add use_default_vpc option for VPC stack

Author: ksmin23

web_analytics/vpc.py

@@ -1,5 +1,8 @@
 #!/usr/bin/env python3
+# -*- encoding: utf-8 -*-
+# vim: tabstop=2 shiftwidth=2 softtabstop=2 expandtab
 
+import os
 import aws_cdk as cdk
 
 from aws_cdk import (
@@ -21,40 +24,40 @@ def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
     # for example,
     # cdk -c vpc_name=your-existing-vpc syth
     #
-    # vpc_name = self.node.try_get_context("vpc_name")
-    # vpc = aws_ec2.Vpc.from_lookup(self, "ExistingVPC",
-    #   is_default=True,
-    #   vpc_name=vpc_name)
-
-    #XXX: To use more than 2 AZs, be sure to specify the account and region on your stack.
-    #XXX: https://docs.aws.amazon.com/cdk/api/latest/python/aws_cdk.aws_ec2/Vpc.html
-    vpc = aws_ec2.Vpc(self, "WebAnalyticsVPC",
-      ip_addresses=aws_ec2.IpAddresses.cidr("10.0.0.0/21"),
-      max_azs=3,
-
-      # 'subnetConfiguration' specifies the "subnet groups" to create.
-      # Every subnet group will have a subnet for each AZ, so this
-      # configuration will create `2 groups × 3 AZs = 6` subnets.
-      subnet_configuration=[
-        {
-          "cidrMask": 24,
-          "name": "Public",
-          "subnetType": aws_ec2.SubnetType.PUBLIC,
-        },
-        {
-          "cidrMask": 24,
-          "name": "Private",
-          "subnetType": aws_ec2.SubnetType.PRIVATE_WITH_EGRESS
+    if str(os.environ.get('USE_DEFAULT_VPC', 'false')).lower() == 'true':
+      vpc_name = self.node.try_get_context("vpc_name")
+      self.vpc = aws_ec2.Vpc.from_lookup(self, "ExistingVPC",
+        is_default=True,
+        vpc_name=vpc_name)
+    else:
+      #XXX: To use more than 2 AZs, be sure to specify the account and region on your stack.
+      #XXX: https://docs.aws.amazon.com/cdk/api/latest/python/aws_cdk.aws_ec2/Vpc.html
+      self.vpc = aws_ec2.Vpc(self, "WebAnalyticsVPC",
+        ip_addresses=aws_ec2.IpAddresses.cidr("10.0.0.0/21"),
+        max_azs=3,
+
+        # 'subnetConfiguration' specifies the "subnet groups" to create.
+        # Every subnet group will have a subnet for each AZ, so this
+        # configuration will create `2 groups × 3 AZs = 6` subnets.
+        subnet_configuration=[
+          {
+            "cidrMask": 24,
+            "name": "Public",
+            "subnetType": aws_ec2.SubnetType.PUBLIC,
+          },
+          {
+            "cidrMask": 24,
+            "name": "Private",
+            "subnetType": aws_ec2.SubnetType.PRIVATE_WITH_EGRESS
+          }
+        ],
+        gateway_endpoints={
+          "S3": aws_ec2.GatewayVpcEndpointOptions(
+            service=aws_ec2.GatewayVpcEndpointAwsService.S3
+          )
         }
-      ],
-      gateway_endpoints={
-        "S3": aws_ec2.GatewayVpcEndpointOptions(
-          service=aws_ec2.GatewayVpcEndpointAwsService.S3
-        )
-      }
-    )
-
-    self.vpc = vpc
-
-    cdk.CfnOutput(self, '{}_VPCID'.format(self.stack_name), value=self.vpc.vpc_id,
-      export_name='VPCID')
+      )
+
+
+    cdk.CfnOutput(self, 'VPCID', value=self.vpc.vpc_id,
+      export_name=f'{self.stack_name}-VPCID')