkg/cluster/cluster.go

@@ -459,6 +459,15 @@ func (c *Cluster) compareStatefulSetWith(statefulSet *appsv1.StatefulSet) *compa
 		}
 	}
 
+	// we assume any change in priority happens by rolling out a new priority class
+	// changing the priority value in an existing class is not supproted
+	if c.Statefulset.Spec.Template.Spec.PriorityClassName != statefulSet.Spec.Template.Spec.PriorityClassName {
+		match = false
+		needsReplace = true
+		needsRollUpdate = true
+		reasons = append(reasons, "new statefulset's pod priority class in spec doesn't match the current one")
+	}
+
 	// lazy Spilo update: modify the image in the statefulset itself but let its pods run with the old image
 	// until they are re-created for other reasons, for example node rotation
 	if c.OpConfig.EnableLazySpiloUpgrade && !reflect.DeepEqual(c.Statefulset.Spec.Template.Spec.Containers[0].Image, statefulSet.Spec.Template.Spec.Containers[0].Image) {