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/*
This file is part of jellything (https://codeberg.org/metamuffin/jellything)
which is licensed under the GNU Affero General Public License (version 3); see /COPYING.
Copyright (C) 2023 metamuffin <metamuffin.org>
*/
use crate::{AssetLocationExt, CONF};
use anyhow::{anyhow, Context};
use base64::Engine;
use bincode::{Decode, Encode};
use jellycommon::AssetLocation;
use log::{info, warn};
use std::{
any::Any,
collections::{BTreeMap, HashMap},
future::Future,
io::Seek,
sync::{
atomic::{AtomicUsize, Ordering},
Arc, LazyLock, RwLock,
},
time::Instant,
};
use tokio::sync::Mutex;
pub fn cache_location(seed: &[&str]) -> (usize, AssetLocation) {
use sha2::Digest;
let mut d = sha2::Sha512::new();
for s in seed {
d.update(s.as_bytes());
d.update(b"\0");
}
let d = d.finalize();
let n = d[0] as usize | (d[1] as usize) << 8 | (d[2] as usize) << 16 | (d[3] as usize) << 24;
let fname = base64::engine::general_purpose::URL_SAFE.encode(d);
let fname = &fname[..22];
let fname = format!("{}-{}", seed[0], fname); // about 128 bits
(n, AssetLocation::Cache(fname.into()))
}
const CACHE_GENERATION_BUCKET_COUNT: usize = 1024;
pub static CACHE_GENERATION_LOCKS: LazyLock<[Mutex<()>; CACHE_GENERATION_BUCKET_COUNT]> =
LazyLock::new(|| [(); CACHE_GENERATION_BUCKET_COUNT].map(|_| Mutex::new(())));
pub async fn async_cache_file<Fun, Fut>(
seed: &[&str],
generate: Fun,
) -> Result<AssetLocation, anyhow::Error>
where
Fun: FnOnce(tokio::fs::File) -> Fut,
Fut: Future<Output = Result<(), anyhow::Error>>,
{
let (bucket, location) = cache_location(seed);
// we need a lock even if it exists since somebody might be still in the process of writing.
let _guard = CACHE_GENERATION_LOCKS[bucket % CACHE_GENERATION_BUCKET_COUNT]
.lock()
.await;
let exists = tokio::fs::try_exists(location.path())
.await
.context("unable to test for cache file existance")?;
if !exists {
let f = tokio::fs::File::create(location.path())
.await
.context("creating new cache file")?;
match generate(f).await {
Ok(()) => (),
Err(e) => {
warn!("cache generation failed, unlinking entry");
tokio::fs::remove_file(location.path()).await?;
return Err(e);
}
}
}
drop(_guard);
Ok(location)
}
pub fn cache_file<Fun>(seed: &[&str], mut generate: Fun) -> Result<AssetLocation, anyhow::Error>
where
Fun: FnMut(std::fs::File) -> Result<(), anyhow::Error>,
{
let (bucket, location) = cache_location(seed);
// we need a lock even if it exists since somebody might be still in the process of writing.
let _guard = CACHE_GENERATION_LOCKS[bucket % CACHE_GENERATION_BUCKET_COUNT].blocking_lock();
let exists = location.path().exists();
if !exists {
let f = std::fs::File::create(location.path()).context("creating new cache file")?;
match generate(f) {
Ok(()) => (),
Err(e) => {
warn!("cache generation failed, unlinking entry");
std::fs::remove_file(location.path())?;
return Err(e);
}
}
}
drop(_guard);
Ok(location)
}
pub struct InMemoryCacheEntry {
size: usize,
last_access: Instant,
object: Arc<dyn Any + Send + Sync + 'static>,
}
pub static CACHE_IN_MEMORY_OBJECTS: LazyLock<RwLock<HashMap<AssetLocation, InMemoryCacheEntry>>> =
LazyLock::new(|| RwLock::new(HashMap::new()));
pub static CACHE_IN_MEMORY_SIZE: AtomicUsize = AtomicUsize::new(0);
pub fn cache_memory<Fun, T>(seed: &[&str], mut generate: Fun) -> Result<Arc<T>, anyhow::Error>
where
Fun: FnMut() -> Result<T, anyhow::Error>,
T: Encode + Decode + Send + Sync + 'static,
{
let (_, location) = cache_location(seed);
{
let mut g = CACHE_IN_MEMORY_OBJECTS.write().unwrap();
if let Some(entry) = g.get_mut(&location) {
entry.last_access = Instant::now();
let object = entry
.object
.clone()
.downcast::<T>()
.map_err(|_| anyhow!("inconsistent types for in-memory cache"))?;
return Ok(object);
}
}
let location = cache_file(seed, move |mut file| {
let object = generate()?;
bincode::encode_into_std_write(&object, &mut file, bincode::config::standard())
.context("encoding cache object")?;
Ok(())
})?;
let mut file = std::fs::File::open(location.path())?;
let object = bincode::decode_from_std_read::<T, _, _>(&mut file, bincode::config::standard())
.context("decoding cache object")?;
let object = Arc::new(object);
let size = file.stream_position()? as usize; // this is an approximation mainly since varint is used in bincode
{
let mut g = CACHE_IN_MEMORY_OBJECTS.write().unwrap();
g.insert(
location,
InMemoryCacheEntry {
size,
last_access: Instant::now(),
object: object.clone(),
},
);
CACHE_IN_MEMORY_SIZE.fetch_add(size, Ordering::Relaxed);
}
cleanup_cache();
Ok(object)
}
pub fn cleanup_cache() {
let current_size = CACHE_IN_MEMORY_SIZE.load(Ordering::Relaxed);
if current_size < CONF.max_in_memory_cache_size {
return;
}
info!("running cache eviction");
let mut g = CACHE_IN_MEMORY_OBJECTS.write().unwrap();
// TODO: if two entries have *exactly* the same size, only one of the will be remove; this is fine for now
let mut k = BTreeMap::new();
for (loc, entry) in g.iter() {
k.insert(entry.last_access.elapsed(), (loc.to_owned(), entry.size));
}
let mut reduction = 0;
for (loc, size) in k.values().rev().take(k.len().div_ceil(2)) {
g.remove(loc);
reduction += size;
}
CACHE_IN_MEMORY_SIZE.fetch_sub(reduction, Ordering::Relaxed);
drop(g);
info!("done");
}
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