What does the Staking.EraPaid event mean?

Question

According to Polkadot's events description page, the Staking.EraPaid event means the following:

The era payout has been set; the first balance is the validator-payout; the second is the remainder from the maximum amount of reward. [era_index, validator_payout, remainder].

However, I'd like to know for sure if this event means any balance change has just happened.

More specifically, would I be correct if I said that the validator of the current block would receive validator_payout as a reward? Or do I have to do some math with remainder?

Answer 1

validator_payout is the amount that will be paid to all the validators (and their nominators) after an era (not the payment for one validator for the current block).

The EraPaid event is deposited after computing the payout for a particular era with the end_era function: https://github.com/paritytech/substrate/blob/master/frame/staking/src/pallet/impls.rs (this payout is for all validators/their nominators)

the remainder is got by substracting the validator_payout from max_payout in the era_payout function:

   fn era_payout(
        total_staked: Balance,
        total_issuance: Balance,
        era_duration_millis: u64,
    ) -> (Balance, Balance) {
        let (validator_payout, max_payout) = 
        inflation::compute_total_payout(
            &T::get(),
            total_staked,
            total_issuance,
            // Duration of era; more than u64::MAX is rewarded as u64::MAX.
            era_duration_millis,
        );
        let rest = max_payout.saturating_sub(validator_payout.clone());
        (validator_payout, rest)
    }