Read system parameters that exist in config

.changelog/18486.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+resource/aws_docdb_cluster_parameter_group: Read all user parameters and parameters specified in the configuration.
+```

aws/resource_aws_docdb_cluster_parameter_group.go

@@ -155,15 +155,14 @@ func resourceAwsDocDBClusterParameterGroupRead(d *schema.ResourceData, meta inte
 
 	describeParametersOpts := &docdb.DescribeDBClusterParametersInput{
 		DBClusterParameterGroupName: aws.String(d.Id()),
-		Source:                      aws.String("user"),
 	}
 
 	describeParametersResp, err := conn.DescribeDBClusterParameters(describeParametersOpts)
 	if err != nil {
 		return fmt.Errorf("error reading DocDB Cluster Parameter Group (%s) parameters: %s", d.Id(), err)
 	}
 
-	if err := d.Set("parameter", flattenDocDBParameters(describeParametersResp.Parameters)); err != nil {
+	if err := d.Set("parameter", flattenDocDBParameters(describeParametersResp.Parameters, d)); err != nil {
 		return fmt.Errorf("error setting docdb cluster parameter: %s", err)
 	}
 

aws/resource_aws_docdb_cluster_parameter_group_test.go

@@ -47,6 +47,35 @@ func TestAccAWSDocDBClusterParameterGroup_basic(t *testing.T) {
 	})
 }
 
+func TestAccAWSDocDBClusterParameterGroup_systemParameter(t *testing.T) {
+	var v docdb.DBClusterParameterGroup
+	resourceName := "aws_docdb_cluster_parameter_group.bar"
+
+	parameterGroupName := fmt.Sprintf("cluster-parameter-group-test-terraform-%d", acctest.RandInt())
+
+	resource.ParallelTest(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		ErrorCheck:   testAccErrorCheck(t, docdb.EndpointsID),
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckAWSDocDBClusterParameterGroupDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccAWSDocDBClusterParameterGroupConfig_SystemParameter(parameterGroupName),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckAWSDocDBClusterParameterGroupExists(resourceName, &v),
+					testAccCheckAWSDocDBClusterParameterGroupAttributes(&v, parameterGroupName),
+					testAccMatchResourceAttrRegionalARN(resourceName, "arn", "rds", regexp.MustCompile(fmt.Sprintf("cluster-pg:%s$", parameterGroupName))),
+					resource.TestCheckResourceAttr(resourceName, "name", parameterGroupName),
+					resource.TestCheckResourceAttr(resourceName, "family", "docdb3.6"),
+					resource.TestCheckResourceAttr(resourceName, "description", "Managed by Terraform"),
+					resource.TestCheckResourceAttr(resourceName, "parameter.#", "1"),
+					resource.TestCheckResourceAttr(resourceName, "tags.%", "0"),
+				),
+			},
+		},
+	})
+}
+
 func TestAccAWSDocDBClusterParameterGroup_namePrefix(t *testing.T) {
 	var v docdb.DBClusterParameterGroup
 
@@ -352,6 +381,21 @@ resource "aws_docdb_cluster_parameter_group" "bar" {
 `, name)
 }
 
+func testAccAWSDocDBClusterParameterGroupConfig_SystemParameter(name string) string {
+	return fmt.Sprintf(`
+resource "aws_docdb_cluster_parameter_group" "bar" {
+  family = "docdb3.6"
+  name   = "%s"
+
+  parameter {
+    name         = "tls"
+    value        = "enabled"
+    apply_method = "pending-reboot"
+  }
+}
+`, name)
+}
+
 func testAccAWSDocDBClusterParameterGroupConfig_Description(name, description string) string {
 	return fmt.Sprintf(`
 resource "aws_docdb_cluster_parameter_group" "bar" {

aws/structure.go

@@ -955,10 +955,25 @@ func flattenNeptuneParameters(list []*neptune.Parameter) []map[string]interface{
 }
 
 // Flattens an array of Parameters into a []map[string]interface{}
-func flattenDocDBParameters(list []*docdb.Parameter) []map[string]interface{} {
+func flattenDocDBParameters(list []*docdb.Parameter, d *schema.ResourceData) []map[string]interface{} {
 	result := make([]map[string]interface{}, 0, len(list))
 	for _, i := range list {
 		if i.ParameterValue != nil {
+			name := aws.StringValue(i.ParameterName)
+
+			// Check if any non-user parameters are specified in the configuration.
+			parameterFound := false
+			for _, configParameter := range d.Get("parameter").(*schema.Set).List() {
+				if configParameter.(map[string]interface{})["name"] == name {
+					parameterFound = true
+				}
+			}
+
+			// Skip parameters that are not user defined or specified in the configuration.
+			if aws.StringValue(i.Source) != "user" && !parameterFound {
+				continue
+			}
+
 			result = append(result, map[string]interface{}{
 				"apply_method": aws.StringValue(i.ApplyMethod),
 				"name":         aws.StringValue(i.ParameterName),