Fee modules

Fee modules are smart contracts with the purpose of calculating the execution fee for a given job. Similarly to execution modules, a job commits to a fee module upon creation. However, data for a job within a fee module can be updated and a job can even migrate to use another fee module with time. Fee modules must implement the IFeeModule interface:

interface IFeeModule {
    function onExecuteJob(uint256 _index, address _caller, uint32 _executionWindow, uint256 _executionTime, uint256 _variableGasConsumption) external returns (uint256, address);
    function onCreateJob(uint256 _index, bytes calldata _inputs) external;
    function onDeleteJob(uint256 _index) external;
    function onUpdateData(uint256 _index, bytes calldata _inputs) external;
    function getEncodedData(uint256 _index) external view returns (bytes memory);
}

The onExecuteJob callback function is called by the JobRegistry upon execution. It returns the execution fee and execution fee token. The onCreateJob callback function is called upon creation of a job and is passed arbitrary input data in form of the argument _input. It can be used to initialise auxiliary data structures within the module. Similarly, the onDeleteJob callback function is called by the JobRegistry contract upon deletion of a job. The jobIsExpired function returns a bool whether a job is expired and can be canceled. jobIsInExecutionMode returns whether the job is in execution mode. Lastly, the getEncodedData function returns all data stored in the fee module contract for a job index as an encoded bytes array.

Similarly to execution modules, fee modules are created and tested by the EES before being supported by the JobRegistry contract. The modularity of fee computation allows implementation of new fee mechanisms which might be relevant in the future.

Note: The execution fee returned by the onExecuteJob function is the amount withdrawn from the sponsor of the job upon execution.

Warning: Updating or migrating to another fee module is not permitted while a job is in execution mode.