Possible bug with concurrent modification of QueryMetrics

[leventov]

Reported here: #3954 (comment)

Possible fix: https://github.com/druid-io/druid/files/1002579/queryPlus.txt

Similar to #3803

@pjain1

[pjain1]

can you please do it in a branch, that would be easier to test ?

[leventov]

@pjain1 https://github.com/druid-io/druid/tree/queryMetrics-concurrency-fix

[pjain1]

@leventov thanks

[himanshug]

@leventov its passing our integration testing env. please do the pr.

[pjain1]

@leventov I tried this and integration tests seems to be passing

[leventov]

@himanshug @pjain1 please check #4288