refactored to use programmatic flush instead of timed flush of the write cache

Cargo.toml

@@ -89,7 +89,7 @@ thread_local = "1.1.3"
 [features]
 default = ["conduit_bin", "backend_sqlite"]
 backend_sled = ["sled"]
-backend_persy = ["persy"]
+backend_persy = ["persy","num_cpus"]
 backend_sqlite = ["sqlite"]
 backend_heed = ["heed", "crossbeam"]
 sqlite = ["rusqlite", "parking_lot", "crossbeam", "tokio/signal"]

src/database/abstraction.rs

@@ -49,4 +49,3 @@ pub trait Tree: Send + Sync {
         Ok(())
     }
 }
-

src/database/abstraction/persy.rs

@@ -1,29 +1,31 @@
+use crate::{
+    database::{
+        abstraction::{DatabaseEngine, Tree},
+        Config,
+    },
+    Result,
+};
 use persy::{ByteVec, OpenOptions, Persy, ValueMode};
-use timer::Timer;
-use crate::database::abstraction::{DatabaseEngine, Tree};
-use crate::database::Config;
-use crate::Result;
 
 use std::{
-    future::Future, pin::Pin,
     cmp::Ordering,
-    collections::{BTreeMap,btree_map::Entry, BTreeSet},
+    collections::{btree_map::Entry, BTreeMap, BTreeSet},
+    future::Future,
     iter::Peekable,
+    pin::Pin,
+    sync::{Arc, RwLock},
     time::{Duration, Instant},
-    sync::{RwLock, Arc}
 };
 
 pub struct PersyEngine {
     persy: Persy,
     write_cache: Arc<RwLock<WriteCache>>,
-    #[allow(unused)]
-    timer: Timer,
 }
 
 impl DatabaseEngine for PersyEngine {
     fn open(config: &Config) -> Result<Arc<Self>> {
         let mut cfg = persy::Config::new();
-        cfg.change_cache_size(config.db_cache_capacity_mb as u64 *1048576f64 as u64);
+        cfg.change_cache_size((config.db_cache_capacity_mb * 1024.0 * 1024.0) as u64);
 
         let persy = OpenOptions::new()
             .create(true)
@@ -36,17 +38,16 @@ impl DatabaseEngine for PersyEngine {
             write_cache_size,
             Duration::from_millis(write_cache_window_millisecs),
         )));
+        /*
+        use timer::Timer;
         let timer = Timer::new();
         let timer_write_cache = write_cache.clone();
         timer.schedule_repeating(
             chrono::Duration::milliseconds((write_cache_window_millisecs / 4) as i64),
             move || timer_write_cache.write().unwrap().flush_timed().unwrap(),
         );
-        Ok(Arc::new(PersyEngine {
-            persy,
-            write_cache,
-            timer,
-        }))
+        */
+        Ok(Arc::new(PersyEngine { persy, write_cache }))
     }
 
     fn open_tree(self: &Arc<Self>, name: &'static str) -> Result<Arc<dyn Tree>> {
@@ -66,6 +67,7 @@ impl DatabaseEngine for PersyEngine {
     }
 
     fn flush(self: &Arc<Self>) -> Result<()> {
+        self.write_cache.write().unwrap().flush_changes()?;
         Ok(())
     }
 }
@@ -223,7 +225,7 @@ impl WriteCache {
         index: &str,
         from: &[u8],
         backwards: bool,
-        mut iter: Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)> + Send+ 'a>,
+        mut iter: Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)> + Send + 'a>,
     ) -> Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)> + Send + 'a> {
         if let Some(adds) = self.add_cache.get(index) {
             let range = if backwards {
@@ -299,23 +301,12 @@ impl WriteCache {
     }
 }
 
-#[cfg(feature = "persy")]
-impl Drop for WriteCache {
-    fn drop(&mut self) {
-        if self.changes_count > 0 {
-            self.flush_changes().unwrap();
-        }
-    }
-}
-
-#[cfg(feature = "persy")]
 struct UnionIter<T: Iterator<Item = I>, T1: Iterator<Item = I>, I> {
     first: Peekable<T>,
     second: Peekable<T1>,
     backwards: bool,
 }
 
-#[cfg(feature = "persy")]
 impl<T: Iterator<Item = I>, T1: Iterator<Item = I>, I> UnionIter<T, T1, I> {
     fn new(first: T, second: T1, backwards: bool) -> Self {
         UnionIter {
@@ -326,7 +317,6 @@ impl<T: Iterator<Item = I>, T1: Iterator<Item = I>, I> UnionIter<T, T1, I> {
     }
 }
 
-#[cfg(feature = "persy")]
 impl<K: Ord, V, T, T1> Iterator for UnionIter<T, T1, (K, V)>
 where
     T: Iterator<Item = (K, V)>,
@@ -450,7 +440,8 @@ impl Tree for PersyTree {
                         .map(|val| (k.0.to_owned().into(), val.0.to_owned().into()))
                         .next()
                 });
-                let result: Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)> + Send+'a > = if backwards {
+                let result: Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)> + Send + 'a> = if backwards
+                {
                     Box::new(map.rev())
                 } else {
                     Box::new(map)
@@ -478,7 +469,7 @@ impl Tree for PersyTree {
     fn scan_prefix<'a>(
         &'a self,
         prefix: Vec<u8>,
-    ) -> Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)> + Send+ 'a> {
+    ) -> Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)> + Send + 'a> {
         let range_prefix = ByteVec(prefix.to_owned());
         let range = self
             .persy