I'm running a Relay Chain with 4 validators. And trying to add a new collator to a running parachain.

Which I've changed the desiredCandidates from 0 to 2 in the Chain Specification file. And when I try to add a new collator using the collatorSelection pallet I get the error : collatorSelection.ValidatorNotRegistered Error

How can I solve this?

1 Answer 1


The specific error that you are seeing here is because you haven't previously registered the new node as a validator candidate. Here is the source code that generates the error.

The relevant bits are below:

/// Register this account as a collator candidate. The account must (a) already have
/// registered session keys and (b) be able to reserve the `CandidacyBond`.
/// This call is not available to `Invulnerable` collators.
pub fn register_as_candidate(origin: OriginFor<T>) -> DispatchResultWithPostInfo {
        let who = ensure_signed(origin)?;


        let validator_key = T::ValidatorIdOf::convert(who.clone())

You can see that it asks the config's ValidatorRegistration if the validator key has been registered. Assuming you are using the most common pallets, pallet-session is the one that implements the trait, and it has a set_keys extrinsic which can be called by the account attempting to become a validator.

You can get session keys from the (usually protected) runtime call author - rotate_keys.

So the most likely steps are:

  1. Make the runtime call rotate_keys in the author pallet.
  2. Use the keys you get to submit a set_keys extrinsic in the session pallet. This might require some SCALE-decoding, depending on how you do it.
  3. Register as a candidate the way you already do.

However, this might change depending on your chain setup.

  • 1
    Thanks for the answer, I`ve done something similar to that. Thanks for the answer ! Commented Nov 7, 2022 at 13:56

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