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stake: Allow stakes with unmatched credits observed to merge (#18985) 

* stake: Allow stakes with unmatched credits observed to merge

* Address feedback

* Remove branch by doing a ceiling in one calc
This commit is contained in:
Jon Cinque 2021-08-04 10:43:34 -04:00 committed by GitHub
parent 31a620c42b
commit 2b33c0c165
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4 changed files with 350 additions and 5 deletions
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71
Cargo.lock generated
View File

@ -289,6 +289,21 @@ dependencies = [
"shlex",
]
[[package]]
name = "bit-set"
version = "0.5.2"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "6e11e16035ea35e4e5997b393eacbf6f63983188f7a2ad25bfb13465f5ad59de"
dependencies = [
"bit-vec",
]
[[package]]
name = "bit-vec"
version = "0.6.3"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "349f9b6a179ed607305526ca489b34ad0a41aed5f7980fa90eb03160b69598fb"
[[package]]
name = "bitflags"
version = "1.2.1"
@ -3265,6 +3280,26 @@ dependencies = [
"unicode-xid 0.2.0",
]
[[package]]
name = "proptest"
version = "1.0.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "1e0d9cc07f18492d879586c92b485def06bc850da3118075cd45d50e9c95b0e5"
dependencies = [
"bit-set",
"bitflags",
"byteorder",
"lazy_static",
"num-traits",
"quick-error 2.0.1",
"rand 0.8.3",
"rand_chacha 0.3.0",
"rand_xorshift 0.3.0",
"regex-syntax",
"rusty-fork",
"tempfile",
]
[[package]]
name = "prost"
version = "0.8.0"
@ -3325,6 +3360,18 @@ dependencies = [
"percent-encoding 2.1.0",
]
[[package]]
name = "quick-error"
version = "1.2.3"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "a1d01941d82fa2ab50be1e79e6714289dd7cde78eba4c074bc5a4374f650dfe0"
[[package]]
name = "quick-error"
version = "2.0.1"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "a993555f31e5a609f617c12db6250dedcac1b0a85076912c436e6fc9b2c8e6a3"
[[package]]
name = "quote"
version = "0.6.13"
@ -3377,7 +3424,7 @@ dependencies = [
"rand_jitter",
"rand_os",
"rand_pcg 0.1.2",
"rand_xorshift",
"rand_xorshift 0.1.1",
"winapi 0.3.8",
]
@ -3559,6 +3606,15 @@ dependencies = [
"rand_core 0.3.1",
]
[[package]]
name = "rand_xorshift"
version = "0.3.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "d25bf25ec5ae4a3f1b92f929810509a2f53d7dca2f50b794ff57e3face536c8f"
dependencies = [
"rand_core 0.6.3",
]
[[package]]
name = "raptorq"
version = "1.6.4"
@ -3826,6 +3882,18 @@ version = "1.0.5"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "61b3909d758bb75c79f23d4736fac9433868679d3ad2ea7a61e3c25cfda9a088"
[[package]]
name = "rusty-fork"
version = "0.3.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "cb3dcc6e454c328bb824492db107ab7c0ae8fcffe4ad210136ef014458c1bc4f"
dependencies = [
"fnv",
"quick-error 1.2.3",
"tempfile",
"wait-timeout",
]
[[package]]
name = "ryu"
version = "1.0.4"
@ -5668,6 +5736,7 @@ dependencies = [
"log 0.4.14",
"num-derive",
"num-traits",
"proptest",
"rustc_version 0.4.0",
"serde",
"serde_derive",

1
programs/stake/Cargo.toml
View File

@ -25,6 +25,7 @@ solana-config-program = { path = "../config", version = "=1.8.0" }
thiserror = "1.0"
[dev-dependencies]
proptest = "1.0"
solana-logger = { path = "../../logger", version = "=1.8.0" }
[build-dependencies]

