How fees will be paid to relayer?

[Kvenessa]

What is the suggested approach to pay fees to relayers?

Currently cb-sol-cli doesn't support fees during deposit transaction thus resulting in insufficient funds error. This can be avoided by making changes to cli but then how these fees which are added to bridge contract will be given to only that relayer whose transaction is mined first.

What effort/changes is required on relayer side or on smart contract level to achieve this fees workflow.

Is any fees workflow is in the roadmap of chainbridge?

[P1sar]

Hey @Kvenessa! Thanks for your question.
Right now there is no automatic process that makes fees payouts to relayers and the current fee approach is pretty simple:

1. Fee value need's to be specified as a Bridge smart contract constructor value https://github.com/ChainSafe/chainbridge-solidity/blob/v1.0.1/contracts/Bridge.sol#L112 or you can change it later https://github.com/ChainSafe/chainbridge-solidity/blob/v1.0.1/contracts/Bridge.sol#L262
2. The fee is taken from the transaction value (means base currency)
3. Bridge then checks on deposit that the transaction has enough value https://github.com/ChainSafe/chainbridge-solidity/blob/v1.0.1/contracts/Bridge.sol#L112 and this ETH (or other base currency) collected on the Bridge contract
4. Then you can withdraw it manually with the admin key https://github.com/ChainSafe/chainbridge-solidity/blob/master/contracts/Bridge.sol#L500
   So basically there is no fee logic related to relayers at all.

[Kvenessa]

@P1sar Thanks for your quick response. So do we need to manually pay fees to the selected relayer after withdrawal by admin?

How would you suggest to implement this offline payment of fees to only relayer whose transaction is mined first?

[P1sar]

Basically idea was to use some script for Fee payouts. And regarding your questions, you can write some script that parses all the Vote events with the status https://github.com/ChainSafe/chainbridge-solidity/blob/master/contracts/Bridge.sol#L404 Active. And then locally group the by depositNonce and find first of them by blockNumber and index