在Ruby on Rails - Heroku deployment 上，我得到了一个错误，heroku[route]: at=error code=H10 desc="App crashed" method在调试了一些日志文本之后，我得到了日志文件的主要部分：
2022-01-08T11:12:12.754916+00:00 heroku[web.1]: Starting process with command `bin/rails server -p ${PORT:-5000} -e production`
2022-01-08T11:12:16.534794+00:00 app[web.1]: => Booting Puma
2022-01-08T11:12:16.534809+00:00 app[web.1]: => Rails 6.1.4.4 application starting in production
2022-01-08T11:12:16.534810+00:00 app[web.1]: => Run `bin/rails server --help` for more startup options
2022-01-08T11:12:17.742438+00:00 app[web.1]: Exiting
2022-01-08T11:12:17.745593+00:00 app[web.1]: /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:34:in `require': cannot load such file -- net/pop (LoadError)
2022-01-08T11:12:17.745616+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/zeitwerk-2.5.3/lib/zeitwerk/kernel.rb:35:in `require'
2022-01-08T11:12:17.745630+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/mail-2.7.1/lib/mail/network/retriever_methods/pop3.rb:36:in `<class:POP3>'
2022-01-08T11:12:17.745642+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/mail-2.7.1/lib/mail/network/retriever_methods/pop3.rb:35:in `<module:Mail>'
2022-01-08T11:12:17.745655+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/mail-2.7.1/lib/mail/network/retriever_methods/pop3.rb:4:in `<main>'
2022-01-08T11:12:17.745668+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `require'
2022-01-08T11:12:17.745681+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `block in require_with_bootsnap_lfi'
2022-01-08T11:12:17.745694+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/loaded_features_index.rb:100:in `register'
2022-01-08T11:12:17.745708+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require_with_bootsnap_lfi'
2022-01-08T11:12:17.745720+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:31:in `require'
2022-01-08T11:12:17.745733+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/zeitwerk-2.5.3/lib/zeitwerk/kernel.rb:35:in `require'
2022-01-08T11:12:17.745745+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/mail-2.7.1/lib/mail.rb:54:in `block in eager_autoload!'
2022-01-08T11:12:17.745761+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/mail-2.7.1/lib/mail.rb:54:in `each'
2022-01-08T11:12:17.745774+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/mail-2.7.1/lib/mail.rb:54:in `eager_autoload!'
2022-01-08T11:12:17.745786+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/actionmailer-6.1.4.4/lib/action_mailer.rb:61:in `eager_load!'
2022-01-08T11:12:17.745799+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/railties-6.1.4.4/lib/rails/application/finisher.rb:134:in `each'
2022-01-08T11:12:17.745811+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/railties-6.1.4.4/lib/rails/application/finisher.rb:134:in `block in <module:Finisher>'
2022-01-08T11:12:17.745824+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/railties-6.1.4.4/lib/rails/initializable.rb:32:in `instance_exec'
2022-01-08T11:12:17.745838+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/railties-6.1.4.4/lib/rails/initializable.rb:32:in `run'
2022-01-08T11:12:17.745850+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/railties-6.1.4.4/lib/rails/initializable.rb:61:in `block in run_initializers'
2022-01-08T11:12:17.745863+00:00 app[web.1]: from /app/vendor/ruby-3.1.0/lib/ruby/3.1.0/tsort.rb:228:in `block in tsort_each'
2022-01-08T11:12:17.745875+00:00 app[web.1]: from /app/vendor/ruby-3.1.0/lib/ruby/3.1.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
2022-01-08T11:12:17.745888+00:00 app[web.1]: from /app/vendor/ruby-3.1.0/lib/ruby/3.1.0/tsort.rb:431:in `each_strongly_connected_component_from'
2022-01-08T11:12:17.745900+00:00 app[web.1]: from /app/vendor/ruby-3.1.0/lib/ruby/3.1.0/tsort.rb:349:in `block in each_strongly_connected_component'
2022-01-08T11:12:17.745913+00:00 app[web.1]: from /app/vendor/ruby-3.1.0/lib/ruby/3.1.0/tsort.rb:347:in `each'
2022-01-08T11:12:17.745926+00:00 app[web.1]: from /app/vendor/ruby-3.1.0/lib/ruby/3.1.0/tsort.rb:347:in `call'
2022-01-08T11:12:17.745938+00:00 app[web.1]: from /app/vendor/ruby-3.1.0/lib/ruby/3.1.0/tsort.rb:347:in `each_strongly_connected_component'
2022-01-08T11:12:17.745950+00:00 app[web.1]: from /app/vendor/ruby-3.1.0/lib/ruby/3.1.0/tsort.rb:226:in `tsort_each'
2022-01-08T11:12:17.745963+00:00 app[web.1]: from /app/vendor/ruby-3.1.0/lib/ruby/3.1.0/tsort.rb:205:in `tsort_each'
2022-01-08T11:12:17.745975+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/railties-6.1.4.4/lib/rails/initializable.rb:60:in `run_initializers'
2022-01-08T11:12:17.745988+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/railties-6.1.4.4/lib/rails/application.rb:391:in `initialize!'
