aweisberg commented on code in PR #3068:
URL: https://github.com/apache/cassandra/pull/3068#discussion_r1476237255
##########
src/java/org/apache/cassandra/metrics/CassandraMetricsRegistry.java:
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@@ -250,6 +271,43 @@ private void removeAlias(MetricName name)
if (mBeanServer.isRegistered(name.getMBeanName()))
MBeanWrapper.instance.unregisterMBean(name.getMBeanName(),
MBeanWrapper.OnException.IGNORE);
}
+
+ /**
+ * Very infrequently used meters generate a linear amount of tick work
based on how long it has been
+ * since the meter was last marked or read. On scales of a year this can
be enough to cause the first request
+ * that needs to mark the meter to time out. Once a day read every meter
to force them to run Meter.tickIfNecessary
+ * so we only ever run at most one day worth of tick work per meter in the
request path.
+ *
+ * This can be removed if we ever upgrade and switch the default
MovingAverage from EWMA to SlidingWindowTimeAverages
+ */
+ private void tickMeters()
+ {
+ List<Throwable> failures = new ArrayList<>();
+ int droppedFailures = 0;
+ for (Meter meter : getMeters().values())
Review Comment:
This gets called once a day in a background thread. Assume 100 meters per
table and 1000 tables it takes about 26 seconds on my laptop. This is to
process a days worth of ticks on every meter as if it were unused.
So maybe `0.00003761574` of daily CPU time on an 8 core server. The time is
dominated by actually ticking not iterating the metrics.
I really don't think it's worth the extra lines of code to make iteration
faster.
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