tests: Log network interfaces before and after destroy

For better upstream Terraform debugging we would like to log the network
interfaces related to the VPC. For further details see:
hashicorp/terraform-provider-aws#1051

tests/rspec/lib/aws_cluster.rb

@@ -8,6 +8,7 @@
 require 'env_var'
 require 'aws_iam'
 require 'aws_support'
+require 'tfstate_file'
 
 # AWSCluster represents a k8s cluster on AWS cloud provider
 class AwsCluster < Cluster
@@ -110,4 +111,30 @@ def tectonic_console_url
       ingress_ext
     end
   end
+
+  private
+
+  def destroy
+    # For debugging purposes (see: https://github.com/terraform-providers/terraform-provider-aws/pull/1051)
+    describe_network_interfaces
+
+    super
+
+    # For debugging purposes (see: https://github.com/terraform-providers/terraform-provider-aws/pull/1051)
+    describe_network_interfaces
+  end
+
+  def describe_network_interfaces
+    puts 'describing network interfaces for debugging purposes'
+    vpc_id = @tfstate_file.value('module.vpc.aws_vpc.cluster_vpc', 'id')
+    filter = "--filters=Name=vpc-id,Values=#{vpc_id}"
+    region = "--region #{@aws_region}"
+
+    success = system("aws ec2 describe-network-interfaces #{filter}  #{region}")
+    raise 'failed to describe network interfaces by vpc' unless success
+
+  # Do not fail build. This is only for debugging purposes
+  rescue => e
+    puts e
+  end
 end

tests/rspec/lib/cluster.rb

@@ -4,6 +4,7 @@
 require 'securerandom'
 require 'jenkins'
 require 'tfvars_file'
+require 'tfstate_file'
 require 'fileutils'
 require 'name_generator'
 require 'password_generator'
@@ -12,7 +13,7 @@
 # Cluster represents a k8s cluster
 class Cluster
   attr_reader :tfvars_file, :kubeconfig, :manifest_path, :build_path,
-              :tectonic_admin_email, :tectonic_admin_password
+              :tectonic_admin_email, :tectonic_admin_password, :tfstate_file
 
   def initialize(tfvars_file)
     @tfvars_file = tfvars_file
@@ -26,6 +27,8 @@ def initialize(tfvars_file)
     @build_path = File.join(File.realpath('../../'), "build/#{@name}")
     @manifest_path = File.join(@build_path, 'generated')
     @kubeconfig = File.join(manifest_path, 'auth/kubeconfig')
+    @tfstate_file = TFStateFile.new(@build_path)
+
     check_prerequisites
     localconfig
     prepare_assets

tests/rspec/lib/tfstate_file.rb

@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+# TFStateFile represents a Terraform state file
+class TFStateFile
+  def initialize(build_path)
+    @build_path = build_path
+  end
+
+  def value(address, wanted_key)
+    file_exists?
+
+    Dir.chdir(@build_path) do
+      state = `terraform state show #{address}`.chomp.split("\n")
+      state.each do |value|
+        key, value = value.split('=')
+        key = key.strip.chomp
+        value = value.strip.chomp
+        return value if key == wanted_key
+      end
+    end
+
+    msg = "could not find value for key \"#{wanted_key}\" in tfstate file #{@build_path}"
+    raise TFStateFileValueForKeyDoesNotExist, msg
+  end
+
+  def file_exists?
+    tfstate_file = File.join(@build_path, 'terraform.tfstate')
+    raise "tfstate file #{tfstate_file} does not exist" unless File.exist? tfstate_file
+  end
+end
+
+class TFStateFileValueForKeyDoesNotExist < StandardError; end