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Hi Pradeep,

HPE has investigated the use of Cassandra for Monasca and came to the conclusion that it is not a good choice. One of the problems is that Cassandra is not performant when querying across big data sets with many dimension key-value combinations. As KairosDB is based on Cassandra it suffers from the same problems.

The excerpt from KariosDB documentation [1]:

“So if you have a million tag/value combinations, phase 1 will always take a few seconds to complete. Phase 2 could be fast if you filter by tags so that only a few partitions are read or it could be slow if you have to read the data from all one million partitions.

How do you know if what you are planning is going to be fast enough? From our experience if you have 10's of thousands of tag combinations you will be fine. Once you start getting towards a million you will be in for trouble.”


The existing code for Cassandra is planned to be removed.


Greetings
Witek

[1] https://github.com/kairosdb/kairosdb/wiki/Query-Performance


From: Pradeep Singh [mailto:ps4openstack at gmail.com]
Sent: Mittwoch, 1. März 2017 06:51
To: Shinya Kawabata <s-kawabata at wx.jp.nec.com>
Cc: OpenStack Development Mailing List (not for usage questions) <openstack-dev at lists.openstack.org>; roland.hochmuth at hpe.com
Subject: Re: [openstack-dev] [monasca] cassandra support in Monasca

Hello,

I have registered a BP[1] for that.
Please let me know if you have any concerns.

[1]https://blueprints.launchpad.net/monasca/+spec/kairosdb-support


Thanks,
Pradeep Singh

On Fri, Feb 24, 2017 at 2:20 PM, Shinya Kawabata <s-kawabata at wx.jp.nec.com<mailto:s-kawabata at wx.jp.nec.com>> wrote:
Hi Pradeep

Basic Cassandra support is already implemented.
But there are some performance problems.
These performance problems are difficult to enhance.
So we are planning to switch other DB and will let Cassandra deprecated.
KariosDB is one of candidates and not implemented yet.
KariosDB is build-on Cassandra so you might have problems we had.

Regards
Shinya Kawabata

> -----Original Message-----
> From: Pradeep Singh [mailto:ps4openstack at gmail.com<mailto:ps4openstack at gmail.com>]
> Sent: Thursday, February 23, 2017 2:39 PM
> To: OpenStack Development Mailing List (not for usage questions)
> <openstack-dev at lists.openstack.org<mailto:openstack-dev at lists.openstack.org>>
> Cc: Kawabata Shinya <s-kawabata at wx.jp.nec.com<mailto:s-kawabata at wx.jp.nec.com>>;
> santhosh.fernandes at gmail.com<mailto:santhosh.fernandes at gmail.com>
> Subject: [openstack-dev][monasca] cassandra support in Monasca
>
> Hello,
>
> Could you please suggest status of Cassandra support in Monasca.
> Is there any plan to support  kairosdb?
> If it is not implemented then we can take kairosdb support work.
>
> Thanks,
> Pradeep Singh

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