In my opinion and experience, this isn’t a real problem, since you define a list of seeds as the first few nodes you add to a cluster. When would you add a node to an existing cluster and mark itself as a seed? It’s neither practical or something you’d do by accident.
> On Feb 23, 2018, at 10:17 AM, Jeff Jirsa <jji...@gmail.com> wrote: > > > On Fri, Feb 23, 2018 at 10:12 AM, Oleksandr Shulgin > <oleksandr.shul...@zalando.de <mailto:oleksandr.shul...@zalando.de>> wrote: > On Fri, Feb 23, 2018 at 7:02 PM, Jeff Jirsa <jji...@gmail.com > <mailto:jji...@gmail.com>> wrote: > Yes, seeds don't bootstrap. But why? I don't think I ever seen a > comprehensive explanation of this. > > The meaning of seed in the most common sense is "connect to this host, and > use it as the starting point for adding this node to the cluster". > > If you specify that a joining node is the seed, the implication is that it's > already a member of the cluster (or, alternatively, authoritative on the > cluster's state). Given that implication, why would it make sense to then > proceed to bootstrap? By setting it as a seed, you've told it that it already > knows what the cluster is. > > Well, there is certain logic in that. However, bootstrap is about streaming > in the data, isn't it? And being seed is about knowing the topology, i.e. > which nodes exist in the cluster. There is actually 0 overlap of these two > concerns, so I don't really see why a seed node shouldn't be able to > bootstrap. Would it break anything if it could, e.g. if you're explicit > about it and request auto_boostrap=true? > > > I dont *think* it would break anything, but the more obvious answer is just > not to list the node as a seed if it needs to bootstrap. > > This comes up a lot, and it's certainly one of those rough operator edges > that we can do better with. There's no strict requirement to have all of the > seeds exactly the same in a cluster, so if you need to bootstrap a new seed, > just join it with it not a seed, then bounce it to make it think it's a seed > after it's joined. > > The easier answer is probably "give people a way to change seeds after > they're running", and it sorta exists, but it's hard to invoke intentionally. > We should just make that easier, and the rough edges will get a little less > rough.
