add fee burning (#4818)

core/src/rpc.rs

@@ -806,6 +806,7 @@ mod tests {
         let expected = json!({
             "jsonrpc": "2.0",
             "result": [ blockhash.to_string(), {
+                "burnPercent": 50,
                 "lamportsPerSignature": 0,
                 "maxLamportsPerSignature": 0,
                 "minLamportsPerSignature": 0,

genesis/src/main.rs

@@ -316,7 +316,7 @@ fn main() -> Result<(), Box<dyn error::Error>> {
         value_t_or_exit!(matches, "target_lamports_per_signature", u64);
     fee_calculator.target_signatures_per_slot =
         value_t_or_exit!(matches, "target_signatures_per_slot", usize);
-    builder = builder.fee_calculator(&FeeCalculator::new_derived(&fee_calculator, 0));
+    builder = builder.fee_calculator(FeeCalculator::new_derived(&fee_calculator, 0));
 
     let mut poh_config = PohConfig::default();
     poh_config.target_tick_duration =
@@ -345,7 +345,7 @@ fn main() -> Result<(), Box<dyn error::Error>> {
             poh_config.hashes_per_tick = Some(value_t_or_exit!(matches, "hashes_per_tick", u64));
         }
     }
-    builder = builder.poh_config(&poh_config);
+    builder = builder.poh_config(poh_config);
 
     if let Some(file) = matches.value_of("primordial_accounts_file") {
         builder = append_primordial_accounts(file, AccountFileFormat::Pubkey, builder)?;

runtime/src/bank.rs

@@ -487,8 +487,10 @@ impl Bank {
         let mut hash = self.hash.write().unwrap();
         if *hash == Hash::default() {
             let collector_fees = self.collector_fees.load(Ordering::Relaxed) as u64;
+
             if collector_fees != 0 {
-                self.deposit(&self.collector_id, collector_fees);
+                // burn a portion of fees
+                self.deposit(&self.collector_id, self.fee_calculator.burn(collector_fees));
             }
             //  freeze is a one-way trip, idempotent
             *hash = self.hash_internal_state();
@@ -1723,28 +1725,44 @@ mod tests {
 
     #[test]
     fn test_bank_tx_fee() {
+        let arbitrary_transfer_amount = 42;
+        let mint = arbitrary_transfer_amount * 100;
         let leader = Pubkey::new_rand();
         let GenesisBlockInfo {
             mut genesis_block,
             mint_keypair,
             ..
-        } = create_genesis_block_with_leader(100, &leader, 3);
-        genesis_block.fee_calculator.lamports_per_signature = 3;
+        } = create_genesis_block_with_leader(mint, &leader, 3);
+        genesis_block.fee_calculator.lamports_per_signature = 4; // something divisible by 2
+
+        let expected_fee_paid = genesis_block.fee_calculator.lamports_per_signature;
+        let expected_fee_collected = genesis_block.fee_calculator.burn(expected_fee_paid);
+
         let mut bank = Bank::new(&genesis_block);
 
         let key = Keypair::new();
-        let tx =
-            system_transaction::transfer(&mint_keypair, &key.pubkey(), 2, bank.last_blockhash());
+        let tx = system_transaction::transfer(
+            &mint_keypair,
+            &key.pubkey(),
+            arbitrary_transfer_amount,
+            bank.last_blockhash(),
+        );
 
         let initial_balance = bank.get_balance(&leader);
         assert_eq!(bank.process_transaction(&tx), Ok(()));
-        assert_eq!(bank.get_balance(&key.pubkey()), 2);
-        assert_eq!(bank.get_balance(&mint_keypair.pubkey()), 100 - 5);
+        assert_eq!(bank.get_balance(&key.pubkey()), arbitrary_transfer_amount);
+        assert_eq!(
+            bank.get_balance(&mint_keypair.pubkey()),
+            mint - arbitrary_transfer_amount - expected_fee_paid
+        );
 
         assert_eq!(bank.get_balance(&leader), initial_balance);
         goto_end_of_slot(&mut bank);
         assert_eq!(bank.signature_count(), 1);
-        assert_eq!(bank.get_balance(&leader), initial_balance + 3); // Leader collects fee after the bank is frozen
+        assert_eq!(
+            bank.get_balance(&leader),
+            initial_balance + expected_fee_collected
+        ); // Leader collects fee after the bank is frozen
 
