add the possibility to create a standby cluster that streams from a remote primary

charts/postgres-operator/crds/postgresqls.yaml

@@ -474,6 +474,10 @@ spec:
                     type: string
                   gs_wal_path:
                     type: string
+                  standby_host:
+                    type: string
+                  standby_port:
+                    type: string
               streams:
                 type: array
                 nullable: true

docs/reference/cluster_manifest.md

@@ -385,17 +385,25 @@ under the `clone` top-level key and do not affect the already running cluster.
 ## Standby cluster
 
 On startup, an existing `standby` top-level key creates a standby Postgres
-cluster streaming from a remote location. So far streaming from S3 and GCS WAL
-archives is supported.
+cluster streaming from a remote location. Either from a S3 or GCS WAL
+archive or a remote primary. When both of them are set, `standby_host`
+takes precedence.
 
 * **s3_wal_path**
   the url to S3 bucket containing the WAL archive of the remote primary.
-  Optional, but `s3_wal_path`  or `gs_wal_path` is required.
+  Required when the `standby` section is present even when `standby_host` is set.
 
 * **gs_wal_path**
   the url to GS bucket containing the WAL archive of the remote primary.
   Optional, but `s3_wal_path`  or `gs_wal_path` is required.
 
+* **standby_host**
+  hostname or IP address of the primary to stream from.
+  When set, `s3_wal_path` is ignored.
+
+* **standby_port**
+  TCP port on which the primary is listening for connections.
+
 ## Volume properties
 
 Those parameters are grouped under the `volume` top-level key and define the

manifests/postgresql.crd.yaml

@@ -472,6 +472,10 @@ spec:
                     type: string
                   gs_wal_path:
                     type: string
+                  standby_host:
+                    type: string
+                  standby_port:
+                    type: string
               streams:
                 type: array
                 nullable: true

manifests/standby-manifest.yaml

@@ -10,6 +10,8 @@ spec:
   numberOfInstances: 1
   postgresql:
     version: "14"
-# Make this a standby cluster and provide the s3 bucket path of source cluster for continuous streaming.
+  # Make this a standby cluster and provide either the s3 bucket path of source cluster or the remote primary host for continuous streaming.
   standby:
     s3_wal_path: "s3://path/to/bucket/containing/wal/of/source/cluster/"
+    # standby_host: ""
+    # standby_port: ""

pkg/apis/acid.zalan.do/v1/crds.go

@@ -714,6 +714,12 @@ var PostgresCRDResourceValidation = apiextv1.CustomResourceValidation{
 							"gs_wal_path": {
 								Type: "string",
 							},
+							"standby_host": {
+								Type: "string",
+							},
+							"standby_port": {
+								Type: "string",
+							},
 						},
 					},
 					"streams": {

pkg/apis/acid.zalan.do/v1/postgresql_type.go

@@ -168,10 +168,12 @@ type Patroni struct {
 	SynchronousNodeCount  uint32                       `json:"synchronous_node_count,omitempty" defaults:1`
 }
 
-// StandbyDescription contains s3 wal path
+// StandbyDescription contains remote primary config or s3 wal path
 type StandbyDescription struct {
 	S3WalPath string `json:"s3_wal_path,omitempty"`
 	GSWalPath string `json:"gs_wal_path,omitempty"`
+	StandbyHost string `json:"standby_host,omitempty"`
+	StandbyPort string `json:"standby_port,omitempty"`
 }
 
 // TLSDescription specs TLS properties

pkg/cluster/k8sres.go

@@ -1093,9 +1093,10 @@ func (c *Cluster) generateStatefulSet(spec *acidv1.PostgresSpec) (*appsv1.Statef
 	sort.Slice(customPodEnvVarsList,
 		func(i, j int) bool { return customPodEnvVarsList[i].Name < customPodEnvVarsList[j].Name })
 
-	if spec.StandbyCluster != nil && spec.StandbyCluster.S3WalPath == "" &&
-		spec.StandbyCluster.GSWalPath == "" {
-		return nil, fmt.Errorf("one of s3_wal_path or gs_wal_path must be set for standby cluster")
+	if spec.StandbyCluster != nil {
+		if spec.StandbyCluster.S3WalPath == "" && spec.StandbyCluster.GSWalPath == "" && spec.StandbyCluster.StandbyHost == "" {
+			return nil, fmt.Errorf("s3_wal_path, gs_wal_path and standby_host are empty for standby cluster")
+		}
 	}
 
