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use std::{
borrow::Borrow,
fs::{self, File},
io::{BufWriter, Read, Write},
mem::transmute,
path::PathBuf,
sync::atomic::{AtomicUsize, Ordering},
};
use anyhow::{Ok, Result};
use byteorder::WriteBytesExt;
use rustc_hash::FxHashMap;
use turbo_tasks::FxDashMap;
use crate::database::{
by_key_space::ByKeySpace,
key_value_database::{KeySpace, KeyValueDatabase},
write_batch::{
BaseWriteBatch, ConcurrentWriteBatch, SerialWriteBatch, WriteBatch, WriteBuffer,
},
};
const CACHE_SIZE_LIMIT: usize = 100 * 1024 * 1024;
const PAIR_HEADER_SIZE: usize = 9;
pub enum ValueBuffer<'l, T: KeyValueDatabase>
where
T: 'l,
{
Database(T::ValueBuffer<'l>),
Cached(&'l [u8]),
}
impl<T: KeyValueDatabase> Borrow<[u8]> for ValueBuffer<'_, T> {
fn borrow(&self) -> &[u8] {
match self {
ValueBuffer::Database(value) => value.borrow(),
ValueBuffer::Cached(value) => value,
}
}
}
type Cache = ByKeySpace<FxDashMap<Vec<u8>, Option<Vec<u8>>>>;
pub struct StartupCacheLayer<T: KeyValueDatabase> {
database: T,
path: PathBuf,
fresh_db: bool,
cache_size: AtomicUsize,
cache: Cache,
restored_map: ByKeySpace<FxHashMap<&'static [u8], &'static [u8]>>,
// Need to be kept around to keep the restored_map reference alive
_restored: Vec<u8>,
}
impl<T: KeyValueDatabase> StartupCacheLayer<T> {
pub fn new(database: T, path: PathBuf, fresh_db: bool) -> Result<Self> {
let mut restored = Vec::new();
let mut restored_map = ByKeySpace::new(|_| FxHashMap::default());
if !fresh_db {
if let Result::Ok(mut cache_file) = File::open(&path) {
cache_file.read_to_end(&mut restored)?;
drop(cache_file);
let mut pos = 0;
while pos < restored.len() {
let (key_space, key, value) = read_key_value_pair(&restored, &mut pos)?;
let map = restored_map.get_mut(key_space);
unsafe {
// Safety: This is a self reference, it's valid as long the `restored`
// buffer is alive
map.insert(
transmute::<&'_ [u8], &'static [u8]>(key),
transmute::<&'_ [u8], &'static [u8]>(value),
);
}
}
}
}
Ok(Self {
database,
path,
fresh_db,
cache_size: AtomicUsize::new(0),
cache: ByKeySpace::new(|key_space| {
FxDashMap::with_capacity_and_hasher(
match key_space {
KeySpace::Infra => 8,
KeySpace::TaskMeta => 1024 * 1024,
KeySpace::TaskData => 1024 * 1024,
KeySpace::ForwardTaskCache => 1024 * 1024,
KeySpace::ReverseTaskCache => 1024 * 1024,
},
Default::default(),
)
}),
_restored: restored,
restored_map,
})
}
}
impl<T: KeyValueDatabase> KeyValueDatabase for StartupCacheLayer<T> {
type ReadTransaction<'l>
= T::ReadTransaction<'l>
where
Self: 'l;
fn is_empty(&self) -> bool {
self.database.is_empty()
}
fn begin_read_transaction(&self) -> Result<Self::ReadTransaction<'_>> {
self.database.begin_read_transaction()
}
type ValueBuffer<'l>
= ValueBuffer<'l, T>
where
Self: 'l;
fn get<'l, 'db: 'l>(
&'l self,
transaction: &'l Self::ReadTransaction<'db>,
key_space: KeySpace,
key: &[u8],
) -> Result<Option<Self::ValueBuffer<'l>>> {
if self.fresh_db {
return Ok(self
.database
.get(transaction, key_space, key)?
.map(ValueBuffer::Database));
}
let value = {
if let Some(value) = self.restored_map.get(key_space).get(key) {
Some(ValueBuffer::Cached(value))
} else {
self.database
.get(transaction, key_space, key)?
