Fix memory leak in get_with and friend methods of future::Cache

CHANGELOG.md

@@ -1,5 +1,15 @@
 # Moka Cache — Change Log
 
+## Version 0.12.1
+
+### Fixed
+
+- Fixed memory leak in `future::Cache` that occurred when `get_with()`,
+  `entry().or_insert_with()`, and similar methods were used ([#329][gh-issue-0329]).
+    - This bug was introduced in `v0.12.0`. Versions prior to `v0.12.0` do not
+      have this bug.
+
+
 ## Version 0.12.0
 
 > **Note**
@@ -702,6 +712,7 @@ The minimum supported Rust version (MSRV) is now 1.51.0 (Mar 25, 2021).
 [gh-Swatinem]: https://github.com/Swatinem
 [gh-tinou98]: https://github.com/tinou98
 
+[gh-issue-0329]: https://github.com/moka-rs/moka/issues/329/
 [gh-issue-0322]: https://github.com/moka-rs/moka/issues/322/
 [gh-issue-0255]: https://github.com/moka-rs/moka/issues/255/
 [gh-issue-0252]: https://github.com/moka-rs/moka/issues/252/

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "moka"
-version = "0.12.0"
+version = "0.12.1"
 edition = "2018"
 # Rust 1.65 was released on Nov 3, 2022.
 rust-version = "1.65"

src/future/base_cache.rs

@@ -498,7 +498,7 @@ where
 
         // TODO: Instead using Arc<AtomicU8> to check if the actual operation was
         // insert or update, check the return value of insert_with_or_modify. If it
-        // is_some, the value was inserted, otherwise the value was updated.
+        // is_some, the value was updated, otherwise the value was inserted.
 
         // Since the cache (cht::SegmentedHashMap) employs optimistic locking
         // strategy, insert_with_or_modify() may get an insert/modify operation

src/future/value_initializer.rs

@@ -58,8 +58,8 @@ where
     S: BuildHasher,
 {
     is_waiter_value_set: bool,
-    cht_key: (Arc<K>, TypeId),
-    hash: u64,
+    w_key: (Arc<K>, TypeId),
+    w_hash: u64,
     waiters: TrioArc<WaiterMap<K, V, S>>,
     write_lock: RwLockWriteGuard<'a, WaiterValue<V>>,
 }
@@ -71,15 +71,15 @@ where
     S: BuildHasher,
 {
     fn new(
-        cht_key: (Arc<K>, TypeId),
-        hash: u64,
+        w_key: (Arc<K>, TypeId),
+        w_hash: u64,
         waiters: TrioArc<WaiterMap<K, V, S>>,
         write_lock: RwLockWriteGuard<'a, WaiterValue<V>>,
     ) -> Self {
         Self {
             is_waiter_value_set: false,
-            cht_key,
-            hash,
+            w_key,
+            w_hash,
             waiters,
             write_lock,
         }
@@ -103,7 +103,7 @@ where
             // has been aborted. Remove our waiter to prevent the issue described in
             // https://github.com/moka-rs/moka/issues/59
             *self.write_lock = WaiterValue::EnclosingFutureAborted;
-            remove_waiter(&self.waiters, self.cht_key.clone(), self.hash);
+            remove_waiter(&self.waiters, self.w_key.clone(), self.w_hash);
             self.is_waiter_value_set = true;
         }
     }
@@ -147,8 +147,8 @@ where
     #[allow(clippy::too_many_arguments)]
     pub(crate) async fn try_init_or_read<'a, C, I, O, E>(
         &'a self,
-        key: &Arc<K>,
-        hash: u64,
+        c_key: &Arc<K>,
+        c_hash: u64,
         type_id: TypeId,
         cache: &C,
         ignore_if: Arc<Mutex<Option<I>>>,
@@ -169,35 +169,35 @@ where
         const MAX_RETRIES: usize = 200;
         let mut retries = 0;
 
-        let cht_key = (Arc::clone(key), type_id);
+        let (w_key, w_hash) = waiter_key_hash(&self.waiters, c_key, type_id);
 
         loop {
             let waiter = TrioArc::new(RwLock::new(WaiterValue::Computing));
             let lock = waiter.write().await;
 
-            match try_insert_waiter(&self.waiters, cht_key.clone(), hash, &waiter) {
+            match try_insert_waiter(&self.waiters, w_key.clone(), w_hash, &waiter) {
                 None => {
                     // Our waiter was inserted.
 