         // Verify that an InstructionError collects fees, too
         let mut bank = Bank::new_from_parent(&Arc::new(bank), &leader, 1);
@@ -1755,13 +1773,19 @@ mod tests {
 
         bank.process_transaction(&tx)
             .expect_err("instruction error");
-        assert_eq!(bank.get_balance(&key.pubkey()), 2); // no change
-        assert_eq!(bank.get_balance(&mint_keypair.pubkey()), 100 - 5 - 3); // mint_keypair still pays a fee
+        assert_eq!(bank.get_balance(&key.pubkey()), arbitrary_transfer_amount); // no change
+        assert_eq!(
+            bank.get_balance(&mint_keypair.pubkey()),
+            mint - arbitrary_transfer_amount - 2 * expected_fee_paid
+        ); // mint_keypair still pays a fee
         goto_end_of_slot(&mut bank);
         assert_eq!(bank.signature_count(), 1);
 
         // Profit! 2 transaction signatures processed at 3 lamports each
-        assert_eq!(bank.get_balance(&leader), initial_balance + 6);
+        assert_eq!(
+            bank.get_balance(&leader),
+            initial_balance + 2 * expected_fee_collected
+        );
     }
 
     #[test]
@@ -1840,11 +1864,17 @@ mod tests {
                 InstructionError::new_result_with_negative_lamports(),
             )),
         ];
-
         let initial_balance = bank.get_balance(&leader);
+
         let results = bank.filter_program_errors_and_collect_fee(&vec![tx1, tx2], &results);
         bank.freeze();
-        assert_eq!(bank.get_balance(&leader), initial_balance + 2 + 2);
+        assert_eq!(
+            bank.get_balance(&leader),
+            initial_balance
+                + bank
+                    .fee_calculator
+                    .burn(bank.fee_calculator.lamports_per_signature * 2)
+        );
         assert_eq!(results[0], Ok(()));
         assert_eq!(results[1], Ok(()));
     }
@@ -2436,11 +2466,11 @@ mod tests {
     fn test_bank_inherit_fee_calculator() {
         let (mut genesis_block, _mint_keypair) = create_genesis_block(500);
         genesis_block.fee_calculator.target_lamports_per_signature = 123;
-        assert_eq!(genesis_block.fee_calculator.target_signatures_per_slot, 0);
+
         let bank0 = Arc::new(Bank::new(&genesis_block));
         let bank1 = Arc::new(new_from_parent(&bank0));
         assert_eq!(
-            bank0.fee_calculator.target_lamports_per_signature,
+            bank0.fee_calculator.target_lamports_per_signature / 2,
             bank1.fee_calculator.lamports_per_signature
         );
     }

runtime/src/genesis_utils.rs

@@ -1,8 +1,11 @@
-use solana_sdk::account::Account;
-use solana_sdk::genesis_block::{Builder, GenesisBlock};
-use solana_sdk::pubkey::Pubkey;
-use solana_sdk::signature::{Keypair, KeypairUtil};
-use solana_sdk::system_program;
+use solana_sdk::{
+    account::Account,
+    fee_calculator::FeeCalculator,
+    genesis_block::{Builder, GenesisBlock},
+    pubkey::Pubkey,
+    signature::{Keypair, KeypairUtil},
+    system_program,
+};
 use solana_stake_api;
 use solana_vote_api::vote_state;
 
@@ -67,7 +70,8 @@ pub fn create_genesis_block_with_leader(
             solana_bpf_loader_program!(),
             solana_vote_program!(),
             solana_stake_program!(),
-        ]);
+        ])
+        .fee_calculator(FeeCalculator::new(0)); // most tests don't want fees
 
     builder = solana_stake_api::rewards_pools::genesis(builder);
     builder = solana_storage_api::rewards_pools::genesis(builder);

sdk/src/fee_calculator.rs

@@ -1,7 +1,8 @@
 use crate::message::Message;
+use crate::timing::{DEFAULT_NUM_TICKS_PER_SECOND, DEFAULT_TICKS_PER_SLOT};
 use log::*;
 