2022-01-08T11:12:17.746002+00:00 app[web.1]: from /app/config/environment.rb:5:in `<main>'
2022-01-08T11:12:17.746015+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `require'
2022-01-08T11:12:17.746027+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `block in require_with_bootsnap_lfi'
2022-01-08T11:12:17.746040+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/loaded_features_index.rb:100:in `register'
2022-01-08T11:12:17.746053+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require_with_bootsnap_lfi'
2022-01-08T11:12:17.746066+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:31:in `require'
2022-01-08T11:12:17.746079+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/zeitwerk-2.5.3/lib/zeitwerk/kernel.rb:35:in `require'
2022-01-08T11:12:17.746092+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/activesupport-6.1.4.4/lib/active_support/dependencies.rb:332:in `block in require'
2022-01-08T11:12:17.746104+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/activesupport-6.1.4.4/lib/active_support/dependencies.rb:299:in `load_dependency'
2022-01-08T11:12:17.746117+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/activesupport-6.1.4.4/lib/active_support/dependencies.rb:332:in `require'
2022-01-08T11:12:17.746130+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:54:in `require_relative'
2022-01-08T11:12:17.746143+00:00 app[web.1]: from config.ru:3:in `block in <main>'
2022-01-08T11:12:17.746156+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/rack-2.2.3/lib/rack/builder.rb:116:in `eval'
2022-01-08T11:12:17.746169+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/rack-2.2.3/lib/rack/builder.rb:116:in `new_from_string'
2022-01-08T11:12:17.746181+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/rack-2.2.3/lib/rack/builder.rb:105:in `load_file'
2022-01-08T11:12:17.746194+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/rack-2.2.3/lib/rack/builder.rb:66:in `parse_file'
2022-01-08T11:12:17.746206+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/rack-2.2.3/lib/rack/server.rb:349:in `build_app_and_options_from_config'
2022-01-08T11:12:17.746219+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/rack-2.2.3/lib/rack/server.rb:249:in `app'
2022-01-08T11:12:17.746232+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/rack-2.2.3/lib/rack/server.rb:422:in `wrapped_app'
2022-01-08T11:12:17.746245+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/rack-2.2.3/lib/rack/server.rb:312:in `block in start'
2022-01-08T11:12:17.746258+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/rack-2.2.3/lib/rack/server.rb:379:in `handle_profiling'
2022-01-08T11:12:17.746270+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/rack-2.2.3/lib/rack/server.rb:311:in `start'
2022-01-08T11:12:17.746283+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/railties-6.1.4.4/lib/rails/commands/server/server_command.rb:39:in `start'
2022-01-08T11:12:17.746297+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/railties-6.1.4.4/lib/rails/commands/server/server_command.rb:144:in `block in perform'
2022-01-08T11:12:17.746309+00:00 app[web.1]: from <internal:kernel>:90:in `tap'
2022-01-08T11:12:17.746322+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/railties-6.1.4.4/lib/rails/commands/server/server_command.rb:135:in `perform'
2022-01-08T11:12:17.746335+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/thor-1.2.1/lib/thor/command.rb:27:in `run'
2022-01-08T11:12:17.746348+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/thor-1.2.1/lib/thor/invocation.rb:127:in `invoke_command'
2022-01-08T11:12:17.746361+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/thor-1.2.1/lib/thor.rb:392:in `dispatch'
2022-01-08T11:12:17.746373+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/railties-6.1.4.4/lib/rails/command/base.rb:69:in `perform'
2022-01-08T11:12:17.746386+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/railties-6.1.4.4/lib/rails/command.rb:48:in `invoke'
2022-01-08T11:12:17.746399+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/railties-6.1.4.4/lib/rails/commands.rb:18:in `<main>'
2022-01-08T11:12:17.746412+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `require'
2022-01-08T11:12:17.746424+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `block in require_with_bootsnap_lfi'
2022-01-08T11:12:17.746437+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/loaded_features_index.rb:100:in `register'
2022-01-08T11:12:17.746451+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require_with_bootsnap_lfi'
2022-01-08T11:12:17.746463+00:00 app[web.1]: from /app/vendor/bundle/ruby/3.1.0/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:31:in `require'
2022-01-08T11:12:17.746476+00:00 app[web.1]: from bin/rails:5:in `<main>'
2022-01-08T11:12:17.961296+00:00 heroku[web.1]: Process exited with status 1
2022-01-08T11:12:18.044550+00:00 heroku[web.1]: State changed from starting to crashed
虽然这是生产环境日志全文的主题，但是在本地开发环境中，启动Rails服务器时没有发现任何问题！在开发环境中一切正常。
此外，该 URL 显示以下文本：
Application error An error occurred in the application and your page could not be served. If you are the application owner, check your logs for details. You can do this from the Heroku CLI with the command heroku logs --tail
And the console is showing this: Failed to load resource: the server responded with a status of 503 (Service Unavailable)