heroku mongohq and mongoid Mongo::ConnectionFailure

Question

UPDATE 9th june 2012:

Setup with mongoid 3.0.0.rc at heroku, see this gist: https://gist.github.com/2900804

UPDATE 22th jan 2011:

Uri now takes precedence in mongoid.yml

https://github.com/mongoid/mongoid/issues/issue/266

UPDATE 12th aug 2010: Although I got an accepted answer 6th may from Jackues Crocker, there are aspects of this issue that makes it easy to mess up! It happened to me yet again and I decided to research the mongoid source code. So, here it goes:

Currently, host: port: name/database: settings TAKE PRECEDENCE OVER the uri: setting. Hence, the awfully uninformative error message is happening due to a request to localhost:xxxx and not to flame.local.mongohq.com:xxxx

This will break!

defaults: &defaults
  host: localhost  <- THIS 'OVERWRITES' host in the uri!

production:
  <<: *defaults    <- BE CAREFUL WITH WHAT YOU BRING IN. THE host: FROM DEFAULTS WILL BE THE ONE APPLIED, not your uri host.
  uri: <%= ENV['MONGOHQ_URL'] %>

fix it with either removing the host: in defaults, and/or removing the <<: *defaults

---

ORIGINAL Q:

I have added the mongoHQ addon for mongodb at heroku. It crashes with :

connect_to_master': failed to connect to any given host:port (Mongo::ConnectionFailure)

The descriptions online (heroku mongohq) are more directed towards mongomapper, as I see it. I'm running ruby 1.9.1 and rails 3-beta with mongoid.

My feeling says that there's something with ENV['MONGOHQ_URL'], which it says the MongoHQ addon sets, but I haven't set MONGOHQ_URL anywhere in my app. I guess the problem is in my mongoid.yml ?

defaults: &defaults
  host: localhost

development:
  <<: *defaults
  database: aliado_development

test:
  <<: *defaults
  database: aliado_test

# set these environment variables on your prod server
production:
  <<: *defaults
  host: <%= ENV['MONGOID_HOST'] %>
  port: <%= ENV['MONGOID_PORT'] %>
  username: <%= ENV['MONGOID_USERNAME'] %>
  password: <%= ENV['MONGOID_PASSWORD'] %>
  database: <%= ENV['MONGOID_DATABASE'] %>

It works fine locally, but fails at heroku, more stack trace:

==> crashlog.log <==
Cannot write to outdated .bundle/environment.rb to update it
/disk1/home/slugs/176479_b14df52_b875/mnt/.bundle/gems/gems/rack-1.1.0/lib/rack.rb:14: warning: already initialized constant VERSION
/disk1/home/slugs/176479_b14df52_b875/mnt/.bundle/gems/gems/mongo-0.20.1/lib/mongo/connection.rb:435:in `connect_to_master': failed to connect to any given host:port (Mongo::ConnectionFailure)
    from /disk1/home/slugs/176479_b14df52_b875/mnt/.bundle/gems/gems/mongo-0.20.1/lib/mongo/connection.rb:112:in `initialize'
    from /disk1/home/slugs/176479_b14df52_b875/mnt/.bundle/gems/gems/mongoid-2.0.0.beta4
/lib/mongoid/railtie.rb:32:in `new'
    from /disk1/home/slugs/176479_b14df52_b875/mnt/.bundle/gems/gems/mongoid-2.0.0.beta4/lib/mongoid/railtie.rb:32:in `block (2 levels) in <class:Railtie>'
    from /disk1/home/slugs/176479_b14df52_b875/mnt/.bundle/gems/gems/mongoid-2.0.0.beta4/lib/mongoid.rb:110:in `configure'
    from /disk1/home/slugs/176479_b14df52_b875/mnt/.bundle/gems/gems/mongoid-2.0.0.beta4/lib/mongoid/railtie.rb:21:in `block in <class:Railtie>'
    from /disk1/home/slugs/176479_b14df52_b875/mnt/.bundle/gems/gems/railties-3.0.0.beta3/lib/rails/initializable.rb:25:in `instance_exec'
.....

It all works locally, both tests and app. I'm out of ideas... Any suggestions?

PS: Somebody with high repu mind create the tag 'mongohq'?

Answer 1

Mongoid (master) now has a URI option in mongoid.yml. So you could do:

production:
  uri: <%= ENV['MONGOHQ_URL'] %>

To use mongoid master in your project, set this in your Gemfile

gem "mongoid", :git => "[email protected]:mongoid/mongoid.git"

Hopefully a new gem will be released soon which will clean things up.

Answer 2

It seems to me that specifying host in the defaults hash overrides the value in uri. To fix it just remove the host from the default, here is my config/mongo.yml:

defaults: &defaults
  allow_dynamic_fields: true
  parameterize_keys: true
  persist_in_safe_mode: true
  raise_not_found_error: true
  reconnect_time: 3
  use_object_ids: true

production:
  <<: *defaults
  uri: <%= ENV['MONGOHQ_URL'] %>

Here is the snippet from mongoid's config.rb:

  mongo_uri = settings["uri"].present? ? URI.parse(settings["uri"]) : OpenStruct.new

  name = settings["database"] || mongo_uri.path.to_s.sub("/", "")
  host = settings["host"] || mongo_uri.host || "localhost" # <= look here
  port = settings["port"] || mongo_uri.port || 27017