278
programs/stake/src/stake_state.rs
View File

@ -8,6 +8,7 @@ use {
account::{AccountSharedData, ReadableAccount, WritableAccount},
account_utils::{State, StateMut},
clock::{Clock, Epoch},
feature_set::stake_merge_with_unmatched_credits_observed,
ic_msg,
instruction::{checked_add, InstructionError},
keyed_account::KeyedAccount,
@ -957,6 +958,7 @@ impl MergeKind {
}
}
// Remove this when the `stake_merge_with_unmatched_credits_observed` feature is removed
fn active_stakes_can_merge(
invoke_context: &dyn InvokeContext,
stake: &Stake,
@ -988,7 +990,19 @@ impl MergeKind {
Self::metas_can_merge(invoke_context, self.meta(), source.meta(), clock)?;
self.active_stake()
.zip(source.active_stake())
.map(|(stake, source)| Self::active_stakes_can_merge(invoke_context, stake, source))
.map(|(stake, source)| {
if invoke_context
.is_feature_active(&stake_merge_with_unmatched_credits_observed::id())
{
Self::active_delegations_can_merge(
invoke_context,
&stake.delegation,
&source.delegation,
)
} else {
Self::active_stakes_can_merge(invoke_context, stake, source)
}
})
.unwrap_or(Ok(()))?;
let merged_state = match (self, source) {
(Self::Inactive(_, _), Self::Inactive(_, _)) => None,
@ -1005,7 +1019,12 @@ impl MergeKind {
source_meta.rent_exempt_reserve,
source_stake.delegation.stake,
)?;
stake.delegation.stake = checked_add(stake.delegation.stake, source_lamports)?;
merge_delegation_stake_and_credits_observed(
invoke_context,
&mut stake,
source_lamports,
source_stake.credits_observed,
)?;
Some(StakeState::Stake(meta, stake))
}
(Self::FullyActive(meta, mut stake), Self::FullyActive(_, source_stake)) => {
@ -1013,8 +1032,12 @@ impl MergeKind {
// protect against the magic activation loophole. It will
// instead be moved into the destination account as extra,
// withdrawable `lamports`
stake.delegation.stake =
checked_add(stake.delegation.stake, source_stake.delegation.stake)?;
merge_delegation_stake_and_credits_observed(
invoke_context,
&mut stake,
source_stake.delegation.stake,
source_stake.credits_observed,
)?;
Some(StakeState::Stake(meta, stake))
}
_ => return Err(StakeError::MergeMismatch.into()),
@ -1023,6 +1046,69 @@ impl MergeKind {
}
}
fn merge_delegation_stake_and_credits_observed(
invoke_context: &dyn InvokeContext,
stake: &mut Stake,
absorbed_lamports: u64,
absorbed_credits_observed: u64,
) -> Result<(), InstructionError> {
if invoke_context.is_feature_active(&stake_merge_with_unmatched_credits_observed::id()) {
stake.credits_observed =
stake_weighted_credits_observed(stake, absorbed_lamports, absorbed_credits_observed)
.ok_or(InstructionError::ArithmeticOverflow)?;
}
stake.delegation.stake = checked_add(stake.delegation.stake, absorbed_lamports)?;
Ok(())
}
/// Calculate the effective credits observed for two stakes when merging
///
/// When merging two `ActivationEpoch` or `FullyActive` stakes, the credits
/// observed of the merged stake is the weighted average of the two stakes'
/// credits observed.
///
/// This is because we can derive the effective credits_observed by reversing the staking
/// rewards equation, _while keeping the rewards unchanged after merge (i.e. strong
/// requirement)_, like below:
///
/// a(N) => account, r => rewards, s => stake, c => credits:
/// assume:
/// a3 = merge(a1, a2)
/// then:
/// a3.s = a1.s + a2.s
///
/// Next, given:
/// aN.r = aN.c * aN.s (for every N)
/// finally:
/// a3.r = a1.r + a2.r
/// a3.c * a3.s = a1.c * a1.s + a2.c * a2.s
/// a3.c = (a1.c * a1.s + a2.c * a2.s) / (a1.s + a2.s) // QED
///
/// (For this discussion, we omitted irrelevant variables, including distance
/// calculation against vote_account and point indirection.)
