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/// HTTP2 Ping usage
///
/// hyper uses HTTP2 pings for two purposes:
///
/// 1. Adaptive flow control using BDP
/// 2. Connection keep-alive
///
/// Both cases are optional.
///
/// # BDP Algorithm
///
/// 1. When receiving a DATA frame, if a BDP ping isn't outstanding:
/// 1a. Record current time.
/// 1b. Send a BDP ping.
/// 2. Increment the number of received bytes.
/// 3. When the BDP ping ack is received:
/// 3a. Record duration from sent time.
/// 3b. Merge RTT with a running average.
/// 3c. Calculate bdp as bytes/rtt.
/// 3d. If bdp is over 2/3 max, set new max to bdp and update windows.
#[cfg(feature = "runtime")]
use std::fmt;
#[cfg(feature = "runtime")]
use std::future::Future;
#[cfg(feature = "runtime")]
use std::pin::Pin;
use std::sync::{Arc, Mutex};
use std::task::{self, Poll};
use std::time::Duration;
#[cfg(not(feature = "runtime"))]
use std::time::Instant;
use h2::{Ping, PingPong};
#[cfg(feature = "runtime")]
use tokio::time::{Instant, Sleep};
use tracing::{debug, trace};
type WindowSize = u32;
pub(super) fn disabled() -> Recorder {
Recorder { shared: None }
}
pub(super) fn channel(ping_pong: PingPong, config: Config) -> (Recorder, Ponger) {
debug_assert!(
config.is_enabled(),
"ping channel requires bdp or keep-alive config",
);
let bdp = config.bdp_initial_window.map(|wnd| Bdp {
bdp: wnd,
max_bandwidth: 0.0,
rtt: 0.0,
ping_delay: Duration::from_millis(100),
stable_count: 0,
});
let (bytes, next_bdp_at) = if bdp.is_some() {
(Some(0), Some(Instant::now()))
} else {
(None, None)
};
#[cfg(feature = "runtime")]
let keep_alive = config.keep_alive_interval.map(|interval| KeepAlive {
interval,
timeout: config.keep_alive_timeout,
while_idle: config.keep_alive_while_idle,
timer: Box::pin(tokio::time::sleep(interval)),
state: KeepAliveState::Init,
});
#[cfg(feature = "runtime")]
let last_read_at = keep_alive.as_ref().map(|_| Instant::now());
let shared = Arc::new(Mutex::new(Shared {
bytes,
#[cfg(feature = "runtime")]
last_read_at,
#[cfg(feature = "runtime")]
is_keep_alive_timed_out: false,
ping_pong,
ping_sent_at: None,
next_bdp_at,
}));
(
Recorder {
shared: Some(shared.clone()),
},
Ponger {
bdp,
#[cfg(feature = "runtime")]
keep_alive,
shared,
},
)
}
#[derive(Clone)]
pub(super) struct Config {
pub(super) bdp_initial_window: Option<WindowSize>,
/// If no frames are received in this amount of time, a PING frame is sent.
#[cfg(feature = "runtime")]
pub(super) keep_alive_interval: Option<Duration>,
/// After sending a keepalive PING, the connection will be closed if
/// a pong is not received in this amount of time.
#[cfg(feature = "runtime")]
pub(super) keep_alive_timeout: Duration,
/// If true, sends pings even when there are no active streams.
#[cfg(feature = "runtime")]
pub(super) keep_alive_while_idle: bool,
}
#[derive(Clone)]
pub(crate) struct Recorder {
shared: Option<Arc<Mutex<Shared>>>,
}
pub(super) struct Ponger {
bdp: Option<Bdp>,
#[cfg(feature = "runtime")]
keep_alive: Option<KeepAlive>,
shared: Arc<Mutex<Shared>>,
}
struct Shared {
ping_pong: PingPong,
ping_sent_at: Option<Instant>,
// bdp
/// If `Some`, bdp is enabled, and this tracks how many bytes have been
/// read during the current sample.
bytes: Option<usize>,
/// We delay a variable amount of time between BDP pings. This allows us
/// to send less pings as the bandwidth stabilizes.
next_bdp_at: Option<Instant>,
// keep-alive
/// If `Some`, keep-alive is enabled, and the Instant is how long ago
/// the connection read the last frame.
#[cfg(feature = "runtime")]
last_read_at: Option<Instant>,
#[cfg(feature = "runtime")]
is_keep_alive_timed_out: bool,
}
struct Bdp {
/// Current BDP in bytes
bdp: u32,
/// Largest bandwidth we've seen so far.
max_bandwidth: f64,
/// Round trip time in seconds
rtt: f64,
/// Delay the next ping by this amount.
