Adapted from aave/flashloan-box by mrdavey.
This Brownie mix comes with everything you need to start developing on flash loans.
This mix is configured for use with Ganache on a forked mainnet.
It supports both Aave V1 and V2.
-
Install Brownie & Ganache-CLI, if you haven't already.
-
Sign up for Infura and generate an API key. Store it in the
WEB3_INFURA_PROJECT_IDenvironment variable. You can learn more about environment variables here. If you're unfamiliar with environment variables you can just add all these commands to your.envfile and runsource .envwhen you're done.
export WEB3_INFURA_PROJECT_ID=YourProjectID- Sign up for Etherscan and generate an API key. This is required for fetching source codes of the mainnet contracts we will be interacting with. Store the API key in the
ETHERSCAN_TOKENenvironment variable.
export ETHERSCAN_TOKEN=YourApiToken- Download the mix.
brownie bake aave-flashloan- Add your
PRIVATE_KEYenvironment variable, with a private key from you wallet.. *Note: If using metamask, you'll have to add a0xto the start of your private key)
We can see our flash loans on Etherscan via the Kovan testnet. If you're rather *run everything locally, check out the Basic Console Use.
- Get some WETH. We need this to pay the preimum that flash loans cost.
$ brownie run scripts/get_weth.py --network kovan- Deploy the flash loan contract. This will also fund the contract with WETH to pay the flash loan fee if it's not funded.
$ brownie run scripts/deployment_v2.py --network kovan- Execute the flash loan
$ brownie run scripts/run_flash_loan_v2.py --network kovanThis will print out an etherscan URL to see the flash loan transaction. Like this one.
To perform a simple flash loan in a development environment:
- Open the Brownie console. This automatically launches Ganache on a forked mainnet.
$ brownie console- Create variables for the Aave lending pool.
>>> aave_lending_pool_v2 = "0xB53C1a33016B2DC2fF3653530bfF1848a515c8c5"- Deploy the
FlashloanV2.solcontract.
>>> flashloan = FlashloanV2.deploy(aave_lending_pool_v2, {"from": accounts[0]})
Transaction sent: 0xb0f70b42d2cec9c027b664e9f37490ad50fb934e61f0c58cfe5a77d96dfad681
Gas price: 0.0 gwei Gas limit: 12000000 Nonce: 8
FlashloanV2.constructor confirmed - Block: 11577534 Gas used: 957504 (7.98%)
FlashloanV2 deployed at: 0x420b1099B9eF5baba6D92029594eF45E19A04A4A- Transfer some Ether in form of WETH to the newly deployed contract. We must do this because we have not implemented any custom flash loan logic, otherwise the loan will fail from an inability to pay the fee.
>>> WETH = Contract("0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2")
>>> accounts[0].transfer(WETH, "1 ether")
Transaction sent: 0x29ac98c861356bc65e19407d8389e53f8c3d9a05513a8610c9de2ef013aac525
Gas price: 0.0 gwei Gas limit: 12000000 Nonce: 10
Transaction confirmed - Block: 11577536 Gas used: 28431 (0.24%)
>>> WETH.transfer(flashloan, "1 ether", {"from": accounts[0]})
Transaction sent: 0x1bff7e44779eb92d426bc432d22ecb9821e0b66afb66d48404a23e37b34044e6
Gas price: 0.0 gwei Gas limit: 12000000 Nonce: 11
ERC20.transfer confirmed - Block: 11577537 Gas used: 36794 (0.31%)- Now we are ready to perform our first flash loan!
>>> tx = flashloan.flashloan(WETH, {"from": accounts[0]})
Transaction sent: 0x335530e6d2b7588ee4727b35ae1ed8634a264aca04b325640101ec1c2b89d499
Gas price: 0.0 gwei Gas limit: 12000000 Nonce: 12
FlashloanV2.flashloan confirmed - Block: 11577538 Gas used: 193010 (1.61%)contracts/v2/FlashloanV2.sol is where you implement your own logic for flash loans. In particular:
- The size of the loan is set in line 89 in
flashloan. - Custom flash loan logic is added after line 31 in
executeOperation.
See the Aave documentation on Performing a Flash Loan for more detailed information.
To run the tests:
brownie test
The example tests provided in this mix start by transfering funds to the FlashloanV2.sol contract. This ensures that the loan executes succesfully without any custom logic. Once you have built your own logic, you should edit tests/test_flashloan_v2.py and remove this initial funding logic.
See the Brownie documentation for more detailed information on testing your project.
