Question

Context: MySQL server deployed with MysqldResource java class (Connector/MXJ lib). They app using mysql server may crash for some reason and could be finished without shutting down the MySQL.

The setup and run of MySQL done as following:

mr = new MysqldResource(runtimeDir, dataDir);
mr.start("My MySQL", options);

Goal: Write code to ensure that MySQL is not running (MysqldResource.pid doesn’t exist, or pid doesn’t exist). If MySQL I would like to kill it.

Note: I am not going to start mysqld!

Finally,

How do I archieve the Goal using MysqldResource interface, is it even possible? Or I should workout with .pid file for that manually?

In particular will the following code work correctly for me:

mr = new MysqldResource(runtimeDir, dataDir);
mr.shutdown();

assuming its running after in another session after program crashed and without starting mysql first? In other words, will this code kill existing MySQL instance running?

Answer 1

The following code will work:

mr = new MysqldResource(runtimeDir, dataDir);
mr.shutdown();

It works even if it’s running on another VM or with another mr instance. Also following method can be used to check if the MySQL deployed is running:

mr.isRunning();

To proof that shutdown also works even if called on newly created mr instance check the shutdown code – it uses pidFile() to check the existence of process:

 /**
  * Kills the MySQL process.
  */
    public synchronized void shutdown() {
        boolean haveShell = (getShell() != null);
        if (!pidFile().exists() && !haveShell) {
            printMessage("Mysqld not running. No file: " + pidFile());
            return;
        }
        printMessage("stopping mysqld (process: " + pid() + ")");

        issueNormalKill();

        if (processRunning()) {
            issueForceKill();
        }

        if (shellRunning()) {
            destroyShell();
        }
        setShell(null);

        if (processRunning()) {
            printWarning("Process " + pid + "still running; not deleting " 
                    + pidFile());
        } else {
            threads.pause(150);
            System.gc();
            threads.pause(150);
            pidFile().deleteOnExit();
            pidFile().delete();
            pidFile = null;
            pid = null;
        }

        setReadyForConnection(false);

        printMessage("clearing options");
        options.clear();
        out.flush();

        printMessage("shutdown complete");
    }