Working in progress

.gitignore

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+*.gem
+*.rbc
+/.config
+/coverage/
+/InstalledFiles
+/pkg/
+/spec/reports/
+/spec/examples.txt
+/test/tmp/
+/test/version_tmp/
+/tmp/
+
+# Used by dotenv library to load environment variables.
+# # .env
+#
+# ## Specific to RubyMotion:
+# .dat*
+# .repl_history
+# build/
+# *.bridgesupport
+# build-iPhoneOS/
+# build-iPhoneSimulator/
+#
+# ## Specific to RubyMotion (use of CocoaPods):
+# #
+# # We recommend against adding the Pods directory to your .gitignore. However
+# # you should judge for yourself, the pros and cons are mentioned at:
+# # https://guides.cocoapods.org/using/using-cocoapods.html#should-i-check-the-pods-directory-into-source-control
+# #
+# # vendor/Pods/
+#
+# ## Documentation cache and generated files:
+# /.yardoc/
+# /_yardoc/
+# /doc/
+# /rdoc/
+#
+# ## Environment normalization:
+# /.bundle/
+# /vendor/bundle
+# /lib/bundler/man/
+#
+# # for a library or gem, you might want to ignore these files since the code
+# is
+# # intended to run in multiple environments; otherwise, check them in:
+# # Gemfile.lock
+# # .ruby-version
+# # .ruby-gemset
+#
+# # unless supporting rvm < 1.11.0 or doing something fancy, ignore this:
+# .rvmrc

.rspec

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+--color
+--require spec_helper

Gemfile

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+source 'https://rubygems.org'
+
+group :development, :test do
+  gem 'rspec', '~> 3.5'
+end

Gemfile.lock

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+GEM
+  remote: https://rubygems.org/
+  specs:
+    diff-lcs (1.3)
+    rspec (3.5.0)
+      rspec-core (~> 3.5.0)
+      rspec-expectations (~> 3.5.0)
+      rspec-mocks (~> 3.5.0)
+    rspec-core (3.5.4)
+      rspec-support (~> 3.5.0)
+    rspec-expectations (3.5.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.5.0)
+    rspec-mocks (3.5.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.5.0)
+    rspec-support (3.5.0)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  rspec (~> 3.5)
+
+BUNDLED WITH
+   1.13.7

lib/hiera/backend/aws_parameter_store_backend.rb

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+class Hiera
+  module Backend
+    class Aws_parameter_store_backend
+      def initialize(cache=nil)
+        require 'aws-sdk'
+        Hiera.debug("AWS Parameter Store backend starting")
+
+        @cache = read_parameters_from_aws_parameter_store()
+        Hiera.debug("Cache=#{@cache}")
+      end
+
+      def lookup(key, scope, order_override, resolution_type)
+        answer = nil
+
+        Hiera.debug("Looking up #{key} in AWS Parameter Store backend")
+        if @cache.include?(key)
+          # Extra logging that we found the key. This can be outputted
+          # multiple times if the resolution type is array or hash but that
+          # should be expected as the logging will then tell the user ALL the
+          # places where the key is found.
+          Hiera.debug("Found #{key}")
+
+          # for array resolution we just append to the array whatever
+          # we find, we then goes onto the next file and keep adding to
+          # the array
+          #
+          # for priority searches we break after the first found data item
+          new_answer = Backend.parse_answer(@cache[key], scope)
+          case resolution_type
+          when :array
+            raise Exception, "Hiera type mismatch: expected Array and got #{new_answer.class}" unless new_answer.kind_of? Array or new_answer.kind_of? String
+            answer ||= []
+            answer << new_answer
+          when :hash
+            raise Exception, "Hiera type mismatch: expected Hash and got #{new_answer.class}" unless new_answer.kind_of? Hash
+            answer ||= {}
+            answer = Backend.merge_answer(new_answer,answer)
+          else
+            answer = new_answer
+          end
+        end
+
+        return answer
+      end
+
+      private
+
+      def read_parameters_from_aws_parameter_store()
+        Hiera.debug("Creating AWS client")
+        client = Aws::SSM::Client.new()
+
+        prefix = Config[:aws_parameter_store][:prefix]
+        max_results = Config[:aws_parameter_store][:max_results] || 50
+
+        Hiera.debug("Obtaining parameters from AWS Parameter Store with prefix #{prefix}")
+        parameters = {}
+        next_token = nil
+        loop do
+          resp = client.describe_parameters({
+            filters: [
+              {
+                key: "Name",
+                values: [ prefix ],
+              },
+            ],
+            max_results: max_results,
+            next_token: next_token
+            })
+          resp.parameters.each do |parameter|
+            Hiera.debug("Found paramenter: #{parameter}")
+            Aws_parameter_store_backend.add_parameter_to_hash(parameter.name[prefix.length..-1], "test_value", parameters)
+          end
+          next_token = resp.next_token
+          break unless next_token
+        end
+        parameters
+      end
+
+      def self.add_parameter_to_hash(name, value, hash)
+        def self.add_parameter_to_hash_helper(name_list, value, current_hash)
+          raise "Can not add value if name is empty or invalid" if name_list.empty?
+          head = name_list.shift
+          if name_list.empty?
+            raise "Element already exists" if current_hash.has_key?(head)
+            current_hash[head]=value
+            return
+          end
+          current_hash[head] = {} unless current_hash.has_key?(head)
+          new_hash = current_hash[head]
+          raise "Parent element already exists" unless new_hash.is_a?(Hash)
+          add_parameter_to_hash_helper(name_list, value, current_hash[head])
+        end
+        add_parameter_to_hash_helper(name.split('.'), value, hash)
+      end
+    end
+  end
+end

