program: add-spot-borrow-insurance-limits

programs/drift/src/controller/orders.rs

@@ -3619,7 +3619,7 @@ pub fn fill_spot_order(
 
     spot_market_map
         .get_ref(&order_market_index)?
-        .validate_max_token_deposits()?;
+        .validate_max_token_deposits_and_borrows()?;
 
     user.update_last_active_slot(slot);
 

programs/drift/src/controller/spot_balance/tests.rs

@@ -1671,3 +1671,128 @@ fn check_usdc_spot_market_twap() {
         966501
     );
 }
+
+
+
+#[test]
+fn check_spot_market_max_borrow_fraction() {
+    let _now = 30_i64;
+    let _slot = 0_u64;
+
+    let _oracle_price = get_pyth_price(1, 6);
+    let mut spot_market = SpotMarket {
+        market_index: 0,
+        oracle_source: OracleSource::QuoteAsset,
+        cumulative_deposit_interest: SPOT_CUMULATIVE_INTEREST_PRECISION,
+        cumulative_borrow_interest: SPOT_CUMULATIVE_INTEREST_PRECISION,
+        decimals: 6,
+        initial_asset_weight: SPOT_WEIGHT_PRECISION,
+        maintenance_asset_weight: SPOT_WEIGHT_PRECISION,
+        deposit_balance: 100_000_000 * SPOT_BALANCE_PRECISION, //$100M usdc
+        borrow_balance: 0,
+        deposit_token_twap: QUOTE_PRECISION_U64 / 2,
+        historical_oracle_data: HistoricalOracleData::default_quote_oracle(),
+        status: MarketStatus::Active,
+        min_borrow_rate: 0,
+        max_token_borrows_fraction: 1,
+        ..SpotMarket::default()
+    };
+
+    assert_eq!(
+        spot_market.get_deposits().unwrap(),
+        100_000_000 * QUOTE_PRECISION
+    );
+
+    assert!(spot_market.validate_max_token_deposits_and_borrows().is_ok());
+
+    spot_market.borrow_balance = spot_market.deposit_balance;
+    assert!(spot_market.validate_max_token_deposits_and_borrows().is_ok());
+
+    spot_market.max_token_deposits = (100_000_000 * QUOTE_PRECISION) as u64;
+
+    assert!(spot_market.validate_max_token_deposits_and_borrows().is_err());
+    spot_market.borrow_balance = spot_market.deposit_balance/100;
+    assert!(spot_market.validate_max_token_deposits_and_borrows().is_err());
+
+    spot_market.borrow_balance = spot_market.deposit_balance/(10000-2); // just above 10000th
+    assert!(spot_market.validate_max_token_deposits_and_borrows().is_err());
+
+    spot_market.borrow_balance = spot_market.deposit_balance/(10000); // exactly 10000th of deposit
+    assert!(spot_market.validate_max_token_deposits_and_borrows().is_ok());
+
+    spot_market.borrow_balance = spot_market.deposit_balance/(10000+1); // < 10000th of deposit
+    assert!(spot_market.validate_max_token_deposits_and_borrows().is_ok());
+
+    spot_market.borrow_balance = spot_market.deposit_balance/100000; // 1/10th of 10000
+    assert!(spot_market.validate_max_token_deposits_and_borrows().is_ok());
+
+}
+
+#[test]
+fn check_spot_market_min_borrow_rate() {
+    let now = 30_i64;
+    let _slot = 0_u64;
+
+    let _oracle_price = get_pyth_price(1, 6);
+    let mut spot_market = SpotMarket {
+        market_index: 0,
+        oracle_source: OracleSource::QuoteAsset,
+        cumulative_deposit_interest: SPOT_CUMULATIVE_INTEREST_PRECISION,
+        cumulative_borrow_interest: SPOT_CUMULATIVE_INTEREST_PRECISION,
+        decimals: 6,
+        initial_asset_weight: SPOT_WEIGHT_PRECISION,
+        maintenance_asset_weight: SPOT_WEIGHT_PRECISION,
+        deposit_balance: 100_000_000 * SPOT_BALANCE_PRECISION, //$100M usdc
+        borrow_balance: 0,
+        deposit_token_twap: QUOTE_PRECISION_U64 / 2,
+        historical_oracle_data: HistoricalOracleData::default_quote_oracle(),
+        status: MarketStatus::Active,
+        min_borrow_rate: 0,
+        ..SpotMarket::default()
+    };
+
+    assert_eq!(
+        spot_market.get_deposits().unwrap(),
+        100_000_000 * QUOTE_PRECISION
+    );
+
+    let accum_interest = calculate_accumulated_interest(&spot_market, now + 10000).unwrap();
+
+    assert_eq!(accum_interest.borrow_interest, 0);
+    assert_eq!(accum_interest.deposit_interest, 0);
+
+    spot_market.min_borrow_rate = 1; // .5%
+
+    let accum_interest = calculate_accumulated_interest(&spot_market, now + 10000).unwrap();
+
+    assert_eq!(accum_interest.borrow_interest, 0);
+    assert_eq!(accum_interest.deposit_interest, 0);
+
+    spot_market.min_borrow_rate = 1; // .5%
+    spot_market.borrow_balance = spot_market.deposit_balance / 100;
+    let accum_interest = calculate_accumulated_interest(&spot_market, now + 10000).unwrap();
+
+    assert_eq!(accum_interest.borrow_interest, 15903);
+    assert_eq!(accum_interest.deposit_interest, 159);
+
+    spot_market.min_borrow_rate = 10; // 5%
+    spot_market.borrow_balance = spot_market.deposit_balance / 100;
+    let accum_interest = calculate_accumulated_interest(&spot_market, now + 10000).unwrap();
+
+    assert_eq!(accum_interest.borrow_interest, 159025);
+    assert_eq!(accum_interest.deposit_interest, 1590);
+
+    spot_market.min_borrow_rate = 10; // 5%
+    spot_market.borrow_balance = spot_market.deposit_balance / 100;
+    let accum_interest = calculate_accumulated_interest(&spot_market, now + 1000000).unwrap();
+
+    assert_eq!(accum_interest.borrow_interest, 15855372);
+    assert_eq!(accum_interest.deposit_interest, 158553);
+
+    spot_market.min_borrow_rate = 200; // 100%
+    spot_market.borrow_balance = spot_market.deposit_balance / 100;
+    let accum_interest = calculate_accumulated_interest(&spot_market, now + 1000000).unwrap();
+
+    assert_eq!(accum_interest.borrow_interest, 317107433);
+    assert_eq!(accum_interest.deposit_interest, 3171074);
+}

