Add query cache hit count and field data cache hit count to rest API

[clandry94]

Describe the feature:

I was investigating cache hit ratios in Elasticsearch clusters recently and noticed that the request_cache has a hit_count and miss_count exposed through the rest API but the query_cache and fielddata cache do not as seen h ere

elasticsearch/server/src/main/java/org/elasticsearch/rest/action/cat/RestNodesAction.java

Lines 157 to 169 in 18f5690

	table.addCell("fielddata.memory_size", "alias:fm,fielddataMemory;default:false;text-align:right;desc:used fielddata cache");
	table.addCell("fielddata.evictions", "alias:fe,fielddataEvictions;default:false;text-align:right;desc:fielddata evictions");
	table.addCell("query_cache.memory_size", "alias:qcm,queryCacheMemory;default:false;text-align:right;desc:used query cache");
	table.addCell("query_cache.evictions", "alias:qce,queryCacheEvictions;default:false;text-align:right;desc:query cache evictions");
	table.addCell("request_cache.memory_size", "alias:rcm,requestCacheMemory;default:false;text-align:right;desc:used request cache");
	table.addCell("request_cache.evictions",
	"alias:rce,requestCacheEvictions;default:false;text-align:right;desc:request cache evictions");
	table.addCell("request_cache.hit_count",
	"alias:rchc,requestCacheHitCount;default:false;text-align:right;desc:request cache hit counts");
	table.addCell("request_cache.miss_count",
	"alias:rcmc,requestCacheMissCount;default:false;text-align:right;desc:request cache miss counts");

.

The values seem to be available within the QueryCacheStats class but not FieldDataStats class so would it make sense to make the QueryCache rest API on parity to the RequestCache rest API? Also having the field data cache hit and miss counts would be very useful as well but seems to be a bit more work to implement.

I can implement these features if it would be useful

[elasticmachine]

Pinging @elastic/es-core-features (:Core/Features/CAT APIs)

[jtibshirani]

As a point of clarification -- it seems the node stats API returns this information, but it is not available in the cat nodes API.

[samz007]

@clandry94 I am a beginner in open source contributions, Can I start working on this?

[clandry94]

@samz007 sure 🙂 feel free to comment if you have any questions and I can try to help out.

[abhishek8gupta]

Is anyone picking up this one? or can I pick up? I am beginner to ES group.

[samz007]

@clandry94 Started working on this issue. Thanks.

[ak-24]

Is this issue still open and unassigned ?

[clandry94]

I won't have time to work on this for the foreseeable future, so if someone else would like to grab it feel free 😄

[parthpunkster]

Can I start working on this one?

[Priya-Raut]

Is this issue still unassigned? Can I start working on it?