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Re: [DISCUSS] changing default token behavior for 4.0


Also agree it should be lowered, but definitely not to 1, and probably something closer to 32 than 4.

-- 
Jeff Jirsa


> On Sep 21, 2018, at 8:24 PM, Jeremy Hanna <jeremy.hanna1234@xxxxxxxxx> wrote:
> 
> I agree that it should be lowered. What I’ve seen debated a bit in the past is the number but I don’t think anyone thinks that it should remain 256.
> 
>> On Sep 21, 2018, at 7:05 PM, Jonathan Haddad <jon@xxxxxxxxxxxxx> wrote:
>> 
>> One thing that's really, really bothered me for a while is how we default
>> to 256 tokens still.  There's no experienced operator that leaves it as is
>> at this point, meaning the only people using 256 are the poor folks that
>> just got started using C*.  I've worked with over a hundred clusters in the
>> last couple years, and I think I only worked with one that had lowered it
>> to something else.
>> 
>> I think it's time we changed the default to 4 (or 8, up for debate).
>> 
>> To improve the behavior, we need to change a couple other things.  The
>> allocate_tokens_for_keyspace setting is... odd.  It requires you have a
>> keyspace already created, which doesn't help on new clusters.  What I'd
>> like to do is add a new setting, allocate_tokens_for_rf, and set it to 3 by
>> default.
>> 
>> To handle clusters that are already using 256 tokens, we could prevent the
>> new node from joining unless a -D flag is set to explicitly allow
>> imbalanced tokens.
>> 
>> We've agreed to a trunk freeze, but I feel like this is important enough
>> (and pretty trivial) to do now.  I'd also personally characterize this as a
>> bug fix since 256 is horribly broken when the cluster gets to any
>> reasonable size, but maybe I'm alone there.
>> 
>> I honestly can't think of a use case where random tokens is a good choice
>> anymore, so I'd be fine / ecstatic with removing it completely and
>> requiring either allocate_tokens_for_keyspace (for existing clusters)
>> or allocate_tokens_for_rf
>> to be set.
>> 
>> Thoughts?  Objections?
>> -- 
>> Jon Haddad
>> http://www.rustyrazorblade.com
>> twitter: rustyrazorblade
> 
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