programs/drift/src/error.rs

@@ -541,6 +541,8 @@ pub enum ErrorCode {
     OracleStaleForAMM,
     #[msg("Unable to parse pull oracle message")]
     UnableToParsePullOracleMessage,
+    #[msg("Can not borow more than max borrows")]
+    MaxBorrows,
 }
 
 #[macro_export]

programs/drift/src/instructions/admin.rs

@@ -18,7 +18,7 @@ use crate::math::constants::{
     INSURANCE_SPECULATIVE_MAX, LIQUIDATION_FEE_PRECISION, MAX_CONCENTRATION_COEFFICIENT,
     MAX_SQRT_K, MAX_UPDATE_K_PRICE_CHANGE, QUOTE_SPOT_MARKET_INDEX,
     SPOT_CUMULATIVE_INTEREST_PRECISION, SPOT_IMF_PRECISION, SPOT_WEIGHT_PRECISION, THIRTEEN_DAY,
-    TWENTY_FOUR_HOUR,
+    TWENTY_FOUR_HOUR, PERCENTAGE_PRECISION
 };
 use crate::math::cp_curve::get_update_k_result;
 use crate::math::orders::is_multiple_of_step_size;
@@ -128,7 +128,7 @@ pub fn handle_initialize_spot_market(
         return Err(ErrorCode::InvalidInsuranceFundAuthority.into());
     }
 
-    validate_borrow_rate(optimal_utilization, optimal_borrow_rate, max_borrow_rate)?;
+    validate_borrow_rate(optimal_utilization, optimal_borrow_rate, max_borrow_rate, 0)?;
 
     let spot_market_index = get_then_update_id!(state, number_of_spot_markets);
 