spec/lib/hiera/backend/aws_parameter_store_backend_spec.rb

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+require 'spec_helper'
+require 'hiera/backend/aws_parameter_store_backend'
+
+describe Hiera::Backend::Aws_parameter_store_backend do
+  describe "#add_parameter_to_hash" do
+    it "when name is empty" do
+      hash = {}
+      parameter_name = ''
+      parameter_value = 'value'
+      expect {
+        Hiera::Backend::Aws_parameter_store_backend.send(:add_parameter_to_hash, parameter_name, parameter_value, hash)
+      }.to raise_error(RuntimeError)
+    end
+
+    it "when name is direct string" do
+      hash = {}
+      parameter_name = 'name'
+      parameter_value = 'value'
+      Hiera::Backend::Aws_parameter_store_backend.send(:add_parameter_to_hash, parameter_name, parameter_value, hash)
+      expect(hash).to include(
+        parameter_name => parameter_value
+      )
+    end
+
+    it "when name contains one dot" do
+      hash = {}
+      parameter_name = 'first.name'
+      parameter_value = 'value'
+      Hiera::Backend::Aws_parameter_store_backend.send(:add_parameter_to_hash, parameter_name, parameter_value, hash)
+      expect(hash).to include(
+        "first" => {
+          "name" => parameter_value
+        }
+      )
+    end
+
+    it "when name contains one dot but hash contains the first element" do
+      hash = { "first" => "first_value" }
+      parameter_name = 'first.name'
+      parameter_value = 'value'
+      expect {
+        Hiera::Backend::Aws_parameter_store_backend.send(:add_parameter_to_hash, parameter_name, parameter_value, hash)
+      }.to raise_error(RuntimeError)
+    end
+  end
+end

