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From "Kunal Khatua" <ku...@apache.org>
Subject Re: Apache drill issue - cpu spiking to 100%
Date Mon, 22 Oct 2018 21:48:17 GMT
Hi Bala/Srihari

 In the Drill query profile, I dont see the query running for more than a second. The example
you gave is with 350msec. I'm not sure what the backend Mongo storage plugin is doing. You'll
probably need to profile the Drillbit using something like Yourkit or JVisualVM to identify
what threads are burning CPU and the possible hotspots. I dont see anything hinting at a problem. 


On 10/20/2018 12:30:50 AM, Srihari Prabhakar <sriharip316@gmail.com> wrote:
Hi Kunal,

I have Web UI enabled, but queries are not being run from there. Queries are being run through
JDBC. Attaching the Drill query, drill profile. Also I have enabled profiling on MongoDB and
captured all the queries triggered by drill on MongoDB. I have grouped all MongoDB queries
by shape and taken the count of each query.
If I understand correctly, drill doesn't store MongoDB schema, so one count query and one
simple find on collection is expected, as it has to capture schema information. But, I see
count and find being run 43 times each for one single query in drill.

On Sat, 20 Oct 2018 at 00:06, Kunal Khatua <kunal@apache.org [mailto:kunal@apache.org]>

Hi Bala

Can you share details of the profiles itself? It might be that the MongoDB storage plugin
is translating the query into 100 mongo queries because of some (100?) specific filter criteria
in the Drill query?

JVM Heap usage fluctuation would indicate frequent object creation and garbage collection,
probably by the Mongo storage plugin itself. Are you running the query through the WebUI
or via JDBC? As long as you are not seeing any GC logs indicating a leak in the heap memory,
the heap usage fluctuating is normal for your 6GB heap allocation. 

If you are using the WebUI or REST API, it is possible that there is overhead in Drill rendering
the resultset that can cause higher heap and CPU usage.

On 10/18/2018 1:10:25 PM, Balasubramanian Naganathan <balsu19.n@gmail.com [mailto:balsu19.n@gmail.com]>
We have tableau BI tool which is getting data from MongoDB using Apache
We are running drill on 5 nodes each having 8 core and 16 GB RAM, but they
are not running as a cluster. Each node is an individual instance. We have
a Load Balancer to load balance across these 5 nodes.
-Xms6G -Xmx6G -XX:MaxDirectMemorySize=13G -XX:ReservedCodeCacheSize=1024m
-Ddrill.exec.enable-epoll=false -Dproperty=value -Duser.timezone=UTC
-XX:+UseStringDeduplication -Dproperty=value -Duser.timezone=UTC
-Duser.timezone=UTC -Dcom.sun.management.jmxremote
-Dcom.sun.management.jmxremote.ssl=false -XX:+UseG1GC
-Dlog.query.path=/opt/apache-drill-1.14.0/log/drillbit_queries.json -cp

We see that apache drill is reaching 100% CPU when we run 30 queries per
second. All the queries are very simple queries without any aggregation.
Also each query in Apache drill is getting converted to 100 queries in
Mongo. 97% of the queries are find(1) and count() mongoDB Queries. Not sure
why they are triggered.

Also we tried adding "-XX:+UseStringDeduplication", JVM parameter, We saw
the load become uneven after adding this parameter. Are there any other JVM
parameters that we can add to improve drill performance?
Even though there are no calls to drill, the heap memory usage is
fluctuating. It goes up to around 70% (~4GB) and comes back to around 1GB.


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