复现步骤：
- 设置一个干净的 Discourse 环境。
- 创建备份。
- 还原备份。
- 还原失败，出现以下错误：
摘要
[2019-10-23 22:51:31] ALTER TABLE
[2019-10-23 22:51:31] 正在迁移数据库...
[2019-10-23 22:51:35] 正在重新连接数据库...
[2019-10-23 22:51:35] 异常：nil:NilClass 未定义方法 `config_filename'
[2019-10-23 22:51:35] /var/www/discourse/vendor/bundle/ruby/2.6.0/gems/rails_multisite-2.0.7/lib/rails_multisite/connection_management.rb:38:in `reload'
/var/www/discourse/lib/backup_restore/restorer.rb:407:in `reconnect_database'
/var/www/discourse/lib/backup_restore/restorer.rb:86:in `run'
/var/www/discourse/lib/backup_restore.rb:166:in `block in start!'
/var/www/discourse/lib/backup_restore.rb:163:in `fork'
/var/www/discourse/lib/backup_restore.rb:163:in `start!'
/var/www/discourse/lib/backup_restore.rb:22:in `restore!'
/var/www/discourse/app/controllers/admin/backups_controller.rb:119:in `restore'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_controller/metal/basic_implicit_render.rb:6:in `send_action'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/abstract_controller/base.rb:196:in `process_action'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_controller/metal/rendering.rb:30:in `process_action'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/abstract_controller/callbacks.rb:42:in `block in process_action'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/activesupport-6.0.0/lib/active_support/callbacks.rb:135:in `run_callbacks'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/abstract_controller/callbacks.rb:41:in `process_action'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_controller/metal/rescue.rb:22:in `process_action'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_controller/metal/instrumentation.rb:33:in `block in process_action'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/activesupport-6.0.0/lib/active_support/notifications.rb:180:in `block in instrument'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/activesupport-6.0.0/lib/active_support/notifications/instrumenter.rb:24:in `instrument'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/activesupport-6.0.0/lib/active_support/notifications.rb:180:in `instrument'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_controller/metal/instrumentation.rb:32:in `process_action'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_controller/metal/params_wrapper.rb:245:in `process_action'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/activerecord-6.0.0/lib/active_record/railties/controller_runtime.rb:27:in `process_action'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/abstract_controller/base.rb:136:in `process'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionview-6.0.0/lib/action_view/rendering.rb:39:in `process'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/rack-mini-profiler-1.1.0/lib/mini_profiler/profiling_methods.rb:104:in `block in profile_method'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_controller/metal.rb:191:in `dispatch'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_controller/metal.rb:252:in `dispatch'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/routing/route_set.rb:51:in `dispatch'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/routing/route_set.rb:33:in `serve'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/routing/mapper.rb:18:in `block in <class:Constraints>'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/routing/mapper.rb:48:in `serve'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/journey/router.rb:49:in `block in serve'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/journey/router.rb:32:in `each'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/journey/router.rb:32:in `serve'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/routing/route_set.rb:837:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/rack-protection-2.0.7/lib/rack/protection/frame_options.rb:31:in `call'
/var/www/discourse/lib/middleware/omniauth_bypass_middleware.rb:68:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/rack-2.0.7/lib/rack/tempfile_reaper.rb:15:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/rack-2.0.7/lib/rack/conditional_get.rb:38:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/rack-2.0.7/lib/rack/head.rb:12:in `call'
/var/www/discourse/lib/content_security_policy/middleware.rb:12:in `call'
/var/www/discourse/lib/middleware/anonymous_cache.rb:274:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/rack-2.0.7/lib/rack/session/abstract/id.rb:232:in `context'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/rack-2.0.7/lib/rack/session/abstract/id.rb:226:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/middleware/cookies.rb:648:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/middleware/callbacks.rb:27:in `block in call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/activesupport-6.0.0/lib/active_support/callbacks.rb:101:in `run_callbacks'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/middleware/callbacks.rb:26:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/middleware/actionable_exceptions.rb:17:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/middleware/debug_exceptions.rb:32:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/middleware/show_exceptions.rb:33:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/logster-2.4.1/lib/logster/middleware/reporter.rb:43:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/railties-6.0.0/lib/rails/rack/logger.rb:38:in `call_app'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/railties-6.0.0/lib/rails/rack/logger.rb:28:in `call'
/var/www/discourse/config/initializers/100-quiet_logger.rb:18:in `call'
/var/www/discourse/config/initializers/100-silence_logger.rb:31:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/middleware/remote_ip.rb:81:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/middleware/request_id.rb:27:in `call'
/var/www/discourse/lib/middleware/enforce_hostname.rb:17:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/rack-2.0.7/lib/rack/method_override.rb:22:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/middleware/executor.rb:14:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/rack-2.0.7/lib/rack/sendfile.rb:111:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/middleware/host_authorization.rb:77:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/rack-mini-profiler-1.1.0/lib/mini_profiler/profiler.rb:296:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/message_bus-2.2.3/lib/message_bus/rack/middleware.rb:57:in `call'
/var/www/discourse/lib/middleware/request_tracker.rb:176:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/railties-6.0.0/lib/rails/engine.rb:526:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/railties-6.0.0/lib/rails/railtie.rb:190:in `public_send'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/railties-6.0.0/lib/rails/railtie.rb:190:in `method_missing'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/rack-2.0.7/lib/rack/urlmap.rb:68:in `block in call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/rack-2.0.7/lib/rack/urlmap.rb:53:in `each'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/rack-2.0.7/lib/rack/urlmap.rb:53:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/unicorn-5.5.1/lib/unicorn/http_server.rb:605:in `process_client'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/unicorn-5.5.1/lib/unicorn/http_server.rb:700:in `worker_loop'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/unicorn-5.5.1/lib/unicorn/http_server.rb:548:in `spawn_missing_workers'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/unicorn-5.5.1/lib/unicorn/http_server.rb:144:in `start'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/unicorn-5.5.1/bin/unicorn:128:in `<top (required)>'
/var/www/discourse/vendor/bundle/ruby/2.6.0/bin/unicorn:23:in `load'
/var/www/discourse/vendor/bundle/ruby/2.6.0/bin/unicorn:23:in `<main>'
[2019-10-23 22:51:35] 正在尝试回滚...
[2019-10-23 22:51:35] 正在回滚...
[2019-10-23 22:51:36] 正在清理...
[2019-10-23 22:51:36] 正在从 discourse_functions 架构中删除函数
[2019-10-23 22:51:36] 正在移除临时目录 '/var/www/discourse/tmp/restores/default/2019-10-23-225058'...
[2019-10-23 22:51:36] 正在恢复 sidekiq...
[2019-10-23 22:51:36] 正在禁用只读模式...
[2019-10-23 22:51:36] 正在标记还原为已完成...
[2019-10-23 22:51:36] 正在通知 'serrano' 还原结束...