Add a new AWS backend using Amazon Machine Images

The existing AWS backend uses system containers backed on to the AWS
hosted NFS service (EFS). This has some advantages, but also some
disadvantages.

Using the EFS service allows building a container on one instance,
with the state being held on the EFS, and then launching a new
instance to run the container. Using EFS also provides persistence, at
least beyond individual EC2 instances.

However, build performance when using EFS is poor compared with a
local store without the overhead of the network latency. Additionally,
the startup speed of the container running off EFS is slow compared to
local storage.

This backend doesn't use EFS, instead the Guix store sits on instance
storage. Rather than using a system container for a Mini Environment,
an Amazon Machine Image (AMI) is built instead. The fast local storage
makes builds faster, and using EBS storage for the Mini Envirnoments
as well as not having the overhead of starting Ubuntu, then starting
the container also makes startup faster.

1 files changed, 8 insertions, 4 deletions

diff --git a/app/services/govuk_guix/build_mini_environment.rb b/app/services/govuk_guix/build_mini_environment.rb
index 9cada20..a87c4da 100644
--- a/app/services/govuk_guix/build_mini_environment.rb
+++ b/app/services/govuk_guix/build_mini_environment.rb
@@ -72,12 +72,16 @@ module GovukGuix::BuildMiniEnvironment
       run_remotely_on_host: remote_host
     )
 
-    build_output = output.last.strip
-
-    raise 'InvalidOutput' unless build_output.starts_with? '/gnu/store'
-
+    last_non_empty_line = output.reverse.find do |line|
+      !line.strip.empty?
+    end
+    build_output = last_non_empty_line.strip
     logger.debug(self.class) { "build_output: #{build_output}" }
 
+    unless options[:arguments][:type] == 'aws-packer-ami'
+      raise 'InvalidOutput' unless build_output.starts_with? '/gnu/store'
+    end
+
     mini_environment.update(
       backend_data: {
         build_output: build_output