Rails项目启动报错：加载delayed_job_active_record gem失败求助

问题重现 #

执行rails server -e development启动开发服务器时，触发Bundler::GemRequireError，核心错误为加载delayed_job_active_record gem失败，提示：

undefined method `yaml_as' for ActiveRecord::Base:Class
Did you mean?  yaml_tag

已安装Node.js，但问题未解决，完整报错堆栈如下：

/home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/activesupport-3.2.9/lib/active_support/values/time_zone.rb:270: warning: circular argument reference - now
Traceback (most recent call last):
        13: from script/rails:6:in `<main>'
        12: from script/rails:6:in `require'
        11: from /home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/railties-3.2.9/lib/rails/commands.rb:50:in `<top (required)>'
        10: from /home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/railties-3.2.9/lib/rails/commands.rb:50:in `tap'
         9: from /home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/railties-3.2.9/lib/rails/commands.rb:53:in `block in <top (required)>'
         8: from /home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/railties-3.2.9/lib/rails/commands.rb:53:in `require'
         7: from /home/deployer/apps/isg/20220314091757/config/application.rb:15:in `<top (required)>'
         6: from /usr/lib/ruby/vendor_ruby/bundler.rb:114:in `require'
         5: from /usr/lib/ruby/vendor_ruby/bundler/runtime.rb:65:in `require'
         4: from /usr/lib/ruby/vendor_ruby/bundler/runtime.rb:65:in `each'
         3: from /usr/lib/ruby/vendor_ruby/bundler/runtime.rb:76:in `block in require'
         2: from /usr/lib/ruby/vendor_ruby/bundler/runtime.rb:76:in `each'
         1: from /usr/lib/ruby/vendor_ruby/bundler/runtime.rb:80:in `block (2 levels) in require'
/usr/lib/ruby/vendor_ruby/bundler/runtime.rb:84:in `rescue in block (2 levels) in require': There was an error while trying to load the gem 'delayed_job_active_record'. (Bundler::GemRequireError)
Gem Load Error is: undefined method `yaml_as' for ActiveRecord::Base:Class
Did you mean?  yaml_tag
Backtrace for gem load error is:
/home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/activerecord-3.2.9/lib/active_record/dynamic_matchers.rb:50:in `method_missing'
/home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/delayed_job-4.0.4/lib/delayed/serialization/active_record.rb:4:in `<class:Base>'
/home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/delayed_job-4.0.4/lib/delayed/serialization/active_record.rb:3:in `<module:ActiveRecord>'
/home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/delayed_job-4.0.4/lib/delayed/serialization/active_record.rb:2:in `<top (required)>'
/home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/activesupport-3.2.9/lib/active_support/dependencies.rb:251:in `require'
/home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/activesupport-3.2.9/lib/active_support/dependencies.rb:251:in `block in require'
/home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/activesupport-3.2.9/lib/active_support/dependencies.rb:236:in `load_dependency'
/home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/activesupport-3.2.9/lib/active_support/dependencies.rb:251:in `require'
/home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/delayed_job-4.0.4/lib/delayed/worker.rb:64:in `backend='
/home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/delayed_job_active_record-4.0.2/lib/delayed_job_active_record.rb:5:in `<top (required)>'
/usr/lib/ruby/vendor_ruby/bundler/runtime.rb:81:in `require'
/usr/lib/ruby/vendor_ruby/bundler/runtime.rb:81:in `block (2 levels) in require'
/usr/lib/ruby/vendor_ruby/bundler/runtime.rb:76:in `each'
/usr/lib/ruby/vendor_ruby/bundler/runtime.rb:76:in `block in require'
/usr/lib/ruby/vendor_ruby/bundler/runtime.rb:65:in `each'
/usr/lib/ruby/vendor_ruby/bundler/runtime.rb:65:in `require'
/usr/lib/ruby/vendor_ruby/bundler.rb:114:in `require'
/home/deployer/apps/isg/20220314091757/config/application.rb:15:in `<top (required)>'
/home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/railties-3.2.9/lib/rails/commands.rb:53:in `require'
/home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/railties-3.2.9/lib/rails/commands.rb:53:in `block in <top (required)>'
/home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/railties-3.2.9/lib/rails/commands.rb:50:in `tap'
/home/deployer/apps/isg/20220314091757/vendor/bundle/ruby/2.5.0/gems/railties-3.2.9/lib/rails/commands.rb:50:in `<top (required)>'
script/rails:6:in `require'
script/rails:6:in `<main>'
Bundler Error Backtrace:

原因分析 #

Rails 3.2.x版本的ActiveRecord::Base中，yaml_as方法已被移除，替换为yaml_tag。而当前使用的delayed_job（4.0.4）和delayed_job_active_record（4.0.2）是针对更高版本Rails开发的，代码中仍调用了已废弃的yaml_as方法，导致版本不兼容报错。

解决方案 #

方案一：降级delayed_job到兼容版本 #

修改项目的Gemfile，指定与Rails 3.2.x兼容的delayed_job系列版本（3.x分支）：

gem 'delayed_job', '~> 3.0.5'
gem 'delayed_job_active_record', '~> 3.0.5'

执行以下命令更新依赖：

bundle install

完成后重新启动服务器即可。

方案二：临时修改gem代码（不推荐长期使用） #

找到delayed_job的序列化文件，将yaml_as替换为yaml_tag：

1. 定位文件：vendor/bundle/ruby/2.5.0/gems/delayed_job-4.0.4/lib/delayed/serialization/active_record.rb
2. 修改第4行代码：
   原代码：

   yaml_as "tag:ruby.yaml.org,2002:ActiveRecord::Base"
   

   修改为：

   yaml_tag "tag:ruby.yaml.org,2002:ActiveRecord::Base"
   

注意：此方法在执行bundle update后会失效，仅作为临时应急方案，优先推荐方案一。

内容的提问来源于stack exchange，提问作者tarikcn34