Phil Yang created HBASE-15742:
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Summary: o.a.h.metrics2.lib.Interns cache only 2010 MetricsInfo
Key: HBASE-15742
URL: https://issues.apache.org/jira/browse/HBASE-15742
Project: HBase
Issue Type: Bug
Affects Versions: 0.98.19, 1.1.4, 1.0.3, 1.2.1, 1.3.0
Reporter: Phil Yang
We use JMX and o.a.h.metrics2 to do some metrics on regions, tables, region
servers and cluster. We use MetricsInfo to show the information of metrics, and
we use Interns to cache MetricsInfo objects because it won't be changed.
However, in Interns there are some static values to limit the max cached
objects. We can only cache 2010 metrics, but we have dozens of metrics for one
region and we have some RS-level metrics in each RS and all metrics for all
regions will be saved in master. So each server will have thousands of metrics,
and we can not cache most of them. When we collect metrics by JMX, we will
create many objects which can be avoid. It increases the pressure of GC and JMX
has some caching logic so the objects can not be removed immediately which
increases the pressure more.
Interns is in Hadoop project, and I think the implementation is not suitable
for HBase. Because we can not know how many MetricsInfo we have, it depends on
the number of regions. And we can not set it unlimited because we should remove
the objects whose region is split, moved, or dropped. I think we can use
Guava's cache with expireAfterAccess which is very simple and convenient.
So we can add a new Interns class in HBase project first, and put it to
upstream later.
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