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From Robert Coli <rc...@eventbrite.com>
Subject Re: Restart Cassandra automatically
Date Tue, 09 Feb 2016 21:41:02 GMT
On Tue, Feb 9, 2016 at 6:20 AM, <SEAN_R_DURITY@homedepot.com> wrote:

> Call me naïve, but we do use an in-house built program for keeping nodes
> started (based on a flag-check). The program is something that was written
> for all kinds of daemon processes here, not Cassandra specifically. The
> basic idea is that is runs a status check. If that fails, and the flag is
> set, start Cassandra. In my opinion, it has helped more than hurt us –
> especially with the very fragile 1.1 releases that were prone to heap
> problems.
>

Ok, you're naïve.. ;P

But seriously, think of this scenario :

1) Node A, responsible for range A-M, goes down due to hardware failure of
a disk in a RAID
2) Node B is put into service and is made responsible for A-M
3) Months pass
4) Node A comes back up, announces that it is responsible for A-M, and the
cluster agrees

Consistency is now permanently broken for any involved rows. Why doesn't it
(usually) matter?

It's not so much that you are naïve but that you are providing still more
support for the Coli Conjecture : "If you are using a distributed database
you probably do not care about consistency, even if you think you do." You
have repeatedly chosen Availability over Consistency and it has never had a
negative impact on your actual application.

=Rob

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