Testing netsplit in Riak

Andrey Ershov andrershov at gmail.com
Wed Feb 22 14:17:43 EST 2017

Alexander, thanks for your reply!

1) I've set erlang.distribution.nettick_time to 1 second and writes after
netsplit are very fast now. So this point is resolved. Do you know how this
parameter affects false positive ratio? Riak docs stay that every
nettick_time seconds netkernal will initiate remote processes
life-checking. However, it does not say anything about the mechanism. Do
you know how this failure detector works?
2) As for hinted handoff, I still can not find any solution. Variables that
I've tried to change:
   - vnode_management_timer from 10s to 1s
   - transfer_limit from 2 to 100
But still transfer take about a minute. Any other variables that I should
take a look at?

2017-02-22 21:12 GMT+03:00 Alexander Sicular <siculars at basho.com>:

> 1. Check the erlang vm variable "nettick", I believe.
> 2. Hinted handoff resource allocation are configurable via config file or
> at runtime.
> On Wed, Feb 22, 2017 at 12:07 Andrey Ershov <andrershov at gmail.com> wrote:
>> Hi, guys!
>> I'm testing netsplit in Riak and can not achieve satisfiable behaviour.
>> I've just two nodes cluster and bucket with the following settings n=3,
>> w=2, r=2. And I have just a couple of entries.
>> Basically I have two problems:
>> 1) After the split, writes on one side of the partition start lagging
>> hard. It takes more than 1 minute for the first write to be become
>> successful. I understand that this is related to the process of setting up
>> backup vnodes in Riak, but is any way to speed up the process?  Which
>> configuration parameters influence that?
>> 2) More weird problem is after netsplit. "riak-admin transfers" command
>> immediately reports that there should 5 partition transfers from one node
>> to another and 5 partition transfers in the opposite direction. But active
>> transfers output is empty!
>> I've put a watch on this command and active transfers are always empty.
>> Finally, it takes several minutes for Riak to finish hinted handoff.
>> Several minutes just for several keys!
>> What Riak is doing all this time? Anyway to speed up the process?
>> 3) The reason why I'm concerned about hinted-handoff speed is because, I
>> noticed that until this process finishes, I read stale data on both sides
>> of ex-netsplit.
>> --
>> Thanks,
>> Andrey
>> _______________________________________________
>> riak-users mailing list
>> riak-users at lists.basho.com
>> http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
> --
> Alexander Sicular
> Solutions Architect
> Basho Technologies
> 9175130679
> @siculars

С уважением,
Ершов Андрей
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