1 files changed, 138 insertions, 0 deletions
diff --git a/lib/gitlab/cache/ci/project_pipeline_status.rb b/lib/gitlab/cache/ci/project_pipeline_status.rb
new file mode 100644
index 00000000000..4fc9a075edc
--- /dev/null
+++ b/lib/gitlab/cache/ci/project_pipeline_status.rb
@@ -0,0 +1,138 @@
+# This class is not backed by a table in the main database.
+# It loads the latest Pipeline for the HEAD of a repository, and caches that
+# in Redis.
+module Gitlab
+  module Cache
+    module Ci
+      class ProjectPipelineStatus
+        attr_accessor :sha, :status, :ref, :project, :loaded
+
+        delegate :commit, to: :project
+
+        def self.load_for_project(project)
+          new(project).tap do |status|
+            status.load_status
+          end
+        end
+
+        def self.load_in_batch_for_projects(projects)
+          cached_results_for_projects(projects).zip(projects).each do |result, project|
+            project.pipeline_status = new(project, result)
+            project.pipeline_status.load_status
+          end
+        end
+
+        def self.cached_results_for_projects(projects)
+          result = Gitlab::Redis.with do |redis|
+            redis.multi do
+              projects.each do |project|
+                cache_key = cache_key_for_project(project)
+                redis.exists(cache_key)
+                redis.hmget(cache_key, :sha, :status, :ref)
+              end
+            end
+          end
+
+          result.each_slice(2).map do |(cache_key_exists, (sha, status, ref))|
+            pipeline_info = { sha: sha, status: status, ref: ref }
+            { loaded_from_cache: cache_key_exists, pipeline_info: pipeline_info }
+          end
+        end
+
+        def self.cache_key_for_project(project)
+          "projects/#{project.id}/pipeline_status"
+        end
+
+        def self.update_for_pipeline(pipeline)
+          pipeline_info = {
+            sha: pipeline.sha,
+            status: pipeline.status,
+            ref: pipeline.ref
+          }
+
+          new(pipeline.project, pipeline_info: pipeline_info).
+            store_in_cache_if_needed
+        end
+
+        def initialize(project, pipeline_info: {}, loaded_from_cache: nil)
+          @project = project
+          @sha = pipeline_info[:sha]
+          @ref = pipeline_info[:ref]
+          @status = pipeline_info[:status]
+          @loaded = loaded_from_cache
+        end
+
+        def has_status?
+          loaded? && sha.present? && status.present?
+        end
+
+        def load_status
+          return if loaded?
+
+          if has_cache?
+            load_from_cache
+          else
+            load_from_project
+            store_in_cache
+          end
+
+          self.loaded = true
+        end
+
+        def load_from_project
+          return unless commit
+
+          self.sha = commit.sha
+          self.status = commit.status
+          self.ref = project.default_branch
+        end
+
+        # We only cache the status for the HEAD commit of a project
+        # This status is rendered in project lists
+        def store_in_cache_if_needed
+          return delete_from_cache unless commit
+          return unless sha
+          return unless ref
+
+          if commit.sha == sha && project.default_branch == ref
+            store_in_cache
+          end
+        end
+
+        def load_from_cache
+          Gitlab::Redis.with do |redis|
+            self.sha, self.status, self.ref = redis.hmget(cache_key, :sha, :status, :ref)
+          end
+        end
+
+        def store_in_cache
+          Gitlab::Redis.with do |redis|
+            redis.mapped_hmset(cache_key, { sha: sha, status: status, ref: ref })
+          end
+        end
+
+        def delete_from_cache
+          Gitlab::Redis.with do |redis|
+            redis.del(cache_key)
+          end
+        end
+
+        def has_cache?
+          return self.loaded unless self.loaded.nil?
+
+          Gitlab::Redis.with do |redis|
+            redis.exists(cache_key)
+          end
+        end
+
+        def loaded?
+          self.loaded
+        end
+
+        def cache_key
+          self.class.cache_key_for_project(project)
+        end
+      end
+    end
+  end
+end