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FoundationDB: Fix read version cache expiration logic

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This commit is contained in:
Maurus Decimus
2026-06-11 15:54:00 +02:00
parent 6cfad95dfb
commit 2cc3903cda
5 changed files with 325 additions and 66 deletions
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85
crates/store/src/backend/foundationdb/mod.rs
View File

@@ -5,7 +5,10 @@
*/
use foundationdb::{Database, FdbError};
use std::time::{Duration, Instant};
use std::{
sync::atomic::{AtomicBool, AtomicI64, AtomicU64, Ordering},
time::{Duration, Instant},
};
pub mod blob;
pub mod main;
@@ -13,40 +16,96 @@ pub mod read;
pub mod write;
const MAX_VALUE_SIZE: usize = 100000;
pub const TRANSACTION_EXPIRY: Duration = Duration::from_secs(1);
const REFRESH_READ_VERSION_AFTER: Duration = Duration::from_secs(1);
const MAX_READ_VERSION_AGE: Duration = Duration::from_secs(4);
pub struct FdbStore {
db: Database,
version: parking_lot::Mutex<ReadVersion>,
version: ReadVersion,
}
pub(crate) struct ReadVersion {
version: i64,
expires: Instant,
base: Instant,
version: AtomicI64,
obtained: AtomicU64,
refreshing: AtomicBool,
}
impl ReadVersion {
pub fn new(version: i64) -> Self {
Self {
version,
expires: Instant::now() + TRANSACTION_EXPIRY,
fn now(&self) -> u64 {
self.base.elapsed().as_nanos() as u64
}
fn current(&self) -> i64 {
self.version.load(Ordering::Acquire)
}
fn age(&self) -> u64 {
self.now()
.saturating_sub(self.obtained.load(Ordering::Acquire))
}
fn store_max(&self, version: i64) {
let mut current = self.version.load(Ordering::Relaxed);
while version > current {
match self.version.compare_exchange_weak(
current,
version,
Ordering::Release,
Ordering::Relaxed,
) {
Ok(_) => break,
Err(actual) => current = actual,
}
}
}
pub fn is_expired(&self) -> bool {
self.expires < Instant::now()
fn refreshed(&self, version: i64) {
self.store_max(version);
self.obtained.store(self.now(), Ordering::Release);
}
fn raise_floor(&self, version: i64) {
self.store_max(version);
}
fn expire(&self) {
self.obtained.store(0, Ordering::Release);
}
fn try_begin_refresh(&self) -> Option<RefreshGuard<'_>> {
if self
.refreshing
.compare_exchange(false, true, Ordering::AcqRel, Ordering::Relaxed)
.is_ok()
{
Some(RefreshGuard(&self.refreshing))
} else {
None
}
}
}
impl Default for ReadVersion {
fn default() -> Self {
Self {
version: 0,
expires: Instant::now(),
base: Instant::now(),
version: AtomicI64::new(0),
obtained: AtomicU64::new(0),
refreshing: AtomicBool::new(false),
}
}
}
pub(crate) struct RefreshGuard<'a>(&'a AtomicBool);
impl Drop for RefreshGuard<'_> {
fn drop(&mut self) {
self.0.store(false, Ordering::Release);
}
}
#[inline(always)]
fn into_error(error: FdbError) -> trc::Error {
trc::StoreEvent::FoundationdbError

