VpcSpecValidator_snippet

    def get_ip_of_peer_instances_and_write_to_settings_file(self):
        '''
        This is run on the source EC2 instance as part of UserData bootstrapping
        1) Look at the peer(s)' VPC CloudFormation Stack's Outputs for a list of subnets, public or private as defined
        in the constructor.
        2) Find instances in those subnets created by this library
        3) Get the Private IP address of target instances and write it to a local configuration file          
        '''

        # Query for peer CloudFormation, get instances
        target_subnet_list = []
        target_ip_list = []
        with open(self.config_file_path, 'r') as ymlfile:
            cfg = yaml.load(ymlfile)

        for peer in self.peers_list:
            peer_stack_name = self.project_name + '-vpc-' + peer + '-' + cfg['region']

            # Look at each peer's CloudFormation Stack Outputs and get a list of subnets (public or private)
            client = boto3.client('cloudformation')
            response = client.describe_stacks(
                StackName=peer_stack_name
            )


            for i in range(0,len(response['Stacks'][0]['Outputs'])):
                if self.public_or_private_subnet == 'public':
                    if 'Subnet' in response['Stacks'][0]['Outputs'][i]['OutputKey'] and 'Public' in \
                            response['Stacks'][0]['Outputs'][i]['OutputKey']:
                        subnet_id = response['Stacks'][0]['Outputs'][i]['OutputValue']
                        target_subnet_list.append(subnet_id)

                else:
                    if 'Subnet' in response['Stacks'][0]['Outputs'][i]['OutputKey'] and 'Private' in \
                            response['Stacks'][0]['Outputs'][i]['OutputKey']:
                        subnet_id = response['Stacks'][0]['Outputs'][i]['OutputValue']
                        target_subnet_list.append(subnet_id)


            # Search the instances in the targeted subnets for a Name tag of VpcSpecValidator
            client = boto3.client('ec2')
            describe_response = client.describe_instances(
                Filters=[{
                    'Name': 'tag:Name',
                    'Values': ['VpcSpecValidator-test-runner-' + peer + '*']
                }]
            )

            # Get Private IP addresses of these instances and write them to target_ip_list.settings

            for i in range(0,len(describe_response['Reservations'])):
                target_ip_list.append(describe_response['Reservations'][i]['Instances'][0]['PrivateIpAddress'])

            # Write the list to a configuration file used at runtime for EC2 instance
            with open('config/env_settings/target_ip_list.settings', 'w') as ymlfile:
                ymlfile.write(str(target_ip_list))