[jira] [Created] (CASSANDRA-20446) Reduce level of duplication for properties in JMX ObjectName for metrics

["Dmitry Konstantinov (Jira)" <ji...@apache.org>]

Dmitry Konstantinov created CASSANDRA-20446:
-----------------------------------------------

             Summary: Reduce level of duplication for properties in JMX ObjectName for metrics
                 Key: CASSANDRA-20446
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-20446
             Project: Apache Cassandra
          Issue Type: Improvement
          Components: Observability/JMX
            Reporter: Dmitry Konstantinov
         Attachments: image-2025-03-17-18-14-01-628.png, image-2025-03-17-18-14-48-658.png

Currently we construct ObjectName when we publish our metrics via JMX by concatenating key/value pairs and providing the result to ObjectName constructor:

org.apache.cassandra.metrics.CassandraMetricsRegistry.MetricName#MetricName(...)
{code:java}
public MetricName(String group, String type, String name, String scope)
{
    this(group, type, name, scope, createMBeanName(group, type, name, scope));
}

private static String createMBeanName(String group, String type, String name, String scope)
{
    final StringBuilder nameBuilder = new StringBuilder();
    nameBuilder.append(ObjectName.quote(group));
    nameBuilder.append(":type=");
    nameBuilder.append(ObjectName.quote(type));
    if (scope != null)
    {
        nameBuilder.append(",scope=");
        nameBuilder.append(ObjectName.quote(scope));
    }
    if (name.length() > 0)
    {
        nameBuilder.append(",name=");
        nameBuilder.append(ObjectName.quote(name));
    }
    return nameBuilder.toString();
} 

public ObjectName getMBeanName()
{    String mname = mBeanName;    if (mname == null)
        mname = getMetricName();    try
    {        return new ObjectName(mname);
    } catch (MalformedObjectNameException e)
    {
        try
        {
            return new ObjectName(ObjectName.quote(mname));
        } catch (MalformedObjectNameException e1)
        {
            throw new RuntimeException(e1);
        }
    }
}{code}
later ObjectName parse and split them back to fill internal _propertyList map.
As a result we get a lot of duplicated property name/value String objects stored within JMX repository.
I have found this issue during an analysis of memory usage for a dev instance of Cassandra (4.1 + JDK 11) where we want to have memory usage to be small to reduce cost of dev envs.
There are 275 tables for the instance (including all system ones), it has 395MiB heap used and about 52MiB from them are consumed by com.sun.jmx.mbeanserver.JmxMBeanServer, where about 41 MiB is spent for ObjectName objects:

!image-2025-03-17-18-14-01-628.png|width=400! 
!image-2025-03-17-18-14-48-658.png|width=400!

The possible way to reduce this _propertyList duplication is to use another constructor to build ObjectName: ObjectName(String domain, Hashtable<String, String> table) and provide the properties as a map, in this way we can avoid duplicates in properties across the instances. 



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