solana/streamer/src/nonblocking/stream_throttle.rs

439 lines
16 KiB
Rust

use {
crate::{
nonblocking::quic::ConnectionPeerType,
quic::{StreamStats, MAX_UNSTAKED_CONNECTIONS},
},
percentage::Percentage,
std::{
cmp,
sync::{
atomic::{AtomicU64, Ordering},
Arc, RwLock,
},
time::{Duration, Instant},
},
};
/// Limit to 250K PPS
const MAX_STREAMS_PER_MS: u64 = 250;
const MAX_UNSTAKED_STREAMS_PERCENT: u64 = 20;
const STREAM_THROTTLING_INTERVAL_MS: u64 = 100;
pub const STREAM_STOP_CODE_THROTTLING: u32 = 15;
const STREAM_LOAD_EMA_INTERVAL_MS: u64 = 5;
const STREAM_LOAD_EMA_INTERVAL_COUNT: u64 = 10;
const MIN_STREAMS_PER_THROTTLING_INTERVAL_FOR_STAKED_CONNECTION: u64 = 8;
pub(crate) struct StakedStreamLoadEMA {
current_load_ema: AtomicU64,
load_in_recent_interval: AtomicU64,
last_update: RwLock<Instant>,
stats: Arc<StreamStats>,
}
impl StakedStreamLoadEMA {
pub(crate) fn new(stats: Arc<StreamStats>) -> Self {
Self {
current_load_ema: AtomicU64::default(),
load_in_recent_interval: AtomicU64::default(),
last_update: RwLock::new(Instant::now()),
stats,
}
}
fn ema_function(current_ema: u128, recent_load: u128) -> u128 {
// Using the EMA multiplier helps in avoiding the floating point math during EMA related calculations
const STREAM_LOAD_EMA_MULTIPLIER: u128 = 1024;
let multiplied_smoothing_factor: u128 =
2 * STREAM_LOAD_EMA_MULTIPLIER / (u128::from(STREAM_LOAD_EMA_INTERVAL_COUNT) + 1);
// The formula is
// updated_ema = recent_load * smoothing_factor + current_ema * (1 - smoothing_factor)
// To avoid floating point math, we are using STREAM_LOAD_EMA_MULTIPLIER
// updated_ema = (recent_load * multiplied_smoothing_factor
// + current_ema * (multiplier - multiplied_smoothing_factor)) / multiplier
(recent_load * multiplied_smoothing_factor
+ current_ema * (STREAM_LOAD_EMA_MULTIPLIER - multiplied_smoothing_factor))
/ STREAM_LOAD_EMA_MULTIPLIER
}
fn update_ema(&self, time_since_last_update_ms: u128) {
// if time_since_last_update_ms > STREAM_LOAD_EMA_INTERVAL_MS, there might be intervals where ema was not updated.
// count how many updates (1 + missed intervals) are needed.
let num_extra_updates =
time_since_last_update_ms.saturating_sub(1) / u128::from(STREAM_LOAD_EMA_INTERVAL_MS);
let load_in_recent_interval =
u128::from(self.load_in_recent_interval.swap(0, Ordering::Relaxed));
let mut updated_load_ema = Self::ema_function(
u128::from(self.current_load_ema.load(Ordering::Relaxed)),
load_in_recent_interval,
);
for _ in 0..num_extra_updates {
updated_load_ema = Self::ema_function(updated_load_ema, load_in_recent_interval);
}
let Ok(updated_load_ema) = u64::try_from(updated_load_ema) else {
error!(
"Failed to convert EMA {} to a u64. Not updating the load EMA",
updated_load_ema
);
self.stats
.stream_load_ema_overflow
.fetch_add(1, Ordering::Relaxed);
return;
};
self.current_load_ema
.store(updated_load_ema, Ordering::Relaxed);
self.stats
.stream_load_ema
.store(updated_load_ema as usize, Ordering::Relaxed);
}
pub(crate) fn update_ema_if_needed(&self) {
const EMA_DURATION: Duration = Duration::from_millis(STREAM_LOAD_EMA_INTERVAL_MS);
// Read lock enables multiple connection handlers to run in parallel if interval is not expired
if Instant::now().duration_since(*self.last_update.read().unwrap()) >= EMA_DURATION {
let mut last_update_w = self.last_update.write().unwrap();
// Recheck as some other thread might have updated the ema since this thread tried to acquire the write lock.
