David Manning created HBASE-27159: ------------------------------------- Summary: Emit source metrics for BlockCacheExpressHitPercent, getHitCachingRatio, getHitCachingCount, getMissCachingCount Key: HBASE-27159 URL: https://issues.apache.org/jira/browse/HBASE-27159 Project: HBase Issue Type: Improvement Components: BlockCache, metrics Affects Versions: 2.0.0, 3.0.0-alpha-1 Reporter: David Manning
[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. We should emit blockCache{{{}HitCachingCount{}}} and {{blockCacheMissCachingCount}} along with the current metrics. -- This message was sent by Atlassian Jira (v8.20.7#820007)