Add concurrencyPolicy to backup CronJobs

Only one pgBackRest backup can run at a time. A scheduled backup that
runs too long can cause the next scheduled backup to fail and retry
multiple times. Skip that next one instead.

Co-authored-by: Scott Zelenka <szelenka@cisco.com>
Issue: #3439

Author: szelenka

internal/controller/postgrescluster/pgbackrest.go

@@ -2880,8 +2880,9 @@ func (r *Reconciler) reconcilePGBackRestCronJob(
 	pgBackRestCronJob := &batchv1.CronJob{
 		ObjectMeta: objectmeta,
 		Spec: batchv1.CronJobSpec{
-			Schedule: *schedule,
-			Suspend:  &suspend,
+			Schedule:          *schedule,
+			Suspend:           &suspend,
+			ConcurrencyPolicy: batchv1.ForbidConcurrent,
 			JobTemplate: batchv1.JobTemplateSpec{
 				ObjectMeta: metav1.ObjectMeta{
 					Annotations: annotations,

internal/controller/postgrescluster/pgbackrest_test.go

@@ -528,6 +528,7 @@ topologySpreadConstraints:
 		// check returned cronjob matches set spec
 		assert.Equal(t, returnedCronJob.Name, "hippocluster-repo1-full")
 		assert.Equal(t, returnedCronJob.Spec.Schedule, testCronSchedule)
+		assert.Equal(t, returnedCronJob.Spec.ConcurrencyPolicy, batchv1.ForbidConcurrent)
 		assert.Equal(t, returnedCronJob.Spec.JobTemplate.Spec.Template.Spec.Containers[0].Name,
 			"pgbackrest")
 		assert.Assert(t, returnedCronJob.Spec.JobTemplate.Spec.Template.Spec.Containers[0].SecurityContext != &corev1.SecurityContext{})
@@ -3641,6 +3642,7 @@ func TestReconcileScheduledBackups(t *testing.T) {
 						// check returned cronjob matches set spec
 						assert.Equal(t, returnedCronJob.Name, cronJobName)
 						assert.Equal(t, returnedCronJob.Spec.Schedule, testCronSchedule)
+						assert.Equal(t, returnedCronJob.Spec.ConcurrencyPolicy, batchv1.ForbidConcurrent)
 						assert.Equal(t, returnedCronJob.Spec.JobTemplate.Spec.Template.Spec.PriorityClassName, "some-priority-class")
 						assert.Equal(t, returnedCronJob.Spec.JobTemplate.Spec.Template.Spec.Containers[0].Name,
 							"pgbackrest")