Introduce the explicit definition for production environments

This commit introduces the 'tier' column to 'environments' table
in order to explicit define environment tiers.

app/models/environment.rb

@@ -39,6 +39,7 @@ class Environment < ApplicationRecord
   before_validation :generate_slug, if: ->(env) { env.slug.blank? }
 
   before_save :set_environment_type
+  before_save :ensure_environment_tier
   after_save :clear_reactive_cache!
 
   validates :name,
@@ -87,6 +88,7 @@ class Environment < ApplicationRecord
   end
 
   scope :for_project, -> (project) { where(project_id: project) }
+  scope :for_tier, -> (tier) { where(tier: tier).where('tier IS NOT NULL') }
   scope :with_deployment, -> (sha) { where('EXISTS (?)', Deployment.select(1).where('deployments.environment_id = environments.id').where(sha: sha)) }
   scope :unfoldered, -> { where(environment_type: nil) }
   scope :with_rank, -> do
@@ -94,6 +96,14 @@ class Environment < ApplicationRecord
   end
   scope :for_id, -> (id) { where(id: id) }
 
+  enum tier: {
+    production: 0,
+    staging: 1,
+    testing: 2,
+    development: 3,
+    other: 4
+  }
+
   state_machine :state, initial: :available do
     event :start do
       transition stopped: :available
@@ -429,6 +439,24 @@ class Environment < ApplicationRecord
   def generate_slug
     self.slug = Gitlab::Slug::Environment.new(name).generate
   end
+
+  def ensure_environment_tier
+    return unless ::Feature.enabled?(:environment_tier, project, default_enabled: :yaml)
+
+    self.tier ||= guess_tier
+  end
+
+  # Guessing the tier of the environment if it's not explicitly specified by users.
+  # See https://en.wikipedia.org/wiki/Deployment_environment for industry standard deployment environments
+  def guess_tier
+    case name
+    when %r{dev|review|trunk}i then self.class.tiers[:development]
+    when %r{test|qc}i then self.class.tiers[:testing]
+    when %r{st(a|)g|mod(e|)l|pre|demo}i then self.class.tiers[:staging]
+    when %r{pr(o|)d|live}i then self.class.tiers[:production]
+    else self.class.tiers[:other]
+    end
+  end
 end
 
 Environment.prepend_if_ee('EE::Environment')

changelogs/unreleased/environment-tier.yml

+---
+title: Add tier column to the environments table
+merge_request: 55471
+author:
+type: added

config/feature_flags/development/environment_tier.yml

+---
+name: environment_tier
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/55471
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/323166
+milestone: '13.10'
+type: development
+group: group::release
+default_enabled: false

db/migrate/20210301150451_add_tier_to_environments.rb

+# frozen_string_literal: true
+
+class AddTierToEnvironments < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def up
+    with_lock_retries do
+      add_column :environments, :tier, :smallint
+    end
+  end
+
+  def down
+    with_lock_retries do
+      remove_column :environments, :tier
+    end
+  end
+end

db/migrate/20210303091651_add_index_to_environments_tier.rb

+# frozen_string_literal: true
+
+class AddIndexToEnvironmentsTier < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  INDEX_NAME = 'index_environments_on_project_id_and_tier'
+
+  DOWNTIME = false
+
+  def up
+    add_concurrent_index :environments, [:project_id, :tier], where: 'tier IS NOT NULL', name: INDEX_NAME
+  end
+
+  def down
+    remove_concurrent_index :environments, :state, name: INDEX_NAME
+  end
+end

db/schema_migrations/20210301150451

+6c52ab55814241b37014949976c4f3a0c63bea0a4f9a301735cc9f4c509f433d
\ No newline at end of file

db/schema_migrations/20210303091651

+e1641d84828e3d87aea626dbce6b3b2d231d08fcf1475991fe8d11714cdb0af0
\ No newline at end of file

db/structure.sql

@@ -12144,7 +12144,8 @@ CREATE TABLE environments (
     state character varying DEFAULT 'available'::character varying NOT NULL,
     slug character varying NOT NULL,
     auto_stop_at timestamp with time zone,
-    auto_delete_at timestamp with time zone
+    auto_delete_at timestamp with time zone,
+    tier smallint
 );
 
 CREATE SEQUENCE environments_id_seq
@@ -22179,6 +22180,8 @@ CREATE UNIQUE INDEX index_environments_on_project_id_and_name ON environments US
 
 CREATE UNIQUE INDEX index_environments_on_project_id_and_slug ON environments USING btree (project_id, slug);
 
+CREATE INDEX index_environments_on_project_id_and_tier ON environments USING btree (project_id, tier) WHERE (tier IS NOT NULL);
+
 CREATE INDEX index_environments_on_project_id_state_environment_type ON environments USING btree (project_id, state, environment_type);
 
