method

connected_to

v6.1.3.1 - Show latest stable - 0 notes - Class: ConnectionHandling

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connected_to(database: nil, role: nil, shard: nil, prevent_writes: false, &blk) public

Connects to a role (ex writing, reading or a custom role) and/or shard for the duration of the block. At the end of the block the connection will be returned to the original role / shard.

If only a role is passed, Active Record will look up the connection based on the requested role. If a non-established role is requested an +ActiveRecord::ConnectionNotEstablished+ error will be raised:

ActiveRecord::Base.connected_to(role: :writing) do
  Dog.create! # creates dog using dog writing connection
end

ActiveRecord::Base.connected_to(role: :reading) do
  Dog.create! # throws exception because we're on a replica
end

When swapping to a shard, the role must be passed as well. If a non-existent shard is passed, an +ActiveRecord::ConnectionNotEstablished+ error will be raised.

When a shard and role is passed, Active Record will first lookup the role, and then look up the connection by shard key.

ActiveRecord::Base.connected_to(role: :reading, shard: :shard_one_replica) do
  Dog.first # finds first Dog record stored on the shard one replica
end

The database kwarg is deprecated and will be removed in 6.2.0 without replacement.

Show source

# File activerecord/lib/active_record/connection_handling.rb, line 139
    def connected_to(database: nil, role: nil, shard: nil, prevent_writes: false, &blk)
      if legacy_connection_handling
        if self != Base
          raise NotImplementedError, "`connected_to` can only be called on ActiveRecord::Base with legacy connection handling."
        end
      else
        if self != Base && !abstract_class
          raise NotImplementedError, "calling `connected_to` is only allowed on ActiveRecord::Base or abstract classes."
        end

        if name != connection_specification_name && !primary_class?
          raise NotImplementedError, "calling `connected_to` is only allowed on the abstract class that established the connection."
        end
      end

      if database && (role || shard)
        raise ArgumentError, "`connected_to` cannot accept a `database` argument with any other arguments."
      elsif database
        ActiveSupport::Deprecation.warn("The database key in `connected_to` is deprecated. It will be removed in Rails 6.2.0 without replacement.")

        if database.is_a?(Hash)
          role, database = database.first
          role = role.to_sym
        end

        db_config, owner_name = resolve_config_for_connection(database)
        handler = lookup_connection_handler(role)

        handler.establish_connection(db_config, owner_name: owner_name, role: role)

        with_handler(role, &blk)
      elsif role || shard
        unless role
          raise ArgumentError, "`connected_to` cannot accept a `shard` argument without a `role`."
        end

        with_role_and_shard(role, shard, prevent_writes, &blk)
      else
        raise ArgumentError, "must provide a `shard` and/or `role`."
      end
    end

connected_to

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