abhishek sen created PHOENIX-5436:
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Summary: Histogram view of Global Client Metrics
Key: PHOENIX-5436
URL: https://issues.apache.org/jira/browse/PHOENIX-5436
Project: Phoenix
Issue Type: Improvement
Reporter: abhishek sen
Currently the
[GlobalClientMetrics|https://github.com/apache/phoenix/blob/master/phoenix-core/src/main/java/org/apache/phoenix/monitoring/GlobalClientMetrics.java]
enum-class defines Phoenix Global Client Metrics as an enum and each
metric-enum tracks a [Phoenix
Metric|https://github.com/apache/phoenix/blob/master/phoenix-core/src/main/java/org/apache/phoenix/monitoring/Metric.java]
object implemented by
[AtomicMetric|https://github.com/apache/phoenix/blob/master/phoenix-core/src/main/java/org/apache/phoenix/monitoring/AtomicMetric.java]
class. This tracks a single counter, but in some use cases we want the
distribution of a particular metric value over some period of time. One example
could be the metric
[TASK_EXECUTION_TIME|https://github.com/apache/phoenix/blob/master/phoenix-core/src/main/java/org/apache/phoenix/monitoring/MetricType.java#L47].
The Global Client metric tracks the aggregate value for the execution time of
the task. More useful information to monitor would be the distribution of task
execution time instead.
Now, in order to incorporate histogram view of the metric, we can use the
[Histogram
Implementation|https://github.com/apache/hbase/blob/master/hbase-metrics/src/main/java/org/apache/hadoop/hbase/metrics/impl/HistogramImpl.java]
from hbase-metrics-api package. The current GlobalClientMetric also ultimately
adapts to hbase-metrics-api interface but it
[implements|https://github.com/apache/phoenix/blob/master/phoenix-core/src/main/java/org/apache/phoenix/monitoring/GlobalClientMetrics.java#L155]
the
[Gauge|https://github.com/apache/hbase/blob/master/hbase-metrics-api/src/main/java/org/apache/hadoop/hbase/metrics/Gauge.java]
class which can only keep track of a single value not a histogram. So one way
could be to create a new GlobalClientHistogramMetrics enum class which keeps
track of a Histogram (based on
[MutableTimeHistogram|https://github.com/apache/hbase/blob/master/hbase-hadoop2-compat/src/main/java/org/apache/hadoop/metrics2/lib/MutableTimeHistogram.java])
for each enum-metric instead of a single counter as it is now. The updating of
the these new metric can go
[here|https://github.com/apache/phoenix/blob/master/phoenix-core/src/main/java/org/apache/phoenix/job/JobManager.java#L289]
within JobManager class where the currently available Global as well as
request-level metrics are being updated.
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