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From "Erik Krogen (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-13782) Make MutableRates metrics thread-local write, aggregate-on-read
Date Thu, 03 Nov 2016 23:22:58 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-13782?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Erik Krogen updated HADOOP-13782:
---------------------------------
    Attachment: HADOOP-13782.001.patch

Seems checkstyle does not like lambda syntax... Attaching v001 patch with test and checkstyle
fixes. 

Leaving two checkstyle points unaddressed: 
1. Complains about {{MutableRatesWithAggregation.rates}} not being private, but this is standard
for {{@Metric}} metrics.
2. Complains about MutableRatesWithAggregation.java:60 being long. I'm hesitant to break up
a type statement; looks pretty ugly if I do. 

> Make MutableRates metrics thread-local write, aggregate-on-read
> ---------------------------------------------------------------
>
>                 Key: HADOOP-13782
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13782
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: metrics
>            Reporter: Erik Krogen
>            Assignee: Erik Krogen
>         Attachments: HADOOP-13782.000.patch, HADOOP-13782.001.patch
>
>
> Currently the {{MutableRates}} metrics class serializes all writes to metrics it contains
because of its use of {{MetricsRegistry.add()}} (i.e., even two increments of unrelated metrics
contained within the same {{MutableRates}} object will serialize w.r.t. each other). This
class is used by {{RpcDetailedMetrics}}, which may have many hundreds of threads contending
to modify these metrics. Instead we should allow updates to unrelated metrics objects to happen
concurrently. To do so we can let each thread locally collect metrics, and on a {{snapshot}},
aggregate the metrics from all of the threads. 
> I have collected some benchmark performance numbers in HADOOP-13747 (https://issues.apache.org/jira/secure/attachment/12835043/benchmark_results)
which indicate that this can bring significantly higher performance in high contention situations.




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