let since_last_update = Instant::now().duration_since(*last_update_w);
if since_last_update >= EMA_DURATION {
*last_update_w = Instant::now();
self.update_ema(since_last_update.as_millis());
}
}
}
pub(crate) fn increment_load(&self) {
self.load_in_recent_interval.fetch_add(1, Ordering::Relaxed);
self.update_ema_if_needed();
}
pub(crate) fn available_load_capacity_in_throttling_duration(
&self,
stake: u64,
total_stake: u64,
) -> u64 {
let ema_window_ms = STREAM_LOAD_EMA_INTERVAL_MS * STREAM_LOAD_EMA_INTERVAL_COUNT;
let max_load_in_ema_window = u128::from(
(MAX_STREAMS_PER_MS
- Percentage::from(MAX_UNSTAKED_STREAMS_PERCENT).apply_to(MAX_STREAMS_PER_MS))
* ema_window_ms,
);
// If the current load is low, cap it to 25% of max_load.
let current_load = cmp::max(
u128::from(self.current_load_ema.load(Ordering::Relaxed)),
max_load_in_ema_window / 4,
);
// Formula is (max_load ^ 2 / current_load) * (stake / total_stake)
let capacity_in_ema_window =
(max_load_in_ema_window * max_load_in_ema_window * u128::from(stake))
/ (current_load * u128::from(total_stake));
let calculated_capacity = capacity_in_ema_window
* u128::from(STREAM_THROTTLING_INTERVAL_MS)
/ u128::from(ema_window_ms);
let calculated_capacity = u64::try_from(calculated_capacity).unwrap_or_else(|_| {
error!(
"Failed to convert stream capacity {} to u64. Using minimum load capacity",
calculated_capacity
);
self.stats
.stream_load_capacity_overflow
.fetch_add(1, Ordering::Relaxed);
MIN_STREAMS_PER_THROTTLING_INTERVAL_FOR_STAKED_CONNECTION
});
cmp::max(
calculated_capacity,
MIN_STREAMS_PER_THROTTLING_INTERVAL_FOR_STAKED_CONNECTION,
)
}
}
pub(crate) fn max_streams_for_connection_in_throttling_duration(
connection_type: ConnectionPeerType,
stake: u64,
total_stake: u64,
ema_load: Arc<StakedStreamLoadEMA>,
) -> u64 {
if matches!(connection_type, ConnectionPeerType::Unstaked) || stake == 0 {
let max_num_connections = u64::try_from(MAX_UNSTAKED_CONNECTIONS).unwrap_or_else(|_| {
error!(
"Failed to convert maximum number of unstaked connections {} to u64.",
MAX_UNSTAKED_CONNECTIONS
);
500
});
Percentage::from(MAX_UNSTAKED_STREAMS_PERCENT)
.apply_to(MAX_STREAMS_PER_MS * STREAM_THROTTLING_INTERVAL_MS)
.saturating_div(max_num_connections)
} else {
ema_load.available_load_capacity_in_throttling_duration(stake, total_stake)
}
}
#[derive(Debug)]
pub(crate) struct ConnectionStreamCounter {
pub(crate) stream_count: AtomicU64,
last_throttling_instant: RwLock<tokio::time::Instant>,
}
impl ConnectionStreamCounter {
pub(crate) fn new() -> Self {
Self {
stream_count: AtomicU64::default(),
last_throttling_instant: RwLock::new(tokio::time::Instant::now()),
}
}
pub(crate) fn reset_throttling_params_if_needed(&self) {
const THROTTLING_INTERVAL: Duration = Duration::from_millis(STREAM_THROTTLING_INTERVAL_MS);
if tokio::time::Instant::now().duration_since(*self.last_throttling_instant.read().unwrap())
> THROTTLING_INTERVAL
{
let mut last_throttling_instant = self.last_throttling_instant.write().unwrap();
// Recheck as some other thread might have done throttling since this thread tried to acquire the write lock.
