Database Explorer connection pool exhaustion with no configurable pool parameters or diagnostic visibility

Answering the Three Questions

1. Programmatic exposure of HikariCP metrics – NetBeans does not expose pool settings in the Data Sources UI, but you can enable Hikari’s built‑in JMX support by creating a small wrapper driver that sets registerMbeans=true before the pool is instantiated. Once the MBean is registered, tools such as jconsole, jvisualvm, or a custom JMX client can read maximumPoolSize, activeConnections, and idleConnections in real time.

2. Custom JDBC wrapper or JMX client – Yes. Implement java.sql.Driver, delegate to the real driver, and inside connect() create a HikariConfig with the desired pool size and registerMbeans=true. Register the wrapper via the NetBeans module system (Services/META-INF/services/java.sql.Driver), then use it in the New Connection wizard. A JMX client can connect to the NetBeans JVM and query the com.zaxxer.hikari domain.

3. Extension points for injecting pool configuration – The public Database Explorer API (org.netbeans.api.db.explorer.DatabaseConnection) does not expose the underlying DataSource or HikariConfig. The only supported hook is DatabaseConnection.getDriverInstance(), which returns the raw java.sql.Driver. Therefore, there is no documented SPI for injecting pool parameters; the wrapper approach is the only supported path.

Practical Steps for Your IDE

1. Verify NetBeans JVM and JMX availability

   Open a terminal and run:

   jcmd <netbeans-pid> VM.system_properties | grep java
   

   Confirm you can attach a JMX client. If you prefer a GUI, launch jconsole and connect to the NetBeans process.

2. Create a wrapper driver module
   • In your module project, implement java.sql.Driver.
   • In connect() build a HikariConfig:

   HikariConfig cfg = new HikariConfig();
   cfg.setJdbcUrl(url);
   cfg.setUsername(user);
   cfg.setPassword(pass);
   cfg.setMaximumPoolSize(20); // adjust per your server limits
   cfg.setRegisterMbeans(true);
   HikariDataSource ds = new HikariDataSource(cfg);
   return ds.getConnection();
   

   • Register the driver via Services/META-INF/services/java.sql.Driver.
   • Build and install the module through Tools → Plugins → Downloaded → Add….
3. Create a new connection using the wrapper driver

   In the Data Sources UI, choose the wrapper class as the driver. The connection will now use your configured pool.

4. Observe metrics via JMX

   In jconsole, navigate to com.zaxxer.hikari → Pool → yourPoolName. Inspect attributes like MaximumPoolSize, ActiveConnections, IdleConnections, and QueueSize.

   If you need programmatic access, write a small Java program that connects to the same MBeanServer:

   MBeanServer server = ManagementFactory.getPlatformMBeanServer();
   ObjectName name = new ObjectName("com.zaxxer.hikari:type=Pool,Name=yourPoolName");
   Integer max = (Integer) server.getAttribute(name, "MaximumPoolSize");
   System.out.println("Max pool: " + max);
   

What We Still Need to Know

To fine‑tune the wrapper, could you confirm which NetBeans version you’re running and how many data sources you typically open? That will help decide whether a single shared pool or per‑connection pools are more appropriate.

Key Take‑aways

• NetBeans does not expose HikariCP tuning via UI.
• Enabling registerMbeans is the only programmatic path to metrics.
• No public API exists to inject pool config; a wrapper driver is the supported workaround.
• JMX clients (jconsole, custom code) can monitor pool state once the MBean is registered.