[jira] [Commented] (SOLR-8785) Use Metrics library for core metrics

["Shalin Shekhar Mangar (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-8785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15683596#comment-15683596 ] 

Shalin Shekhar Mangar commented on SOLR-8785:
---------------------------------------------

I have an interest in this. I'll take a look at the changes.

> Use Metrics library for core metrics
> ------------------------------------
>
>                 Key: SOLR-8785
>                 URL: https://issues.apache.org/jira/browse/SOLR-8785
>             Project: Solr
>          Issue Type: Improvement
>    Affects Versions: 4.1
>            Reporter: Jeff Wartes
>              Labels: patch, patch-available
>
> The Metrics library (https://dropwizard.github.io/metrics/3.1.0/) is a well-known way to track metrics about applications. 
> In SOLR-1972, latency percentile tracking was added. The comment list is long, so here’s my synopsis:
> 1. An attempt was made to use the Metrics library
> 2. That attempt failed due to a memory leak in Metrics v2.1.1
> 3. Large parts of Metrics were then copied wholesale into the org.apache.solr.util.stats package space and that was used instead.
> Copy/pasting Metrics code into Solr may have been the correct solution at the time, but I submit that it isn’t correct any more. 
> The leak in Metrics was fixed even before SOLR-1972 was released, and by copy/pasting a subset of the functionality, we miss access to other important things that the Metrics library provides, particularly the concept of a Reporter. (https://dropwizard.github.io/metrics/3.1.0/manual/core/#reporters)
> Further, Metrics v3.0.2 is already packaged with Solr anyway, because it’s used in two contrib modules. (map-reduce and morphines-core)
> I’m proposing that:
> 1. Metrics as bundled with Solr be upgraded to the current v3.1.2
> 2. Most of the org.apache.solr.util.stats package space be deleted outright, or gutted and replaced with simple calls to Metrics. Due to the copy/paste origin, the concepts should mostly map 1:1.
> I’d further recommend a usage pattern like:
> SharedMetricRegistries.getOrCreate(System.getProperty(“solr.metrics.registry”, “solr-registry”))
> There are all kinds of areas in Solr that could benefit from metrics tracking and reporting. This pattern allows diverse areas of code to track metrics within a single, named registry. This well-known-name then becomes a handle you can use to easily attach a Reporter and ship all of those metrics off-box.



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