Welcome to Solend
Protocol
Architecture
User Instructions
Interact program to program via these instructions, or refer to the github here:
solana-program-library/instruction.rs at mainnet · solendprotocol/solana-program-library
GitHub
DepositReserveLiquidityAndObligationCollateral (Supply)
- Deposit reserve liquidity (Transfer) + mint cTokens (MintTo) + Transfer cTokens into CollateralSupplyAddress (Transfer)
- Does not require RefreshReserve as it is impossible to worsen an obligation’s health by repaying.
WithdrawObligationCollateralAndRedeemReserveCollateral
- Redeem cTokens from CollateralSupplyAddress
- Exchange cTokens into Tokens using the cToken Rate
- Requires RefreshReserve - to ensure that the user is able to withdraw without defaulting his existing borrows.
- RefreshReserve → RefreshObligation → WithdrawObligationCollateralAndRedeemReserveCollateral
BorrowObligationLiquidity
- Bundled with Refresh Reserve
- if “borrow_reserve.last_update.is_stale(clock.slot)? {” fails, reserve is considered stale (refreshreserve + borrow must be in the same slot)
- RefreshReserve → RefreshObligation → Borrow
RepayObligationLiquidity
- Does not require RefreshReserve as it is impossible to worsen an obligation’s health by repaying.
cToken Instructions:
DepositReserveLiquidity
- Deposit funds into the reserve, mint cToken
- No need to escrow the cTokens in the CollateralSupplyAddress
- Relies on cToken:Token Ratio
WithdrawObligationCollateral
- Withdraw Funds, burn cTokens
- Relies on cToken:Token Ratio
Monitoring/Misc Instructions
RefreshReserve
- Update the price of every reserves, usually done before RefreshObligation
- Pulls Oracle Prices
- Updates CumulativeBorrowRate to calculate interest paid since last refreshed block
- Update the Obligation CumulativeBorrowRate to apply an increase in borrow value
- Update cToken Rate for supply side users.
- done 2x for every reserve, supply and borrow side
RefreshObligation
- Done after RefreshReserves
- Calculate individual Obligations that ran the Withdraw or Borrow tx to calculate LTV before borrows
- Assess whether the tx can go through based on account health.
Notes:
RefreshReserve/RefreshObligation used to be required for all transactions, but was removed to reduce oracle reliance after Jan2022’s network issues.
Liquidator will call RefreshObligation before liquidating
However, borrow/withdraw has to check whether the obligation is refreshed in the SAME slot. But obligations requires that reserves are refreshed.
RefreshReserve → RefreshObligation (repeated through all the positions) requires a lot of memory, which is a Solana limit, and thus limits our positions to 6.
Last modified 1mo ago
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