fn stake_weighted_credits_observed(
stake: &Stake,
absorbed_lamports: u64,
absorbed_credits_observed: u64,
) -> Option<u64> {
if stake.credits_observed == absorbed_credits_observed {
Some(stake.credits_observed)
} else {
let total_stake = u128::from(stake.delegation.stake.checked_add(absorbed_lamports)?);
let stake_weighted_credits =
u128::from(stake.credits_observed).checked_mul(u128::from(stake.delegation.stake))?;
let absorbed_weighted_credits =
u128::from(absorbed_credits_observed).checked_mul(u128::from(absorbed_lamports))?;
// Discard fractional credits as a merge side-effect friction by taking
// the ceiling, done by adding `denominator - 1` to the numerator.
let total_weighted_credits = stake_weighted_credits
.checked_add(absorbed_weighted_credits)?
.checked_add(total_stake)?
.checked_sub(1)?;
u64::try_from(total_weighted_credits.checked_div(total_stake)?).ok()
}
}
// utility function, used by runtime
// returns a tuple of (stakers_reward,voters_reward)
pub fn redeem_rewards(
@ -1281,6 +1367,7 @@ fn do_create_account(
#[cfg(test)]
mod tests {
use super::*;
use proptest::prelude::*;
use solana_sdk::{
account::{AccountSharedData, WritableAccount},
clock::UnixTimestamp,
@ -6649,4 +6736,187 @@ mod tests {
let delegation = new_state.delegation().unwrap();
assert_eq!(delegation.stake, 2 * stake.delegation.stake);
}
#[test]
fn test_active_stake_merge() {
let delegation_a = 4_242_424_242u64;
let delegation_b = 6_200_000_000u64;
let credits_a = 124_521_000u64;
let rent_exempt_reserve = 227_000_000u64;
let meta = Meta {
rent_exempt_reserve,
..Meta::default()
};
let stake_a = Stake {
delegation: Delegation {
stake: delegation_a,
..Delegation::default()
},
credits_observed: credits_a,
};
let stake_b = Stake {
delegation: Delegation {
stake: delegation_b,
..Delegation::default()
},
credits_observed: credits_a,
};
let invoke_context = MockInvokeContext::new(vec![]);
// activating stake merge, match credits observed
let activation_epoch_a = MergeKind::ActivationEpoch(meta, stake_a);
let activation_epoch_b = MergeKind::ActivationEpoch(meta, stake_b);
let new_stake = activation_epoch_a
.merge(&invoke_context, activation_epoch_b, None)
.unwrap()
.unwrap()
.stake()
.unwrap();
assert_eq!(new_stake.credits_observed, credits_a);
assert_eq!(
new_stake.delegation.stake,
delegation_a + delegation_b + rent_exempt_reserve
);
// active stake merge, match credits observed
let fully_active_a = MergeKind::FullyActive(meta, stake_a);
let fully_active_b = MergeKind::FullyActive(meta, stake_b);
let new_stake = fully_active_a
.merge(&invoke_context, fully_active_b, None)
.unwrap()
.unwrap()
.stake()
.unwrap();
assert_eq!(new_stake.credits_observed, credits_a);
assert_eq!(new_stake.delegation.stake, delegation_a + delegation_b);
// activating stake merge, unmatched credits observed
let credits_b = 125_124_521u64;
let stake_b = Stake {
delegation: Delegation {
stake: delegation_b,
..Delegation::default()
},
credits_observed: credits_b,
};
let activation_epoch_a = MergeKind::ActivationEpoch(meta, stake_a);
let activation_epoch_b = MergeKind::ActivationEpoch(meta, stake_b);
let new_stake = activation_epoch_a
.merge(&invoke_context, activation_epoch_b, None)
.unwrap()
.unwrap()
.stake()
.unwrap();
assert_eq!(
new_stake.credits_observed,
(credits_a * delegation_a + credits_b * (delegation_b + rent_exempt_reserve))
/ (delegation_a + delegation_b + rent_exempt_reserve)
+ 1
);
assert_eq!(
new_stake.delegation.stake,
delegation_a + delegation_b + rent_exempt_reserve
);
// active stake merge, unmatched credits observed
let fully_active_a = MergeKind::FullyActive(meta, stake_a);