 CREATE INDEX index_environments_on_state_and_auto_stop_at ON environments USING btree (state, auto_stop_at) WHERE ((auto_stop_at IS NOT NULL) AND ((state)::text = 'available'::text));

spec/factories/environments.rb

@@ -15,6 +15,22 @@ FactoryBot.define do
       state { :stopped }
     end
 
+    trait :production do
+      tier { :production }
+    end
+
+    trait :staging do
+      tier { :staging }
+    end
+
+    trait :testing do
+      tier { :testing }
+    end
+
+    trait :development do
+      tier { :development }
+    end
+
     trait :with_review_app do |environment|
       transient do
         ref { 'master' }

spec/models/environment_spec.rb

@@ -34,6 +34,39 @@ RSpec.describe Environment, :use_clean_rails_memory_store_caching do
 
   it { is_expected.to validate_length_of(:external_url).is_at_most(255) }
 
+  describe '.before_save' do
+    it 'ensures environment tier when a new object is created' do
+      environment = build(:environment, name: 'gprd', tier: nil)
+
+      expect { environment.save }.to change { environment.tier }.from(nil).to('production')
+    end
+
+    it 'ensures environment tier when an existing object is updated' do
+      environment = create(:environment, name: 'gprd')
+      environment.update_column(:tier, nil)
+
+      expect { environment.stop! }.to change { environment.reload.tier }.from(nil).to('production')
+    end
+
+    it 'does not overwrite the existing environment tier' do
+      environment = create(:environment, name: 'gprd', tier: :production)
+
+      expect { environment.update!(name: 'gstg') }.not_to change { environment.reload.tier }
+    end
+
+    context 'when environment_tier feature flag is disabled' do
+      before do
+        stub_feature_flags(environment_tier: false)
+      end
+
+      it 'does not ensure environment tier' do
+        environment = build(:environment, name: 'gprd', tier: nil)
+
+        expect { environment.save }.not_to change { environment.tier }
+      end
+    end
+  end
+
   describe '.order_by_last_deployed_at' do
     let!(:environment1) { create(:environment, project: project) }
     let!(:environment2) { create(:environment, project: project) }
@@ -195,6 +228,62 @@ RSpec.describe Environment, :use_clean_rails_memory_store_caching do
     end
   end
 
+  describe '.for_tier' do
+    let_it_be(:environment) { create(:environment, :production) }
+
+    it 'returns the production environment when searching for production tier' do
+      expect(described_class.for_tier(:production)).to eq([environment])
+    end
+
+    it 'returns nothing when searching for staging tier' do
+      expect(described_class.for_tier(:staging)).to be_empty
+    end
+  end
+
+  describe '#guess_tier' do
+    using RSpec::Parameterized::TableSyntax
+
+    subject { environment.send(:guess_tier) }
+
+    let(:environment) { build(:environment, name: name) }
+
+    where(:name, :tier) do
+      'review/feature'     | described_class.tiers[:development]
+      'review/product'     | described_class.tiers[:development]
+      'DEV'                | described_class.tiers[:development]
+      'development'        | described_class.tiers[:development]
+      'trunk'              | described_class.tiers[:development]
+      'test'               | described_class.tiers[:testing]
+      'TEST'               | described_class.tiers[:testing]
+      'testing'            | described_class.tiers[:testing]
+      'testing-prd'        | described_class.tiers[:testing]
+      'acceptance-testing' | described_class.tiers[:testing]
+      'QC'                 | described_class.tiers[:testing]
+      'gstg'               | described_class.tiers[:staging]
+      'staging'            | described_class.tiers[:staging]
+      'stage'              | described_class.tiers[:staging]
+      'Model'              | described_class.tiers[:staging]
+      'MODL'               | described_class.tiers[:staging]
+      'Pre-production'     | described_class.tiers[:staging]
+      'pre'                | described_class.tiers[:staging]
+      'Demo'               | described_class.tiers[:staging]
+      'gprd'               | described_class.tiers[:production]
+      'gprd-cny'           | described_class.tiers[:production]
+      'production'         | described_class.tiers[:production]
+      'Production'         | described_class.tiers[:production]
+      'prod'               | described_class.tiers[:production]
+      'PROD'               | described_class.tiers[:production]
+      'Live'               | described_class.tiers[:production]
+      'canary'             | described_class.tiers[:other]
+      'other'              | described_class.tiers[:other]
+      'EXP'                | described_class.tiers[:other]
+    end
+
+    with_them do
+      it { is_expected.to eq(tier) }
+    end
+  end
+
   describe '#expire_etag_cache' do
     let(:store) { Gitlab::EtagCaching::Store.new }