Allow `rake cache:clear` clearing pipeline status cache

* Use the correct key prefix
* Clear old cache keys

TODO:

At some point we could remove clearing old cache keys.

changelogs/unreleased/44582-clear-pipeline-status-cache.yml

+---
+title: Now `rake cache:clear` will also clear pipeline status cache
+merge_request: 18257
+author:
+type: fixed

lib/gitlab/cache/ci/project_pipeline_status.rb

@@ -40,7 +40,7 @@ module Gitlab
         end
 
         def self.cache_key_for_project(project)
-          "projects/#{project.id}/pipeline_status"
+          "#{Gitlab::Redis::Cache::CACHE_NAMESPACE}:projects/#{project.id}/pipeline_status"
         end
 
         def self.update_for_pipeline(pipeline)

lib/tasks/cache.rake

@@ -6,11 +6,15 @@ namespace :cache do
     desc "GitLab | Clear redis cache"
     task redis: :environment do
       Gitlab::Redis::Cache.with do |redis|
+        cache_key_pattern = %W[#{Gitlab::Redis::Cache::CACHE_NAMESPACE}*
+                               projects/*/pipeline_status]
+
+        cache_key_pattern.each do |match|
           cursor = REDIS_SCAN_START_STOP
           loop do
             cursor, keys = redis.scan(
               cursor,
-            match: "#{Gitlab::Redis::Cache::CACHE_NAMESPACE}*",
+              match: match,
               count: REDIS_CLEAR_BATCH_SIZE
             )
 
@@ -20,6 +24,7 @@ namespace :cache do
           end
         end
       end
+    end
 
     task all: [:redis]
   end

spec/lib/gitlab/cache/ci/project_pipeline_status_spec.rb

@@ -3,7 +3,7 @@ require 'spec_helper'
 describe Gitlab::Cache::Ci::ProjectPipelineStatus, :clean_gitlab_redis_cache do
   let!(:project) { create(:project, :repository) }
   let(:pipeline_status) { described_class.new(project) }
-  let(:cache_key) { "projects/#{project.id}/pipeline_status" }
+  let(:cache_key) { described_class.cache_key_for_project(project) }
 
   describe '.load_for_project' do
     it "loads the status" do

spec/tasks/cache/clear/redis_spec.rb

+require 'rake_helper'
+
+describe 'clearing redis cache' do
+  before do
+    Rake.application.rake_require 'tasks/cache'
+  end
+
+  describe 'clearing pipeline status cache' do
+    let(:pipeline_status) { create(:ci_pipeline).project.pipeline_status }
+
+    before do
+      allow(pipeline_status).to receive(:loaded).and_return(nil)
+    end
+
+    it 'clears pipeline status cache' do
+      expect { run_rake_task('cache:clear:redis') }.to change { pipeline_status.has_cache? }
+    end
+  end
+end