spec/spec_helper.rb

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+# This file was generated by the `rspec --init` command. Conventionally, all
+# specs live under a `spec` directory, which RSpec adds to the `$LOAD_PATH`.
+# The generated `.rspec` file contains `--require spec_helper` which will cause
+# this file to always be loaded, without a need to explicitly require it in any
+# files.
+#
+# Given that it is always loaded, you are encouraged to keep this file as
+# light-weight as possible. Requiring heavyweight dependencies from this file
+# will add to the boot time of your test suite on EVERY test run, even for an
+# individual file that may not need all of that loaded. Instead, consider making
+# a separate helper file that requires the additional dependencies and performs
+# the additional setup, and require it from the spec files that actually need
+# it.
+#
+# The `.rspec` file also contains a few flags that are not defaults but that
+# users commonly want.
+#
+# See http://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
+RSpec.configure do |config|
+  # rspec-expectations config goes here. You can use an alternate
+  # assertion/expectation library such as wrong or the stdlib/minitest
+  # assertions if you prefer.
+  config.expect_with :rspec do |expectations|
+    # This option will default to `true` in RSpec 4. It makes the `description`
+    # and `failure_message` of custom matchers include text for helper methods
+    # defined using `chain`, e.g.:
+    #     be_bigger_than(2).and_smaller_than(4).description
+    #     # => "be bigger than 2 and smaller than 4"
+    # ...rather than:
+    #     # => "be bigger than 2"
+    expectations.include_chain_clauses_in_custom_matcher_descriptions = true
+  end
+
+  # rspec-mocks config goes here. You can use an alternate test double
+  # library (such as bogus or mocha) by changing the `mock_with` option here.
+  config.mock_with :rspec do |mocks|
+    # Prevents you from mocking or stubbing a method that does not exist on
+    # a real object. This is generally recommended, and will default to
+    # `true` in RSpec 4.
+    mocks.verify_partial_doubles = true
+  end
+
+  # This option will default to `:apply_to_host_groups` in RSpec 4 (and will
+  # have no way to turn it off -- the option exists only for backwards
+  # compatibility in RSpec 3). It causes shared context metadata to be
+  # inherited by the metadata hash of host groups and examples, rather than
+  # triggering implicit auto-inclusion in groups with matching metadata.
+  config.shared_context_metadata_behavior = :apply_to_host_groups
+
+# The settings below are suggested to provide a good initial experience
+# with RSpec, but feel free to customize to your heart's content.
+=begin
+  # This allows you to limit a spec run to individual examples or groups
+  # you care about by tagging them with `:focus` metadata. When nothing
+  # is tagged with `:focus`, all examples get run. RSpec also provides
+  # aliases for `it`, `describe`, and `context` that include `:focus`
+  # metadata: `fit`, `fdescribe` and `fcontext`, respectively.
+  config.filter_run_when_matching :focus
+
+  # Allows RSpec to persist some state between runs in order to support
+  # the `--only-failures` and `--next-failure` CLI options. We recommend
+  # you configure your source control system to ignore this file.
+  config.example_status_persistence_file_path = "spec/examples.txt"
+
+  # Limits the available syntax to the non-monkey patched syntax that is
+  # recommended. For more details, see:
+  #   - http://rspec.info/blog/2012/06/rspecs-new-expectation-syntax/
+  #   - http://www.teaisaweso.me/blog/2013/05/27/rspecs-new-message-expectation-syntax/
+  #   - http://rspec.info/blog/2014/05/notable-changes-in-rspec-3/#zero-monkey-patching-mode
+  config.disable_monkey_patching!
+
+  # This setting enables warnings. It's recommended, but in some cases may
+  # be too noisy due to issues in dependencies.
+  config.warnings = true
+
+  # Many RSpec users commonly either run the entire suite or an individual
+  # file, and it's useful to allow more verbose output when running an
+  # individual spec file.
+  if config.files_to_run.one?
+    # Use the documentation formatter for detailed output,
+    # unless a formatter has already been configured
+    # (e.g. via a command-line flag).
+    config.default_formatter = 'doc'
+  end
+
+  # Print the 10 slowest examples and example groups at the
+  # end of the spec run, to help surface which specs are running
+  # particularly slow.
+  config.profile_examples = 10
+
+  # Run specs in random order to surface order dependencies. If you find an
+  # order dependency and want to debug it, you can fix the order by providing
+  # the seed, which is printed after each run.
+  #     --seed 1234
+  config.order = :random
+
+  # Seed global randomization in this process using the `--seed` CLI option.
+  # Setting this allows you to use `--seed` to deterministically reproduce
+  # test failures related to randomization by passing the same `--seed` value
+  # as the one that triggered the failure.
+  Kernel.srand config.seed
+=end
+end