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From "Maysam Yabandeh (JIRA)" <j...@apache.org>
Subject [jira] [Work stopped] (HADOOP-11301) [optionally] update jmx cache to drop old metrics
Date Tue, 18 Nov 2014 01:16:35 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-11301?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Work on HADOOP-11301 stopped by Maysam Yabandeh.
> [optionally] update jmx cache to drop old metrics
> -------------------------------------------------
>                 Key: HADOOP-11301
>                 URL: https://issues.apache.org/jira/browse/HADOOP-11301
>             Project: Hadoop Common
>          Issue Type: Improvement
>            Reporter: Maysam Yabandeh
>            Assignee: Maysam Yabandeh
>         Attachments: HADOOP-11301.v01.patch
> MetricsSourceAdapter::updateJmxCache() skips updating the info cache if no new metric
is added since last time:
> {code}
>       int oldCacheSize = attrCache.size();
>       int newCacheSize = updateAttrCache();
>       if (oldCacheSize < newCacheSize) {
>         updateInfoCache();
>       }
> {code}
> This behavior is not desirable in some applications. For example nntop (HDFS-6982) reports
the top users via jmx. The list is updated after each report. The previously reported top
users hence should be removed from the cache upon each report request.
> In our production run of nntop we made a change to ignore the size check and always perform
updateInfoCache. I am planning to submit a patch including this change. The feature can be
enabled by a configuration parameter.

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