Removes all usage of block_on, and use a oneshot channel instead. (#1315

)

* Removes all usage of block_on, and use a oneshot channel instead.

Calling `block_on` panics in certain context.
For instance, it panics when it is called in a the context of another
call to block.

Using it in tantivy is unnecessary. We replace it by a thin wrapper
around a oneshot channel that supports both async/sync.

* Removing needless uses of async in the API.

Co-authored-by: PSeitz <PSeitz@users.noreply.github.com>

Cargo.toml

@@ -13,6 +13,7 @@ keywords = ["search", "information", "retrieval"]
 edition = "2018"
 
 [dependencies]
+oneshot = "0.1"
 base64 = "0.13"
 byteorder = "1.4.3"
 crc32fast = "1.2.1"
@@ -32,7 +33,6 @@ fs2={ version = "0.4.3", optional = true }
 levenshtein_automata = "0.2"
 uuid = { version = "0.8.2", features = ["v4", "serde"] }
 crossbeam = "0.8.1"
-futures = { version = "0.3.15", features = ["thread-pool"] }
 tantivy-query-grammar = { version="0.15.0", path="./query-grammar" }
 tantivy-bitpacker = { version="0.1", path="./bitpacker" }
 common = { version = "0.2", path = "./common/", package = "tantivy-common" }
@@ -71,6 +71,7 @@ criterion = "0.3.5"
 test-log = "0.2.8"
 env_logger = "0.9.0"
 pprof = {version= "0.7", features=["flamegraph", "criterion"]}
+futures = "0.3.15"
 
 [dev-dependencies.fail]
 version = "0.5"

src/aggregation/mod.rs

@@ -305,8 +305,6 @@ pub(crate) fn f64_to_fastfield_u64(val: f64, field_type: &Type) -> Option<u64> {
 
 #[cfg(test)]
 mod tests {
-
-    use futures::executor::block_on;
     use serde_json::Value;
 
     use super::agg_req::{Aggregation, Aggregations, BucketAggregation};
@@ -378,7 +376,7 @@ mod tests {
                 .searchable_segment_ids()
                 .expect("Searchable segments failed.");
             let mut index_writer = index.writer_for_tests()?;
-            block_on(index_writer.merge(&segment_ids))?;
+            index_writer.merge(&segment_ids).wait()?;
             index_writer.wait_merging_threads()?;
         }
 
@@ -597,7 +595,7 @@ mod tests {
                 .searchable_segment_ids()
                 .expect("Searchable segments failed.");
             let mut index_writer = index.writer_for_tests()?;
-            block_on(index_writer.merge(&segment_ids))?;
+            index_writer.merge(&segment_ids).wait()?;
             index_writer.wait_merging_threads()?;
         }
 
@@ -1033,7 +1031,7 @@ mod tests {
                     .searchable_segment_ids()
                     .expect("Searchable segments failed.");
                 let mut index_writer = index.writer_for_tests()?;
-                block_on(index_writer.merge(&segment_ids))?;
+                index_writer.merge(&segment_ids).wait()?;
                 index_writer.wait_merging_threads()?;
             }
 

src/core/index.rs

@@ -781,24 +781,24 @@ mod tests {
         for i in 0u64..8_000u64 {
             writer.add_document(doc!(field => i))?;
         }
-        let (sender, receiver) = crossbeam::channel::unbounded();
-        let _handle = directory.watch(WatchCallback::new(move || {
-            let _ = sender.send(());
-        }));
+
         writer.commit()?;
         let mem_right_after_commit = directory.total_mem_usage();
-        assert!(receiver.recv().is_ok());
+
         let reader = index
             .reader_builder()
             .reload_policy(ReloadPolicy::Manual)
             .try_into()?;
-
         assert_eq!(reader.searcher().num_docs(), 8_000);
+        assert_eq!(reader.searcher().segment_readers().len(), 8);
+
         writer.wait_merging_threads()?;
+
         let mem_right_after_merge_finished = directory.total_mem_usage();
 
         reader.reload().unwrap();
         let searcher = reader.searcher();
+        assert_eq!(searcher.segment_readers().len(), 1);
         assert_eq!(searcher.num_docs(), 8_000);
         assert!(
             mem_right_after_merge_finished < mem_right_after_commit,