173
crates/store/src/backend/foundationdb/read.rs
View File

@@ -4,18 +4,21 @@
* SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
*/
use super::{FdbStore, MAX_VALUE_SIZE, ReadVersion, into_error};
use super::{
FdbStore, MAX_READ_VERSION_AGE, MAX_VALUE_SIZE, REFRESH_READ_VERSION_AFTER, into_error,
};
use crate::{
Deserialize, IterateParams, Key, ValueKey, WITH_SUBSPACE,
backend::deserialize_i64_le,
write::{ValueClass, key::KeySerializer},
write::{MAX_COMMIT_ATTEMPTS, MAX_COMMIT_TIME, ValueClass, key::KeySerializer},
};
use foundationdb::{
KeySelector, RangeOption, Transaction,
FdbError, KeySelector, RangeOption, Transaction,
future::FdbSlice,
options::{self},
};
use futures::TryStreamExt;
use std::time::Instant;
#[allow(dead_code)]
pub(crate) enum ChunkedValue {
@@ -35,26 +38,44 @@ impl FdbStore {
U: Deserialize,
{
let key = key.serialize(WITH_SUBSPACE);
let trx = self.read_trx().await?;
let mut retry_count = 0;
let start = Instant::now();
match read_chunked_value(&key, &trx, true).await? {
ChunkedValue::Single(bytes) => {
U::deserialize_with_key(key.get(1..).unwrap_or_default(), &bytes).map(Some)
loop {
let trx = self.read_trx().await?;
match read_chunked_value(&key, &trx, true).await {
Ok(ChunkedValue::Single(bytes)) => {
return U::deserialize_with_key(key.get(1..).unwrap_or_default(), &bytes)
.map(Some);
}
Ok(ChunkedValue::Chunked { bytes, .. }) => {
return U::deserialize_owned_with_key(key.get(1..).unwrap_or_default(), bytes)
.map(Some);
}
Ok(ChunkedValue::None) => return Ok(None),
Err(err) => {
self.on_read_error(trx, err, &mut retry_count, start).await?;
}
}
ChunkedValue::Chunked { bytes, .. } => {
U::deserialize_owned_with_key(key.get(1..).unwrap_or_default(), bytes).map(Some)
}
ChunkedValue::None => Ok(None),
}
}
pub(crate) async fn key_exists(&self, key: impl Key) -> trc::Result<bool> {
let key = key.serialize(WITH_SUBSPACE);
let trx = self.read_trx().await?;
let mut retry_count = 0;
let start = Instant::now();
match read_chunked_value(&key, &trx, true).await? {
ChunkedValue::Single(_) | ChunkedValue::Chunked { .. } => Ok(true),
ChunkedValue::None => Ok(false),
loop {
let trx = self.read_trx().await?;
match read_chunked_value(&key, &trx, true).await {
Ok(ChunkedValue::Single(_) | ChunkedValue::Chunked { .. }) => return Ok(true),
Ok(ChunkedValue::None) => return Ok(false),
Err(err) => {
self.on_read_error(trx, err, &mut retry_count, start).await?;
}
}
}
}
@@ -65,6 +86,8 @@ impl FdbStore {
) -> trc::Result<()> {
let begin = params.begin.serialize(WITH_SUBSPACE);
let end = params.end.serialize(WITH_SUBSPACE);
let mut retry_count = 0;
let start = Instant::now();
if !params.first {
let mut last_key = vec![];
@@ -144,11 +167,25 @@ impl FdbStore {
break 'outer;
}
Err(e) => {
drop(values);
if e.code() == 1007 && !last_key_.is_empty() {
// Transaction is too old to perform reads or be committed
drop(values);
last_key = last_key_;
continue 'outer;
} else if e.is_retryable()
&& retry_count < MAX_COMMIT_ATTEMPTS
&& start.elapsed() < MAX_COMMIT_TIME
{
// Transient error such as a cached read version ahead of lagging
// storage servers (code 1009); resume from the last key read,
// refresh the read version and back off before retrying.
if !last_key_.is_empty() {
last_key = last_key_;
}
self.version.expire();
trx.on_error(e).await.map_err(into_error)?;
retry_count += 1;
continue 'outer;
} else {
return Err(into_error(e));
}
@@ -157,20 +194,30 @@ impl FdbStore {
}
}
} else {
let trx = self.read_trx().await?;
let mut values = trx.get_ranges_keyvalues(
RangeOption {
begin: KeySelector::first_greater_or_equal(&begin),
end: KeySelector::first_greater_than(&end),
mode: options::StreamingMode::Small,
reverse: !params.ascending,
..Default::default()
},
true,
);
loop {
let trx = self.read_trx().await?;
let mut values = trx.get_ranges_keyvalues(
RangeOption {
begin: KeySelector::first_greater_or_equal(&begin),
end: KeySelector::first_greater_than(&end),
mode: options::StreamingMode::Small,