if tokio::time::Instant::now().duration_since(*last_throttling_instant)
> THROTTLING_INTERVAL
{
*last_throttling_instant = tokio::time::Instant::now();
self.stream_count.store(0, Ordering::Relaxed);
}
}
}
}
#[cfg(test)]
pub mod test {
use {
super::*,
crate::{
nonblocking::{
quic::ConnectionPeerType,
stream_throttle::{
max_streams_for_connection_in_throttling_duration,
MIN_STREAMS_PER_THROTTLING_INTERVAL_FOR_STAKED_CONNECTION,
STREAM_LOAD_EMA_INTERVAL_MS,
},
},
quic::StreamStats,
},
std::{
sync::{atomic::Ordering, Arc},
time::{Duration, Instant},
},
};
#[test]
fn test_max_streams_for_unstaked_connection() {
let load_ema = Arc::new(StakedStreamLoadEMA::new(Arc::new(StreamStats::default())));
// 25K packets per ms * 20% / 500 max unstaked connections
assert_eq!(
max_streams_for_connection_in_throttling_duration(
ConnectionPeerType::Unstaked,
0,
10000,
load_ema.clone(),
),
10
);
// 25K packets per ms * 20% / 500 max unstaked connections
assert_eq!(
max_streams_for_connection_in_throttling_duration(
ConnectionPeerType::Unstaked,
10,
10000,
load_ema.clone(),
),
10
);
// If stake is 0, same limits as unstaked connections will apply.
// 25K packets per ms * 20% / 500 max unstaked connections
assert_eq!(
max_streams_for_connection_in_throttling_duration(
ConnectionPeerType::Staked,
0,
10000,
load_ema.clone(),
),
10
);
}
#[test]
fn test_max_streams_for_staked_connection() {
let load_ema = Arc::new(StakedStreamLoadEMA::new(Arc::new(StreamStats::default())));
// EMA load is used for staked connections to calculate max number of allowed streams.
// EMA window = 5ms interval * 10 intervals = 50ms
// max streams per window = 250K streams/sec * 80% = 200K/sec = 10K per 50ms
// max_streams in 50ms = ((10K * 10K) / ema_load) * stake / total_stake
//
// Stream throttling window is 100ms. So it'll double the amount of max streams.
// max_streams in 100ms (throttling window) = 2 * ((10K * 10K) / ema_load) * stake / total_stake
load_ema.current_load_ema.store(10000, Ordering::Relaxed);
// ema_load = 10K, stake = 15, total_stake = 10K
// max_streams in 100ms (throttling window) = 2 * ((10K * 10K) / 10K) * 15 / 10K = 30
assert_eq!(
max_streams_for_connection_in_throttling_duration(
ConnectionPeerType::Staked,
15,
10000,
load_ema.clone(),
),
30
);
// ema_load = 10K, stake = 1K, total_stake = 10K
// max_streams in 100ms (throttling window) = 2 * ((10K * 10K) / 10K) * 1K / 10K = 2K
assert_eq!(
max_streams_for_connection_in_throttling_duration(
ConnectionPeerType::Staked,
1000,
10000,
load_ema.clone(),
),
2000
);
load_ema.current_load_ema.store(2500, Ordering::Relaxed);
// ema_load = 2.5K, stake = 15, total_stake = 10K
// max_streams in 100ms (throttling window) = 2 * ((10K * 10K) / 2.5K) * 15 / 10K = 120
assert_eq!(
max_streams_for_connection_in_throttling_duration(
ConnectionPeerType::Staked,
15,
10000,
load_ema.clone(),
),
120
);
// ema_load = 2.5K, stake = 1K, total_stake = 10K
// max_streams in 100ms (throttling window) = 2 * ((10K * 10K) / 2.5K) * 1K / 10K = 8000
assert_eq!(
max_streams_for_connection_in_throttling_duration(
ConnectionPeerType::Staked,
1000,
10000,
load_ema.clone(),
),
8000
);
// At 2000, the load is less than 25% of max_load (10K).
