Small changes in the Executor API. (#2391)

Warning, this change is mildly not backward compatible
so I bumped tantivy's version.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "tantivy"
-version = "0.22.0"
+version = "0.23.0"
 authors = ["Paul Masurel <paul.masurel@gmail.com>"]
 license = "MIT"
 categories = ["database-implementations", "data-structures"]
@@ -15,12 +15,16 @@ rust-version = "1.63"
 exclude = ["benches/*.json", "benches/*.txt"]
 
 [dependencies]
-oneshot = "0.1.5"
+# Switch back to the non-forked oneshot crate once https://github.com/faern/oneshot/pull/35 is merged
+oneshot = { git = "https://github.com/fulmicoton/oneshot.git", rev = "c10a3ba" }
 base64 = "0.22.0"
 byteorder = "1.4.3"
 crc32fast = "1.3.2"
 once_cell = "1.10.0"
-regex = { version = "1.5.5", default-features = false, features = ["std", "unicode"] }
+regex = { version = "1.5.5", default-features = false, features = [
+    "std",
+    "unicode",
+] }
 aho-corasick = "1.0"
 tantivy-fst = "0.5"
 memmap2 = { version = "0.9.0", optional = true }
@@ -36,7 +40,9 @@ uuid = { version = "1.0.0", features = ["v4", "serde"] }
 crossbeam-channel = "0.5.4"
 rust-stemmers = "1.2.0"
 downcast-rs = "1.2.0"
-bitpacking = { version = "0.9.2", default-features = false, features = ["bitpacker4x"] }
+bitpacking = { version = "0.9.2", default-features = false, features = [
+    "bitpacker4x",
+] }
 census = "0.4.2"
 rustc-hash = "1.1.0"
 thiserror = "1.0.30"
@@ -51,13 +57,13 @@ itertools = "0.12.0"
 measure_time = "0.8.2"
 arc-swap = "1.5.0"
 
-columnar = { version= "0.3", path="./columnar", package ="tantivy-columnar" }
-sstable = { version= "0.3", path="./sstable", package ="tantivy-sstable", optional = true }
-stacker = { version= "0.3", path="./stacker", package ="tantivy-stacker" }
-query-grammar = { version= "0.22.0", path="./query-grammar", package = "tantivy-query-grammar" }
-tantivy-bitpacker = { version= "0.6", path="./bitpacker" }
-common = { version= "0.7", path = "./common/", package = "tantivy-common" }
-tokenizer-api = { version= "0.3", path="./tokenizer-api", package="tantivy-tokenizer-api" }
+columnar = { version = "0.3", path = "./columnar", package = "tantivy-columnar" }
+sstable = { version = "0.3", path = "./sstable", package = "tantivy-sstable", optional = true }
+stacker = { version = "0.3", path = "./stacker", package = "tantivy-stacker" }
+query-grammar = { version = "0.22.0", path = "./query-grammar", package = "tantivy-query-grammar" }
+tantivy-bitpacker = { version = "0.6", path = "./bitpacker" }
+common = { version = "0.7", path = "./common/", package = "tantivy-common" }
+tokenizer-api = { version = "0.3", path = "./tokenizer-api", package = "tantivy-tokenizer-api" }
 sketches-ddsketch = { version = "0.2.1", features = ["use_serde"] }
 futures-util = { version = "0.3.28", optional = true }
 fnv = "1.0.7"
@@ -66,7 +72,7 @@ fnv = "1.0.7"
 winapi = "0.3.9"
 
 [dev-dependencies]
-binggan = "0.5.1"
+binggan = "0.5.2"
 rand = "0.8.5"
 maplit = "1.0.2"
 matches = "0.1.9"
@@ -112,7 +118,7 @@ lz4-compression = ["lz4_flex"]
 zstd-compression = ["zstd"]
 
 failpoints = ["fail", "fail/failpoints"]
-unstable = [] # useful for benches.
+unstable = []                            # useful for benches.
 
 quickwit = ["sstable", "futures-util"]
 
@@ -122,7 +128,16 @@ quickwit = ["sstable", "futures-util"]
 compare_hash_only = ["stacker/compare_hash_only"]
 
 [workspace]
-members = ["query-grammar", "bitpacker", "common", "ownedbytes", "stacker", "sstable", "tokenizer-api", "columnar"]
+members = [
+    "query-grammar",
+    "bitpacker",
+    "common",
+    "ownedbytes",
+    "stacker",
+    "sstable",
+    "tokenizer-api",
+    "columnar",
+]
 
 # Following the "fail" crate best practises, we isolate
 # tests that define specific behavior in fail check points
@@ -147,4 +162,3 @@ harness = false
 [[bench]]
 name = "agg_bench"
 harness = false
-

src/core/executor.rs

@@ -1,21 +1,25 @@
+use std::sync::Arc;
+
 #[cfg(feature = "quickwit")]
 use futures_util::{future::Either, FutureExt};
-use rayon::{ThreadPool, ThreadPoolBuilder};
 
 use crate::TantivyError;
 
