From a60b2982ad8b2a9966fb16aa251ea21a376d711a Mon Sep 17 00:00:00 2001
From: Christopher Baines <mail@cbaines.net>
Date: Sat, 23 Jun 2018 23:45:03 +0100
Subject: Switch to using the public AWS domain of the build machine

Rather than the configured domain, as the corresponding SSH key
shouldn't change for the AWS domain (whereas it does for the
configured domain, if the machine changes).
---
 app/controllers/govuk_guix/revisions_controller.rb |  6 +++++-
 .../backends/terraform_aws/backend_methods.rb      | 10 +++++++++-
 .../terraform_aws/mini_environment_methods.rb      | 22 ++++++++++++++++++++--
 terraform/aws/backend/main.tf                      |  4 ++++
 test/models/backends/terraform_aws_test.rb         | 11 +++++++++++
 5 files changed, 49 insertions(+), 4 deletions(-)

diff --git a/app/controllers/govuk_guix/revisions_controller.rb b/app/controllers/govuk_guix/revisions_controller.rb
index 838bdae..6e75e82 100644
--- a/app/controllers/govuk_guix/revisions_controller.rb
+++ b/app/controllers/govuk_guix/revisions_controller.rb
@@ -33,8 +33,12 @@ class GovukGuix::RevisionsController < ApplicationController
       # Assume that the AWS backend is in use
       backend = Backends::TerraformAws.first
 
+      remote_host = backend.backend_latest_terraform_state.output_value(
+        'guix_daemon_public_dns'
+      )
+
       options = {
-        run_remotely_on_host: "ubuntu@guix-daemon.#{backend.domain}"
+        run_remotely_on_host: "ubuntu@#{remote_host}"
       }
     end
 
diff --git a/app/models/backends/terraform_aws/backend_methods.rb b/app/models/backends/terraform_aws/backend_methods.rb
index 89509bd..b21c83e 100644
--- a/app/models/backends/terraform_aws/backend_methods.rb
+++ b/app/models/backends/terraform_aws/backend_methods.rb
@@ -20,8 +20,12 @@
 
 module Backends::TerraformAws::BackendMethods
   def create_data_snapshot
+    remote_host = backend_latest_terraform_state.output_value(
+      'guix_daemon_public_dns'
+    )
+
     GovukGuix::CreateDataSnapshotJob.enqueue(
-      run_remotely_on_host: "ubuntu@guix-daemon.#{domain}",
+      run_remotely_on_host: "ubuntu@#{remote_host}",
       backend_type: self.class.name,
       backend_id: id
     )
@@ -101,6 +105,10 @@ module Backends::TerraformAws::BackendMethods
     )
   end
 
+  def backend_latest_terraform_state
+    backend_terraform_states.order(:id).last
+  end
+
   def status
     latest_terraform_state = backend_terraform_states.order(:id).last
 
diff --git a/app/models/backends/terraform_aws/mini_environment_methods.rb b/app/models/backends/terraform_aws/mini_environment_methods.rb
index e0fe03b..6049829 100644
--- a/app/models/backends/terraform_aws/mini_environment_methods.rb
+++ b/app/models/backends/terraform_aws/mini_environment_methods.rb
@@ -22,6 +22,14 @@ module Backends::TerraformAws::MiniEnvironmentMethods
   def build(mini_environment)
     slug = mini_environment.name.parameterize
 
+    remote_build_host =
+      mini_environment
+        .backend
+        .backend_latest_terraform_state
+        .output_value(
+          'guix_daemon_public_dns'
+        )
+
     GovukGuix::BuildMiniEnvironment.build(
       mini_environment.id,
       services: mini_environment.services.map(&:build_argument_string),
@@ -42,7 +50,7 @@ module Backends::TerraformAws::MiniEnvironmentMethods
           '/var/log/govuk-mini-environment-admin=/var/log'
         ]
       },
-      run_remotely_on_host: "ubuntu@guix-daemon.#{domain}"
+      run_remotely_on_host: "ubuntu@#{remote_build_host}"
     )
   end
 
@@ -74,13 +82,23 @@ module Backends::TerraformAws::MiniEnvironmentMethods
     end
   end
 
+  def terraform_states(mini_environment)
+    TerraformState.where(
+      state_id: mini_environment_state_id(mini_environment)
+    )
+  end
+
   def within_terraform_working_directory(mini_environment, &block)
     TerraformWorkingDirectory.new(
-      "mini_environment/#{mini_environment.id}",
+      mini_environment_state_id(mini_environment),
       'terraform/aws/mini_environment'
     ).within_working_directory(&block)
   end
 
+  def mini_environment_state_id(mini_environment)
+    "mini_environment/#{mini_environment.id}"
+  end
+
   def signon_url(mini_environment)
     "https://signon.#{mini_environment.name.parameterize}.#{domain}"
   end
diff --git a/terraform/aws/backend/main.tf b/terraform/aws/backend/main.tf
index 24dd3d8..c3fcf60 100644
--- a/terraform/aws/backend/main.tf
+++ b/terraform/aws/backend/main.tf
@@ -352,6 +352,10 @@ output "guix_daemon_private_dns" {
   value = "${aws_spot_instance_request.main.private_dns}"
 }
 
+output "guix_daemon_public_dns" {
+  value = "${aws_spot_instance_request.main.public_dns}"
+}
+
 output "efs_file_system_dns_name" {
   value = "${aws_efs_file_system.main.dns_name}"
 }
diff --git a/test/models/backends/terraform_aws_test.rb b/test/models/backends/terraform_aws_test.rb
index 1a98440..f9a34f3 100644
--- a/test/models/backends/terraform_aws_test.rb
+++ b/test/models/backends/terraform_aws_test.rb
@@ -3,9 +3,20 @@ require 'test_helper'
 class Backends::TerraformAwsTest < ActiveSupport::TestCase
   setup do
     @backend = Backends::TerraformAws.new
+
+    backend_latest_terraform_state = mock
+    backend_latest_terraform_state
+      .stubs(:output_value)
+      .returns('example.com')
+
+    @backend.stubs(:backend_latest_terraform_state).returns(
+      backend_latest_terraform_state
+    )
+
     @mini_environment = MiniEnvironment.new(
       id: 1,
       name: 'Test Mini Environment',
+      backend: @backend,
       backend_data: {
         'build_output' => '/gnu/store/testbuildoutput'
       }
-- 
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