Use the --interactive flag to open a console immediatly after each failing test:
brownie test --interactive
Within the console, transaction data is available in the history container:
>>> history
[<Transaction '0x50f41e2a3c3f44e5d57ae294a8f872f7b97de0cb79b2a4f43cf9f2b6bac61fb4'>,
<Transaction '0x7af1ce1c30de8b939f481fd6c340226415428f7e6b59e09d7fa5383939091824'>]Examine the TransactionReceipt for the failed test to determine what went wrong. For example, to view a traceback:
>>> tx = history[-1]
>>> tx.traceback()
Traceback for '0x7af1ce1c30de8b939f481fd6c340226415428f7e6b59e09d7fa5383939091824':
Trace step 13656, program counter 6555:
File "contracts/protocol/lendingpool/LendingPool.sol", lines 532-536, in LendingPool.flashLoan:
IERC20(vars.currentAsset).safeTransferFrom(
receiverAddress,
vars.currentATokenAddress,
vars.currentAmountPlusPremium
);
Trace step 13750, program counter 11619:
File "contracts/dependencies/openzeppelin/contracts/SafeERC20.sol", line 36, in SafeERC20.safeTransferFrom:
callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
Trace step 13937, program counter 16308:
File "contracts/dependencies/openzeppelin/contracts/SafeERC20.sol", line 55, in SafeERC20.callOptionalReturn:
(bool success, bytes memory returndata) = address(token).call(data);
Trace step 13937, program counter 16308:
File "contracts/dependencies/openzeppelin/contracts/SafeERC20.sol", line 55, in SafeERC20.callOptionalReturn:
(bool success, bytes memory returndata) = address(token).call(data);To view a tree map of how the transaction executed:
>>> tx.call_trace()
Call trace for '0x7af1ce1c30de8b939f481fd6c340226415428f7e6b59e09d7fa5383939091824':
Initial call cost [21432 gas]
FlashloanV2.flashloan 0:14132 [3717 / 174153 gas]
└── ILendingPoolV2.flashLoan [CALL] 662:14120 [1996 / 170436 gas]
└── LendingPool.flashLoan [DELEGATECALL] 759:14107 [218057 / 168440 gas]
├── ValidationLogic.validateFlashloan 1428:1461 [106 gas]
├── SafeMath.mul 1752:1779 [100 gas]
├── SafeMath.div 1783:1831 [161 gas]
├── IAtoken [CALL] 1963:2807 [1914 / 20764 gas]
│ └── AToken.transferUnderlyingTo [DELEGATECALL] 2060:2795 [2988 / 18850 gas]
│ └── ERC20.transfer [CALL] 2422:2695 [15862 gas]
├── FlashloanV2.executeOperation [CALL] 3252:3904 [3035 / 11055 gas]
│ └── ERC20.approve [CALL] 3681:3836 [8020 gas]
├── SafeMath.add 4186:4204 [59 gas]
├── ReserveLogic.updateState 4270:5480 [10868 / 17605 gas]
│ ├── InitializableImmutableAdminUpgradeabilityProxy.scaledTotalSupply [STATICCALL] 4322:4500 [1908 / 3663 gas]
│ │ └── VariableDebtToken.scaledTotalSupply [DELEGATECALL] 4419:4488 [1755 gas]
│ ├── ReserveLogic._updateIndexes 4593:4758 [995 / 1352 gas]
│ │ ├── MathUtils.calculateLinearInterest 4620:4678 [53 / 183 gas]
│ │ │ └── SafeMath.sub 4630:4671 [130 gas]
│ │ ├── WadRayMath.ray 4685:4689 [15 gas]
│ │ ├── SafeMath.mul 4696:4723 [100 gas]
│ │ └── SafeMath.add 4732:4750 [59 gas]
│ ├── WadRayMath.rayMul 4766:4836 [238 gas]
│ ├── MathUtils.calculateCompoundedInterest 4919:4985 [80 / 210 gas]
│ │ └── SafeMath.sub 4937:4978 [130 gas]
│ ├── WadRayMath.rayMul 5018:5088 [238 gas]
│ ├── WadRayMath.rayMul 5097:5167 [244 gas]
│ ├── SafeMath.mul 5179:5206 [100 gas]
│ ├── SafeMath.mul 5210:5237 [100 gas]
│ ├── SafeMath.mul 5256:5283 [100 gas]
│ ├── SafeMath.mul 5287:5314 [100 gas]
│ ├── SafeMath.mul 5318:5345 [100 gas]
│ ├── SafeMath.mul 5363:5390 [100 gas]
│ ├── WadRayMath.ray 5394:5398 [15 gas]
│ ├── SafeMath.add 5402:5420 [59 gas]
│ ├── SafeMath.add 5424:5442 [59 gas]
│ └── SafeMath.add 5446:5464 [59 gas]
├── WadRayMath.rayMul 5495:5565 [245 gas]
├── ReserveLogic._mintToTreasury 5672:7537 [2857 / 14960 gas]
│ ├── ReserveConfiguration.getReserveFactor 5748:5756 [824 gas]
│ ├── InitializableImmutableAdminUpgradeabilityProxy.getSupplyData [STATICCALL] 5820:6706 [1929 / 9318 gas]
│ │ └── StableDebtToken.getSupplyData [DELEGATECALL] 5917:6694 [7389 gas]