                     // Create a guard. This will ensure to remove our waiter when the
                     // enclosing future has been aborted:
                     // https://github.com/moka-rs/moka/issues/59
                     let mut waiter_guard = WaiterGuard::new(
-                        cht_key.clone(),
-                        hash,
+                        w_key.clone(),
+                        w_hash,
                         TrioArc::clone(&self.waiters),
                         lock,
                     );
 
                     // Check if the value has already been inserted by other thread.
                     if let Some(value) = cache
-                        .get_without_recording(key, hash, ignore_if.lock().await.as_mut())
+                        .get_without_recording(c_key, c_hash, ignore_if.lock().await.as_mut())
                         .await
                     {
                         // Yes. Set the waiter value, remove our waiter, and return
                         // the existing value.
                         waiter_guard.set_waiter_value(WaiterValue::Ready(Ok(value.clone())));
-                        remove_waiter(&self.waiters, cht_key, hash);
+                        remove_waiter(&self.waiters, w_key, w_hash);
                         return InitResult::ReadExisting(value);
                     }
 
@@ -209,7 +209,7 @@ where
                         Ok(value) => {
                             let (waiter_val, init_res) = match post_init(value) {
                                 Ok(value) => {
-                                    cache.insert(Arc::clone(key), hash, value.clone()).await;
+                                    cache.insert(Arc::clone(c_key), c_hash, value.clone()).await;
                                     (
                                         WaiterValue::Ready(Ok(value.clone())),
                                         InitResult::Initialized(value),
@@ -224,14 +224,14 @@ where
                                 }
                             };
                             waiter_guard.set_waiter_value(waiter_val);
-                            remove_waiter(&self.waiters, cht_key, hash);
+                            remove_waiter(&self.waiters, w_key, w_hash);
                             return init_res;
                         }
                         // Panicked.
                         Err(payload) => {
                             waiter_guard.set_waiter_value(WaiterValue::InitFuturePanicked);
                             // Remove the waiter so that others can retry.
-                            remove_waiter(&self.waiters, cht_key, hash);
+                            remove_waiter(&self.waiters, w_key, w_hash);
                             resume_unwind(payload);
                         }
                     } // The lock will be unlocked here.
@@ -311,27 +311,42 @@ where
 }
 
 #[inline]
-fn remove_waiter<K, V, S>(waiter_map: &WaiterMap<K, V, S>, cht_key: (Arc<K>, TypeId), hash: u64)
+fn remove_waiter<K, V, S>(waiter_map: &WaiterMap<K, V, S>, w_key: (Arc<K>, TypeId), w_hash: u64)
 where
     (Arc<K>, TypeId): Eq + Hash,
     S: BuildHasher,
 {
-    waiter_map.remove(hash, |k| k == &cht_key);
+    waiter_map.remove(w_hash, |k| k == &w_key);
 }
 
 #[inline]
 fn try_insert_waiter<K, V, S>(
     waiter_map: &WaiterMap<K, V, S>,
-    cht_key: (Arc<K>, TypeId),
-    hash: u64,
+    w_key: (Arc<K>, TypeId),
+    w_hash: u64,
     waiter: &Waiter<V>,
 ) -> Option<Waiter<V>>
 where
     (Arc<K>, TypeId): Eq + Hash,
     S: BuildHasher,
 {
     let waiter = TrioArc::clone(waiter);
-    waiter_map.insert_if_not_present(cht_key, hash, waiter)
+    waiter_map.insert_if_not_present(w_key, w_hash, waiter)
+}
+
+#[inline]
+fn waiter_key_hash<K, V, S>(
+    waiter_map: &WaiterMap<K, V, S>,
+    c_key: &Arc<K>,
+    type_id: TypeId,
+) -> ((Arc<K>, TypeId), u64)
+where
+    (Arc<K>, TypeId): Eq + Hash,
+    S: BuildHasher,
+{
+    let w_key = (Arc::clone(c_key), type_id);
+    let w_hash = waiter_map.hash(&w_key);
+    (w_key, w_hash)
 }
 
 fn panic_if_retry_exhausted_for_panicking(retries: usize, max: usize) {

src/sync/value_initializer.rs

@@ -68,21 +68,21 @@ where
         const MAX_RETRIES: usize = 200;
         let mut retries = 0;
 
