Concurrent cache

Cargo.lock

@@ -306,6 +306,7 @@ dependencies = [
  "async-lock",
  "base64-turbo",
  "boml",
+ "dashmap",
  "form_urlencoded",
  "giallo",
  "log",

Cargo.toml

@@ -12,6 +12,8 @@ async-lock = "3.4.2"
 base64-turbo = "0.2.0"
 # TOML parser
 boml = "2.0.0"
+# Concurrent hash map for caching
+dashmap = "6.2.1"
 #flate2 = "1.1.8"
 # request parsing
 form_urlencoded = "1.2.2"

src/cache.rs

@@ -1,47 +1,50 @@
+use dashmap::DashMap;
 use std::{
 	borrow::Borrow,
-	collections::{HashMap, VecDeque},
 	hash::Hash,
-	time::Instant,
+	sync::atomic::{AtomicU64, Ordering::Relaxed},
 };
 
 pub struct CacheEntry<T> {
 	inner: T,
-	time: u64,
+	time: AtomicU64,
 }
 
 #[derive(Default)]
-pub struct Cache<K, V> {
+pub struct Cache<K: Eq + Hash, V> {
 	ttl: u64,
 	size: usize,
-	content: HashMap<K, CacheEntry<V>>,
+	content: DashMap<K, CacheEntry<V>>,
 }
 
 impl<K: Clone + Eq + Hash, V: Clone> Cache<K, V> {
-	pub fn sweep(&mut self) {
+	pub fn sweep(&self) {
 		let now = std::time::UNIX_EPOCH.elapsed().unwrap().as_secs();
-		self.content.retain(|_k, entry| entry.time + self.ttl < now);
+		self.content
+			.retain(|_k, entry| entry.time.load(Relaxed) + self.ttl < now);
 	}
 
-	fn sweep_oldest(&mut self) {
+	fn sweep_oldest(&self) {
 		// TODO sweep the N oldest
 		let mut oldest = None;
 		let mut time = u64::MAX;
-		for (key, entry) in self.content.iter() {
-			if entry.time < time {
-				time = entry.time;
-				oldest = Some(key);
+		for item in self.content.iter() {
+			let (key, entry) = item.pair();
+			let entry_time = entry.time.load(Relaxed);
+			if entry_time < time {
+				time = entry_time;
+				oldest = Some(key.clone());
 			}
 		}
-		if let Some(oldest) = oldest.cloned() {
+		if let Some(oldest) = oldest {
 			self.content.remove(&oldest);
 		}
 	}
 
-	pub fn fetch(&mut self, key: impl Borrow<K>, f: impl Fn(K) -> Option<V>) -> Option<V> {
-		if let Some(entry) = self.content.get_mut(key.borrow()) {
+	pub fn fetch(&self, key: impl Borrow<K>, f: impl Fn(K) -> Option<V>) -> Option<V> {
+		if let Some(entry) = self.content.get(key.borrow()) {
 			let now = std::time::UNIX_EPOCH.elapsed().unwrap().as_secs();
-			entry.time = now;
+			entry.time.store(now, Relaxed);
 			Some(entry.inner.clone())
 		} else if let Some(inner) = (f)(key.borrow().clone()) {
 			if self.content.len() >= self.size {
@@ -49,7 +52,7 @@ impl<K: Clone + Eq + Hash, V: Clone> Cache<K, V> {
 			}
 			let now = std::time::UNIX_EPOCH.elapsed().unwrap().as_secs();
 			let entry = CacheEntry {
-				time: now,
+				time: AtomicU64::new(now),
 				inner: inner.clone(),
 			};
 			self.content.insert(key.borrow().clone(), entry);

src/server.rs

@@ -1,7 +1,6 @@
 use crate::{cache, config::Config, repo::ReadRepoMetadataError, templates};
 
 use askama::Template;
-use async_lock::Mutex;
 use log::error;
 use std::{
 	io::{ErrorKind, Read},
@@ -15,14 +14,12 @@ pub fn make_router(config: &'static Config) -> impl Handler {
 	hl_registry.link_grammars();
 	let hl_registry: &'static _ = Box::leak(Box::new(hl_registry));
 
-	let metadata_cache: &'static _ = Box::leak(Box::new(Mutex::new(cache::Cache::<
+	let metadata_cache: &'static _ = Box::leak(Box::new(cache::Cache::<
 		String,
 		templates::Directory,
-	>::default())));
-	let file_cache: &'static _ = Box::leak(Box::new(Mutex::new(cache::Cache::<
-		(String, String),
-		String,
-	>::default())));
+	>::default()));
+	let file_cache: &'static _ =
+		Box::leak(Box::new(cache::Cache::<(String, String), String>::default()));
 	let client: &'static _ = Box::leak(Box::new(async_lock::Mutex::new(
 		crate::api_client::make_client(),
 	)));
@@ -133,11 +130,8 @@ pub fn make_router(config: &'static Config) -> impl Handler {
 						}
 						Some(root)
 					};
-					// TODO replace mutex with better thing (less contention or async mutex)
-					let Some(root) = metadata_cache
-						.lock()
-						.await
-						.fetch(repo_hash_str.to_string(), fetch_metadata)
+					let Some(root) =
+						metadata_cache.fetch(repo_hash_str.to_string(), fetch_metadata)
 					else {
 						return conn.with_status(404);
 					};
@@ -169,7 +163,7 @@ pub fn make_router(config: &'static Config) -> impl Handler {
 
 						Some(buf)
 					};
-					let Some(file_content) = file_cache.lock().await.fetch(
+					let Some(file_content) = file_cache.fetch(
 						(repo_hash_str.to_string(), file_hash.to_string()),
 						fetch_file,
 					) else {

src/templates.rs

@@ -1,7 +1,4 @@
-use std::{
-	collections::{BTreeMap, BTreeSet, HashMap, btree_map, btree_set},
-	iter::Peekable,
-};
+use std::{collections::BTreeMap, iter::Peekable};
 
 use log::warn;
 use trillium_askama::Template;