-#[derive(Serialize, Deserialize, PartialEq, Eq, Clone, Debug, Default)]
+#[derive(Serialize, Deserialize, PartialEq, Eq, Clone, Debug)]
 #[serde(rename_all = "camelCase")]
 pub struct FeeCalculator {
     // The current cost of a signature  This amount may increase/decrease over time based on
@@ -19,6 +20,28 @@ pub struct FeeCalculator {
 
     pub min_lamports_per_signature: u64,
     pub max_lamports_per_signature: u64,
+
+    // What portion of collected fees are to be destroyed, percentage-wise
+    pub burn_percent: u8,
+}
+
+/// TODO: determine good values for these
+pub const DEFAULT_TARGET_LAMPORTS_PER_SIGNATURE: u64 = 42;
+pub const DEFAULT_TARGET_SIGNATURES_PER_SLOT: usize =
+    710_000 * DEFAULT_TICKS_PER_SLOT as usize / DEFAULT_NUM_TICKS_PER_SECOND as usize;
+pub const DEFAULT_BURN_PERCENT: u8 = 50;
+
+impl Default for FeeCalculator {
+    fn default() -> Self {
+        FeeCalculator {
+            lamports_per_signature: 0,
+            target_lamports_per_signature: DEFAULT_TARGET_LAMPORTS_PER_SIGNATURE,
+            target_signatures_per_slot: DEFAULT_TARGET_SIGNATURES_PER_SLOT,
+            min_lamports_per_signature: 0,
+            max_lamports_per_signature: 0,
+            burn_percent: DEFAULT_BURN_PERCENT,
+        }
+    }
 }
 
 impl FeeCalculator {
@@ -26,6 +49,7 @@ impl FeeCalculator {
         let base_fee_calculator = Self {
             target_lamports_per_signature,
             lamports_per_signature: target_lamports_per_signature,
+            target_signatures_per_slot: 0,
             ..FeeCalculator::default()
         };
 
@@ -48,15 +72,14 @@ impl FeeCalculator {
             me.max_lamports_per_signature = me.target_lamports_per_signature * 10;
 
             // What the cluster should charge at `latest_signatures_per_slot`
-            let desired_lamports_per_signature = std::cmp::min(
-                me.max_lamports_per_signature,
-                std::cmp::max(
-                    me.min_lamports_per_signature,
-                    me.target_lamports_per_signature
-                        * std::cmp::min(latest_signatures_per_slot, std::u32::MAX as usize) as u64
-                        / me.target_signatures_per_slot as u64,
-                ),
-            );
+            let desired_lamports_per_signature =
+                me.max_lamports_per_signature
+                    .min(me.min_lamports_per_signature.max(
+                        me.target_lamports_per_signature
+                            * std::cmp::min(latest_signatures_per_slot, std::u32::MAX as usize)
+                                as u64
+                            / me.target_signatures_per_slot as u64,
+                    ));
 
             trace!(
                 "desired_lamports_per_signature: {}",
@@ -82,13 +105,11 @@ impl FeeCalculator {
                     gap_adjust
                 );
 
-                me.lamports_per_signature = std::cmp::min(
-                    me.max_lamports_per_signature,
-                    std::cmp::max(
-                        me.min_lamports_per_signature,
-                        (base_fee_calculator.lamports_per_signature as i64 + gap_adjust) as u64,
-                    ),
-                );
+                me.lamports_per_signature =
+                    me.max_lamports_per_signature
+                        .min(me.min_lamports_per_signature.max(
+                            (base_fee_calculator.lamports_per_signature as i64 + gap_adjust) as u64,
+                        ));
             }
         } else {
             me.lamports_per_signature = base_fee_calculator.target_lamports_per_signature;
@@ -105,6 +126,11 @@ impl FeeCalculator {
     pub fn calculate_fee(&self, message: &Message) -> u64 {
         self.lamports_per_signature * u64::from(message.header.num_required_signatures)
     }
+
+    /// calculate unburned fee from a fee total
+    pub fn burn(&self, fees: u64) -> u64 {
+        fees * u64::from(100 - self.burn_percent) / 100
+    }
 }
 
 #[cfg(test)]
@@ -113,6 +139,19 @@ mod tests {
     use crate::pubkey::Pubkey;
     use crate::system_instruction;
 
+    #[test]
+    fn test_fee_calculator_burn() {
+        let mut fee_calculator = FeeCalculator::default();
+
+        assert_eq!(fee_calculator.burn(2), 1);
+
+        fee_calculator.burn_percent = 0;
+
+        assert_eq!(fee_calculator.burn(2), 2);
+        fee_calculator.burn_percent = 100;
+        assert_eq!(fee_calculator.burn(2), 0);
+    }
+
     #[test]
     fn test_fee_calculator_calculate_fee() {
         // Default: no fee.
@@ -140,18 +179,24 @@ mod tests {
     fn test_fee_calculator_derived_default() {
         solana_logger::setup();
 
