Add a maximum size to stempool (#1895)

* Add a maximum size to stempool

* Simplify logic

config/src/comments.rs

@@ -240,6 +240,13 @@ fn comments() -> HashMap<String, String> {
 ".to_string(),
 	);
 
+	retval.insert(
+		"max_stempool_size".to_string(),
+		"
+#maximum number of transactions allowed in the stempool
+".to_string(),
+	);
+
 	retval.insert(
 		"[server.stratum_mining_config]".to_string(),
 		"

pool/src/transaction_pool.rs

@@ -141,7 +141,7 @@ impl TransactionPool {
 		}
 
 		// Do we have the capacity to accept this transaction?
-		self.is_acceptable(&tx)?;
+		self.is_acceptable(&tx, stem)?;
 
 		// Make sure the transaction is valid before anything else.
 		tx.validate(self.verifier_cache.clone())
@@ -215,12 +215,20 @@ impl TransactionPool {
 
 	/// Whether the transaction is acceptable to the pool, given both how
 	/// full the pool is and the transaction weight.
-	fn is_acceptable(&self, tx: &Transaction) -> Result<(), PoolError> {
+	fn is_acceptable(&self, tx: &Transaction, stem: bool) -> Result<(), PoolError> {
 		if self.total_size() > self.config.max_pool_size {
 			// TODO evict old/large transactions instead
 			return Err(PoolError::OverCapacity);
 		}
 
+		// Check that the stempool can accept this transaction
+		if stem {
+			if self.stempool.size() > self.config.max_stempool_size {
+				// TODO evict old/large transactions instead
+				return Err(PoolError::OverCapacity);
+			}
+		}
+
 		// for a basic transaction (1 input, 2 outputs) -
 		// (-1 * 1) + (4 * 2) + 1 = 8
 		// 8 * 10 = 80

pool/src/types.rs

@@ -96,6 +96,10 @@ pub struct PoolConfig {
 	/// Maximum capacity of the pool in number of transactions
 	#[serde = "default_max_pool_size"]
 	pub max_pool_size: usize,
+
+	/// Maximum capacity of the pool in number of transactions
+	#[serde = "default_max_stempool_size"]
+	pub max_stempool_size: usize,
 }
 
 impl Default for PoolConfig {
@@ -103,6 +107,7 @@ impl Default for PoolConfig {
 		PoolConfig {
 			accept_fee_base: default_accept_fee_base(),
 			max_pool_size: default_max_pool_size(),
+			max_stempool_size: default_max_stempool_size(),
 		}
 	}
 }
@@ -113,6 +118,9 @@ fn default_accept_fee_base() -> u64 {
 fn default_max_pool_size() -> usize {
 	50_000
 }
+fn default_max_stempool_size() -> usize {
+	50_000
+}
 
 /// Represents a single entry in the pool.
 /// A single (possibly aggregated) transaction.

pool/tests/common/mod.rs

@@ -168,6 +168,7 @@ pub fn test_setup(
 		PoolConfig {
 			accept_fee_base: 0,
 			max_pool_size: 50,
+			max_stempool_size: 50,
 		},
 		chain.clone(),
 		verifier_cache.clone(),