Dmitry Konstantinov created CASSANDRA-20446:
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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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