feat: Managed Connection Pooling support for AlloyDB (#15330)

Author: nancynh

mmv1/products/alloydb/Instance.yaml

@@ -474,3 +474,31 @@ properties:
     output: true
     item_type:
       type: String
+  - name: 'connectionPoolConfig'
+    type: NestedObject
+    description: |
+      Configuration for Managed Connection Pool.
+    custom_flatten: 'templates/terraform/custom_flatten/alloydb_instance_connectionpoolconfig_flatten.go.tmpl'
+    properties:
+      - name: 'enabled'
+        type: Boolean
+        description: |
+          Whether to enabled Managed Connection Pool.
+        required: true
+      - name: 'poolerCount'
+        type: Integer
+        output: true
+        description: |
+          The number of running poolers per instance.
+      - name: 'flags'
+        type: KeyValuePairs
+        description: |
+          Flags for configuring managed connection pooling when it is enabled.
+          These flags will only be set if `connection_pool_config.enabled` is
+          true.
+          Please see
+          https://cloud.google.com/alloydb/docs/configure-managed-connection-pooling#configuration-options
+          for a comprehensive list of flags that can be set. To specify the flags
+          in Terraform, please remove the "connection-pooling-" prefix and use
+          underscores instead of dashes in the name. For example,
+          "connection-pooling-pool-mode" would be "pool_mode".

mmv1/templates/terraform/custom_flatten/alloydb_instance_connectionpoolconfig_flatten.go.tmpl

@@ -0,0 +1,64 @@
+{{/*
+	The license inside this block applies to this file
+	Copyright 2024 Google Inc.
+	Licensed under the Apache License, Version 2.0 (the "License");
+	you may not use this file except in compliance with the License.
+	You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+	Unless required by applicable law or agreed to in writing, software
+	distributed under the License is distributed on an "AS IS" BASIS,
+	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+	See the License for the specific language governing permissions and
+	limitations under the License.
+*/ -}}
+func flatten{{$.GetPrefix}}{{$.TitlelizeProperty}}(v interface{}, d *schema.ResourceData, config *transport_tpg.Config) interface{} {
+	if v == nil {
+		return nil
+	}
+	original := v.(map[string]interface{})
+	if len(original) == 0 {
+		return flattenAlloyDBInstanceEmptyConnectionPoolConfig(v, d, config)
+	}
+	transformed := make(map[string]interface{})
+	transformed["enabled"] =
+		flattenAlloydbInstanceConnectionPoolConfigEnabled(original["enabled"], d, config)
+	transformed["pooler_count"] =
+		flattenAlloydbInstanceConnectionPoolConfigPoolerCount(original["poolerCount"], d, config)
+	transformed["flags"] =
+		flattenAlloydbInstanceConnectionPoolConfigFlags(original["flags"], d, config)
+	return []interface{}{transformed}
+}
+
+func flattenAlloyDBInstanceEmptyConnectionPoolConfig(v interface{}, d *schema.ResourceData, config *transport_tpg.Config) interface{} {
+	// The API returns an nil/empty value for connectionPoolConfig.enabled when
+	// it's set to false. So keep the user's value to avoid a permadiff.
+	return []interface{}{
+		map[string]interface{}{
+			"enabled":     d.Get("connection_pool_config.0.enabled"),
+		},
+	}
+}
+
+func flattenAlloydbInstanceConnectionPoolConfigEnabled(v interface{}, d *schema.ResourceData, config *transport_tpg.Config) interface{} {
+	return v
+}
+
+func flattenAlloydbInstanceConnectionPoolConfigPoolerCount(v interface{}, d *schema.ResourceData, config *transport_tpg.Config) interface{} {
+	// Handles the string fixed64 format
+	if strVal, ok := v.(string); ok {
+		if intVal, err := tpgresource.StringToFixed64(strVal); err == nil {
+			return intVal
+		}
+	}
+
+	// number values are represented as float64
+	if floatVal, ok := v.(float64); ok {
+		intVal := int(floatVal)
+		return intVal
+	}
+
+	return v // let terraform core handle it otherwise
+}
+
+func flattenAlloydbInstanceConnectionPoolConfigFlags(v interface{}, d *schema.ResourceData, config *transport_tpg.Config) interface{} {
+	return v
+}