mongodb/mongoid · error · Mongoid::Errors::NoDefaultClient

No default client configuration is defined.

Error message

No default client configuration is defined.

What it means

Raised by Mongoid::Config::Validators::Client.validate when the clients configuration hash defines one or more clients but none of them is named :default. Mongoid requires a default client as the fallback for all models and operations that do not name a client explicitly; the faulting input is the clients hash lacking a default key.

Solutions

1. Add a default: entry under clients in mongoid.yml
2. Rename the intended primary client to :default

When it happens

Trigger: Thrown at lib/mongoid/config/validators/client.rb:20 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of mongodb/mongoid@0da0e23d71 (2026-08-23). Data as JSON: /api/errors/6f692b7a385d8f91. Report an issue: GitHub.

Appendix: source

Thrown at lib/mongoid/config/validators/client.rb:20

module Mongoid
  module Config
    module Validators
      # Validator for client specific configuration.
      module Client
        extend self

        # Standard configuration options.
        STANDARD = %i[database hosts username password].freeze

        # Validate the client configuration.
        #
        # @example Validate the client config.
        #   Client.validate({ default: { hosts: [ "localhost:27017" ] }})
        #
        # @param [ Hash ] clients The clients config.
        def validate(clients)
          raise Errors::NoDefaultClient.new(clients.keys) unless clients.has_key?(:default)

          clients.each_pair do |name, config|
            validate_client_database(name, config)
            validate_client_hosts(name, config)
            validate_client_uri(name, config)
          end
        end

        private

        # Validate that the client config has database.
        #
        # @api private
        #
        # @example Validate the client has database.
        #   validator.validate_client_database(:default, {})
        #
        # @param [ String | Symbol ] name The config key.

View on GitHub (pinned to 0da0e23d71)