src/directory/file_watcher.rs

@@ -53,7 +53,9 @@ impl FileWatcher {
                         if metafile_has_changed {
                             info!("Meta file {:?} was modified", path);
                             current_checksum_opt = Some(checksum);
-                            futures::executor::block_on(callbacks.broadcast());
+                            // We actually ignore callbacks failing here.
+                            // We just wait for the end of their execution.
+                            let _ = callbacks.broadcast().wait();
                         }
                     }
 

src/directory/tests.rs

@@ -6,9 +6,6 @@ use std::sync::atomic::{AtomicBool, AtomicUsize};
 use std::sync::Arc;
 use std::time::Duration;
 
-use futures::channel::oneshot;
-use futures::executor::block_on;
-
 use super::*;
 
 #[cfg(feature = "mmap")]
@@ -249,8 +246,8 @@ fn test_lock_blocking(directory: &dyn Directory) {
     std::thread::spawn(move || {
         //< lock_a_res is sent to the thread.
         in_thread_clone.store(true, SeqCst);
-        let _just_sync = block_on(receiver);
-        // explicitely droping lock_a_res. It would have been sufficient to just force it
+        let _just_sync = receiver.recv();
+        // explicitely dropping lock_a_res. It would have been sufficient to just force it
         // to be part of the move, but the intent seems clearer that way.
         drop(lock_a_res);
     });
@@ -273,7 +270,7 @@ fn test_lock_blocking(directory: &dyn Directory) {
         assert!(in_thread.load(SeqCst));
         assert!(lock_a_res.is_ok());
     });
-    assert!(block_on(receiver2).is_ok());
+    assert!(receiver2.recv().is_ok());
     assert!(sender.send(()).is_ok());
     assert!(join_handle.join().is_ok());
 }

src/directory/watch_event_router.rs

@@ -1,7 +1,6 @@
 use std::sync::{Arc, RwLock, Weak};
 
-use futures::channel::oneshot;
-use futures::{Future, TryFutureExt};
+use crate::FutureResult;
 
 /// Cloneable wrapper for callbacks registered when watching files of a `Directory`.
 #[derive(Clone)]
@@ -74,12 +73,11 @@ impl WatchCallbackList {
     }
 
     /// Triggers all callbacks
-    pub fn broadcast(&self) -> impl Future<Output = ()> {
+    pub fn broadcast(&self) -> FutureResult<()> {
         let callbacks = self.list_callback();
-        let (sender, receiver) = oneshot::channel();
-        let result = receiver.unwrap_or_else(|_| ());
+        let (result, sender) = FutureResult::create("One of the callback panicked.");
         if callbacks.is_empty() {
-            let _ = sender.send(());
+            let _ = sender.send(Ok(()));
             return result;
         }
         let spawn_res = std::thread::Builder::new()
@@ -88,7 +86,7 @@ impl WatchCallbackList {
                 for callback in callbacks {
                     callback.call();
                 }
-                let _ = sender.send(());
+                let _ = sender.send(Ok(()));
             });
         if let Err(err) = spawn_res {
             error!(
@@ -106,8 +104,6 @@ mod tests {
     use std::sync::atomic::{AtomicUsize, Ordering};
     use std::sync::Arc;
 
-    use futures::executor::block_on;
-
     use crate::directory::{WatchCallback, WatchCallbackList};
 
     #[test]
@@ -118,22 +114,18 @@ mod tests {
         let inc_callback = WatchCallback::new(move || {
             counter_clone.fetch_add(1, Ordering::SeqCst);
         });
-        block_on(watch_event_router.broadcast());
+        watch_event_router.broadcast().wait().unwrap();
         assert_eq!(0, counter.load(Ordering::SeqCst));
         let handle_a = watch_event_router.subscribe(inc_callback);
         assert_eq!(0, counter.load(Ordering::SeqCst));
-        block_on(watch_event_router.broadcast());
+        watch_event_router.broadcast().wait().unwrap();
         assert_eq!(1, counter.load(Ordering::SeqCst));
-        block_on(async {
-            (
-                watch_event_router.broadcast().await,
-                watch_event_router.broadcast().await,
-                watch_event_router.broadcast().await,
-            )
-        });
+        watch_event_router.broadcast().wait().unwrap();
+        watch_event_router.broadcast().wait().unwrap();
+        watch_event_router.broadcast().wait().unwrap();
         assert_eq!(4, counter.load(Ordering::SeqCst));
         mem::drop(handle_a);
-        block_on(watch_event_router.broadcast());
+        watch_event_router.broadcast().wait().unwrap();
         assert_eq!(4, counter.load(Ordering::SeqCst));
     }
 
