[jira] [Comment Edited] (HBASE-27159) Emit source metrics for BlockCacheExpressHitPercent, blockCache counts of hits and misses for cacheable requests

["Andrew Kyle Purtell (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-27159?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17565205#comment-17565205 ] 

Andrew Kyle Purtell edited comment on HBASE-27159 at 7/12/22 12:50 AM:
-----------------------------------------------------------------------

Note recent metrics improvements proposals (with approved PRs) HBASE-27186 especially and HBASE-27188. 

The proposal here also sounds good and could make 2.5.0 along with the others if a patch becomes available this week. [~dmanning]


was (Author: apurtell):
Note recent metrics improvements proposals (with approved PRs) HBASE-27186 especially and HBASE-27188. 

The proposal here also sounds good and could make 2.5.0 if a patch becomes available this week. [~dmanning]

> Emit source metrics for BlockCacheExpressHitPercent, blockCache counts of hits and misses for cacheable requests
> ----------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-27159
>                 URL: https://issues.apache.org/jira/browse/HBASE-27159
>             Project: HBase
>          Issue Type: Improvement
>          Components: BlockCache, metrics
>    Affects Versions: 3.0.0-alpha-1, 2.0.0
>            Reporter: David Manning
>            Priority: Minor
>
> [https://github.com/apache/hbase/blob/d447fa01ba36a11d57927b78cce1bbca361b1d52/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/CacheStats.java#L346-L400]
> {code:java}
> public double getHitCachingRatio() {
>   double requestCachingCount = getRequestCachingCount();
>   if (requestCachingCount == 0) {
>     return 0;
>   }
>   return getHitCachingCount() / requestCachingCount;
> } {code}
> This code is responsible for the metric {{{}BlockCacheExpressHitPercent{}}}. The metric represents the percentage of requests which were cacheable, but not found in the cache. Unfortunately, since the counters are process-level counters, the ratio is for the lifetime of the process. This makes it less useful for looking at cache behavior during a smaller time period.
> The underlying counters are {{hitCachingCount}} and {{{}missCachingCount{}}}. Having access to the underlying counters allows for offline computation of the same metric for any given time period. But these counters are not emitted today from {{{}MetricsRegionServerWrapperImpl.java{}}}.
> Compare this to {{hitCount}} and {{missCount}} which are emitted as metrics {{blockCacheHitCount}} and {{{}blockCacheMissCount{}}}. But these are raw counts for the cache, which include requests that are not cacheable. The cacheable metrics are more interesting, since it can be common to miss on a request which is not cacheable.
> Interestingly, these metrics are emitted regularly as part of a log line in {{{}StatisticsThread.logStats{}}}.
> We should emit blockCache{{{}HitCachingCount{}}} and {{blockCacheMissCachingCount}} along with the current metrics.



--
This message was sent by Atlassian Jira
(v8.20.10#820010)