Prevent empty syncs (#922)

There is a possibility to pass nil as one of the specs and an empty spec
into syncConnectionPooler. In this case it will perfom a syncronization
because nil != empty struct. Avoid such cases and make it testable by
returning list of syncronization reasons on top together with the final
error.

pkg/cluster/cluster.go

@@ -741,7 +741,8 @@ func (c *Cluster) Update(oldSpec, newSpec *acidv1.Postgresql) error {
 	}
 
 	// sync connection pooler
-	if err := c.syncConnectionPooler(oldSpec, newSpec, c.installLookupFunction); err != nil {
+	if _, err := c.syncConnectionPooler(oldSpec, newSpec,
+		c.installLookupFunction); err != nil {
 		return fmt.Errorf("could not sync connection pooler: %v", err)
 	}
 

pkg/cluster/sync.go

@@ -111,7 +111,7 @@ func (c *Cluster) Sync(newSpec *acidv1.Postgresql) error {
 	}
 
 	// sync connection pooler
-	if err = c.syncConnectionPooler(&oldSpec, newSpec, c.installLookupFunction); err != nil {
+	if _, err = c.syncConnectionPooler(&oldSpec, newSpec, c.installLookupFunction); err != nil {
 		return fmt.Errorf("could not sync connection pooler: %v", err)
 	}
 
@@ -620,7 +620,13 @@ func (c *Cluster) syncLogicalBackupJob() error {
 	return nil
 }
 
-func (c *Cluster) syncConnectionPooler(oldSpec, newSpec *acidv1.Postgresql, lookup InstallFunction) error {
+func (c *Cluster) syncConnectionPooler(oldSpec,
+	newSpec *acidv1.Postgresql,
+	lookup InstallFunction) (SyncReason, error) {
+
+	var reason SyncReason
+	var err error
+
 	if c.ConnectionPooler == nil {
 		c.ConnectionPooler = &ConnectionPoolerObjects{}
 	}
@@ -657,20 +663,20 @@ func (c *Cluster) syncConnectionPooler(oldSpec, newSpec *acidv1.Postgresql, look
 				specUser,
 				c.OpConfig.ConnectionPooler.User)
 
-			if err := lookup(schema, user); err != nil {
+			if err = lookup(schema, user); err != nil {
-				return err
+				return NoSync, err
 			}
 		}
 
-		if err := c.syncConnectionPoolerWorker(oldSpec, newSpec); err != nil {
+		if reason, err = c.syncConnectionPoolerWorker(oldSpec, newSpec); err != nil {
 			c.logger.Errorf("could not sync connection pooler: %v", err)
-			return err
+			return reason, err
 		}
 	}
 
 	if oldNeedConnectionPooler && !newNeedConnectionPooler {
 		// delete and cleanup resources
-		if err := c.deleteConnectionPooler(); err != nil {
+		if err = c.deleteConnectionPooler(); err != nil {
 			c.logger.Warningf("could not remove connection pooler: %v", err)
 		}
 	}
@@ -681,20 +687,22 @@ func (c *Cluster) syncConnectionPooler(oldSpec, newSpec *acidv1.Postgresql, look
 			(c.ConnectionPooler.Deployment != nil ||
 				c.ConnectionPooler.Service != nil) {
 
-			if err := c.deleteConnectionPooler(); err != nil {
+			if err = c.deleteConnectionPooler(); err != nil {
 				c.logger.Warningf("could not remove connection pooler: %v", err)
 			}
 		}
 	}
 
-	return nil
+	return reason, nil
 }
 
 // Synchronize connection pooler resources. Effectively we're interested only in
 // synchronizing the corresponding deployment, but in case of deployment or
 // service is missing, create it. After checking, also remember an object for
 // the future references.
-func (c *Cluster) syncConnectionPoolerWorker(oldSpec, newSpec *acidv1.Postgresql) error {
+func (c *Cluster) syncConnectionPoolerWorker(oldSpec, newSpec *acidv1.Postgresql) (
+	SyncReason, error) {
+
 	deployment, err := c.KubeClient.
 		Deployments(c.Namespace).
 		Get(context.TODO(), c.connectionPoolerName(), metav1.GetOptions{})
@@ -706,7 +714,7 @@ func (c *Cluster) syncConnectionPoolerWorker(oldSpec, newSpec *acidv1.Postgresql
 		deploymentSpec, err := c.generateConnectionPoolerDeployment(&newSpec.Spec)
 		if err != nil {
 			msg = "could not generate deployment for connection pooler: %v"
-			return fmt.Errorf(msg, err)
+			return NoSync, fmt.Errorf(msg, err)
 		}
 
 		deployment, err := c.KubeClient.
@@ -714,18 +722,35 @@ func (c *Cluster) syncConnectionPoolerWorker(oldSpec, newSpec *acidv1.Postgresql
 			Create(context.TODO(), deploymentSpec, metav1.CreateOptions{})
 
 		if err != nil {
-			return err
+			return NoSync, err
 		}
 
 		c.ConnectionPooler.Deployment = deployment
 	} else if err != nil {
-		return fmt.Errorf("could not get connection pooler deployment to sync: %v", err)
+		msg := "could not get connection pooler deployment to sync: %v"
+		return NoSync, fmt.Errorf(msg, err)
 	} else {
 		c.ConnectionPooler.Deployment = deployment
 
