Rollbar::Mode

The idea behind Rollbar::Mode is inspired from the Emacs major and minor modes, which alter the behaviour of the editor in certain cases. This is the equivalent of a "minor mode", which alters the way Rollbar integrates with your code:

• In development it automatically re-raises exceptions logged with Rollbar
• In production it alters some default values for better integration with Heroku

In development (i.e. when the Rollbar token is not set), the reporter will not send errors to Rollbar but re-raise them, allowing the following code pattern to work well both in development and in production:

def find(id)
  user = method_that_could_raise_exception(id)
rescue StandardError => exception
  Rollbar.error(exception)

  nil
end

As of v2.22 of the gem, Rollbar has a setting called raise_on_error but will only work if Rollbar believes it's enabled (the access token is enabled). See the early return in the code snippet below, taken from Rollbar::Notifier#log:

def log(level, *args)
  return 'disabled' unless enabled?

  message, exception, extra, context = extract_arguments(args)
  use_exception_level_filters = use_exception_level_filters?(extra)

  return 'ignored' if ignored?(exception, use_exception_level_filters)

  begin
    status = call_before_process(:level => level,
                                 :exception => exception,
                                 :message => message,
                                 :extra => extra)
    return 'ignored' if status == 'ignored'
  rescue Rollbar::Ignore
    return 'ignored'
  end

  level = lookup_exception_level(level, exception,
                                 use_exception_level_filters)

  ret = report_with_rescue(level, message, exception, extra, context)

  raise(exception) if configuration.raise_on_error && exception

  ret
end

If the Rollbar access token is not availble and the raise_on_errror setting is set to true, this gem will monkeypatch the log method described above to side-steps the error delivery mechanism and automatically re-raise the exception.

In order to make sure that the gem only affects your code in development, you can enable it only in the Bundler development group:

group :development do
  gem 'rollbar-mode'
end

Rollbar has several configuration options that help with error reporting, like:

• code_version for linking stack traces to GitHub (SemVer, git SHA)
• environment which defaults to "unspecified"
• populate_empty_backtraces for manually initialized exceptions
• use_async for reporting errors using either girl_friday or threading

Rollbar::Mode will alter the default configuration for Rollbar to these values:

• code_version will be set to the value of HEROKU_SLUG_COMMIT if available
• environment will be set to the value of HEROKU_APP_NAME, if available
• populate_empty_backtraces will be set to true (normal default is false)
• use_async will be set to true (normal default is false)

The HEROKU_* environment variables are provided by the Dyno Metadata feature and has to be enabled manually.

If you do not want these changes, make sure the gem is in the development group.

Bug reports and pull requests are welcome on GitHub at https://github.com/andreimaxim/rollbar-mode.