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From Eric Stevens <migh...@gmail.com>
Subject Re: Would we have data corruption if we bootstrapped 10 nodes at once?
Date Mon, 19 Oct 2015 15:48:49 GMT
It seems to me that as long as cleanup hasn't happened, if you
*decommission* the newly joined nodes, they'll stream whatever writes they
took back to the original replicas.  Presumably that should be pretty quick
as they won't have nearly as much data as the original nodes (as they only
hold data written while they were online).  Then as long as cleanup hasn't
happened, your cluster should have returned to a consistent view of the
data.  You can now bootstrap the new nodes again.

If you have done a cleanup, then the data is probably irreversibly
corrupted, you will have to figure out how to restore the missing data
incrementally from backups if they are available.

On Sun, Oct 18, 2015 at 10:37 PM Raj Chudasama <raj.chudasama@gmail.com>
wrote:

> In this can does it make sense to remove newly added nodes, correct the
> configuration and have them rejoin one at a time ?
>
> Thx
>
> Sent from my iPhone
>
> On Oct 18, 2015, at 11:19 PM, Jeff Jirsa <jeff.jirsa@crowdstrike.com>
> wrote:
>
> Take a snapshot now, before you get rid of any data (whatever you do,
> don’t run cleanup).
>
> If you identify missing data, you can go back to those snapshots, find the
> nodes that had the data previously (sstable2json, for example), and either
> re-stream that data into the cluster with sstableloader or copy it to a new
> host and `nodetool refresh` it into the new system.
>
>
>
> From: <burtonator2011@gmail.com> on behalf of Kevin Burton
> Reply-To: "user@cassandra.apache.org"
> Date: Sunday, October 18, 2015 at 8:10 PM
> To: "user@cassandra.apache.org"
> Subject: Re: Would we have data corruption if we bootstrapped 10 nodes at
> once?
>
> ouch.. OK.. I think I really shot myself in the foot here then.  This
> might be bad.
>
> I'm not sure if I would have missing data.  I mean basically the data is
> on the other nodes.. but the cluster has been running with 10 nodes
> accidentally bootstrapped with auto_bootstrap=false.
>
> So they have new data and seem to be missing values.
>
> this is somewhat misleading... Initially if you start it up and run
> nodetool status , it only returns one node.
>
> So I assumed auto_bootstrap=false meant that it just doesn't join the
> cluster.
>
> I'm running a nodetool repair now to hopefully fix this.
>
>
>
> On Sun, Oct 18, 2015 at 7:25 PM, Jeff Jirsa <jeff.jirsa@crowdstrike.com>
> wrote:
>
>> auto_bootstrap=false tells it to join the cluster without running
>> bootstrap – the node assumes it has all of the necessary data, and won’t
>> stream any missing data.
>>
>> This generally violates consistency guarantees, but if done on a single
>> node, is typically correctable with `nodetool repair`.
>>
>> If you do it on many  nodes at once, it’s possible that the new nodes
>> could represent all 3 replicas of the data, but don’t physically have any
>> of that data, leading to missing records.
>>
>>
>>
>> From: <burtonator2011@gmail.com> on behalf of Kevin Burton
>> Reply-To: "user@cassandra.apache.org"
>> Date: Sunday, October 18, 2015 at 3:44 PM
>> To: "user@cassandra.apache.org"
>> Subject: Re: Would we have data corruption if we bootstrapped 10 nodes
>> at once?
>>
>> An shit.. I think we're seeing corruption.. missing records :-/
>>
>> On Sat, Oct 17, 2015 at 10:45 AM, Kevin Burton <burton@spinn3r.com>
>> wrote:
>>
>>> We just migrated from a 30 node cluster to a 45 node cluster. (so 15 new
>>> nodes)
>>>
>>> By default we have auto_boostrap = false
>>>
>>> so we just push our config to the cluster, the cassandra daemons
>>> restart, and they're not cluster members and are the only nodes in the
>>> cluster.
>>>
>>> Anyway.  While I was about 1/2 way done adding the 15 nodes,  I had
>>> about 7 members of the cluster and 8 not yet joined.
>>>
>>> We are only doing 1 at a time because apparently bootstrapping more than
>>> 1 is unsafe.
>>>
>>> I did a rolling restart whereby I went through and restarted all the
>>> cassandra boxes.
>>>
>>> Somehow the new nodes auto boostrapped themselves EVEN though
>>> auto_bootstrap=false.
>>>
>>> We don't have any errors.  Everything seems functional.  I'm just
>>> worried about data loss.
>>>
>>> Thoughts?
>>>
>>> Kevin
>>>
>>> --
>>>
>>> We’re hiring if you know of any awesome Java Devops or Linux Operations
>>> Engineers!
>>>
>>> Founder/CEO Spinn3r.com
>>> Location: *San Francisco, CA*
>>> blog: http://burtonator.wordpress.com
>>> … or check out my Google+ profile
>>> <https://plus.google.com/102718274791889610666/posts>
>>>
>>>
>>
>>
>> --
>>
>> We’re hiring if you know of any awesome Java Devops or Linux Operations
>> Engineers!
>>
>> Founder/CEO Spinn3r.com
>> Location: *San Francisco, CA*
>> blog: http://burtonator.wordpress.com
>> … or check out my Google+ profile
>> <https://plus.google.com/102718274791889610666/posts>
>>
>>
>
>
> --
>
> We’re hiring if you know of any awesome Java Devops or Linux Operations
> Engineers!
>
> Founder/CEO Spinn3r.com
> Location: *San Francisco, CA*
> blog: http://burtonator.wordpress.com
> … or check out my Google+ profile
> <https://plus.google.com/102718274791889610666/posts>
>
>

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