Package services do not gracefully handle "Too many connections" errors.

[junhaoliao]

Bug

Currently, the database connection logic in various components raises an exception immediately when the database server rejects a connection due to connection limits. This can cause cascading failures when the database is temporarily overloaded.

1. Python Components (clp-package-utils, scripts):

   • Target: components/clp-py-utils/clp_py_utils/sql_adapter.py
   • Logic: Wrap _create_mariadb_connection and _create_mysql_connection with a retry loop catching mariadb.Error / mysql.connector.Error (specifically for "Too many connections").

2. Core (C++):

   • Target: components/core/src/clp/MySQLDB.cpp
   • Logic: In the open or connection establishment method, check for MySQL error codes (e.g., CR_CONNECTION_ERROR, ER_CON_COUNT_ERROR) and retry with backoff.

3. WebUI (Node.js/TypeScript):

   • Target: components/webui/server (uses @fastify/mysql).
   • Logic: Configure the connection pool to retry, or wrap the initial connection logic. @fastify/mysql might expose the underlying pool events or require a custom connection factory wrapper to handle retries during startup or pool acquisition.

4. MCP Server (Python):

   • Target: components/clp-mcp-server (uses aiomysql).
   • Logic: Implement an async retry wrapper around the aiomysql.connect or pool creation calls.

5. API Server (Rust):

   • Target: components/api-server (uses sqlx).
   • Logic: sqlx often has built-in connection pool features (max_connections, acquire_timeout), but explicit retries on "Too many connections" during initial pool creation or individual acquisition might need explicit handling (e.g., using ConnectOptions or a retry crate like backoff).

CLP version

21fa311

Environment

Ubuntu 22.04

Reproduction steps

MariaDB/MySQL ships with mysqlslap, which can spawn many connections concurrently.

Example: 200 connections

mysqlslap \
  --user=youruser \
  --password=yourpassword \
  --host=127.0.0.1 \
  --concurrency=200 \
  --iterations=1 \
  --create-schema=test \
  --query="SELECT 1;"