fix: insert disk cache on hybrid cache fetch miss

foyer/Cargo.toml

@@ -18,6 +18,7 @@ foyer-common = { version = "0.7.3", path = "../foyer-common" }
 foyer-memory = { version = "0.5.2", path = "../foyer-memory" }
 foyer-storage = { version = "0.8.5", path = "../foyer-storage" }
 minitrace = { workspace = true }
+pin-project = "1"
 tokio = { workspace = true }
 tracing = "0.1"
 

foyer/src/hybrid/cache.rs

@@ -17,10 +17,13 @@
     fmt::Debug,
     future::Future,
     hash::Hash,
+    ops::Deref,
+    pin::Pin,
     sync::{
         atomic::{AtomicBool, Ordering},
         Arc,
     },
+    task::{ready, Context, Poll},
     time::Instant,
 };
 
@@ -33,6 +36,7 @@
 use foyer_memory::{Cache, CacheContext, CacheEntry, Fetch, FetchState};
 use foyer_storage::{DeviceStats, Storage, Store};
 use minitrace::prelude::*;
+use pin_project::pin_project;
 use tokio::sync::oneshot;
 
 use crate::HybridCacheWriter;
@@ -387,7 +391,57 @@
 }
 
 /// The future generated by [`HybridCache::fetch`].
-pub type HybridFetch<K, V, S = RandomState> = InRootSpan<Fetch<K, V, anyhow::Error, S>>;
+pub type HybridFetch<K, V, S = RandomState> = InRootSpan<HybridFetchInner<K, V, S>>;
+
+/// A future that is used to get entry value from the remote storage for the hybrid cache.
+#[pin_project]
+pub struct HybridFetchInner<K, V, S = RandomState>
+where
+    K: StorageKey,
+    V: StorageValue,
+    S: HashBuilder + Debug,
+{
+    #[pin]
+    inner: Fetch<K, V, anyhow::Error, S>,
+
+    enqueue: Arc<AtomicBool>,
+    storage: Store<K, V, S>,
+}
+
+impl<K, V, S> Future for HybridFetchInner<K, V, S>
+where
+    K: StorageKey,
+    V: StorageValue,
+    S: HashBuilder + Debug,
+{
+    type Output = anyhow::Result<CacheEntry<K, V, S>>;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let this = self.project();
+        let res = ready!(this.inner.poll(cx));
+
+        if let Ok(entry) = res.as_ref() {
+            if this.enqueue.load(Ordering::Relaxed) {
+                this.storage.enqueue(entry.clone(), false);
+            }
+        }
+
+        Poll::Ready(res)
+    }
+}
+
+impl<K, V, S> Deref for HybridFetchInner<K, V, S>
+where
+    K: StorageKey,
+    V: StorageValue,
+    S: HashBuilder + Debug,
+{
+    type Target = Fetch<K, V, anyhow::Error, S>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.inner
+    }
+}
 
 impl<K, V, S> HybridCache<K, V, S>
 where
@@ -411,11 +465,13 @@
         let now = Instant::now();
 
         let store = self.storage.clone();
+        let enqueue = Arc::<AtomicBool>::default();
         let future = fetch();
-        let res = self.memory.fetch_with_runtime(
+        let inner = self.memory.fetch_with_runtime(
             key.clone(),
             || {
                 let metrics = self.metrics.clone();
+                let enqueue = enqueue.clone();
                 async move {
                     match store.load(&key).await.map_err(anyhow::Error::from)? {
                         None => {}
@@ -431,6 +487,8 @@
                     metrics.hybrid_miss.increment(1);
                     metrics.hybrid_miss_duration.record(now.elapsed());
 
+                    enqueue.store(true, Ordering::Relaxed);
+
                     future
                         .in_span(Span::enter_with_local_parent("foyer::hybrid::fetch::fn"))
                         .await
@@ -440,12 +498,18 @@
             self.storage().runtime(),
         );
 
-        if res.state() == FetchState::Hit {
+        if inner.state() == FetchState::Hit {
             self.metrics.hybrid_hit.increment(1);
             self.metrics.hybrid_hit_duration.record(now.elapsed());
         }
 
-        InRootSpan::new(res, span).with_threshold(self.tracing_config.record_hybrid_fetch_threshold())
+        let inner = HybridFetchInner {
+            inner,
+            enqueue,
+            storage: self.storage.clone(),
+        };
+
+        InRootSpan::new(inner, span).with_threshold(self.tracing_config.record_hybrid_fetch_threshold())
     }
 }
 

foyer/src/prelude.rs

@@ -36,7 +36,7 @@ pub use storage::{
 
 pub use crate::hybrid::{
     builder::{HybridCacheBuilder, HybridCacheBuilderPhaseMemory, HybridCacheBuilderPhaseStorage},
-    cache::{HybridCache, HybridCacheEntry, HybridFetch},
+    cache::{HybridCache, HybridCacheEntry, HybridFetchInner},
     writer::{HybridCacheStorageWriter, HybridCacheWriter},
 };