Add per-project pipeline id

app/models/ci/pipeline.rb

@@ -7,12 +7,15 @@ module Ci
     include Presentable
     include Gitlab::OptimisticLocking
     include Gitlab::Utils::StrongMemoize
+    include AtomicInternalId
 
     belongs_to :project, inverse_of: :pipelines
     belongs_to :user
     belongs_to :auto_canceled_by, class_name: 'Ci::Pipeline'
     belongs_to :pipeline_schedule, class_name: 'Ci::PipelineSchedule'
 
+    has_internal_id :iid, scope: :project, init: ->(s) { s&.project&.pipelines.maximum(:iid) }
+
     has_many :stages
     has_many :statuses, class_name: 'CommitStatus', foreign_key: :commit_id, inverse_of: :pipeline
     has_many :builds, foreign_key: :commit_id, inverse_of: :pipeline

app/models/internal_id.rb

@@ -14,7 +14,7 @@ class InternalId < ActiveRecord::Base
   belongs_to :project
   belongs_to :namespace
 
-  enum usage: { issues: 0, merge_requests: 1, deployments: 2, milestones: 3, epics: 4 }
+  enum usage: { issues: 0, merge_requests: 1, deployments: 2, milestones: 3, epics: 4, ci_pipelines: 5 }
 
   validates :usage, presence: true
 

db/migrate/20180424160449_add_pipeline_iid_to_ci_pipelines.rb

+class AddPipelineIidToCiPipelines < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_column :ci_pipelines, :iid, :integer
+  end
+
+  def down
+    remove_column :ci_pipelines, :iid, :integer
+  end
+end

db/schema.rb

@@ -434,6 +434,7 @@ ActiveRecord::Schema.define(version: 20180425131009) do
     t.integer "config_source"
     t.boolean "protected"
     t.integer "failure_reason"
+    t.integer "iid"
   end
 
   add_index "ci_pipelines", ["auto_canceled_by_id"], name: "index_ci_pipelines_on_auto_canceled_by_id", using: :btree