 	// backward compatible check for InitContainers
@@ -1905,10 +1906,19 @@ func (c *Cluster) generateCloneEnvironment(description *acidv1.CloneDescription)
 func (c *Cluster) generateStandbyEnvironment(description *acidv1.StandbyDescription) []v1.EnvVar {
 	result := make([]v1.EnvVar, 0)
 
-	if description.S3WalPath == "" && description.GSWalPath == "" {
-		return nil
+	if description.StandbyHost != "" {
+		// standby from remote primary
+		result = append(result, v1.EnvVar{
+			Name:  "STANDBY_HOST",
+			Value: description.StandbyHost,
+		})
+		if description.StandbyPort != "" {
+			result = append(result, v1.EnvVar{
+				Name:  "STANDBY_PORT",
+				Value: description.StandbyPort,
+			})
 		}
-
+	} else {
 		if description.S3WalPath != "" {
 			// standby with S3, find out the bucket to setup standby
 			msg := "Standby from S3 bucket using custom parsed S3WalPath from the manifest %s "
@@ -1933,12 +1943,13 @@ func (c *Cluster) generateStandbyEnvironment(description *acidv1.StandbyDescript
 				},
 			}
 			result = append(result, envs...)
-
 		}
 
 		result = append(result, v1.EnvVar{Name: "STANDBY_METHOD", Value: "STANDBY_WITH_WALE"})
 		result = append(result, v1.EnvVar{Name: "STANDBY_WAL_BUCKET_SCOPE_PREFIX", Value: ""})
 
+	}
+
 	return result
 }
 

pkg/cluster/k8sres_test.go

@@ -529,6 +529,83 @@ func TestCloneEnv(t *testing.T) {
 	}
 }
 
+func TestStandbyEnv(t *testing.T) {
+	testName := "TestStandbyEnv"
+	tests := []struct {
+		subTest     string
+		standbyOpts *acidv1.StandbyDescription
+		env         v1.EnvVar
+		envPos      int
+	}{
+		{
+			subTest: "from custom s3 path",
+			standbyOpts: &acidv1.StandbyDescription{
+				S3WalPath: "s3://some/path/",
+			},
+			env: v1.EnvVar{
+				Name:  "STANDBY_WALE_S3_PREFIX",
+				Value: "s3://some/path/",
+			},
+			envPos: 0,
+		},
+		{
+			subTest: "from custom gs path",
+			standbyOpts: &acidv1.StandbyDescription{
+				GSWalPath: "gs://some/path/",
+			},
+			env: v1.EnvVar{
+				Name:  "STANDBY_WALE_GS_PREFIX",
+				Value: "gs://some/path/",
+			},
+			envPos: 0,
+		},
+		{
+			subTest: "from remote primary",
+			standbyOpts: &acidv1.StandbyDescription{
+				S3WalPath:   "s3://some/path/",
+				StandbyHost: "remote-primary",
+			},
+			env: v1.EnvVar{
+				Name:  "STANDBY_HOST",
+				Value: "remote-primary",
+			},
+			envPos: 0,
+		},
+		{
+			subTest: "from remote primary with port",
+			standbyOpts: &acidv1.StandbyDescription{
+				S3WalPath:   "s3://some/path/",
+				StandbyHost: "remote-primary",
+				StandbyPort: "9876",
+			},
+			env: v1.EnvVar{
+				Name:  "STANDBY_PORT",
+				Value: "9876",
+			},
+			envPos: 1,
+		},
+	}
+
+	var cluster = New(
+		Config{}, k8sutil.KubernetesClient{}, acidv1.Postgresql{}, logger, eventRecorder)
+
+	for _, tt := range tests {
+		envs := cluster.generateStandbyEnvironment(tt.standbyOpts)
+
+		env := envs[tt.envPos]
+
+		if env.Name != tt.env.Name {
+			t.Errorf("%s %s: Expected env name %s, have %s instead",
+				testName, tt.subTest, tt.env.Name, env.Name)
+		}
+
+		if env.Value != tt.env.Value {
+			t.Errorf("%s %s: Expected env value %s, have %s instead",
+				testName, tt.subTest, tt.env.Value, env.Value)
+		}
+	}
+}
+
 func TestExtractPgVersionFromBinPath(t *testing.T) {
 	testName := "TestExtractPgVersionFromBinPath"
 	tests := []struct {