Remove the thread pool from sync caches

- Remove `scheduled-thread-pool` crate.
- Remove `thread_pool` and `unsafe_weak_pointers` modules.
- Remove notification `DeliveryMode` as now `sync` caches only support the
  `Immediate` mode (like `future::Cache`).
- Remove `sync::ConcurrentCacheExt`.
- Rename `sync::ConcurrentCacheExt::sync` method to
  `sync::{Cache, SegmentedCache}::run_pending_tasks`.

.cirrus.yml

@@ -66,12 +66,6 @@ linux_arm64_task:
     # Run tests (release, sync feature)
     - cargo test -j 1 --release --features sync -- --test-threads=$NUM_CPUS
 
-    # Run tests (release, sync feature, thread-pool test for sync::Cache)
-    - cargo test --release --lib --features sync sync::cache::tests::enabling_and_disabling_thread_pools -- --exact --ignored
-
-    # Run tests (release, sync feature, thread-pool test for sync::SegmentedCache)
-    - cargo test --release --lib --features sync sync::segment::tests::enabling_and_disabling_thread_pools -- --exact --ignored
-
     # Run tests (sync feature, key lock test for notification)
     - cargo test --release --lib --features sync sync::cache::tests::test_key_lock_used_by_immediate_removal_notifications -- --exact --ignored
 

.github/workflows/CI.yml

@@ -92,18 +92,6 @@ jobs:
         env:
           RUSTFLAGS: '--cfg rustver'
 
-      - name: Run tests (sync feature, thread-pool test for sync::Cache)
-        uses: actions-rs/cargo@v1
-        with:
-          command: test
-          args: --release --lib --features sync sync::cache::tests::enabling_and_disabling_thread_pools -- --exact --ignored
-
-      - name: Run tests (sync feature, thread-pool test for sync::SegmentedCache)
-        uses: actions-rs/cargo@v1
-        with:
-          command: test
-          args: --release --lib --features sync sync::segment::tests::enabling_and_disabling_thread_pools -- --exact --ignored
-
       - name: Run tests (sync feature, key lock test for notification)
         uses: actions-rs/cargo@v1
         with:

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "moka"
-version = "0.12.0-beta.1"
+version = "0.12.0-beta.2"
 edition = "2018"
 # Rust 1.65 was released on Nov 3, 2022.
 rust-version = "1.65"
@@ -16,11 +16,10 @@ exclude = [".circleci", ".devcontainer", ".github", ".gitpod.yml", ".vscode"]
 build = "build.rs"
 
 [features]
-default = ["sync", "atomic64", "quanta"]
+default = ["atomic64", "quanta"]
 
-# This feature is enabled by default. Disable it when you do not need
-# `moka::sync::{Cache, SegmentedCache}`
-sync = ["scheduled-thread-pool"]
+# Enabled this feature to use `moka::sync::{Cache, SegmentedCache}`
+sync = []
 
 # Enable this feature to use `moka::future::Cache`.
 future = ["async-lock", "async-trait", "futures-util"]
@@ -64,9 +63,6 @@ triomphe = { version = "0.1.3", default-features = false }
 # Optional dependencies (enabled by default)
 quanta = { version = "0.11.0", optional = true }
 
-# Optional dependencies (sync)
-scheduled-thread-pool = { version = "0.2.7", optional = true }
-
 # Optional dependencies (future)
 async-lock = { version = "2.4", optional = true }
 async-trait = { version = "0.1.58", optional = true }

examples/eviction_listener.rs

@@ -33,11 +33,9 @@ fn main() {
         // called. If you want to remove all entries immediately, call sync() method
         // repeatedly like the loop below.
         cache.invalidate_all();
-        // This trait provides sync() method.
-        use moka::sync::ConcurrentCacheExt;
         loop {
             // Synchronization is limited to at most 500 entries for each call.
-            cache.sync();
+            cache.run_pending_tasks();
             // Check if all is done. Calling entry_count() requires calling sync()
             // first!
             if cache.entry_count() == 0 {

src/cht.rs

@@ -71,12 +71,10 @@
 //! [Junction]: https://github.com/preshing/junction
 //! [a tech talk]: https://youtu.be/HJ-719EGIts
 
+pub(crate) mod iter;
 pub(crate) mod map;
 pub(crate) mod segment;
 
-#[cfg(feature = "future")]
-pub(crate) mod iter;
-
 #[cfg(test)]
 #[macro_use]
 pub(crate) mod test_util;

src/cht/segment.rs

@@ -35,7 +35,6 @@ use crate::cht::map::{
     DefaultHashBuilder,
 };
 
