Minimal effective gas price in the queue (#8934)

* Minimal effective gas price.

* Fix naming, add test

* Fix minimal entry score and add test.

* Fix worst_transaction.

* Remove effective gas price threshold.

* Don't leak gas_price decisions out of Scoring.

src/pool.rs

@@ -390,7 +390,13 @@ impl<T, S, L> Pool<T, S, L> where
 
 	/// Returns worst transaction in the queue (if any).
 	pub fn worst_transaction(&self) -> Option<Arc<T>> {
-		self.worst_transactions.iter().next().map(|x| x.transaction.transaction.clone())
+		self.worst_transactions.iter().next_back().map(|x| x.transaction.transaction.clone())
+	}
+
+	/// Returns true if the pool is at it's capacity.
+	pub fn is_full(&self) -> bool {
+		self.by_hash.len() >= self.options.max_count
+			|| self.mem_usage >= self.options.max_mem_usage
 	}
 
 	/// Returns an iterator of pending (ready) transactions.
@@ -486,6 +492,11 @@ impl<T, S, L> Pool<T, S, L> where
 		&self.listener
 	}
 
+	/// Borrows scoring instance.
+	pub fn scoring(&self) -> &S {
+		&self.scoring
+	}
+
 	/// Borrows listener mutably.
 	pub fn listener_mut(&mut self) -> &mut L {
 		&mut self.listener

src/tests/mod.rs

@@ -48,6 +48,15 @@ pub type SharedTransaction = Arc<Transaction>;
 
 type TestPool = Pool<Transaction, DummyScoring>;
 
+impl TestPool {
+	pub fn with_limit(max_count: usize) -> Self {
+		Self::with_options(Options {
+			max_count,
+			..Default::default()
+		})
+	}
+}
+
 #[test]
 fn should_clear_queue() {
 	// given
@@ -505,9 +514,27 @@ fn should_return_worst_transaction() {
 
 	// when
 	txq.import(b.tx().nonce(0).gas_price(5).new()).unwrap();
+	txq.import(b.tx().sender(1).nonce(0).gas_price(4).new()).unwrap();
 
 	// then
-	assert!(txq.worst_transaction().is_some());
+	assert_eq!(txq.worst_transaction().unwrap().gas_price, 4.into());
+}
+
+#[test]
+fn should_return_is_full() {
+	// given
+	let b = TransactionBuilder::default();
+	let mut txq = TestPool::with_limit(2);
+	assert!(!txq.is_full());
+
+	// when
+	txq.import(b.tx().nonce(0).gas_price(110).new()).unwrap();
+	assert!(!txq.is_full());
+
+	txq.import(b.tx().sender(1).nonce(0).gas_price(100).new()).unwrap();
+
+	// then
+	assert!(txq.is_full());
 }
 
 mod listener {