-        let mut f0 = FeeCalculator::default();
-        assert_eq!(f0.target_signatures_per_slot, 0);
-        assert_eq!(f0.target_lamports_per_signature, 0);
+        let f0 = FeeCalculator::default();
+        assert_eq!(
+            f0.target_signatures_per_slot,
+            DEFAULT_TARGET_SIGNATURES_PER_SLOT
+        );
+        assert_eq!(
+            f0.target_lamports_per_signature,
+            DEFAULT_TARGET_LAMPORTS_PER_SIGNATURE
+        );
         assert_eq!(f0.lamports_per_signature, 0);
-        f0.target_lamports_per_signature = 42;
 
-        let f1 = FeeCalculator::new_derived(&f0, 4242);
-        assert_eq!(f1.target_signatures_per_slot, 0);
+        let f1 = FeeCalculator::new_derived(&f0, DEFAULT_TARGET_SIGNATURES_PER_SLOT);
+        assert_eq!(
+            f1.target_signatures_per_slot,
+            DEFAULT_TARGET_SIGNATURES_PER_SLOT
+        );
         assert_eq!(f1.target_lamports_per_signature, 42);
-        assert_eq!(f1.lamports_per_signature, 42);
-        assert_eq!(f1.min_lamports_per_signature, 42);
-        assert_eq!(f1.max_lamports_per_signature, 42);
+        assert_eq!(f1.lamports_per_signature, 21); // min
     }
 
     #[test]
@@ -164,27 +209,54 @@ mod tests {
         f = FeeCalculator::new_derived(&f, 0);
 
         // Ramp fees up
-        while f.lamports_per_signature < f.max_lamports_per_signature {
+        let mut count = 0;
+        loop {
+            let last_lamports_per_signature = f.lamports_per_signature;
+
             f = FeeCalculator::new_derived(&f, std::usize::MAX);
             info!("[up] f.lamports_per_signature={}", f.lamports_per_signature);
+
+            // some maximum target reached
+            if f.lamports_per_signature == last_lamports_per_signature {
+                break;
+            }
+            // shouldn't take more than 1000 steps to get to minimum
+            assert!(count < 1000);
+            count += 1;
         }
 
         // Ramp fees down
-        while f.lamports_per_signature > f.min_lamports_per_signature {
+        let mut count = 0;
+        loop {
+            let last_lamports_per_signature = f.lamports_per_signature;
             f = FeeCalculator::new_derived(&f, 0);
+
             info!(
                 "[down] f.lamports_per_signature={}",
                 f.lamports_per_signature
             );
+
+            // some minimum target reached
+            if f.lamports_per_signature == last_lamports_per_signature {
+                break;
+            }
+
+            // shouldn't take more than 1000 steps to get to minimum
+            assert!(count < 1000);
+            count += 1;
         }
 
         // Arrive at target rate
+        let mut count = 0;
         while f.lamports_per_signature != f.target_lamports_per_signature {
             f = FeeCalculator::new_derived(&f, f.target_signatures_per_slot);
             info!(
                 "[target] f.lamports_per_signature={}",
                 f.lamports_per_signature
             );
+            // shouldn't take more than 100 steps to get to target
+            assert!(count < 100);
+            count += 1;
         }
     }
 }

sdk/src/genesis_block.rs

@@ -130,16 +130,16 @@ impl Builder {
         self.genesis_block.ticks_per_slot = ticks_per_slot;
         self
     }
-    pub fn poh_config(mut self, poh_config: &PohConfig) -> Self {
-        self.genesis_block.poh_config = poh_config.clone();
+    pub fn poh_config(mut self, poh_config: PohConfig) -> Self {
+        self.genesis_block.poh_config = poh_config;
         self
     }
-    pub fn fee_calculator(mut self, fee_calculator: &FeeCalculator) -> Self {
-        self.genesis_block.fee_calculator = fee_calculator.clone();
+    pub fn fee_calculator(mut self, fee_calculator: FeeCalculator) -> Self {
+        self.genesis_block.fee_calculator = fee_calculator;
         self
     }
-    pub fn inflation(mut self, inflation: &Inflation) -> Self {
-        self.genesis_block.inflation = inflation.clone();
+    pub fn inflation(mut self, inflation: Inflation) -> Self {
+        self.genesis_block.inflation = inflation;
         self
     }
 }