reverse: !params.ascending,
..Default::default()
},
true,
);
if let Some(value) = values.try_next().await.map_err(into_error)? {
cb(value.key().get(1..).unwrap_or_default(), value.value())?;
match values.try_next().await {
Ok(Some(value)) => {
cb(value.key().get(1..).unwrap_or_default(), value.value())?;
break;
}
Ok(None) => break,
Err(e) => {
drop(values);
self.on_read_error(trx, e, &mut retry_count, start).await?;
}
}
}
}
@@ -182,31 +229,61 @@ impl FdbStore {
key: impl Into<ValueKey<ValueClass>> + Sync + Send,
) -> trc::Result<i64> {
let key = key.into().serialize(WITH_SUBSPACE);
if let Some(bytes) = self
.read_trx()
.await?
.get(&key, true)
.await
.map_err(into_error)?
let mut retry_count = 0;
let start = Instant::now();
loop {
let trx = self.read_trx().await?;
match trx.get(&key, true).await {
Ok(Some(bytes)) => return deserialize_i64_le(&key, &bytes),
Ok(None) => return Ok(0),
Err(e) => {
self.on_read_error(trx, e, &mut retry_count, start).await?;
}
}
}
}
async fn on_read_error(
&self,
trx: Transaction,
err: FdbError,
retry_count: &mut u32,
start: Instant,
) -> trc::Result<()> {
if err.is_retryable()
&& *retry_count < MAX_COMMIT_ATTEMPTS
&& start.elapsed() < MAX_COMMIT_TIME
{
deserialize_i64_le(&key, &bytes)
// The cached read version may be ahead of lagging storage servers under heavy write
// load (code 1009); expire it so the retry obtains a fresh read version, then let
// FoundationDB back off before retrying.
self.version.expire();
trx.on_error(err).await.map_err(into_error)?;
*retry_count += 1;
Ok(())
} else {
Ok(0)
Err(into_error(err))
}
}
pub(crate) async fn read_trx(&self) -> trc::Result<Transaction> {
let (is_expired, mut read_version) = {
let version = self.version.lock();
(version.is_expired(), version.version)
};
let trx = self.db.create_trx().map_err(into_error)?;
let version = self.version.current();
let age = self.version.age();
if is_expired {
read_version = trx.get_read_version().await.map_err(into_error)?;
*self.version.lock() = ReadVersion::new(read_version);
if version != 0 && age < MAX_READ_VERSION_AGE.as_nanos() as u64 {
if age >= REFRESH_READ_VERSION_AFTER.as_nanos() as u64
&& let Some(_guard) = self.version.try_begin_refresh()
{
let read_version = trx.get_read_version().await.map_err(into_error)?;
self.version.refreshed(read_version);
} else {
trx.set_read_version(version);
}
} else {
trx.set_read_version(read_version);
let read_version = trx.get_read_version().await.map_err(into_error)?;
self.version.refreshed(read_version);
}
Ok(trx)
@@ -217,8 +294,8 @@ pub(crate) async fn read_chunked_value(
key: &[u8],
trx: &Transaction,
snapshot: bool,
) -> trc::Result<ChunkedValue> {
if let Some(bytes) = trx.get(key, snapshot).await.map_err(into_error)? {
) -> Result<ChunkedValue, FdbError> {
if let Some(bytes) = trx.get(key, snapshot).await? {
if bytes.len() < MAX_VALUE_SIZE {
Ok(ChunkedValue::Single(bytes))
} else {
@@ -229,7 +306,7 @@ pub(crate) async fn read_chunked_value(
.write(0u8)
.finalize();
while let Some(bytes) = trx.get(&key, snapshot).await.map_err(into_error)? {
while let Some(bytes) = trx.get(&key, snapshot).await? {
value.extend_from_slice(&bytes);
*key.last_mut().unwrap() += 1;
}

8
crates/store/src/backend/foundationdb/write.rs
View File

@@ -5,7 +5,7 @@
*/
use super::{
FdbStore, MAX_VALUE_SIZE, ReadVersion, into_error,
FdbStore, MAX_VALUE_SIZE, into_error,
read::{ChunkedValue, read_chunked_value},
};
use crate::{
@@ -102,6 +102,7 @@ impl FdbStore {
let (merge_result, is_chunked) =
match read_chunked_value(&key, &trx, false)
.await
.map_err(into_error)
.caused_by(trc::location!())?
{
ChunkedValue::Single(slice) => (
@@ -270,10 +271,7 @@ impl FdbStore {
match trx.commit().await {
Ok(result) => {
let commit_version = result.committed_version().map_err(into_error)?;
let mut version = self.version.lock();
if commit_version > version.version {
*version = ReadVersion::new(commit_version);
}
self.version.raise_floor(commit_version);
Ok(true)
}
Err(err) => {