 		// actual synchronization
 		oldConnectionPooler := oldSpec.Spec.ConnectionPooler
 		newConnectionPooler := newSpec.Spec.ConnectionPooler
+
+		// sync implementation below assumes that both old and new specs are
+		// not nil, but it can happen. To avoid any confusion like updating a
+		// deployment because the specification changed from nil to an empty
+		// struct (that was initialized somewhere before) replace any nil with
+		// an empty spec.
+		if oldConnectionPooler == nil {
+			oldConnectionPooler = &acidv1.ConnectionPooler{}
+		}
+
+		if newConnectionPooler == nil {
+			newConnectionPooler = &acidv1.ConnectionPooler{}
+		}
+
+		c.logger.Infof("Old: %+v, New %+v", oldConnectionPooler, newConnectionPooler)
+
 		specSync, specReason := c.needSyncConnectionPoolerSpecs(oldConnectionPooler, newConnectionPooler)
 		defaultsSync, defaultsReason := c.needSyncConnectionPoolerDefaults(newConnectionPooler, deployment)
 		reason := append(specReason, defaultsReason...)
@@ -736,7 +761,7 @@ func (c *Cluster) syncConnectionPoolerWorker(oldSpec, newSpec *acidv1.Postgresql
 			newDeploymentSpec, err := c.generateConnectionPoolerDeployment(&newSpec.Spec)
 			if err != nil {
 				msg := "could not generate deployment for connection pooler: %v"
-				return fmt.Errorf(msg, err)
+				return reason, fmt.Errorf(msg, err)
 			}
 
 			oldDeploymentSpec := c.ConnectionPooler.Deployment
@@ -746,11 +771,11 @@ func (c *Cluster) syncConnectionPoolerWorker(oldSpec, newSpec *acidv1.Postgresql
 				newDeploymentSpec)
 
 			if err != nil {
-				return err
+				return reason, err
 			}
 
 			c.ConnectionPooler.Deployment = deployment
-			return nil
+			return reason, nil
 		}
 	}
 
@@ -768,16 +793,17 @@ func (c *Cluster) syncConnectionPoolerWorker(oldSpec, newSpec *acidv1.Postgresql
 			Create(context.TODO(), serviceSpec, metav1.CreateOptions{})
 
 		if err != nil {
-			return err
+			return NoSync, err
 		}
 
 		c.ConnectionPooler.Service = service
 	} else if err != nil {
-		return fmt.Errorf("could not get connection pooler service to sync: %v", err)
+		msg := "could not get connection pooler service to sync: %v"
+		return NoSync, fmt.Errorf(msg, err)
 	} else {
 		// Service updates are not supported and probably not that useful anyway
 		c.ConnectionPooler.Service = service
 	}
 
-	return nil
+	return NoSync, nil
 }

pkg/cluster/sync_test.go

@@ -2,6 +2,7 @@ package cluster
 
 import (
 	"fmt"
+	"strings"
 	"testing"
 
 	acidv1 "github.com/zalando/postgres-operator/pkg/apis/acid.zalan.do/v1"
@@ -17,7 +18,7 @@ func int32ToPointer(value int32) *int32 {
 	return &value
 }
 
-func deploymentUpdated(cluster *Cluster, err error) error {
+func deploymentUpdated(cluster *Cluster, err error, reason SyncReason) error {
 	if cluster.ConnectionPooler.Deployment.Spec.Replicas == nil ||
 		*cluster.ConnectionPooler.Deployment.Spec.Replicas != 2 {
 		return fmt.Errorf("Wrong nubmer of instances")
@@ -26,7 +27,7 @@ func deploymentUpdated(cluster *Cluster, err error) error {
 	return nil
 }
 
-func objectsAreSaved(cluster *Cluster, err error) error {
+func objectsAreSaved(cluster *Cluster, err error, reason SyncReason) error {
 	if cluster.ConnectionPooler == nil {
 		return fmt.Errorf("Connection pooler resources are empty")
 	}
@@ -42,7 +43,7 @@ func objectsAreSaved(cluster *Cluster, err error) error {
 	return nil
 }
 
-func objectsAreDeleted(cluster *Cluster, err error) error {
+func objectsAreDeleted(cluster *Cluster, err error, reason SyncReason) error {
 	if cluster.ConnectionPooler != nil {
 		return fmt.Errorf("Connection pooler was not deleted")
 	}
@@ -50,6 +51,16 @@ func objectsAreDeleted(cluster *Cluster, err error) error {
 	return nil
 }
 
