[jira] Commented: (HADOOP-3753) metrics: FileContext support overwrite mode

["Lohit Vijayarenu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-3753?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12613386#action_12613386 ] 

Lohit Vijayarenu commented on HADOOP-3753:
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bq. In some scenarios, it would be useful to simply write the current statistics to the file once every period, then overwrite the file for the next period.
Right now FileContext writes metric values every 'period' defined by metricsName.period property. (eg. dfs.period). Your idea about overwriting would be very helpful. How about rollover to new file possibly appended with time stamp. Say, if we roll over every 15 minutes or an hour, then append time stamp. Even better if we could have property something like metricsName.fileRollover=<some value in minutes>. Overwriting will lose the data, cleanup could be done by external application. 

> metrics: FileContext support overwrite mode
> -------------------------------------------
>
>                 Key: HADOOP-3753
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3753
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: metrics
>            Reporter: Craig Macdonald
>            Priority: Minor
>
> FileContext currently continually appends to the metrics log file(s), generating an ever lengthening file.
> In some scenarios, it would be useful to simply write the current statistics to the file once every period, then overwrite the file for the next period.
> For instance, this could be useful if an external application parsed the metrics output - e.g. Cacti to create realtime graphs.

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