wip: implement a resource pool

Author: jpraynaud

Diff for: mithril-aggregator/src/services/prover.rs

@@ -4,14 +4,14 @@ use std::{
     collections::{BTreeMap, BTreeSet, HashMap},
     sync::Arc,
 };
-use tokio::sync::Mutex;
 
 use mithril_common::{
     crypto_helper::{MKMap, MKMapNode, MKTree},
     entities::{
         BlockRange, CardanoDbBeacon, CardanoTransaction, CardanoTransactionsSetProof,
         TransactionHash,
     },
+    resource_pool::ResourcePool,
     signable_builder::BlockRangeRootRetriever,
     StdResult,
 };
@@ -62,7 +62,7 @@ pub trait TransactionsRetriever: Sync + Send {
 pub struct MithrilProverService {
     transaction_retriever: Arc<dyn TransactionsRetriever>,
     block_range_root_retriever: Arc<dyn BlockRangeRootRetriever>,
-    mk_map_cache: Mutex<Option<MKMap<BlockRange, MKMapNode<BlockRange>>>>,
+    mk_map_cache: ResourcePool<MKMap<BlockRange, MKMapNode<BlockRange>>>,
 }
 
 impl MithrilProverService {
@@ -74,7 +74,7 @@ impl MithrilProverService {
         Self {
             transaction_retriever,
             block_range_root_retriever,
-            mk_map_cache: Mutex::new(None),
+            mk_map_cache: ResourcePool::new(vec![]),
         }
     }
 
@@ -139,9 +139,9 @@ impl ProverService for MithrilProverService {
         let mk_trees = BTreeMap::from_iter(mk_trees?);
 
         // 3 - Compute block range roots Merkle map
+        // TODO: the cache computation should be done in the state machine only when new artifact is produced and at node startup
         self.compute_cache(up_to).await?;
-        let mut mk_map = self.mk_map_cache.lock().await;
-        let mk_map = mk_map.as_mut().unwrap();
+        let mut mk_map = self.mk_map_cache.acquire_resource().await;
 
         // 4 - Enrich the Merkle map with the block ranges Merkle trees
         for (block_range, mk_tree) in mk_trees {
@@ -150,6 +150,8 @@ impl ProverService for MithrilProverService {
 
         // 5 - Compute the proof for all transactions
         if let Ok(mk_proof) = mk_map.compute_proof(transaction_hashes) {
+            self.mk_map_cache.return_resource(mk_map).await;
+
             let transaction_hashes_certified: Vec<TransactionHash> = transaction_hashes
                 .iter()
                 .filter(|hash| mk_proof.contains(&hash.as_str().into()).is_ok())
@@ -166,22 +168,27 @@ impl ProverService for MithrilProverService {
     }
 
     async fn compute_cache(&self, up_to: &CardanoDbBeacon) -> StdResult<()> {
-        let mut mk_map = self.mk_map_cache.lock().await;
-        if mk_map.is_none() {
-            println!("Computing Merkle map from block range roots");
+        if self.mk_map_cache.count().await == 0 {
+            println!("Computing Merkle map cache from block range roots");
             let mk_map_cache = self
                 .block_range_root_retriever
                 .compute_merkle_map_from_block_range_roots(up_to.immutable_file_number)
                 .await?;
-            mk_map.replace(mk_map_cache);
+            for i in 0..100 {
+                println!("Computing Merkle map cache from block range roots: {}", i);
+                self.mk_map_cache
+                    .return_resource(mk_map_cache.clone())
+                    .await;
+            }
+            self.mk_map_cache.return_resource(mk_map_cache).await;
+            println!("Done computing Merkle map cache from block range roots");
         }
 
         Ok(())
     }
 
     async fn clear_cache(&self) -> StdResult<()> {
-        let mut mk_map = self.mk_map_cache.lock().await;
-        mk_map.take();
+        self.mk_map_cache.drain().await;
 
         Ok(())
     }

Diff for: mithril-common/src/lib.rs

@@ -59,6 +59,7 @@ pub mod entities;
 pub mod era;
 pub mod messages;
 pub mod protocol;
+pub mod resource_pool;
 pub mod signable_builder;
 
 cfg_test_tools! {

Diff for: mithril-common/src/resource_pool.rs

@@ -0,0 +1,55 @@
+//! Resource pool implementation
+// TODO: automatic return resource to the pool with Guard and Drop
+// TODO: avoid returning stale resources
+// TODO: add tests
+use std::{
+    collections::VecDeque,
+    sync::{Condvar, Mutex},
+};
+
+/// Resource pool
+pub struct ResourcePool<T: Send + Sync> {
+    resources: Mutex<VecDeque<T>>,
+    not_empty: Condvar,
+}
+
+impl<T: Send + Sync> ResourcePool<T> {
+    /// Create a new resource pool
+    pub fn new(resources: Vec<T>) -> Self {
+        Self {
+            resources: Mutex::new(resources.into()),
+            not_empty: Condvar::new(),
+        }
+    }
+
+    /// Acquire a resource from the pool
+    pub async fn acquire_resource(&self) -> T {
+        let mut resources = self.resources.lock().unwrap();
+        while resources.is_empty() {
+            resources = self.not_empty.wait(resources).unwrap();
+        }
+        resources.pop_front().unwrap()
+    }
+
+    /// Return a resource to the pool
+    // TODO: automatic return resource to the pool with Guard and Drop
+    pub async fn return_resource(&self, resource: T) {
+        let mut resources = self.resources.lock().unwrap();
+        resources.push_back(resource);
+        self.not_empty.notify_one();
+    }
+
+    /// Drain the pool
+    pub async fn drain(&self) {
+        let mut resources = self.resources.lock().unwrap();
+        let _ = resources.drain(..).collect::<Vec<_>>();
+    }
+
+    /// Count the resources in the pool
+    pub async fn count(&self) -> usize {
+        self.resources.lock().unwrap().len()
+    }
+}
+
+#[cfg(test)]
+mod tests {}