+func noEmptySync(cluster *Cluster, err error, reason SyncReason) error {
+	for _, msg := range reason {
+		if strings.HasPrefix(msg, "update [] from '<nil>' to '") {
+			return fmt.Errorf("There is an empty reason, %s", msg)
+		}
+	}
+
+	return nil
+}
+
 func TestConnectionPoolerSynchronization(t *testing.T) {
 	testName := "Test connection pooler synchronization"
 	var cluster = New(
@@ -91,15 +102,15 @@ func TestConnectionPoolerSynchronization(t *testing.T) {
 
 	clusterNewDefaultsMock := *cluster
 	clusterNewDefaultsMock.KubeClient = k8sutil.NewMockKubernetesClient()
-	cluster.OpConfig.ConnectionPooler.Image = "pooler:2.0"
-	cluster.OpConfig.ConnectionPooler.NumberOfInstances = int32ToPointer(2)
 
 	tests := []struct {
 		subTest          string
 		oldSpec          *acidv1.Postgresql
 		newSpec          *acidv1.Postgresql
 		cluster          *Cluster
-		check   func(cluster *Cluster, err error) error
+		defaultImage     string
+		defaultInstances int32
+		check            func(cluster *Cluster, err error, reason SyncReason) error
 	}{
 		{
 			subTest: "create if doesn't exist",
@@ -114,6 +125,8 @@ func TestConnectionPoolerSynchronization(t *testing.T) {
 				},
 			},
 			cluster:          &clusterMissingObjects,
+			defaultImage:     "pooler:1.0",
+			defaultInstances: 1,
 			check:            objectsAreSaved,
 		},
 		{
@@ -127,6 +140,8 @@ func TestConnectionPoolerSynchronization(t *testing.T) {
 				},
 			},
 			cluster:          &clusterMissingObjects,
+			defaultImage:     "pooler:1.0",
+			defaultInstances: 1,
 			check:            objectsAreSaved,
 		},
 		{
@@ -140,6 +155,8 @@ func TestConnectionPoolerSynchronization(t *testing.T) {
 				},
 			},
 			cluster:          &clusterMissingObjects,
+			defaultImage:     "pooler:1.0",
+			defaultInstances: 1,
 			check:            objectsAreSaved,
 		},
 		{
@@ -153,6 +170,8 @@ func TestConnectionPoolerSynchronization(t *testing.T) {
 				Spec: acidv1.PostgresSpec{},
 			},
 			cluster:          &clusterMock,
+			defaultImage:     "pooler:1.0",
+			defaultInstances: 1,
 			check:            objectsAreDeleted,
 		},
 		{
@@ -164,6 +183,8 @@ func TestConnectionPoolerSynchronization(t *testing.T) {
 				Spec: acidv1.PostgresSpec{},
 			},
 			cluster:          &clusterDirtyMock,
+			defaultImage:     "pooler:1.0",
+			defaultInstances: 1,
 			check:            objectsAreDeleted,
 		},
 		{
@@ -183,6 +204,8 @@ func TestConnectionPoolerSynchronization(t *testing.T) {
 				},
 			},
 			cluster:          &clusterMock,
+			defaultImage:     "pooler:1.0",
+			defaultInstances: 1,
 			check:            deploymentUpdated,
 		},
 		{
@@ -198,13 +221,39 @@ func TestConnectionPoolerSynchronization(t *testing.T) {
 				},
 			},
 			cluster:          &clusterNewDefaultsMock,
+			defaultImage:     "pooler:2.0",
+			defaultInstances: 2,
 			check:            deploymentUpdated,
 		},
+		{
+			subTest: "there is no sync from nil to an empty spec",
+			oldSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{
+					EnableConnectionPooler: boolToPointer(true),
+					ConnectionPooler:       nil,
+				},
+			},
+			newSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{
+					EnableConnectionPooler: boolToPointer(true),
+					ConnectionPooler:       &acidv1.ConnectionPooler{},
+				},
+			},
+			cluster:          &clusterMock,
+			defaultImage:     "pooler:1.0",
+			defaultInstances: 1,
+			check:            noEmptySync,
+		},
 	}
 	for _, tt := range tests {
-		err := tt.cluster.syncConnectionPooler(tt.oldSpec, tt.newSpec, mockInstallLookupFunction)
+		tt.cluster.OpConfig.ConnectionPooler.Image = tt.defaultImage
+		tt.cluster.OpConfig.ConnectionPooler.NumberOfInstances =
+			int32ToPointer(tt.defaultInstances)
 
-		if err := tt.check(tt.cluster, err); err != nil {
+		reason, err := tt.cluster.syncConnectionPooler(tt.oldSpec,
+			tt.newSpec, mockInstallLookupFunction)
+
+		if err := tt.check(tt.cluster, err, reason); err != nil {
 			t.Errorf("%s [%s]: Could not synchronize, %+v",
 				testName, tt.subTest, err)
 		}

pkg/cluster/types.go

@@ -73,3 +73,8 @@ type ClusterStatus struct {
 type TemplateParams map[string]interface{}
 
 type InstallFunction func(schema string, user string) error
+
+type SyncReason []string
+
+// no sync happened, empty value
+var NoSync SyncReason = []string{}