Extract ProjectStatistics updates into a concern

Refactor existing tests as a shared example

3 files changed, 65 insertions, 32 deletions

diff --git a/app/models/ci/build.rb b/app/models/ci/build.rb
index 5cf9bb4979a..e5236051118 100644
--- a/app/models/ci/build.rb
+++ b/app/models/ci/build.rb
@@ -15,6 +15,7 @@ module Ci
     include Gitlab::Utils::StrongMemoize
     include Deployable
     include HasRef
+    include UpdateProjectStatistics
 
     BuildArchivedError = Class.new(StandardError)
 
@@ -157,8 +158,7 @@ module Ci
       run_after_commit { BuildHooksWorker.perform_async(build.id) }
     end
 
-    after_save :update_project_statistics_after_save, if: :artifacts_size_changed?
-    after_destroy :update_project_statistics_after_destroy, unless: :project_destroyed?
+    update_project_statistics stat: :build_artifacts_size, attribute: :artifacts_size
 
     class << self
       # This is needed for url_for to work,
@@ -847,21 +847,5 @@ module Ci
 
       pipeline.config_processor.build_attributes(name)
     end
-
-    def update_project_statistics_after_save
-      update_project_statistics(read_attribute(:artifacts_size).to_i - artifacts_size_was.to_i)
-    end
-
-    def update_project_statistics_after_destroy
-      update_project_statistics(-artifacts_size)
-    end
-
-    def update_project_statistics(difference)
-      ProjectStatistics.increment_statistic(project_id, :build_artifacts_size, difference)
-    end
-
-    def project_destroyed?
-      project.pending_delete?
-    end
   end
 end
diff --git a/app/models/ci/job_artifact.rb b/app/models/ci/job_artifact.rb
index 9695d49d18b..7c836c6f95c 100644
--- a/app/models/ci/job_artifact.rb
+++ b/app/models/ci/job_artifact.rb
@@ -4,6 +4,7 @@ module Ci
   class JobArtifact < ApplicationRecord
     include AfterCommitQueue
     include ObjectStorage::BackgroundMove
+    include UpdateProjectStatistics
     extend Gitlab::Ci::Model
 
     NotSupportedAdapterError = Class.new(StandardError)
@@ -52,8 +53,8 @@ module Ci
     validates :file_format, presence: true, unless: :trace?, on: :create
     validate :valid_file_format?, unless: :trace?, on: :create
     before_save :set_size, if: :file_changed?
-    after_save :update_project_statistics_after_save, if: :size_changed?
-    after_destroy :update_project_statistics_after_destroy, unless: :project_destroyed?
+
+    update_project_statistics stat: :build_artifacts_size
 
     after_save :update_file_store, if: :file_changed?
 
@@ -176,18 +177,6 @@ module Ci
       self.size = file.size
     end
 
-    def update_project_statistics_after_save
-      update_project_statistics(size.to_i - size_was.to_i)
-    end
-
-    def update_project_statistics_after_destroy
-      update_project_statistics(-self.size.to_i)
-    end
-
-    def update_project_statistics(difference)
-      ProjectStatistics.increment_statistic(project_id, :build_artifacts_size, difference)
-    end
-
     def project_destroyed?
       # Use job.project to avoid extra DB query for project
       job.project.pending_delete?
diff --git a/app/models/concerns/update_project_statistics.rb b/app/models/concerns/update_project_statistics.rb
new file mode 100644
index 00000000000..bffc711c886
--- /dev/null
+++ b/app/models/concerns/update_project_statistics.rb
@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+# This module is providing helpers for updating `ProjectStatistics` with `after_save` and `before_destroy` hooks.
+#
+# It deals with `ProjectStatistics.increment_statistic` making sure not to update statistics on a cascade delete from the
+# project, and keeping track of value deltas on each save. It updates the DB only when a change is needed.
+#
+# How to use
+# - Invoke `update_project_statistics stat: :a_project_statistics_column, attribute: :an_attr_to_track` in a model class body.
+#
+# Expectation
+# - `attribute` must be an ActiveRecord attribute
+# - The model must implement `project` and `project_id`. i.e. direct Project relationship or delegation
+module UpdateProjectStatistics
+  extend ActiveSupport::Concern
+
+  class_methods do
+    attr_reader :statistic_name, :statistic_attribute
+
+    # Configure the model to update +stat+ on ProjectStatistics when +attribute+ changes
+    #
+    # +stat+:: a column of ProjectStatistics to update
+    # +attribute+:: an attribute of the current model, default to +:size+
+    def update_project_statistics(stat:, attribute: :size)
+      @statistic_name = stat
+      @statistic_attribute = attribute
+
+      after_save(:update_project_statistics_after_save, if: :update_project_statistics_attribute_changed?)
+      after_destroy(:update_project_statistics_after_destroy, unless: :project_destroyed?)
+    end
+    private :update_project_statistics
+  end
+
+  included do
+    private
+
+    def project_destroyed?
+      project.pending_delete?
+    end
+
+    def update_project_statistics_attribute_changed?
+      attribute_changed?(self.class.statistic_attribute)
+    end
+
+    def update_project_statistics_after_save
+      attr = self.class.statistic_attribute
+      delta = read_attribute(attr).to_i - attribute_was(attr).to_i
+
+      update_project_statistics(delta)
+    end
+
+    def update_project_statistics_after_destroy
+      update_project_statistics(-read_attribute(self.class.statistic_attribute).to_i)
+    end
+
+    def update_project_statistics(delta)
+      ProjectStatistics.increment_statistic(project_id, self.class.statistic_name, delta)
+    end
+  end
+end