[jira] [Commented] (PHOENIX-4448) Remove complete dependency from Hadoop Metrics

["Josh Elser (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PHOENIX-4448?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16310233#comment-16310233 ] 

Josh Elser commented on PHOENIX-4448:
-------------------------------------

bq. Metrics2 is the framework for transport of metrics (via JMX or custom sinks) as well as creating/defining new metrics. We used this framework for transferring the HBase or Phoenix Apache HTrace traces from source to sink

Ok, tracing != metrics. That's the first area of confusion here. I think you're saying that, prior to PHOENIX-3752, traces were serialized via Metrics2 and this implementation was simplified to not use that extra path.

We, however, have metrics which are collected server-side to better understand Phoenix 2ndary index operations. These are persisted by the Hadoop Metrics2 API inside of HBase. In <HBase2, this was the only way to capture metrics in HBase. This subjected us to problems with the overall stability of the Hadoop Metrics2 API -- performance issues, changes in implementation, changes in API.

In >=HBase2, a "wrapper" library was introduced which is what we refer to as hbase-metrics. This presents an API for collecting metrics inside of HBase which is disjoint from the underlying implementation of where those metrics are sent; however, either approach would presently work.

If your goal is to remove direct use of Hadoop Metrics2 API in Phoenix, then the only solution is to use the new HBase metrics API which is only in >=HBase 2. I don't think you have any solution for <HBase2 that doesn't involve removing some really good information Phoenix is currently generating.

> Remove complete dependency from Hadoop Metrics
> ----------------------------------------------
>
>                 Key: PHOENIX-4448
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-4448
>             Project: Phoenix
>          Issue Type: Bug
>            Reporter: Karan Mehta
>            Assignee: Karan Mehta
>         Attachments: PHOENIX-4448.001.patch
>
>
> PHOENIX-3757 removed the usage of Hadoop Metrics API and the sink. However there are still some classes that are lying in place and probably not being used elsewhere. This JIRA is to track the cleanup of those classes.



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