│ ├── WadRayMath.rayMul 6813:6883 [245 gas]
│ ├── WadRayMath.rayMul 6893:6963 [244 gas]
│ ├── MathUtils.calculateCompoundedInterest 6984:7042 [54 / 191 gas]
│ │ └── SafeMath.sub 6994:7035 [137 gas]
│ ├── WadRayMath.rayMul 7075:7145 [244 gas]
│ ├── WadRayMath.rayMul 7154:7224 [245 gas]
│ ├── SafeMath.mul 7236:7263 [100 gas]
│ ├── SafeMath.mul 7267:7294 [100 gas]
│ ├── SafeMath.mul 7313:7340 [100 gas]
│ ├── SafeMath.mul 7344:7371 [100 gas]
│ ├── SafeMath.mul 7375:7402 [100 gas]
│ ├── SafeMath.mul 7420:7447 [100 gas]
│ ├── WadRayMath.ray 7451:7455 [15 gas]
│ ├── SafeMath.add 7459:7477 [59 gas]
│ ├── SafeMath.add 7481:7499 [59 gas]
│ └── SafeMath.add 7503:7521 [59 gas]
├── WadRayMath.rayMul 7552:7622 [244 gas]
├── SafeMath.add 7650:7668 [59 gas]
├── SafeMath.sub 7672:7713 [137 gas]
├── SafeMath.sub 7724:7765 [137 gas]
├── PercentageMath.percentMul 7788:7860 [255 gas]
├── IAtoken [CALL] 7938:8460 [1911 / 19056 gas]
│ └── AToken.mintToTreasury [DELEGATECALL] 8035:8448 [17145 gas]
├── IAtoken.totalSupply [STATICCALL] 8530:9167 [1908 / 9796 gas]
│ └── AToken.totalSupply [DELEGATECALL] 8627:9155 [3006 / 7888 gas]
│ └── ILendingPoolV2.getReserveNormalizedIncome [STATICCALL] 8755:9048 [1911 / 4882 gas]
│ └── LendingPool.getReserveNormalizedIncome [DELEGATECALL] 8852:9036 [1237 / 2971 gas]
│ └── ReserveLogic.getNormalizedIncome 8963:9006 [1734 gas]
├── ReserveLogic.cumulateToLiquidityIndex 9246:9616 [2768 / 3626 gas]
│ ├── WadRayMath.wadToRay 9253:9294 [131 gas]
│ ├── WadRayMath.wadToRay 9299:9340 [138 gas]
│ ├── WadRayMath.rayDiv 9344:9423 [270 gas]
│ ├── WadRayMath.ray 9431:9435 [15 gas]
│ ├── SafeMath.add 9440:9458 [59 gas]
│ └── WadRayMath.rayMul 9478:9548 [245 gas]
├── ReserveLogic.updateInterestRates 9656:11398 [6759 / 20432 gas]
│ ├── InitializableImmutableAdminUpgradeabilityProxy.getTotalSupplyAndAvgRate [STATICCALL] 9767:10627 [1915 / 7639 gas]
│ │ └── StableDebtToken.getTotalSupplyAndAvgRate [DELEGATECALL] 9864:10615 [5724 gas]
│ ├── InitializableImmutableAdminUpgradeabilityProxy.scaledTotalSupply [STATICCALL] 10769:10947 [1908 / 3663 gas]
│ │ └── VariableDebtToken.scaledTotalSupply [DELEGATECALL] 10866:10935 [1755 gas]
│ ├── WadRayMath.rayMul 11001:11071 [245 gas]
│ ├── ERC20.balanceOf [STATICCALL] 11137:11247 [1934 gas]
│ ├── SafeMath.add 11328:11346 [59 gas]
│ └── SafeMath.sub 11350:11391 [133 gas]
├── ReserveConfiguration.getReserveFactor 11415:11423 [824 gas]
├── DefaultReserveInterestRateStrategy.calculateInterestRates [STATICCALL] 11507:13284 [7330 / 11175 gas]
│ ├── ILendingPoolAddressesProviderV2.getLendingRateOracle [STATICCALL] 11838:11954 [1959 gas]
│ └── LendingRateOracle.getMarketBorrowRate [STATICCALL] 12031:12129 [1886 gas]
└── SafeERC20.safeTransferFrom 13657:14107 [291 / -180413 gas]
└── SafeERC20.callOptionalReturn 13751:14107 [-183382 / -180704 gas]
├── Address.isContract 13762:13784 [769 gas]
└── ERC20.transferFrom [CALL] 13938:14045 [1909 gas]See the Brownie documentation for more detailed information on debugging failed transactions.
When you are finished testing and ready to deploy to the mainnet:
- Import a keystore into Brownie for the account you wish to deploy from. Add this as a
PRIVATE_KEYenvironment variable. - Run the deployment script on the mainnet using the following command:
$ brownie run scripts/deployment_v2.py --network mainnetIf you are using Ganache to fork a network, then you may have issues with the blockchain archive state every 30 minutes. This is due to your node provider (i.e. Infura) only allowing free users access to 30 minutes of archive state. To solve this, upgrade to a paid plan, or simply restart your ganache instance and redploy your contracts.
See our Troubleshooting Errors documentation.
- Aave flash loan documentation
- Aave Developer Discord channel
- Brownie Gitter channel