AvinoamBN opened a new issue #9017: help understanding some basics to overcome query lag URL: https://github.com/apache/incubator-druid/issues/9017 Hi Gian, thank for reaching out. So I'm kinda new to apache druid, and I've been assigned with finding the source of a lag when querying. so far, I've learnt how to read the cluster conf files and how to query for metrics. I was trying to follow the docs to check how I can fine tune the configuration and optimize the historical and broker, but some options values are a mystery to me. like "heap size" and `druid.cache.sizeInBytes` and `druid.server.maxSize`. 1. to reach max heap size of 24G RAM, do i need a 48 cpu cores server? 2. what is the free system memory / druid.server.maxSize ratio? the docs mention "should be set such that a Historical is not allocated an excessive amount of segment data"... what is considered excessive, what the formula? regarding querying the metrics datasource: I'm doing a select query with mysql, and sending it via POST to the broker. example query: ``` { "query": "SELECT * FROM \"metrics\" WHERE \"__time\" BETWEEN TIMESTAMP '2019-12-11 00:00:00' AND TIMESTAMP '2019-12-11 23:59:59' AND \"dataSource\" = 'orgrimmar' AND \"metric\" = 'query/time' AND \"type\" = 'select' AND \"value\" > 10000 ORDER BY 1 limit 10" } ``` this query give results that look like this: ``` { "__time": "2019-12-11T15:00:49.878Z", "count": 1, "dataSource": "orgrimmar", "hasFilters": "true", "host": "druid-broker1:8083", "interval": "2019-11-26T10:18:51.681Z/2019-12-11T15:00:34.664Z", "metric": "query/time", "numComplexMetrics": 0, "numDimensions": 0, "numMetrics": 0, "server": "", "type": "select", "value": 13288 } ``` How can i find out why did this query take 13 seconds to complete? How can i find out what and where is the bottle-neck?
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