providers/aws: main_route_table_id attribute for VPC [GH-193]

CHANGELOG.md

@@ -43,6 +43,7 @@ IMPROVEMENTS:
       `aws_launch_configuration`. [GH-371]
   * providers/aws: Non-destructive update of `desired_capacity` for
       autoscale groups.
+  * providers/aws: Add `main_route_table_id` attribute to VPCs. [GH-193]
   * providers/google: Support `target_tags` for firewalls. [GH-324]
   * providers/google: `google_compute_instance` supports `can_ip_forward` [GH-375]
   * providers/google: `google_compute_disk` supports `type` to support disks

builtin/providers/aws/resource_aws_vpc.go

@@ -36,6 +36,11 @@ func resourceAwsVpc() *schema.Resource {
 				Computed: true,
 			},
 
+			"main_route_table_id": &schema.Schema{
+				Type:     schema.TypeString,
+				Computed: true,
+			},
+
 			"tags": tagsSchema(),
 		},
 	}
@@ -90,7 +95,6 @@ func resourceAwsVpcUpdate(d *schema.ResourceData, meta interface{}) error {
 
 	// Turn on partial mode
 	d.Partial(true)
-	defer d.Partial(false)
 
 	if d.HasChange("enable_dns_hostnames") {
 		options := new(ec2.ModifyVpcAttribute)
@@ -128,7 +132,8 @@ func resourceAwsVpcUpdate(d *schema.ResourceData, meta interface{}) error {
 		d.SetPartial("tags")
 	}
 
-	return nil
+	d.Partial(false)
+	return resourceAwsVpcRead(d, meta)
 }
 
 func resourceAwsVpcDelete(d *schema.ResourceData, meta interface{}) error {
@@ -181,6 +186,18 @@ func resourceAwsVpcRead(d *schema.ResourceData, meta interface{}) error {
 	}
 	d.Set("enable_dns_hostnames", resp.EnableDnsHostnames)
 
+	// Get the main routing table for this VPC
+	filter := ec2.NewFilter()
+	filter.Add("association.main", "true")
+	filter.Add("vpc-id", d.Id())
+	routeResp, err := ec2conn.DescribeRouteTables(nil, filter)
+	if err != nil {
+		return err
+	}
+	if v := routeResp.RouteTables; len(v) > 0 {
+		d.Set("main_route_table_id", v[0].RouteTableId)
+	}
+
 	return nil
 }
 

website/source/docs/providers/aws/r/vpc.html.markdown

@@ -47,4 +47,5 @@ The following attributes are exported:
 * `cidr_block` - The CIDR block of the VPC
 * `enable_dns_support` - Whether or not the VPC has DNS support
 * `enable_dns_hostnames` - Whether or not the VPC has DNS hostname support
-
+* `main_route_table_id` - The ID of the main route table associated with
+     this VPC.