-/// Search executor whether search request are single thread or multithread.
-///
-/// We don't expose Rayon thread pool directly here for several reasons.
-///
-/// First dependency hell. It is not a good idea to expose the
-/// API of a dependency, knowing it might conflict with a different version
-/// used by the client. Second, we may stop using rayon in the future.
+/// Executor makes it possible to run tasks in single thread or
+/// in a thread pool.
+#[derive(Clone)]
 pub enum Executor {
     /// Single thread variant of an Executor
     SingleThread,
     /// Thread pool variant of an Executor
-    ThreadPool(ThreadPool),
+    ThreadPool(Arc<rayon::ThreadPool>),
+}
+
+#[cfg(feature = "quickwit")]
+impl From<Arc<rayon::ThreadPool>> for Executor {
+    fn from(thread_pool: Arc<rayon::ThreadPool>) -> Self {
+        Executor::ThreadPool(thread_pool)
+    }
 }
 
 impl Executor {
@@ -26,11 +30,11 @@ impl Executor {
 
     /// Creates an Executor that dispatches the tasks in a thread pool.
     pub fn multi_thread(num_threads: usize, prefix: &'static str) -> crate::Result<Executor> {
-        let pool = ThreadPoolBuilder::new()
+        let pool = rayon::ThreadPoolBuilder::new()
             .num_threads(num_threads)
             .thread_name(move |num| format!("{prefix}{num}"))
             .build()?;
-        Ok(Executor::ThreadPool(pool))
+        Ok(Executor::ThreadPool(Arc::new(pool)))
     }
 
     /// Perform a map in the thread pool.
@@ -105,7 +109,7 @@ impl Executor {
         match self {
             Executor::SingleThread => Either::Left(std::future::ready(Ok(cpu_intensive_task()))),
             Executor::ThreadPool(pool) => {
-                let (sender, receiver) = oneshot_with_sentinel::channel();
+                let (sender, receiver) = oneshot::channel();
                 pool.spawn(|| {
                     if sender.is_closed() {
                         return;
@@ -121,54 +125,6 @@ impl Executor {
     }
 }
 
-#[cfg(feature = "quickwit")]
-mod oneshot_with_sentinel {
-    use std::pin::Pin;
-    use std::sync::Arc;
-    use std::task::{Context, Poll};
-    // TODO get ride of this if oneshot ever gains a is_closed()
-
-    pub struct SenderWithSentinel<T> {
-        tx: oneshot::Sender<T>,
-        guard: Arc<()>,
-    }
-
-    pub struct ReceiverWithSentinel<T> {
-        rx: oneshot::Receiver<T>,
-        _guard: Arc<()>,
-    }
-
-    pub fn channel<T>() -> (SenderWithSentinel<T>, ReceiverWithSentinel<T>) {
-        let (tx, rx) = oneshot::channel();
-        let guard = Arc::new(());
-        (
-            SenderWithSentinel {
-                tx,
-                guard: guard.clone(),
-            },
-            ReceiverWithSentinel { rx, _guard: guard },
-        )
-    }
-
-    impl<T> SenderWithSentinel<T> {
-        pub fn send(self, message: T) -> Result<(), oneshot::SendError<T>> {
-            self.tx.send(message)
-        }
-
-        pub fn is_closed(&self) -> bool {
-            Arc::strong_count(&self.guard) == 1
-        }
-    }
-
-    impl<T> std::future::Future for ReceiverWithSentinel<T> {
-        type Output = Result<T, oneshot::RecvError>;
-
-        fn poll(mut self: Pin<&mut Self>, ctx: &mut Context<'_>) -> Poll<Self::Output> {
-            Pin::new(&mut self.rx).poll(ctx)
-        }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::Executor;

src/index/index.rs

@@ -3,7 +3,6 @@ use std::fmt;
 #[cfg(feature = "mmap")]
 use std::path::Path;
 use std::path::PathBuf;
-use std::sync::Arc;
 use std::thread::available_parallelism;
 
 use super::segment::Segment;
@@ -294,7 +293,7 @@ pub struct Index {
     directory: ManagedDirectory,
     schema: Schema,
     settings: IndexSettings,
-    executor: Arc<Executor>,
+    executor: Executor,
     tokenizers: TokenizerManager,
     fast_field_tokenizers: TokenizerManager,
     inventory: SegmentMetaInventory,
@@ -319,23 +318,19 @@ impl Index {
     ///
     /// By default the executor is single thread, and simply runs in the calling thread.
     pub fn search_executor(&self) -> &Executor {
-        self.executor.as_ref()
+        &self.executor
     }
 
     /// Replace the default single thread search executor pool
     /// by a thread pool with a given number of threads.
     pub fn set_multithread_executor(&mut self, num_threads: usize) -> crate::Result<()> {
-        self.executor = Arc::new(Executor::multi_thread(num_threads, "tantivy-search-")?);
+        self.executor = Executor::multi_thread(num_threads, "tantivy-search-")?;
         Ok(())
     }
 
     /// Custom thread pool by a outer thread pool.
-    pub fn set_shared_multithread_executor(
-        &mut self,
-        shared_thread_pool: Arc<Executor>,
-    ) -> crate::Result<()> {
-        self.executor = shared_thread_pool.clone();
-        Ok(())
+    pub fn set_executor(&mut self, executor: Executor) {
+        self.executor = executor;
     }
 
     /// Replace the default single thread search executor pool
@@ -419,7 +414,7 @@ impl Index {
             schema,
             tokenizers: TokenizerManager::default(),
             fast_field_tokenizers: TokenizerManager::default(),
-            executor: Arc::new(Executor::single_thread()),
+            executor: Executor::single_thread(),
             inventory,
         }
     }

src/lib.rs

@@ -436,7 +436,6 @@ pub mod tests {
     }
 
     #[test]
-    #[cfg(not(feature = "lz4"))]
     fn test_version_string() {
         use regex::Regex;
         let regex_ptn = Regex::new(