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https://issues.apache.org/jira/browse/HADOOP-15008?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16234887#comment-16234887
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Erik Krogen edited comment on HADOOP-15008 at 11/1/17 10:41 PM:
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Attaching v000 patch. The bug comes from the fact that the {{period}} being
passed into the {{MetricsSinkAdapter}} is in seconds, but the {{logicalTime}}
passed in is milliseconds. The sink adapter gets offered metrics on every
period of the {{MetricsSystemImpl}} (where the period is the GCD of all of the
sinks' periods), and filters based on {{logicalTime % period == 0}}. The
mismatch in units would cause this filter to pass more often than it should.
I fixed the issue (converted {{period}} to milliseconds), added a unit test,
and changed the field names in {{MetricsSinkAdapter}} to reflect that they are
all in milliseconds to hopefully prevent such future mistakes.
was (Author: xkrogen):
Attaching v000 patch. The bug comes from the fact that the {{period}} being
passed into the {{MetricsSinkAdapter}} is in seconds, but the {{logicalTime}}
passed in is milliseconds. The sink adapter gets offered metrics on every
period of the {{MetricsSystemImpl}} (where the period is the GCD of all of the
sinks' periods), and filters based on {{logicalTime % period == 0}}. The
mismatch in units would cause this filter to pass more often than it should.
> Metrics sinks may emit too frequently if multiple sink periods are configured
> -----------------------------------------------------------------------------
>
> Key: HADOOP-15008
> URL: https://issues.apache.org/jira/browse/HADOOP-15008
> Project: Hadoop Common
> Issue Type: Bug
> Components: metrics
> Reporter: Erik Krogen
> Assignee: Erik Krogen
> Priority: Minor
> Attachments: HADOOP-15008.000.patch
>
>
> If there are multiple metrics sink periods configured, depending on what
> those periods are, some sinks may emit too frequently. For example with the
> following:
> {code:title=hadoop-metrics2.properties}
> namenode.sink.file10.class=org.apache.hadoop.metrics2.sink.FileSink
> namenode.sink.file5.class=org.apache.hadoop.metrics2.sink.FileSink
> namenode.sink.file10.filename=namenode-metrics_per10.out
> namenode.sink.file5.filename=namenode-metrics_per5.out
> namenode.sink.file10.period=10
> namenode.sink.file5.period=5
> {code}
> I get the following:
> {code}
> ± for f in namenode-metrics_per*.out; do echo "$f" && grep
> "metricssystem.MetricsSystem" $f | awk '{last=curr; curr=$1} END { print
> curr-last }'; done
> namenode-metrics_per10.out
> 5000
> namenode-metrics_per5.out
> 5000
> {code}
> i.e., for both metrics files, each record is 5000 ms apart, even though one
> of the sinks has been configured to emit at 10s intervals
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