Com o Rails 3, após a atualização do Mongoid 2.x para o Mongoid 3.x, minha configuração Heroku + MongoHQ parou de funcionar. O engraçado é que meus frameworks de desenvolvimento e teste e toda a minha suíte de testes passam muito bem.

Eu suspeito que o problema é com o meu arquivo mongoid.yml, mas eu tentei pesquisar os documentos, google & stackoverflow, e usei todos os formatos sugeridos, incluindo:heroku mongohq e mongóide Mongo :: ConnectionFailure ou na verdade isso:https://gist.github.com/2900804

ATUALIZADO 16 de julho: Isto é como o meu arquivo mongoid.yml parece, depois de tentar várias coisas +Depois do que o Jason do MongoHQ sugeriu:

development:
  sessions:
    default:
      database: development
      hosts:
        - localhost:27017

test:
  sessions:
    default:
      database: test
      hosts:
        - localhost:27017

production:
  sessions:
    default:
      uri: <%= ENV['MONGOHQ_URL'] %>
      options:
        skip_version_check: true
        safe: true

(no meu entender, é essencialmente o mesmo que o dos links acima, exceto que ele usa o uri; eu tentei o outro lado, dividindo o MONGOHQ_URL em campos separados também, mas isso não ajudou)

Eu tentei configurar mongoid como 3.0.0rc e deixando a versão em branco no meu Gemfile. Usar a versão do github falhou devido a certificados HTTPS ou algo assim, então não me incomodei em tentar várias vezes.

O que o controlador de ação diz é isto:

Moped::Errors::OperationFailure in Home#index

Showing /app/app/views/home/index.html.haml where line #2 raised:

The operation: #<Moped::Protocol::Command
  @length=68
  @request_id=4
  @response_to=0
  @op_code=2004
  @flags=[:slave_ok]
  @full_collection_name=".$cmd"
  @skip=0
  @limit=-1
  @selector={:count=>:posts, :query=>{}}
  @fields=nil>
failed with error "db assertion failure"

e quando eu corro

heroku run console 

.. Eu entendi isso:

irb(main):052:0> Location.create!
NoMethodError: undefined method `[]' for nil:NilClass
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/node.rb:74:in `block in command'
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/node.rb:522:in `[]'
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/node.rb:522:in `block (3 levels) in flush'
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/node.rb:521:in `map'
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/node.rb:521:in `block (2 levels) in flush'
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/node.rb:113:in `ensure_connected'
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/node.rb:517:in `block in flush'
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/node.rb:532:in `logging'
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/node.rb:516:in `flush'
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/node.rb:505:in `process'
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/node.rb:70:in `command'
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/node.rb:356:in `refresh'
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/cluster.rb:101:in `block in refresh'
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/cluster.rb:114:in `each'
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/cluster.rb:114:in `refresh'
    from /app/vendor/bundle/ruby/1.9.1/gems/moped-1.1.1/lib/moped/cluster.rb:67:in `nodes'
... 15 levels...
    from /app/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.6/lib/active_support/callbacks.rb:405:in `__run_callback'
    from /app/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.6/lib/active_support/callbacks.rb:385:in `_run_save_callbacks'
    from /app/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.6/lib/active_support/callbacks.rb:81:in `run_callbacks'
    from /app/vendor/bundle/ruby/1.9.1/gems/mongoid-3.0.1/lib/mongoid/callbacks.rb:98:in `run_callbacks'
    from /app/vendor/bundle/ruby/1.9.1/gems/mongoid-3.0.1/lib/mongoid/persistence/insertion.rb:23:in `prepare'
    from /app/vendor/bundle/ruby/1.9.1/gems/mongoid-3.0.1/lib/mongoid/persistence/operations/insert.rb:26:in `persist'
    from /app/vendor/bundle/ruby/1.9.1/gems/mongoid-3.0.1/lib/mongoid/persistence.rb:50:in `insert'
    from /app/vendor/bundle/ruby/1.9.1/gems/mongoid-3.0.1/lib/mongoid/persistence.rb:251:in `block in create!'
    from /app/vendor/bundle/ruby/1.9.1/gems/mongoid-3.0.1/lib/mongoid/threaded/lifecycle.rb:173:in `_creating'
    from /app/vendor/bundle/ruby/1.9.1/gems/mongoid-3.0.1/lib/mongoid/persistence.rb:249:in `create!'
    from (irb):52
    from /app/vendor/bundle/ruby/1.9.1/gems/railties-3.2.6/lib/rails/commands/console.rb:47:in `start'
    from /app/vendor/bundle/ruby/1.9.1/gems/railties-3.2.6/lib/rails/commands/console.rb:8:in `start'
    from /app/vendor/bundle/ruby/1.9.1/gems/railties-3.2.6/lib/rails/commands.rb:41:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'irb(main):053:0> 

Acho que pesquisei tudo, passei por vários problemas do gongub mongoid, li a documentação várias vezes ... e estou ficando sem ideias aqui.

Alguma coisa vem à mente, eu deveria tentar em seguida?

ATUALIZAÇÃO 16 de julho: isso é o que Heroku diz quando eu empurrei o mestre heroku (Depois de fazer o que o Jason do MongoHQ sugeriu):

git push heroku master
Counting objects: 7, done.
Delta compression using up to 16 threads.
Compressing objects: 100% (4/4), done.
Writing objects: 100% (4/4), 372 bytes, done.
Total 4 (delta 3), reused 0 (delta 0)

-----> Heroku receiving push
-----> Ruby/Rails app detected
-----> Installing dependencies using Bundler version 1.2.0.pre
       Running: bundle install --without development:test --path vendor/bundle --binstubs bin/ --deployment
       Using rake (0.9.2.2)
       Using i18n (0.6.0)
       Using multi_json (1.3.6)
       Using activesupport (3.2.6)
       Using builder (3.0.0)
            # ... shortened this #
       Using libv8 (3.3.10.4)
       Using moped (1.1.2)
       Using origin (1.0.4)
       Using mongoid (3.0.0.rc)
       Using omniauth (1.1.0)
       Using quimby (0.4.5)
       Using bundler (1.2.0.pre)
       Using rails (3.2.6)
       Using therubyracer (0.10.1)
       Using thin (1.3.1)
       Your bundle is complete! It was installed into ./vendor/bundle
       Cleaning up the bundler cache.
-----> Writing config/database.yml to read from DATABASE_URL
-----> Preparing app for Rails asset pipeline
       Running: rake assets:precompile
       Asset precompilation completed (31.24s)
-----> Rails plugin injection
       Injecting rails_log_stdout
       Injecting rails3_serve_static_assets
-----> Discovering process types
       Procfile declares types      -> (none)
       Default types for Ruby/Rails -> console, rake, web, worker
-----> Compiled slug size is 18.7MB
-----> Launching... done, v92
       http://xxxxx.herokuapp.com deployed to Heroku

To [email protected]:xxxxx.git
   b2d97xy..7b0aczy  master -> master

ATUALIZAÇÃO 2 16 de julho: fez como Jason & MrKurt disse (primeiro esqueceu de executar o pacote mongoid update, mas isso não ajudou também). Agora o erro mudou, no entanto:

NoMethodError in Home#index

Showing /app/app/views/home/index.html.haml where line #2 raised:

undefined method `[]' for nil:NilClass

Extracted source (around line #2):

    1: %h1 Most recent posts
    2: - if @posts.length > 0