@@ -278,7 +278,9 @@ pub fn handle_initialize_spot_market(
         flash_loan_initial_token_amount: 0,
         total_swap_fee: 0,
         scale_initial_asset_weight_start,
-        padding: [0; 48],
+        max_token_borrows_fraction: 0,
+        min_borrow_rate: 0,
+        padding: [0; 45],
         insurance_fund: InsuranceFund {
             vault: *ctx.accounts.insurance_fund_vault.to_account_info().key,
             unstaking_period: THIRTEEN_DAY,
@@ -2296,9 +2298,15 @@ pub fn handle_update_spot_market_borrow_rate(
     optimal_utilization: u32,
     optimal_borrow_rate: u32,
     max_borrow_rate: u32,
+    min_borrow_rate: Option<u8>,
 ) -> Result<()> {
     let spot_market = &mut load_mut!(ctx.accounts.spot_market)?;
-    validate_borrow_rate(optimal_utilization, optimal_borrow_rate, max_borrow_rate)?;
+    validate_borrow_rate(
+        optimal_utilization,
+        optimal_borrow_rate,
+        max_borrow_rate,
+        min_borrow_rate.unwrap_or(spot_market.min_borrow_rate).cast::<u32>()? * ((PERCENTAGE_PRECISION/200) as u32),
+    )?;
 
     msg!(
         "spot_market.optimal_utilization: {:?} -> {:?}",
@@ -2321,6 +2329,16 @@ pub fn handle_update_spot_market_borrow_rate(
     spot_market.optimal_utilization = optimal_utilization;
     spot_market.optimal_borrow_rate = optimal_borrow_rate;
     spot_market.max_borrow_rate = max_borrow_rate;
+
+    if let Some(min_borrow_rate) = min_borrow_rate {
+        msg!(
+            "spot_market.min_borrow_rate: {:?} -> {:?}",
+            spot_market.min_borrow_rate,
+            min_borrow_rate
+        );
+        spot_market.min_borrow_rate = min_borrow_rate
+    }
+
     Ok(())
 }
 
@@ -2343,6 +2361,39 @@ pub fn handle_update_spot_market_max_token_deposits(
     Ok(())
 }
 
+#[access_control(
+    spot_market_valid(&ctx.accounts.spot_market)
+)]
+pub fn handle_update_spot_market_max_token_borrows(
+    ctx: Context<AdminUpdateSpotMarket>,
+    max_token_borrows_fraction: u16,
+) -> Result<()> {
+    let spot_market = &mut load_mut!(ctx.accounts.spot_market)?;
+
+    msg!(
+        "spot_market.max_token_borrows_fraction: {:?} -> {:?}",
+        spot_market.max_token_borrows_fraction,
+        max_token_borrows_fraction
+    );
+
+    let current_spot_tokens_borrows: u64 = spot_market.get_borrows()?.cast()?;
+    let new_max_token_borrows = spot_market
+    .max_token_deposits
+    .safe_mul(max_token_borrows_fraction.cast()?)?
+    .safe_div(10000)?;
+
+    validate!(
+        current_spot_tokens_borrows <= new_max_token_borrows,
+        ErrorCode::InvalidSpotMarketInitialization,
+        "spot borrows {} > max_token_borrows {}",
+        current_spot_tokens_borrows,
+        max_token_borrows_fraction
+    )?;
+
+    spot_market.max_token_borrows_fraction = max_token_borrows_fraction;
+    Ok(())
+}
+
 #[access_control(
 spot_market_valid(&ctx.accounts.spot_market)
 )]

programs/drift/src/instructions/user.rs

@@ -408,7 +408,7 @@ pub fn handle_deposit<'c: 'info, 'info>(
     };
     emit!(deposit_record);
 
-    spot_market.validate_max_token_deposits()?;
+    spot_market.validate_max_token_deposits_and_borrows()?;
 
     Ok(())
 }
@@ -2003,7 +2003,7 @@ pub fn handle_deposit_into_spot_market_revenue_pool(
         amount,
     )?;
 
-    spot_market.validate_max_token_deposits()?;
+    spot_market.validate_max_token_deposits_and_borrows()?;
     ctx.accounts.spot_market_vault.reload()?;
     math::spot_withdraw::validate_spot_market_vault_amount(
         &spot_market,
@@ -2873,7 +2873,7 @@ pub fn handle_end_swap<'c: 'info, 'info>(
     out_spot_market.flash_loan_initial_token_amount = 0;
     out_spot_market.flash_loan_amount = 0;
 
