Tally Gas Refunder

A generic contract system for reliably refunding the gas costs of transactions. The purpose of the project is to:

• Enable Protocols to specify what contract calls they are willing to sponsor with a set of limitations (e.g gas price)
• Enable anyone to sumbit transactions that are eligible for refunding and get their transaction fee reimbursed in the range of 96% - 99% (more on the different in the range later)
• Provide a central registry for persisting all deployed refunders and their supported refundable transactions

Contract Addresses

Mainnet:

Registry: 0xAe23D33354bf2B7Df421D928Cdbb5aADFA9DFA16

Factory: 0x33DD37A160e7436B28B23FcE005a438A178316D7

Subgraph: https://api.thegraph.com/subgraphs/name/withtally/tally-gas-refunder-mainnet

Contracts

• Refunder factory
• Refunder
• Registry

Factory

Factory contract used for the deployment of Refunder contracts. Anyone is able to deploy a refunder contract and configure it for its own needs.

On refunder deployment msg.sender is the initial owner of the Refunder contract.

Refunder

Refunder contract represents the interest of a given protocol/entity that wants to sponsor a set of function calls.

The contract:

• is ownable. By default set to the deployer
• holds ETH for gas cost reimbursements
• has a mapping of whitelisted refundables

Each refundable has:

• target - contract address (f.e Compound Governance Alpha)
• identifier - function identifier (f.e castVoteBySig)
• validatingContract - Optional validation contract to call when determening whether to refund the msg.sender
• validatingIdentifier - Optional validati identifier to call when determening whether to refund the msg.sender

Important If you want to execute any additional business logic check except for requiring the gas price to be lower than the maxGasPrice set, you can specify validatingContract and validatingIdentifier. The contract + identifier will be called on every relay and refund call. The signature of the validatingIdentifier must be: functionName(address,address,bytes4,bytes) where the first address is the msg.sender that will be refunded, second address is the target contract, bytes4 is the identifier to be called and the last are the arguments that will be passed to that function call.

The contract measures the net gas usage and reimburses the msg.sender for all of the gas costs except for the arguments provided to the relayAndRefund function. This is where the 96-99% fomes from. If the arguments gas costs are big, the refunding proportional to the transaction cost will be lower.

Note: Gas costs for the arguments are as follows:

• 16 gas for each non-zero byte
• 4 gas for each zero byte

Registry

The registry contract stores all Refunders deployed and their supported targetContracts and identifiers. Anyone is able to:

• query all deployed refunder contracts
• query by a given pair of (targetContract, identifierId) the list of refunders that are willing to refund the msg.sender

Development

The project uses the hardhat framework.

Compile

In order to compile, one must execute:

npm run compile

Test

In order to run the unit tests, one must execute: run test

npm run test

Coverage

In order to run the tests with code coverage, one must execute:

npm run coverage

Deployment

There are several deployment scripts defined in the ./scripts folder and referenced using hardhat tasks.

In order to deploy the registry:

npx hardhat deploy-registry --network MY_NETWORK_NAME

In order to deploy the factory:

npx hardhat deploy-factory --network MY_NETWORK_NAME --registry REGISTRY_ADDRESS

In Order to deploy refunder using the factory:

npx hardhat factory-deploy-refunder --network MY_NETWORK_NAME --factory FACTORY_ADDRESS

In Order to deploy refunder without factory:

npx hardhat deploy-refunder --network MY_NETWORK_NAME --registry REGISTRY_ADDRESS

Note: By default, the version of the refunder is 1