-        let (cht_key, hash) = self.cht_key_hash(key, type_id);
+        let (w_key, w_hash) = self.waiter_key_hash(key, type_id);
 
         loop {
             let waiter = TrioArc::new(RwLock::new(None));
             let mut lock = waiter.write();
 
-            match self.try_insert_waiter(cht_key.clone(), hash, &waiter) {
+            match self.try_insert_waiter(w_key.clone(), w_hash, &waiter) {
                 None => {
                     // Our waiter was inserted.
                     // Check if the value has already been inserted by other thread.
                     if let Some(value) = get() {
                         // Yes. Set the waiter value, remove our waiter, and return
                         // the existing value.
                         *lock = Some(Ok(value.clone()));
-                        self.remove_waiter(cht_key, hash);
+                        self.remove_waiter(w_key, w_hash);
                         return InitResult::ReadExisting(value);
                     }
 
@@ -106,14 +106,14 @@ where
                                 }
                             };
                             *lock = waiter_val;
-                            self.remove_waiter(cht_key, hash);
+                            self.remove_waiter(w_key, w_hash);
                             return init_res;
                         }
                         // Panicked.
                         Err(payload) => {
                             *lock = None;
                             // Remove the waiter so that others can retry.
-                            self.remove_waiter(cht_key, hash);
+                            self.remove_waiter(w_key, w_hash);
                             resume_unwind(payload);
                         }
                     } // The write lock will be unlocked here.
@@ -184,25 +184,25 @@ where
     }
 
     #[inline]
-    fn remove_waiter(&self, cht_key: (Arc<K>, TypeId), hash: u64) {
-        self.waiters.remove(hash, |k| k == &cht_key);
+    fn remove_waiter(&self, w_key: (Arc<K>, TypeId), w_hash: u64) {
+        self.waiters.remove(w_hash, |k| k == &w_key);
     }
 
     #[inline]
     fn try_insert_waiter(
         &self,
-        cht_key: (Arc<K>, TypeId),
-        hash: u64,
+        w_key: (Arc<K>, TypeId),
+        w_hash: u64,
         waiter: &Waiter<V>,
     ) -> Option<Waiter<V>> {
         let waiter = TrioArc::clone(waiter);
-        self.waiters.insert_if_not_present(cht_key, hash, waiter)
+        self.waiters.insert_if_not_present(w_key, w_hash, waiter)
     }
 
     #[inline]
-    fn cht_key_hash(&self, key: &Arc<K>, type_id: TypeId) -> ((Arc<K>, TypeId), u64) {
-        let cht_key = (Arc::clone(key), type_id);
-        let hash = self.waiters.hash(&cht_key);
-        (cht_key, hash)
+    fn waiter_key_hash(&self, c_key: &Arc<K>, type_id: TypeId) -> ((Arc<K>, TypeId), u64) {
+        let w_key = (Arc::clone(c_key), type_id);
+        let w_hash = self.waiters.hash(&w_key);
+        (w_key, w_hash)
     }
 }

src/sync_base/base_cache.rs

@@ -495,7 +495,7 @@ where
 
         // TODO: Instead using Arc<AtomicU8> to check if the actual operation was
         // insert or update, check the return value of insert_with_or_modify. If it
-        // is_some, the value was inserted, otherwise the value was updated.
+        // is_some, the value was updated, otherwise the value was inserted.
 
         // Since the cache (cht::SegmentedHashMap) employs optimistic locking
         // strategy, insert_with_or_modify() may get an insert/modify operation