-#[cfg(feature = "future")]
 use super::iter::{Iter, ScanningGet};
 
 use std::{
@@ -206,7 +205,6 @@ impl<K, V, S> HashMap<K, V, S> {
     ///
     /// This method on its own is safe, but other threads can add or remove
     /// elements at any time.
-    #[cfg(any(test, feature = "future"))]
     pub(crate) fn len(&self) -> usize {
         self.len.load(Ordering::Relaxed)
     }
@@ -217,7 +215,6 @@ impl<K, V, S> HashMap<K, V, S> {
     ///
     /// This method on its own is safe, but other threads can add or remove
     /// elements at any time.
-    #[cfg(any(test, feature = "future"))]
     pub(crate) fn is_empty(&self) -> bool {
         self.len() == 0
     }
@@ -252,7 +249,6 @@ impl<K, V, S> HashMap<K, V, S> {
 }
 
 impl<K: Hash + Eq, V, S: BuildHasher> HashMap<K, V, S> {
-    #[cfg(feature = "future")]
     #[inline]
     pub(crate) fn contains_key(&self, hash: u64, eq: impl FnMut(&K) -> bool) -> bool {
         self.get_key_value_and_then(hash, eq, |_, _| Some(()))
@@ -299,7 +295,6 @@ impl<K: Hash + Eq, V, S: BuildHasher> HashMap<K, V, S> {
     ///
     /// If the map did have this key present, both the key and value are
     /// updated.
-    #[cfg(any(test, feature = "future"))]
     #[inline]
     pub fn insert_entry_and<T>(
         &self,
@@ -494,7 +489,6 @@ impl<K: Hash + Eq, V, S: BuildHasher> HashMap<K, V, S> {
         Some(bucket_array_ref.keys(with_key))
     }
 
-    #[cfg(feature = "future")]
     pub(crate) fn iter(&self) -> Iter<'_, K, V>
     where
         K: Clone,
@@ -513,7 +507,6 @@ impl<K: Hash + Eq, V, S: BuildHasher> HashMap<K, V, S> {
     }
 }
 
-#[cfg(feature = "future")]
 impl<K, V, S> ScanningGet<K, V> for HashMap<K, V, S>
 where
     K: Hash + Eq + Clone,

src/common.rs

@@ -64,7 +64,7 @@ pub(crate) fn sketch_capacity(max_capacity: u64) -> u32 {
     max_capacity.try_into().unwrap_or(u32::MAX).max(128)
 }
 
-#[cfg(any(test, feature = "sync"))]
+#[cfg(test)]
 pub(crate) fn available_parallelism() -> usize {
     use std::{num::NonZeroUsize, thread::available_parallelism};
     available_parallelism().map(NonZeroUsize::get).unwrap_or(1)

src/common/builder_utils.rs

@@ -1,8 +1,5 @@
 use std::time::Duration;
 
-#[cfg(feature = "sync")]
-use super::concurrent::housekeeper;
-
 const YEAR_SECONDS: u64 = 365 * 24 * 3600;
 
 pub(crate) fn ensure_expirations_or_panic(
@@ -17,12 +14,3 @@ pub(crate) fn ensure_expirations_or_panic(
         assert!(d <= max_duration, "time_to_idle is longer than 1000 years");
     }
 }
-
-#[cfg(feature = "sync")]
-pub(crate) fn housekeeper_conf(thread_pool_enabled: bool) -> housekeeper::Configuration {
-    if thread_pool_enabled {
-        housekeeper::Configuration::new_thread_pool(true)
-    } else {
-        housekeeper::Configuration::new_blocking()
-    }
-}

src/common/concurrent.rs

@@ -12,12 +12,6 @@ pub(crate) mod entry_info;
 #[cfg(feature = "sync")]
 pub(crate) mod housekeeper;
 
-#[cfg(feature = "sync")]
-pub(crate) mod thread_pool;
-
-#[cfg(feature = "sync")]
-pub(crate) mod unsafe_weak_pointer;
-
 // target_has_atomic is more convenient but yet unstable (Rust 1.55)
 // https://github.com/rust-lang/rust/issues/32976
 // #[cfg_attr(target_has_atomic = "64", path = "common/time_atomic64.rs")]

src/common/concurrent/constants.rs

@@ -7,14 +7,5 @@ pub(crate) const READ_LOG_SIZE: usize = READ_LOG_FLUSH_POINT * (MAX_SYNC_REPEATS
 pub(crate) const WRITE_LOG_FLUSH_POINT: usize = 512;
 pub(crate) const WRITE_LOG_SIZE: usize = WRITE_LOG_FLUSH_POINT * (MAX_SYNC_REPEATS + 2);
 
-#[cfg(feature = "sync")]
-pub(crate) const WRITE_LOG_LOW_WATER_MARK: usize = WRITE_LOG_FLUSH_POINT / 2;
-
 #[cfg(feature = "sync")]
 pub(crate) const WRITE_RETRY_INTERVAL_MICROS: u64 = 50;
-
-#[cfg(feature = "sync")]
-pub(crate) const PERIODICAL_SYNC_NORMAL_PACE_MILLIS: u64 = 300;
-
-#[cfg(feature = "sync")]
-pub(crate) const PERIODICAL_SYNC_FAST_PACE_NANOS: u64 = 500;