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.
-
Install Brownie, if you haven't already.
-
Sign up for Infura and generate an API key. Store it in the
WEB3_INFURA_PROJECT_ID
environment variable.
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_TOKEN
environment variable.
export ETHERSCAN_TOKEN=YourApiToken
- Download the mix.
brownie bake aave-flashloan
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 and ETH reserve addresses. These were obtained from the Aave reserve addresses documentation.
>>> aave_lending_pool = "0x24a42fD28C976A61Df5D00D0599C34c4f90748c8"
>>> eth_reserve = "0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE"
- Deploy the
Flashloan.sol
contract.
>>> flashloan = Flashloan.deploy(aave_lending_pool, {"from": accounts[0]})
Transaction sent: 0xc8a35b3ecbbed196a344ed6b5c7ee6f50faf9b7eee836044d1c7ffe10093ef45
Gas price: 0.0 gwei Gas limit: 6721975
Flashloan.constructor confirmed - Block: 9995378 Gas used: 796934 (11.86%)
Flashloan deployed at: 0x3194cBDC3dbcd3E11a07892e7bA5c3394048Cc87
- Transfer some Ether 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.
>>> accounts[0].transfer(flashloan, "1 ether")
Transaction sent: 0xa70b90eb9a9899e8f6e709c53a436976315b4279c4b6797d0a293e169f94d5b4
Gas price: 0.0 gwei Gas limit: 6721975
Transaction confirmed - Block: 9995379 Gas used: 21055 (0.31%)
- Now we are ready to perform our first flash loan!
>>> tx = flashloan.flashloan(eth_reserve, {"from": accounts[0]})
Transaction sent: 0x1e2a6ce4e749f8c01aef9f747b65f6a63a9945d4e8331e8269c000d3c6779644
Gas price: 0.0 gwei Gas limit: 6721975
Flashloan.flashloan confirmed - Block: 9995380 Gas used: 183858 (2.74%)
contracts/Flashloan.sol
is where you implement your own logic for flash loans. In particular:
- The size of the loan is set in line 39 in
flashloan
. - Custom flash loan logic is added after line 23 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 Flashloan.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.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 '0xb05a87885790b579982983e7079d811c1e269b2c678d99ecb0a3a5104a666138'>]
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 '0xb05a87885790b579982983e7079d811c1e269b2c678d99ecb0a3a5104a666138':
Trace step 393, program counter 961:
File "contracts/Flashloan.sol", line 42, in Flashloan.flashloan:
lendingPool.flashLoan(address(this), _asset, amount, data);
Trace step 430, program counter 119:
File "InitializableAdminUpgradeabilityProxy-flattened.sol", line 884, in InitializableAdminUpgradeabilityProxy:
_fallback();
Trace step 482, program counter 818:
File "InitializableAdminUpgradeabilityProxy-flattened.sol", line 937, in Proxy._fallback:
_delegate(_implementation());
Trace step 494, program counter 1943:
File "InitializableAdminUpgradeabilityProxy-flattened.sol", line 979, in BaseUpgradeabilityProxy._upgradeTo:
emit Upgraded(newImplementation);
Trace step 2071, program counter 8750:
File "LendingPool-flattened.sol", line 5850, in LendingPool.flashLoan:
receiver.executeOperation(_reserve, _amount, amountFee, _params);
Trace step 2278, program counter 1652:
File "contracts/Flashloan.sol", line 31, in Flashloan.executeOperation:
transferFundsBackToPoolInternal(_reserve, totalDebt);
Trace step 2470, program counter 2417:
File "contracts/aave/FlashLoanReceiverBase.sol", line 26, in FlashLoanReceiverBase.transferFundsBackToPoolInternal:
transferInternal(core, _reserve, _amount);
Trace step 2568, program counter 3064:
File "contracts/aave/FlashLoanReceiverBase.sol", line 32, in FlashLoanReceiverBase.transferInternal:
require(success == true, "Couldn't transfer ETH");
To view a tree map of how the transaction executed:
>>> tx.call_trace()
Call trace for '0xb05a87885790b579982983e7079d811c1e269b2c678d99ecb0a3a5104a666138':
Flashloan.flashloan 0:2606 (0x3194cBDC3dbcd3E11a07892e7bA5c3394048Cc87)
├─LendingPoolAddressesProvider.getLendingPool 144:240 (0x24a42fD28C976A61Df5D00D0599C34c4f90748c8)
└─InitializableAdminUpgradeabilityProxy 394:2594 (0x398eC7346DcD622eDc5ae82352F02bE94C62d119)
└─Proxy._fallback 431:2594
├─BaseAdminUpgradeabilityProxy._willFallback 435:470
│ └─BaseUpgradeabilityProxy._setImplementation 440:468
├─BaseAdminUpgradeabilityProxy._admin 475:477
└─BaseUpgradeabilityProxy._upgradeTo 483:2589
└─LendingPool.flashLoan 495:2581 (0x6D252BaEa75459Ed0077410613c5f6e51cAb4750)
├─InitializableAdminUpgradeabilityProxy 764:995 (0x3dfd23A6c5E8BbcFc9581d2E864a68feb6a076d3)
│ ├─Proxy._fallback 801:995
│ │ ├─BaseAdminUpgradeabilityProxy._willFallback 805:840
│ │ │ └─BaseUpgradeabilityProxy._setImplementation 810:838
│ │ ├─BaseAdminUpgradeabilityProxy._admin 845:847
│ │ └─BaseUpgradeabilityProxy._upgradeTo 853:991
│ │ └─LendingPoolCore.getReserveIsActive 865:983 (0x5766067108e534419ce13F05899bC3E3F4344948)
├─EthAddressLib.ethAddress 1042:1046
├─InitializableAdminUpgradeabilityProxy 1133:1308 (0xeAC99f8Fb1996AeB153E8cF0842908973a48C66F)
│ ├─Proxy._fallback 1170:1308
│ │ ├─BaseAdminUpgradeabilityProxy._willFallback 1174:1209
│ │ │ └─BaseUpgradeabilityProxy._setImplementation 1179:1207
│ │ ├─BaseAdminUpgradeabilityProxy._admin 1214:1216
│ │ └─BaseUpgradeabilityProxy._upgradeTo 1222:1304
│ │ └─LendingPoolParametersProvider.getFlashLoanFeesInBips 1234:1296 (0xe800542e56208aC5c496A57926FA7647ed8E5f07)
├─SafeMath.mul 1351:1380
├─SafeMath.div 1386:1409
├─SafeMath.mul 1422:1451
├─SafeMath.div 1457:1480
├─InitializableAdminUpgradeabilityProxy 1607:1930 (0x3dfd23A6c5E8BbcFc9581d2E864a68feb6a076d3)
│ ├─Proxy._fallback 1650:1930
│ │ ├─BaseAdminUpgradeabilityProxy._willFallback 1654:1689
│ │ │ └─BaseUpgradeabilityProxy._setImplementation 1659:1687
│ │ ├─BaseAdminUpgradeabilityProxy._admin 1694:1696
│ │ └─BaseUpgradeabilityProxy._upgradeTo 1702:1926
│ │ └─LendingPoolCore.transferToUser 1714:1918 (0x5766067108e534419ce13F05899bC3E3F4344948)
│ │ ├─EthAddressLib.ethAddress 1827:1831
│ │ └─Flashloan 1873:1886 (0x3194cBDC3dbcd3E11a07892e7bA5c3394048Cc87)
└─Flashloan.executeOperation 2072:2569 (0x3194cBDC3dbcd3E11a07892e7bA5c3394048Cc87)
├─FlashLoanReceiverBase.getBalanceInternal 2207:2238
├─SafeMath.add 2253:2271
└─FlashLoanReceiverBase.transferFundsBackToPoolInternal 2279:2569
├─LendingPoolAddressesProvider.getLendingPoolCore 2329:2441 (0x24a42fD28C976A61Df5D00D0599C34c4f90748c8)
└─FlashLoanReceiverBase.transferInternal 2471:2569
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.
- Edit
scripts/deployment.py
and add your keystore ID according to the comments. - Run the deployment script on the mainnet using the following command:
$ brownie run deployment --network mainnet
You will be prompted to enter your keystore password, and then the contract will be deployed.
If 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