Major Description
JMX Metric avgTimePerRequest (of org.apache.solr.handler.component.SearchHandler) doesn't appear to behave correctly anymore. It was a cumulative value in pre-6.4 versions. Since totalTime metric was removed (which was a base for monitoring calculations), avgTimePerRequest seems like possible alternative to calculate "time spent in requests since last measurement", but it behaves strangely after 6.4.
I did a simple test on gettingstarted collection (just unpacked the Solr 6.4.1 version and started it with "bin/solr start -e cloud -noprompt"). The query I used was:
http://localhost:8983/solr/gettingstarted/select?indent=on&q=*:*&wt=json
I run it 30 times in a row (with approx 1 sec between executions).
At the same time I was looking (with jconsole) at bean solr/gettingstarted_shard2_replica2:type=/select,id=org.apache.solr.handler.component.SearchHandler
Here is how metric was changing over time (first number is "requests" metric, second number is "avgTimePerRequest"):
10 6.6033
12 5.9557
13 0.9015 ---> 13th req would need negative duration if this was cumulative
15 6.7315
16 7.4873
17 0.8458 ---> same case with 17th request
23 6.1076
At the same time bean solr/gettingstarted_shard1_replica2:type=/select,id=org.apache.solr.handler.component.SearchHandler also showed strange values:
6 5.13482
8 10.5694
9 0.504
10 0.344
12 8.8121
18 3.3531
CC ab