-    out_spot_market.validate_max_token_deposits()?;
+    out_spot_market.validate_max_token_deposits_and_borrows()?;
 
     let in_strict_price = StrictOraclePrice::new(
         in_oracle_price,

programs/drift/src/lib.rs

@@ -919,12 +919,14 @@ pub mod drift {
         optimal_utilization: u32,
         optimal_borrow_rate: u32,
         max_borrow_rate: u32,
+        min_borrow_rate: Option<u8>,
     ) -> Result<()> {
         handle_update_spot_market_borrow_rate(
             ctx,
             optimal_utilization,
             optimal_borrow_rate,
             max_borrow_rate,
+            min_borrow_rate,
         )
     }
 

programs/drift/src/math/spot_balance.rs

@@ -158,7 +158,8 @@ pub fn calculate_accumulated_interest(
         utilization
             .safe_mul(borrow_rate_slope)?
             .safe_div(SPOT_UTILIZATION_PRECISION)?
-    };
+    }
+    .max(spot_market.get_min_borrow_rate()?.cast()?);
 
     let time_since_last_update = now
         .cast::<u64>()

programs/drift/src/state/spot_market.rs

@@ -23,7 +23,7 @@ use crate::state::oracle::{HistoricalIndexData, HistoricalOracleData, OracleSour
 use crate::state::paused_operations::{InsuranceFundOperation, SpotOperation};
 use crate::state::perp_market::{MarketStatus, PoolBalance};
 use crate::state::traits::{MarketIndexOffset, Size};
-use crate::validate;
+use crate::{validate, PERCENTAGE_PRECISION};
 
 #[account(zero_copy(unsafe))]
 #[derive(PartialEq, Eq, Debug)]
@@ -178,7 +178,15 @@ pub struct SpotMarket {
     /// disabled when 0
     /// precision: QUOTE_PRECISION
     pub scale_initial_asset_weight_start: u64,
-    pub padding: [u8; 48],
+    /// What fraction of max_token_deposits
+    /// disabled when 0, 1 => 1/10000 => .01% of max_token_deposits
+    /// precision: X/10000
+    pub max_token_borrows_fraction: u16,
+    /// The min borrow rate for this market when the market regardless of utilization
+    /// 1 => 1/200 => .5%
+    /// precision: X/200
+    pub min_borrow_rate: u8,
+    pub padding: [u8; 45],
 }
 
 impl Default for SpotMarket {
@@ -239,7 +247,9 @@ impl Default for SpotMarket {
             flash_loan_initial_token_amount: 0,
             total_swap_fee: 0,
             scale_initial_asset_weight_start: 0,
-            padding: [0; 48],
+            max_token_borrows_fraction: 0,
+            min_borrow_rate: 0,
+            padding: [0; 45],
         }
     }
 }
@@ -414,7 +424,7 @@ impl SpotMarket {
         get_token_amount(self.borrow_balance, self, &SpotBalanceType::Borrow)
     }
 
-    pub fn validate_max_token_deposits(&self) -> DriftResult {
+    pub fn validate_max_token_deposits_and_borrows(&self) -> DriftResult {
         let deposits = self.get_deposits()?;
         let max_token_deposits = self.max_token_deposits.cast::<u128>()?;
 
@@ -426,6 +436,23 @@ impl SpotMarket {
             deposits,
         )?;
 
+        if self.max_token_borrows_fraction > 0 && self.max_token_deposits > 0 {
+            let borrows = self.get_borrows()?;
+            let max_token_borrows = self
+                .max_token_deposits
+                .safe_mul(self.max_token_borrows_fraction.cast()?)?
+                .safe_div(10000)?
+                .cast::<u128>()?;
+
+            validate!(
+                max_token_borrows == 0 || borrows <= max_token_borrows,
+                ErrorCode::MaxBorrows,
+                "max token amount ({}) < borrows ({})",
+                max_token_borrows,
+                borrows,
+            )?;
+        }
+
         Ok(())
     }
 
@@ -458,6 +485,12 @@ impl SpotMarket {
         Ok(self.utilization_twap <= unhealthy_utilization && utilization <= unhealthy_utilization)
     }
 
+    pub fn get_min_borrow_rate(self) -> DriftResult<u32> {
+        self.min_borrow_rate
+            .cast::<u32>()?
+            .safe_mul((PERCENTAGE_PRECISION / 200).cast()?)
+    }
+
     pub fn update_historical_index_price(
         &mut self,
         best_bid: Option<u64>,