Multiple nodes leaving cluster
dmiller at dimagi.com
Wed Feb 8 07:59:24 EST 2017
Thanks Magnus and Shaun, that's very helpful.
On Wed, Feb 8, 2017 at 4:00 AM, Magnus Kessler <mkessler at basho.com> wrote:
> On 7 February 2017 at 23:25, Daniel Miller <dmiller at dimagi.com> wrote:
>> Hi Riak Users,
>> In the documentation
>> <http://docs.basho.com/riak/kv/2.2.0/using/admin/commands/#leave> for riak-admin
>> cluster leave it says “You can stage multiple leave command before
>> planning/committing.” This implies that it is safe to stage multiple nodes
>> leaving the cluster simultaneously. Is that true? Will all data in the
>> cluster be continuously available during the removal period if, for
>> example, I setup and commit a plan for 3 nodes to be leave a 9-node cluster
>> (assuming there is enough space for the data on the remaining 6 nodes)?
>> I had asked a similar question on IRC a couple weeks ago. In that case I
>> was asking about replacing multiple nodes simultaneously using riak-admin
>> cluster replace. The answer I got there left some doubt in my mind as to
>> whether it is safe (i.e., will not result in a period data availability) to
>> have multiple nodes leaving the cluster at once. The documentation for
>> replace implies that it is safe to replace multiple nodes simultaneously as
>> well: “You can stage multiple replace actions before planning/committing.”
>> Note that I am not asking about force-remove or force-replace, which I
>> would expect to result in permanent data loss if multiple nodes are
>> force-removed/replaced simultaneously.
>> My cluster is running Riak 2.1.1 with standard nval of 3.
> Hi Daniel,
> Yes, staging several riak-admin cluster leave steps before riak-admin
> cluster commit is safe. The leaving nodes will perform an ownership
> handoff of all their partitions to other nodes in the cluster before
> shutting themselves down. While this is happening, these nodes remain in
> the cluster as fully functional nodes. The same is true for riak-admin
> cluster replace.
> The reason we recommend staging of multiple leave or join operations is
> that this minimises reshuffling data throughout the cluster. Only set of
> ownership handoffs needs to happen, whereas if you were to perform several
> consecutive leave or join operations, on each commit a substantial amount
> of handoffs throughout the cluster is needed.
> Kind Regards,
> Magnus Kessler
> Client Services Engineer
> Basho Technologies Limited
> Registered Office - 8 Lincoln’s Inn Fields London WC2A 3BP Reg 07970431
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