DEV: Upgrading Discourse to Zeitwerk (#8098)

Zeitwerk simplifies working with dependencies in dev and makes it easier reloading class chains. 

We no longer need to use Rails "require_dependency" anywhere and instead can just use standard 
Ruby patterns to require files.

This is a far reaching change and we expect some followups here.

lib/backup_restore.rb

@@ -0,0 +1,201 @@
+# frozen_string_literal: true
+
+module BackupRestore
+
+  class OperationRunningError < RuntimeError; end
+
+  VERSION_PREFIX = "v".freeze
+  DUMP_FILE = "dump.sql.gz".freeze
+  OLD_DUMP_FILE = "dump.sql".freeze
+  METADATA_FILE = "meta.json"
+  LOGS_CHANNEL = "/admin/backups/logs"
+
+  def self.backup!(user_id, opts = {})
+    if opts[:fork] == false
+      BackupRestore::Backuper.new(user_id, opts).run
+    else
+      start! BackupRestore::Backuper.new(user_id, opts)
+    end
+  end
+
+  def self.restore!(user_id, opts = {})
+    start! BackupRestore::Restorer.new(user_id, opts)
+  end
+
+  def self.rollback!
+    raise BackupRestore::OperationRunningError if BackupRestore.is_operation_running?
+    if can_rollback?
+      move_tables_between_schemas("backup", "public")
+      after_fork
+    end
+  end
+
+  def self.cancel!
+    set_shutdown_signal!
+    true
+  end
+
+  def self.mark_as_running!
+    $redis.setex(running_key, 60, "1")
+    save_start_logs_message_id
+    keep_it_running
+  end
+
+  def self.is_operation_running?
+    !!$redis.get(running_key)
+  end
+
+  def self.mark_as_not_running!
+    $redis.del(running_key)
+  end
+
+  def self.should_shutdown?
+    !!$redis.get(shutdown_signal_key)
+  end
+
+  def self.can_rollback?
+    backup_tables_count > 0
+  end
+
+  def self.operations_status
+    {
+      is_operation_running: is_operation_running?,
+      can_rollback: can_rollback?,
+      allow_restore: Rails.env.development? || SiteSetting.allow_restore
+    }
+  end
+
+  def self.logs
+    id = start_logs_message_id
+    MessageBus.backlog(LOGS_CHANNEL, id).map { |m| m.data }
+  end
+
+  def self.current_version
+    ActiveRecord::Migrator.current_version
+  end
+
+  def self.move_tables_between_schemas(source, destination)
+    DB.exec(move_tables_between_schemas_sql(source, destination))
+  end
+
+  def self.move_tables_between_schemas_sql(source, destination)
+    <<-SQL
+      DO $$DECLARE row record;
+      BEGIN
+        -- create <destination> schema if it does not exists already
+        -- NOTE: DROP & CREATE SCHEMA is easier, but we don't want to drop the public schema
+        -- ortherwise extensions (like hstore & pg_trgm) won't work anymore...
+        CREATE SCHEMA IF NOT EXISTS #{destination};
+        -- move all <source> tables to <destination> schema
+        FOR row IN SELECT tablename FROM pg_tables WHERE schemaname = '#{source}'
+        LOOP
+          EXECUTE 'DROP TABLE IF EXISTS #{destination}.' || quote_ident(row.tablename) || ' CASCADE;';
+          EXECUTE 'ALTER TABLE #{source}.' || quote_ident(row.tablename) || ' SET SCHEMA #{destination};';
+        END LOOP;
+        -- move all <source> views to <destination> schema
+        FOR row IN SELECT viewname FROM pg_views WHERE schemaname = '#{source}'
+        LOOP
+          EXECUTE 'DROP VIEW IF EXISTS #{destination}.' || quote_ident(row.viewname) || ' CASCADE;';
+          EXECUTE 'ALTER VIEW #{source}.' || quote_ident(row.viewname) || ' SET SCHEMA #{destination};';
+        END LOOP;
+      END$$;
+    SQL
+  end
+
+  DatabaseConfiguration = Struct.new(:host, :port, :username, :password, :database)
+
+  def self.database_configuration
+    config = ActiveRecord::Base.connection_pool.spec.config
+    config = config.with_indifferent_access
+
+    DatabaseConfiguration.new(
+      config["backup_host"] || config["host"],
+      config["backup_port"] || config["port"],
+      config["username"] || ENV["USER"] || "postgres",
+      config["password"],
+      config["database"]
+    )
+  end
+
+  private
+
+  def self.running_key
+    "backup_restore_operation_is_running"
+  end
+
+  def self.keep_it_running
+    # extend the expiry by 1 minute every 30 seconds
+    Thread.new do
+      # this thread will be killed when the fork dies
+      while true
+        $redis.expire(running_key, 1.minute)
+        sleep 30.seconds
+      end
+    end
+  end
+
+  def self.shutdown_signal_key
+    "backup_restore_operation_should_shutdown"
+  end
+
+  def self.set_shutdown_signal!
+    $redis.set(shutdown_signal_key, "1")
+  end
+
+  def self.clear_shutdown_signal!
+    $redis.del(shutdown_signal_key)
+  end
+
+  def self.save_start_logs_message_id
+    id = MessageBus.last_id(LOGS_CHANNEL)
+    $redis.set(start_logs_message_id_key, id)
+  end
+
+  def self.start_logs_message_id
+    $redis.get(start_logs_message_id_key).to_i
+  end
+
+  def self.start_logs_message_id_key
+    "start_logs_message_id"
+  end
+
+  def self.start!(runner)
+    child = fork do
+      begin
+        after_fork
+        runner.run
+      rescue Exception => e
+        puts "--------------------------------------------"
+        puts "---------------- EXCEPTION -----------------"
+        puts e.message
+        puts e.backtrace.join("\n")
+        puts "--------------------------------------------"
+      ensure
+        begin
+          clear_shutdown_signal!
+        rescue Exception => e
+          puts "============================================"
+          puts "================ EXCEPTION ================="
+          puts e.message
+          puts e.backtrace.join("\n")
+          puts "============================================"
+        ensure
+          exit!(0)
+        end
+      end
+    end
+
+    Process.detach(child)
+
+    true
+  end
+
+  def self.after_fork
+    Discourse.after_fork
+  end
+
+  def self.backup_tables_count
+    DB.query_single("SELECT COUNT(*) AS count FROM information_schema.tables WHERE table_schema = 'backup'").first.to_i
+  end
+
+end