maintenance: add job to check for database corruption.

Add a job to run pg_amcheck hourly to check for corrupt database indexes.

https://www.postgresql.org/docs/14/app-pgamcheck.html

app/jobs/amcheck_database_job.rb

@@ -0,0 +1,18 @@
+# A job that runs hourly to check the database for corruption. Spawned by {DanbooruMaintenance}.
+# Requires at least PostgreSQL 14.0 to be installed for pg_amcheck to be available.
+#
+# https://www.postgresql.org/docs/14/app-pgamcheck.html
+class AmcheckDatabaseJob < ApplicationJob
+  def perform(options: "--verbose --install-missing --heapallindexed --parent-check")
+    return unless system("pg_amcheck --version")
+
+    connection_url = ApplicationRecord.connection_db_config.url
+    output = %x(PGDATABASE="#{connection_url}" pg_amcheck #{options})
+    notify(output) unless $?.success?
+  end
+
+  def notify(output)
+    DanbooruLogger.info(output)
+    Dmail.create_automated(to: User.owner, title: "pg_amcheck failed", body: output)
+  end
+end

app/logical/danbooru_maintenance.rb

@@ -6,6 +6,7 @@ module DanbooruMaintenance
     queue PrunePostsJob
     queue PruneRateLimitsJob
     queue RegeneratePostCountsJob
+    queue AmcheckDatabaseJob
   end
 
   def daily

test/jobs/amcheck_database_job_test.rb

@@ -0,0 +1,9 @@
+require 'test_helper'
+
+class AmcheckDatabaseJobTest < ActiveJob::TestCase
+  context "AmcheckDatabaseJob" do
+    should "work" do
+      AmcheckDatabaseJob.perform_now
+    end
+  end
+end