[CASSANDRA-13103] incorrect jvm metric names

• Type: Bug
• Status: Resolved
• Priority: Low
• Resolution: Fixed
• Fix Version/s: 2.2.10, 3.0.13, 3.11.0, 4.0-alpha1, 4.0
• Component/s: Legacy/Observability
• Labels: lhf
• Severity: Low
• Assignee: Alain Rastoul
• Reporter: Alain Rastoul

Authors

Alain Rastoul

Reviewers

Stefan Podkowinski

• Created: 05/Jan/17 19:30
• Updated: 15/May/20 08:02
• Resolved: 03/Apr/17 18:08

Description

Some jvm metrics have a double dot in name like:
jvm.memory..total.max , jvm.memory..total.init (etc).
it seems that an extra dot is added at the end of the name in CassandraDaemon.java, around line 367 (in 3.0.10):
...
// enable metrics provided by metrics-jvm.jar
CassandraMetricsRegistry.Metrics.register("jvm.buffers.", new BufferPoolMetricSet(ManagementFactory.getPlatformMBeanServer()));
CassandraMetricsRegistry.Metrics.register("jvm.gc.", new GarbageCollectorMetricSet());
CassandraMetricsRegistry.Metrics.register("jvm.memory.", new MemoryUsageGaugeSet());

and also added in append method of MetricRegistry.
Call stack is:
MetricRegistry>>registerAll(String prefix, MetricSet metrics)
MetricRegistry>>static String name(String name, String... names)
MetricRegistry>>static void append(StringBuilder builder, String part)

and in append the dot is also added:
...
if(builder.length() > 0)

{ builder.append('.'); }

builder.append(part);
...

The codahale MetricRegistry class seems to have no recent modification of name or append methods, so it look like a small bug.
May be the fix could be to simply not to add the final dot in the metric name, ie "jvm.buffers" instead of "jvm.buffers."