Add support for using deployment spec values within appspec.yml file. These same values are also allowed to be used in the hook scripts: https://blogs.aws.amazon.com/application-management/post/Tx1PX2XMPLYPULD/Using-CodeDeploy-Environment-Variables

Author: Eric Hayes

lib/instance_agent/plugins/codedeploy/application_specification/application_specification.rb

@@ -1,3 +1,6 @@
+require 'ostruct'
+require 'erb'
+
 module InstanceAgent
   module Plugins
     module CodeDeployPlugin
@@ -15,7 +18,10 @@ def initialize(yaml_hash, opts = {})
             @permissions = parse_permissions(yaml_hash['permissions'] || [])
           end
 
-          def self.parse(app_spec_string)
+          def self.parse(app_spec_template_string, deployment_spec)
+            # make deployment_spec keys available to the yaml template
+            app_spec_string = ERB.new(app_spec_template_string || '').result(OpenStruct.new(deployment_spec).instance_eval { binding })
+            
             new(YAML.load(app_spec_string))
           end
 

lib/instance_agent/plugins/codedeploy/command_executor.rb

@@ -165,7 +165,14 @@ def last_successful_deployment_dir(deployment_group)
         def default_app_spec(deployment_spec)
           default_app_spec_location = File.join(archive_root_dir(deployment_spec), app_spec_path)
           log(:debug, "Checking for app spec in #{default_app_spec_location}")
-          app_spec =  ApplicationSpecification::ApplicationSpecification.parse(File.read(default_app_spec_location))
+          app_spec =  ApplicationSpecification::ApplicationSpecification.parse(File.read(default_app_spec_location), {
+            :application_name => deployment_spec.application_name,
+            :deployment_id => deployment_spec.deployment_id,
+            :deployment_group_name => deployment_spec.deployment_group_name,
+            :deployment_group_id => deployment_spec.deployment_group_id,
+            :deployment_root_dir => deployment_root_dir(deployment_spec),
+            :last_successful_deployment_dir => last_successful_deployment_dir(deployment_spec.deployment_group_id)
+          })
         end
 
         private

lib/instance_agent/plugins/codedeploy/hook_executor.rb

@@ -179,7 +179,7 @@ def script_absolute_path(script)
         def parse_app_spec
           app_spec_location = File.join(@deployment_archive_dir, @app_spec_path)
           log(:debug, "Checking for app spec in #{app_spec_location}")
-          @app_spec =  ApplicationSpecification::ApplicationSpecification.parse(File.read(app_spec_location))
+          @app_spec =  ApplicationSpecification::ApplicationSpecification.parse(File.read(app_spec_location), deployment_spec)
         end
 
         private
@@ -204,6 +204,18 @@ def mapping_between_hooks_and_deployments
             "ValidateService"=>CURRENT}
         end
 
+        private
+        def deployment_spec
+          {
+            :application_name => @application_name,
+            :deployment_id => @deployment_id,
+            :deployment_group_name => @deployment_group_name,
+            :deployment_group_id => @deployment_group_id,
+            :deployment_root_dir => @current_deployment_root_dir,
+            :last_successful_deployment_dir => @last_successful_deployment_dir
+          }
+        end
+
         private
         def description
           self.class.to_s

test/instance_agent/plugins/codedeploy/command_executor_test.rb

@@ -140,7 +140,7 @@ def generate_signed_message_for(map)
           stubs(:read).
           with("#@archive_root_dir/appspec.yml").
           returns("APP SPEC")
-          ApplicationSpecification::ApplicationSpecification.stubs(:parse).with("APP SPEC").returns(@app_spec)
+          ApplicationSpecification::ApplicationSpecification.stubs(:parse).with("APP SPEC", {}).returns(@app_spec)
         end
 
         should "idempotently create the instructions directory" do