Reuse MySQL connections within requests

src/lib/mysql-connector.cpp

@@ -3,10 +3,9 @@
 #include <stdlib.h>
 #include "mysql-connector.h"
 
-// MySQL handles are request-scoped framework resources. User code may call
-// mysql_disconnect() to close early, but leaked/exception-skipped handles are
-// still closed by cleanup_mysql_connections() at request end. Handles must not
-// be cached across requests or stored in globals/sessions.
+// Same-credential mysql_connect() calls lease one request-local connection.
+// mysql_disconnect() releases a lease; cleanup_mysql_connections() owns the
+// actual close at request end, including exception/fatal recovery paths.
 static void mysql_register_request_connection(MySQL* db)
 {
 	if(!context || !db)
@@ -16,6 +15,31 @@ static void mysql_register_request_connection(MySQL* db)
 		connections.push_back(db);
 }
 
+MySQL* mysql_connect(String host, String username, String password)
+{
+	if(context)
+	{
+		for(void* raw : context->resources.mysql_connections)
+		{
+			MySQL* db = (MySQL*)raw;
+			if(db && db->request_pooled && db->connection && db->request_host == host && db->request_username == username && db->request_password == password)
+			{
+				db->request_leases++;
+				return(db);
+			}
+		}
+	}
+	MySQL* db = new MySQL();
+	db->request_cleanup_delete = true;
+	db->request_pooled = context != 0;
+	db->request_leases = 1;
+	db->request_host = host;
+	db->request_username = username;
+	db->request_password = password;
+	db->connect(host, username, password);
+	return(db);
+}
+
 bool MySQL::connect(String host, String username, String password)
 {
 	// Register regardless of outcome: tracking is about the wrapper's
@@ -325,6 +349,7 @@ void MySQL::disconnect()
 	if(connection)
 		mysql_close((MYSQL*)connection);
 	connection = NULL;
+	request_leases = 0;
 	if(context)
 	{
 		auto& connections = context->resources.mysql_connections;
@@ -389,6 +414,7 @@ void cleanup_mysql_connections()
 		MySQL* db = (MySQL*)context->resources.mysql_connections.back();
 		context->resources.mysql_connections.pop_back();
 		bool should_delete = db->request_cleanup_delete;
+		db->request_pooled = false;
 		db->disconnect();
 		if(should_delete)
 			delete db;

src/lib/mysql-connector.h

@@ -21,6 +21,11 @@ struct MySQL {
 	u64 insert_id = 0;
 	String statement_info = ""; //
 	bool request_cleanup_delete = false;
+	bool request_pooled = false;
+	u32 request_leases = 0;
+	String request_host;
+	String request_username;
+	String request_password;
 
 	std::vector<MySQLFieldInfo> field_info;
 
@@ -33,26 +38,24 @@ struct MySQL {
 	DValue query(String q, StringMap params);
 	DValue get_pending_result();
 
-	// Unregisters from request connection tracking, so stack-allocated instances
-	// cannot leave dangling pointers behind for request cleanup. Heap handles
-	// returned by mysql_connect() are also request-owned and auto-closed at the
-	// end of the request if user code does not call mysql_disconnect() first.
+	// Unregisters non-pooled instances from request tracking. mysql_connect()
+	// handles remain request-owned until cleanup after their leases are released.
 	~MySQL() { disconnect(); }
 
 };
 
-inline MySQL* mysql_connect(String host = "localhost", String username = "root", String password = "")
-{
-	MySQL* m = new MySQL();
-	m->request_cleanup_delete = true;
-	m->connect(host, username, password);
-	return(m);
-}
+MySQL* mysql_connect(String host = "localhost", String username = "root", String password = "");
 
 inline void mysql_disconnect(MySQL* m)
 {
 	if(!m)
 		return;
+	if(m->request_pooled)
+	{
+		if(m->request_leases > 0)
+			m->request_leases--;
+		return;
+	}
 	m->disconnect();
 	delete m;
 }