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https://issues.apache.org/jira/browse/HADOOP-11301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14220330#comment-14220330
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Andrew Wang commented on HADOOP-11301:
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Hey Maysam, thanks for working on this! A few comments:
* Rather than adding a config parameter, I think we can just do this always.
The cost of determining the MBeanInfo seems small compared to gathering all the
metrics, and that you run it in production is evidence in favor of this.
* It's our coding style to avoid wildcard imports, there's one in the new test.
> [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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