// Test that we cap it to 25%, yielding the same result as if load was 2500.
load_ema.current_load_ema.store(2000, Ordering::Relaxed);
// function = ((10K * 10K) / 25% of 10K) * stake / total_stake
assert_eq!(
max_streams_for_connection_in_throttling_duration(
ConnectionPeerType::Staked,
15,
10000,
load_ema.clone(),
),
120
);
// function = ((10K * 10K) / 25% of 10K) * stake / total_stake
assert_eq!(
max_streams_for_connection_in_throttling_duration(
ConnectionPeerType::Staked,
1000,
10000,
load_ema.clone(),
),
8000
);
// At 1/40000 stake weight, and minimum load, it should still allow
// MIN_STREAMS_PER_THROTTLING_INTERVAL_FOR_STAKED_CONNECTION of streams.
assert_eq!(
max_streams_for_connection_in_throttling_duration(
ConnectionPeerType::Staked,
1,
40000,
load_ema.clone(),
),
MIN_STREAMS_PER_THROTTLING_INTERVAL_FOR_STAKED_CONNECTION
);
}
#[test]
fn test_update_ema() {
let stream_load_ema = Arc::new(StakedStreamLoadEMA::new(Arc::new(StreamStats::default())));
stream_load_ema
.load_in_recent_interval
.store(2500, Ordering::Relaxed);
stream_load_ema
.current_load_ema
.store(2000, Ordering::Relaxed);
stream_load_ema.update_ema(5);
let updated_ema = stream_load_ema.current_load_ema.load(Ordering::Relaxed);
assert_eq!(updated_ema, 2090);
stream_load_ema
.load_in_recent_interval
.store(2500, Ordering::Relaxed);
stream_load_ema.update_ema(5);
let updated_ema = stream_load_ema.current_load_ema.load(Ordering::Relaxed);
assert_eq!(updated_ema, 2164);
}
#[test]
fn test_update_ema_missing_interval() {
let stream_load_ema = Arc::new(StakedStreamLoadEMA::new(Arc::new(StreamStats::default())));
stream_load_ema
.load_in_recent_interval
.store(2500, Ordering::Relaxed);
stream_load_ema
.current_load_ema
.store(2000, Ordering::Relaxed);
stream_load_ema.update_ema(8);
let updated_ema = stream_load_ema.current_load_ema.load(Ordering::Relaxed);
assert_eq!(updated_ema, 2164);
}
#[test]
fn test_update_ema_if_needed() {
let stream_load_ema = Arc::new(StakedStreamLoadEMA::new(Arc::new(StreamStats::default())));
stream_load_ema
.load_in_recent_interval
.store(2500, Ordering::Relaxed);
stream_load_ema
.current_load_ema
.store(2000, Ordering::Relaxed);
stream_load_ema.update_ema_if_needed();
let updated_ema = stream_load_ema.current_load_ema.load(Ordering::Relaxed);
assert_eq!(updated_ema, 2000);
let ema_interval = Duration::from_millis(STREAM_LOAD_EMA_INTERVAL_MS);
*stream_load_ema.last_update.write().unwrap() =
Instant::now().checked_sub(ema_interval).unwrap();
stream_load_ema.update_ema_if_needed();
assert!(
Instant::now().duration_since(*stream_load_ema.last_update.read().unwrap())
< ema_interval
);
let updated_ema = stream_load_ema.current_load_ema.load(Ordering::Relaxed);
assert_eq!(updated_ema, 2090);
}
}