let fully_active_b = MergeKind::FullyActive(meta, stake_b);
let new_stake = fully_active_a
.merge(&invoke_context, fully_active_b, None)
.unwrap()
.unwrap()
.stake()
.unwrap();
assert_eq!(
new_stake.credits_observed,
(credits_a * delegation_a + credits_b * delegation_b) / (delegation_a + delegation_b)
+ 1
);
assert_eq!(new_stake.delegation.stake, delegation_a + delegation_b);
// active stake merge, unmatched credits observed, no need to ceiling the calculation
let delegation = 1_000_000u64;
let credits_a = 200_000_000u64;
let credits_b = 100_000_000u64;
let rent_exempt_reserve = 227_000_000u64;
let meta = Meta {
rent_exempt_reserve,
..Meta::default()
};
let stake_a = Stake {
delegation: Delegation {
stake: delegation,
..Delegation::default()
},
credits_observed: credits_a,
};
let stake_b = Stake {
delegation: Delegation {
stake: delegation,
..Delegation::default()
},
credits_observed: credits_b,
};
let fully_active_a = MergeKind::FullyActive(meta, stake_a);
let fully_active_b = MergeKind::FullyActive(meta, stake_b);
let new_stake = fully_active_a
.merge(&invoke_context, fully_active_b, None)
.unwrap()
.unwrap()
.stake()
.unwrap();
assert_eq!(
new_stake.credits_observed,
(credits_a * delegation + credits_b * delegation) / (delegation + delegation)
);
assert_eq!(new_stake.delegation.stake, delegation * 2);
}
prop_compose! {
pub fn sum_within(max: u64)(total in 1..max)
(intermediate in 1..total, total in Just(total))
-> (u64, u64) {
(intermediate, total - intermediate)
}
}
proptest! {
#[test]
fn test_stake_weighted_credits_observed(
(credits_a, credits_b) in sum_within(u64::MAX),
(delegation_a, delegation_b) in sum_within(u64::MAX),
) {
let stake = Stake {
delegation: Delegation {
stake: delegation_a,
..Delegation::default()
},
credits_observed: credits_a
};
let credits_observed = stake_weighted_credits_observed(
&stake,
delegation_b,
credits_b,
).unwrap();
// calculated credits observed should always be between the credits of a and b
if credits_a < credits_b {
assert!(credits_a < credits_observed);
assert!(credits_observed <= credits_b);
} else {
assert!(credits_b <= credits_observed);
assert!(credits_observed <= credits_a);
}
// the difference of the combined weighted credits and the separate weighted credits
// should be 1 or 0
let weighted_credits_total = credits_observed as u128 * (delegation_a + delegation_b) as u128;
let weighted_credits_a = credits_a as u128 * delegation_a as u128;
let weighted_credits_b = credits_b as u128 * delegation_b as u128;
let raw_diff = weighted_credits_total - (weighted_credits_a + weighted_credits_b);
let credits_observed_diff = raw_diff / (delegation_a + delegation_b) as u128;
assert!(credits_observed_diff <= 1);
}
}
}

5
sdk/src/feature_set.rs
View File

@ -187,6 +187,10 @@ pub mod disable_fees_sysvar {
solana_sdk::declare_id!("JAN1trEUEtZjgXYzNBYHU9DYd7GnThhXfFP7SzPXkPsG");
}
pub mod stake_merge_with_unmatched_credits_observed {
solana_sdk::declare_id!("meRgp4ArRPhD3KtCY9c5yAf2med7mBLsjKTPeVUHqBL");
}
lazy_static! {
/// Map of feature identifiers to user-visible description
pub static ref FEATURE_NAMES: HashMap<Pubkey, &'static str> = [
@ -228,6 +232,7 @@ lazy_static! {
(stop_verify_mul64_imm_nonzero::id(), "Sets rbpf vm config verify_mul64_imm_nonzero to false"),
(merge_nonce_error_into_system_error::id(), "merge NonceError into SystemError"),
(disable_fees_sysvar::id(), "disable fees sysvar"),
(stake_merge_with_unmatched_credits_observed::id(), "allow merging active stakes with unmatched credits_observed #18985"),
/*************** ADD NEW FEATURES HERE ***************/
]
.iter()