@@ -150,19 +142,15 @@ mod tests {
         let handle_a = watch_event_router.subscribe(inc_callback(1));
         let handle_a2 = watch_event_router.subscribe(inc_callback(10));
         assert_eq!(0, counter.load(Ordering::SeqCst));
-        block_on(async {
-            futures::join!(
-                watch_event_router.broadcast(),
-                watch_event_router.broadcast()
-            )
-        });
+        watch_event_router.broadcast().wait().unwrap();
+        watch_event_router.broadcast().wait().unwrap();
         assert_eq!(22, counter.load(Ordering::SeqCst));
         mem::drop(handle_a);
-        block_on(watch_event_router.broadcast());
+        watch_event_router.broadcast().wait().unwrap();
         assert_eq!(32, counter.load(Ordering::SeqCst));
         mem::drop(handle_a2);
-        block_on(watch_event_router.broadcast());
-        block_on(watch_event_router.broadcast());
+        watch_event_router.broadcast().wait().unwrap();
+        watch_event_router.broadcast().wait().unwrap();
         assert_eq!(32, counter.load(Ordering::SeqCst));
     }
 
@@ -176,15 +164,12 @@ mod tests {
         });
         let handle_a = watch_event_router.subscribe(inc_callback);
         assert_eq!(0, counter.load(Ordering::SeqCst));
-        block_on(async {
-            let future1 = watch_event_router.broadcast();
-            let future2 = watch_event_router.broadcast();
-            futures::join!(future1, future2)
-        });
+        watch_event_router.broadcast().wait().unwrap();
+        watch_event_router.broadcast().wait().unwrap();
         assert_eq!(2, counter.load(Ordering::SeqCst));
         mem::drop(handle_a);
         let _ = watch_event_router.broadcast();
-        block_on(watch_event_router.broadcast());
+        watch_event_router.broadcast().wait().unwrap();
         assert_eq!(2, counter.load(Ordering::SeqCst));
     }
 }

src/fastfield/mod.rs

@@ -501,8 +501,7 @@ mod tests {
             .map(SegmentReader::segment_id)
             .collect();
         assert_eq!(segment_ids.len(), 2);
-        let merge_future = index_writer.merge(&segment_ids[..]);
-        futures::executor::block_on(merge_future)?;
+        index_writer.merge(&segment_ids[..]).wait().unwrap();
         reader.reload()?;
         assert_eq!(reader.searcher().segment_readers().len(), 1);
         Ok(())

src/fastfield/multivalued/mod.rs

@@ -8,7 +8,6 @@ pub use self::writer::MultiValuedFastFieldWriter;
 mod tests {
 
     use chrono::Duration;
-    use futures::executor::block_on;
     use proptest::strategy::Strategy;
     use proptest::{prop_oneof, proptest};
     use test_log::test;
@@ -268,7 +267,7 @@ mod tests {
                 IndexingOp::Merge => {
                     let segment_ids = index.searchable_segment_ids()?;
                     if segment_ids.len() >= 2 {
-                        block_on(index_writer.merge(&segment_ids))?;
+                        index_writer.merge(&segment_ids).wait()?;
                         index_writer.segment_updater().wait_merging_thread()?;
                     }
                 }
@@ -283,7 +282,7 @@ mod tests {
                 .searchable_segment_ids()
                 .expect("Searchable segments failed.");
             if !segment_ids.is_empty() {
-                block_on(index_writer.merge(&segment_ids)).unwrap();
+                index_writer.merge(&segment_ids).wait()?;
                 assert!(index_writer.wait_merging_threads().is_ok());
             }
         }