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From "Durity, Sean R" <SEAN_R_DUR...@homedepot.com>
Subject RE: [EXTERNAL] Re: Cassandra migration from 1.25 to 3.x
Date Mon, 17 Jun 2019 13:36:47 GMT
The advice so far is exactly correct for an in-place kind of upgrade. The blog post you mentioned
is different. They decided to jump versions in Cassandra by standing up a new cluster and
using a dual-write/dual-read process for their app. They also wrote code to read and interpret
sstables in order to migrate existing data. Getting that right with compaction running, data
consistency, etc. it not easy. That is what Cassandra does, of course. They had to reverse
engineer that process.

I would not personally take that path as it seems a more difficult way to go -- for the DBA/admin.
It is a nice path for the development team, though. They only had to look at their reads and
writes (already encapsulated in a DAO) for the dual clusters. In a multi-upgrade scenario,
drivers and statements probably have to get upgraded at several steps along the way (including
a move from Thrift to CQL, probably). More app testing is required each upgrade. So, the decision
has to be based on which resources you have and trust (app dev and testing + Cassandra upgrades
or data migration and testing). Once you have automated/semi-automated Cassandra upgrades
in place, that is an easier path, but that company obviously hadn't invested there.

Sean Durity

-----Original Message-----
From: Michael Shuler <mshuler@pbandjelly.org> On Behalf Of Michael Shuler
Sent: Monday, June 17, 2019 8:26 AM
To: user@cassandra.apache.org
Subject: [EXTERNAL] Re: Cassandra migration from 1.25 to 3.x

First and foremost, read NEWS.txt from your current version to the version you wish to upgrade
to. There are too may details that you many need to be aware of. For instance, in the 2.0.0
Upgrading notes:

https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_apache_cassandra_blob_cassandra-2D3.11_NEWS.txt-23L1169-2DL1178&d=DwIDaQ&c=MtgQEAMQGqekjTjiAhkudQ&r=aC_gxC6z_4f9GLlbWiKzHm1vucZTtVYWDDvyLkh8IaQ&m=CPWy2XBaDFHzVDapNO4E7kLIFFfbkRd8KqftSrypjSU&s=D3Y18E9gxewpushCMETjHt9cS8lKvLMrhUdhPriF4Dk&e=

I assume you meant 1.2.5, so you're first step is to upgrade to at least
1.2.9 (I would suggest using latest 1.2.x, which is 1.2.19). Then you can to to 2.0.x and
up.

Practicing on a scratch cluster is valuable experience. Reading the upgrade notes in NEWS.txt
is a must.

--
Kind regards,
Michael

On 6/17/19 3:34 AM, Anurag Sharma wrote:
> Thanks Alex,
>
> I came across some interesting and efficient ways of upgrading from
> 1.x to 3.x as described in the blog here
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__medium.com_-40ro
> eezilkha_database-2Dmigration-2Dat-2Dscale-2Dae85c14c3621&d=DwIDaQ&c=M
> tgQEAMQGqekjTjiAhkudQ&r=aC_gxC6z_4f9GLlbWiKzHm1vucZTtVYWDDvyLkh8IaQ&m=
> CPWy2XBaDFHzVDapNO4E7kLIFFfbkRd8KqftSrypjSU&s=7ekpEXHT1Qm_xL9l6_1Kty32
> fDDerlB_PgO1-4K1-VQ&e= > and others. Was curious if someone has
> open-sourced their custom utility.  :D
>
> Regards
> Anurag
>
> On Mon, Jun 17, 2019 at 1:27 PM Oleksandr Shulgin
> <oleksandr.shulgin@zalando.de <mailto:oleksandr.shulgin@zalando.de>> wrote:
>
>     On Mon, Jun 17, 2019 at 9:30 AM Anurag Sharma
>     <anurag.rp.sharma@gmail.com <mailto:anurag.rp.sharma@gmail.com>> wrote:
>
>
>         We are upgrading Cassandra from 1.25 to 3.X. Just curious if
>         there is any recommended open source utility for the same.
>
>
>     Hi,
>
>     The "recommended  open source utility" is the Apache Cassandra
>     itself. ;-)
>
>     Given the huge difference between the major versions, though, you
>     will need a decent amount of planning and preparation to
>     successfully complete such a migration.  Most likely you will want
>     to do it in small steps, first upgrading to the latest minor version
>     in the 1.x series, then making a jump to 2.x, then to 3.0, and only
>     then to 3.x if you really mean to.  On each upgrade step, be sure to
>     examine the release notes carefully to understand if there is any
>     impact for your cluster and/or client applications.  Do have a test
>     system with preferably identical setup and configuration and execute
>     the upgrade steps there first to verify your expectations.
>
>     Good luck!
>     --
>     Alex
>


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