///
/// This will change depending on how stable the current bandwidth is.
ping_delay: Duration,
/// The count of ping round trips where BDP has stayed the same.
stable_count: u32,
}
#[cfg(feature = "runtime")]
struct KeepAlive {
/// If no frames are received in this amount of time, a PING frame is sent.
interval: Duration,
/// After sending a keepalive PING, the connection will be closed if
/// a pong is not received in this amount of time.
timeout: Duration,
/// If true, sends pings even when there are no active streams.
while_idle: bool,
state: KeepAliveState,
timer: Pin<Box<Sleep>>,
}
#[cfg(feature = "runtime")]
enum KeepAliveState {
Init,
Scheduled,
PingSent,
}
pub(super) enum Ponged {
SizeUpdate(WindowSize),
#[cfg(feature = "runtime")]
KeepAliveTimedOut,
}
#[cfg(feature = "runtime")]
#[derive(Debug)]
pub(super) struct KeepAliveTimedOut;
// ===== impl Config =====
impl Config {
pub(super) fn is_enabled(&self) -> bool {
#[cfg(feature = "runtime")]
{
self.bdp_initial_window.is_some() || self.keep_alive_interval.is_some()
}
#[cfg(not(feature = "runtime"))]
{
self.bdp_initial_window.is_some()
}
}
}
// ===== impl Recorder =====
impl Recorder {
pub(crate) fn record_data(&self, len: usize) {
let shared = if let Some(ref shared) = self.shared {
shared
} else {
return;
};
let mut locked = shared.lock().unwrap();
#[cfg(feature = "runtime")]
locked.update_last_read_at();
// are we ready to send another bdp ping?
// if not, we don't need to record bytes either
if let Some(ref next_bdp_at) = locked.next_bdp_at {
if Instant::now() < *next_bdp_at {
return;
} else {
locked.next_bdp_at = None;
}
}
if let Some(ref mut bytes) = locked.bytes {
*bytes += len;
} else {
// no need to send bdp ping if bdp is disabled
return;
}
if !locked.is_ping_sent() {
locked.send_ping();
}
}
pub(crate) fn record_non_data(&self) {
#[cfg(feature = "runtime")]
{
let shared = if let Some(ref shared) = self.shared {
shared
} else {
return;
};
let mut locked = shared.lock().unwrap();
locked.update_last_read_at();
}
}
/// If the incoming stream is already closed, convert self into
/// a disabled reporter.
#[cfg(feature = "client")]
pub(super) fn for_stream(self, stream: &h2::RecvStream) -> Self {
if stream.is_end_stream() {
disabled()
} else {
self
}
}
pub(super) fn ensure_not_timed_out(&self) -> crate::Result<()> {
#[cfg(feature = "runtime")]
{
if let Some(ref shared) = self.shared {
let locked = shared.lock().unwrap();
if locked.is_keep_alive_timed_out {
return Err(KeepAliveTimedOut.crate_error());
}
}
}
// else
Ok(())
}
}
// ===== impl Ponger =====
impl Ponger {
pub(super) fn poll(&mut self, cx: &mut task::Context<'_>) -> Poll<Ponged> {
let now = Instant::now();
let mut locked = self.shared.lock().unwrap();
#[cfg(feature = "runtime")]
let is_idle = self.is_idle();
#[cfg(feature = "runtime")]
{
if let Some(ref mut ka) = self.keep_alive {
ka.schedule(is_idle, &locked);
ka.maybe_ping(cx, &mut locked);
}
}
if !locked.is_ping_sent() {
// XXX: this doesn't register a waker...?
return Poll::Pending;
}
match locked.ping_pong.poll_pong(cx) {
Poll::Ready(Ok(_pong)) => {
let start = locked
.ping_sent_at
.expect("pong received implies ping_sent_at");
locked.ping_sent_at = None;
let rtt = now - start;
trace!("recv pong");
#[cfg(feature = "runtime")]
{
if let Some(ref mut ka) = self.keep_alive {
locked.update_last_read_at();
ka.schedule(is_idle, &locked);
}
}
if let Some(ref mut bdp) = self.bdp {
let bytes = locked.bytes.expect("bdp enabled implies bytes");
locked.bytes = Some(0); // reset
trace!("received BDP ack; bytes = {}, rtt = {:?}", bytes, rtt);
let update = bdp.calculate(bytes, rtt);
locked.next_bdp_at = Some(now + bdp.ping_delay);
if let Some(update) = update {
return Poll::Ready(Ponged::SizeUpdate(update))
}
}
}
Poll::Ready(Err(e)) => {
debug!("pong error: {}", e);
}
Poll::Pending => {
#[cfg(feature = "runtime")]
{
if let Some(ref mut ka) = self.keep_alive {
if let Err(KeepAliveTimedOut) = ka.maybe_timeout(cx) {
self.keep_alive = None;
locked.is_keep_alive_timed_out = true;
return Poll::Ready(Ponged::KeepAliveTimedOut);
}
}
}
}
}
// XXX: this doesn't register a waker...?
