Redmine

gem install mongrel --pre
vim Gemfile
add

gem "mongrel", "~> 1.2.0.pre2" 

bundle install

ruby bin/rails server mongrel -e production -p 9010

redmine-4.0.4$ ruby bin/rails server mongrel -e production -d -p 9010
Traceback (most recent call last):
    16: from bin/rails:4:in `<main>'
    15: from bin/rails:4:in `require'
    14: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/commands.rb:18:in `<top (required)>'
    13: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/command.rb:46:in `invoke'
    12: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/command/base.rb:65:in `perform'
    11: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/thor-1.0.1/lib/thor.rb:392:in `dispatch'
    10: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/thor-1.0.1/lib/thor/invocation.rb:127:in `invoke_command'
     9: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/thor-1.0.1/lib/thor/command.rb:27:in `run'
     8: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/commands/server/server_command.rb:142:in `perform'
     7: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/commands/server/server_command.rb:142:in `tap'
     6: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/commands/server/server_command.rb:147:in `block in 
perform'     5: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/commands/server/server_command.rb:47:in `start'
     4: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/commands/server/server_command.rb:76:in `print_boot
_information'     3: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/commands/server/server_command.rb:105:in `use_puma?
'     2: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/rack-2.2.2/lib/rack/server.rb:331:in `server'
     1: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/rack-2.2.2/lib/rack/handler.rb:24:in `get'
/redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/rack-2.2.2/lib/rack/handler.rb:24:in `const_get': wrong constant name mongrel (NameError)
    20: from bin/rails:4:in `<main>'
    19: from bin/rails:4:in `require'
    18: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/commands.rb:18:in `<top (required)>'
    17: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/command.rb:46:in `invoke'
    16: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/command/base.rb:65:in `perform'
    15: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/thor-1.0.1/lib/thor.rb:392:in `dispatch'
    14: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/thor-1.0.1/lib/thor/invocation.rb:127:in `invoke_command'
    13: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/thor-1.0.1/lib/thor/command.rb:27:in `run'
    12: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/commands/server/server_command.rb:142:in `perform'
    11: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/commands/server/server_command.rb:142:in `tap'
    10: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/commands/server/server_command.rb:147:in `block in 
perform'     9: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/commands/server/server_command.rb:47:in `start'
     8: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/commands/server/server_command.rb:76:in `print_boot
_information'     7: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/commands/server/server_command.rb:105:in `use_puma?
'     6: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/rack-2.2.2/lib/rack/server.rb:331:in `server'
     5: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/rack-2.2.2/lib/rack/handler.rb:18:in `get'
     4: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/rack-2.2.2/lib/rack/handler.rb:79:in `try_require'
     3: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:291:in `require'
     2: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:257:in `load_dependen
cy'     1: from /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:291:in `block in requ
ire'/redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:291:in `require': cannot load such fil
e -- rack/handler/mongrel (LoadError)

bundle info mongrel

The dependency tzinfo-data (>= 0) will be unused by any of the platforms Bundler is installing for. Bundler is installing for ruby but the dep
endency is only for x86-mingw32, x64-mingw32, x86-mswin32. To add those platforms to the bundle, run `bundle lock --add-platform x86-mingw32 x64-mingw32 x86-mswin32`.  * mongrel (1.2.0.pre2)
    Summary: Mongrel is a small library that provides a very fast HTTP 1.1 server for Ruby web applications
    Homepage: http://mongrel.rubyforge.org/
    Path: /redmine/app/ruby-2.6.0/lib/ruby/gems/2.6.0/gems/mongrel-1.2.0.pre2