.map(ValueBuffer::Database)
}
};
if let Some(value) = value.as_ref() {
let value: &[u8] = value.borrow();
let size = self.cache_size.fetch_add(
key.len() + value.len() + PAIR_HEADER_SIZE,
Ordering::Relaxed,
);
if size < CACHE_SIZE_LIMIT {
self.cache
.get(key_space)
.entry(key.to_vec())
.or_insert_with(|| Some(value.to_vec()));
}
}
Ok(value)
}
type SerialWriteBatch<'l>
= StartupCacheWriteBatch<'l, T::SerialWriteBatch<'l>>
where
Self: 'l;
type ConcurrentWriteBatch<'l>
= StartupCacheWriteBatch<'l, T::ConcurrentWriteBatch<'l>>
where
Self: 'l;
fn write_batch(
&self,
) -> Result<WriteBatch<'_, Self::SerialWriteBatch<'_>, Self::ConcurrentWriteBatch<'_>>> {
Ok(match self.database.write_batch()? {
WriteBatch::Serial(batch) => WriteBatch::serial(StartupCacheWriteBatch {
batch,
path: &self.path,
fresh_db: self.fresh_db,
cache: &self.cache,
restored_map: &self.restored_map,
}),
WriteBatch::Concurrent(batch, _) => WriteBatch::concurrent(StartupCacheWriteBatch {
batch,
path: &self.path,
fresh_db: self.fresh_db,
cache: &self.cache,
restored_map: &self.restored_map,
}),
})
}
}
pub struct StartupCacheWriteBatch<'a, B> {
batch: B,
path: &'a PathBuf,
fresh_db: bool,
cache: &'a Cache,
restored_map: &'a ByKeySpace<FxHashMap<&'static [u8], &'static [u8]>>,
}
impl<'a, B: BaseWriteBatch<'a>> BaseWriteBatch<'a> for StartupCacheWriteBatch<'a, B> {
type ValueBuffer<'l>
= B::ValueBuffer<'l>
where
Self: 'l,
'a: 'l;
fn get<'l>(&'l self, key_space: KeySpace, key: &[u8]) -> Result<Option<Self::ValueBuffer<'l>>>
where
'a: 'l,
{
self.batch.get(key_space, key)
}
fn commit(self) -> Result<()> {
if !self.fresh_db {
// Remove file before writing the new snapshot to database to avoid inconsistency
let _ = fs::remove_file(self.path);
}
self.batch.commit()?;
if !self.fresh_db {
// write cache to a temp file to avoid corrupted file
let temp_path = self.path.with_extension("cache.tmp");
let mut writer = BufWriter::new(File::create(&temp_path)?);
let mut size_buffer = [0u8; 4];
let mut pos = 0;
for (key_space, cache) in self.cache.iter() {
for entry in cache.iter() {
if let (key, Some(value)) = entry.pair() {
pos += write_key_value_pair(
&mut writer,
key_space,
key,
value,
&mut size_buffer,
)?;
}
}
}
for (key_space, map) in self.restored_map.iter() {
let cache = self.cache.get(key_space);
for (key, value) in map.iter() {
if !cache.contains_key(*key) {
let size = key.len() + value.len() + PAIR_HEADER_SIZE;
if pos + size < CACHE_SIZE_LIMIT {
pos += write_key_value_pair(
&mut writer,
key_space,
key,
value,
&mut size_buffer,
)?;
if pos + 24 >= CACHE_SIZE_LIMIT {
break;
}
}
}
}
}
// move temp file to the final location
fs::rename(temp_path, self.path)?;
}
Ok(())
}
}
impl<'a, B: SerialWriteBatch<'a>> SerialWriteBatch<'a> for StartupCacheWriteBatch<'a, B> {
fn put(
&mut self,
key_space: KeySpace,
key: WriteBuffer<'_>,
value: WriteBuffer<'_>,
) -> Result<()> {
if !self.fresh_db {
let cache = self.cache.get(key_space);
cache.insert(key.to_vec(), Some(value.to_vec()));
}
self.batch.put(key_space, key, value)
}
fn delete(&mut self, key_space: KeySpace, key: WriteBuffer<'_>) -> Result<()> {
if !self.fresh_db {
let cache = self.cache.get(key_space);
cache.insert(key.to_vec(), None);
}
self.batch.delete(key_space, key)
}
fn flush(&mut self, key_space: KeySpace) -> Result<()> {
self.batch.flush(key_space)
}
}
impl<'a, B: ConcurrentWriteBatch<'a>> ConcurrentWriteBatch<'a> for StartupCacheWriteBatch<'a, B> {
fn put(&self, key_space: KeySpace, key: WriteBuffer<'_>, value: WriteBuffer<'_>) -> Result<()> {
if !self.fresh_db {
let cache = self.cache.get(key_space);
cache.insert(key.to_vec(), Some(value.to_vec()));
}
self.batch.put(key_space, key, value)
}
fn delete(&self, key_space: KeySpace, key: WriteBuffer<'_>) -> Result<()> {
if !self.fresh_db {
let cache = self.cache.get(key_space);
cache.insert(key.to_vec(), None);
}
self.batch.delete(key_space, key)
}
unsafe fn flush(&self, key_space: KeySpace) -> Result<()> {
unsafe { self.batch.flush(key_space) }
}
}
fn write_key_value_pair(
writer: &mut BufWriter<File>,
key_space: KeySpace,
key: &[u8],
value: &[u8],
size_buffer: &mut [u8; 4],
) -> Result<usize> {
writer.write_u8(match key_space {
KeySpace::Infra => 0,
KeySpace::TaskMeta => 1,
KeySpace::TaskData => 2,
KeySpace::ForwardTaskCache => 3,
KeySpace::ReverseTaskCache => 4,
})?;
let key_len = key.len();
size_buffer.copy_from_slice(&(key_len as u32).to_be_bytes());
writer.write_all(&*size_buffer)?;
let value_len = value.len();
size_buffer.copy_from_slice(&(value_len as u32).to_be_bytes());
writer.write_all(&*size_buffer)?;
writer.write_all(key)?;
writer.write_all(value)?;
Ok(9 + key_len + value_len)
}
fn read_key_value_pair<'l>(
buffer: &'l [u8],
pos: &mut usize,
) -> Result<(KeySpace, &'l [u8], &'l [u8])> {
let key_space = match buffer[*pos] {
0 => KeySpace::Infra,
1 => KeySpace::TaskMeta,
2 => KeySpace::TaskData,
3 => KeySpace::ForwardTaskCache,
4 => KeySpace::ReverseTaskCache,
_ => return Err(anyhow::anyhow!("Invalid key space")),
};
*pos += 1;
let key_len = u32::from_be_bytes(buffer[*pos..*pos + 4].try_into()?);
*pos += 4;
let value_len = u32::from_be_bytes(buffer[*pos..*pos + 4].try_into()?);
*pos += 4;
let key = &buffer[*pos..*pos + key_len as usize];
*pos += key_len as usize;
let value = &buffer[*pos..*pos + value_len as usize];
*pos += value_len as usize;
Ok((key_space, key, value))
}
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