Poll::Pending
}
#[cfg(feature = "runtime")]
fn is_idle(&self) -> bool {
Arc::strong_count(&self.shared) <= 2
}
}
// ===== impl Shared =====
impl Shared {
fn send_ping(&mut self) {
match self.ping_pong.send_ping(Ping::opaque()) {
Ok(()) => {
self.ping_sent_at = Some(Instant::now());
trace!("sent ping");
}
Err(err) => {
debug!("error sending ping: {}", err);
}
}
}
fn is_ping_sent(&self) -> bool {
self.ping_sent_at.is_some()
}
#[cfg(feature = "runtime")]
fn update_last_read_at(&mut self) {
if self.last_read_at.is_some() {
self.last_read_at = Some(Instant::now());
}
}
#[cfg(feature = "runtime")]
fn last_read_at(&self) -> Instant {
self.last_read_at.expect("keep_alive expects last_read_at")
}
}
// ===== impl Bdp =====
/// Any higher than this likely will be hitting the TCP flow control.
const BDP_LIMIT: usize = 1024 * 1024 * 16;
impl Bdp {
fn calculate(&mut self, bytes: usize, rtt: Duration) -> Option<WindowSize> {
// No need to do any math if we're at the limit.
if self.bdp as usize == BDP_LIMIT {
self.stabilize_delay();
return None;
}
// average the rtt
let rtt = seconds(rtt);
if self.rtt == 0.0 {
// First sample means rtt is first rtt.
self.rtt = rtt;
} else {
// Weigh this rtt as 1/8 for a moving average.
self.rtt += (rtt - self.rtt) * 0.125;
}
// calculate the current bandwidth
let bw = (bytes as f64) / (self.rtt * 1.5);
trace!("current bandwidth = {:.1}B/s", bw);
if bw < self.max_bandwidth {
// not a faster bandwidth, so don't update
self.stabilize_delay();
return None;
} else {
self.max_bandwidth = bw;
}
// if the current `bytes` sample is at least 2/3 the previous
// bdp, increase to double the current sample.
if bytes >= self.bdp as usize * 2 / 3 {
self.bdp = (bytes * 2).min(BDP_LIMIT) as WindowSize;
trace!("BDP increased to {}", self.bdp);
self.stable_count = 0;
self.ping_delay /= 2;
Some(self.bdp)
} else {
self.stabilize_delay();
None
}
}
fn stabilize_delay(&mut self) {
if self.ping_delay < Duration::from_secs(10) {
self.stable_count += 1;
if self.stable_count >= 2 {
self.ping_delay *= 4;
self.stable_count = 0;
}
}
}
}
fn seconds(dur: Duration) -> f64 {
const NANOS_PER_SEC: f64 = 1_000_000_000.0;
let secs = dur.as_secs() as f64;
secs + (dur.subsec_nanos() as f64) / NANOS_PER_SEC
}
// ===== impl KeepAlive =====
#[cfg(feature = "runtime")]
impl KeepAlive {
fn schedule(&mut self, is_idle: bool, shared: &Shared) {
match self.state {
KeepAliveState::Init => {
if !self.while_idle && is_idle {
return;
}
self.state = KeepAliveState::Scheduled;
let interval = shared.last_read_at() + self.interval;
self.timer.as_mut().reset(interval);
}
KeepAliveState::PingSent => {
if shared.is_ping_sent() {
return;
}
self.state = KeepAliveState::Scheduled;
let interval = shared.last_read_at() + self.interval;
self.timer.as_mut().reset(interval);
}
KeepAliveState::Scheduled => (),
}
}
fn maybe_ping(&mut self, cx: &mut task::Context<'_>, shared: &mut Shared) {
match self.state {
KeepAliveState::Scheduled => {
if Pin::new(&mut self.timer).poll(cx).is_pending() {
return;
}
// check if we've received a frame while we were scheduled
if shared.last_read_at() + self.interval > self.timer.deadline() {
self.state = KeepAliveState::Init;
cx.waker().wake_by_ref(); // schedule us again
return;
}
trace!("keep-alive interval ({:?}) reached", self.interval);
shared.send_ping();
self.state = KeepAliveState::PingSent;
let timeout = Instant::now() + self.timeout;
self.timer.as_mut().reset(timeout);
}
KeepAliveState::Init | KeepAliveState::PingSent => (),
}
}
fn maybe_timeout(&mut self, cx: &mut task::Context<'_>) -> Result<(), KeepAliveTimedOut> {
match self.state {
KeepAliveState::PingSent => {
if Pin::new(&mut self.timer).poll(cx).is_pending() {
return Ok(());
}
trace!("keep-alive timeout ({:?}) reached", self.timeout);
Err(KeepAliveTimedOut)
}
KeepAliveState::Init | KeepAliveState::Scheduled => Ok(()),
}
}
}
// ===== impl KeepAliveTimedOut =====
#[cfg(feature = "runtime")]
impl KeepAliveTimedOut {
pub(super) fn crate_error(self) -> crate::Error {
crate::Error::new(crate::error::Kind::Http2).with(self)
}
}
#[cfg(feature = "runtime")]
impl fmt::Display for KeepAliveTimedOut {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.write_str("keep-alive timed out")
}
}
#[cfg(feature = "runtime")]
impl std::error::Error for KeepAliveTimedOut {
fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
Some(&crate::error::TimedOut)
}
}