Ivan, My opinion the ASYNC rebalancing is a best approach for off-loading 3-d party store, and it provides consistency.
+1 for deprecation of NONE in the next release - ignore NONE and use ASYNC instead For those who require absence of rebalancing for some reason still be possible to use rebalanceDelay=infinity. +1 for removal of rebalanceMode in 3.0. Note what we still require SYNC logic internally for system cache in some places. вт, 21 июл. 2020 г. в 15:59, Ivan Pavlukhin <vololo...@gmail.com>: > Alexey, > > Thank you for explanation. I feel that I miss a couple bits to > understand the picture fully. I am thinking about a case which I tend > to call a Memcached use-case. There is a cache over underlying storage > with read-through and expiration and without any rebalancing at all. > When new nodes enter they take ownership for some partitions from > already running nodes and serve client requests. Entries for not > owning anymore partitions expire according to configuration. > > Actually, I have an idea. My guess is that "rebalancing" is a smarter > and better approach than waiting for expiration. Am I right? > > 2020-07-21 15:31 GMT+03:00, Alexey Goncharuk <alexey.goncha...@gmail.com>: > > Ivan, > > > > In my understanding this mode does not work at all even in the presence > of > > ForceKeysRequest which is now supposed to fetch values from peers in case > > of a miss. In this mode we 1) move partitions to OWNING state > > unconditionally, and 2) choose an arbitrary OWNING node for force keys > > request. Therefore, after a user started two additional nodes in a > cluster, > > the request may be mapped to a node which does not hold any data. We will > > do a read-through in this case, but it will result in significant load > > increase on a third-party storage right after a node started, which means > > that adding a node will increase, not decrease, the load on the database > > being cached. > > All these issues go away when (A)SYNC mode is used. > > > > Val, > > The idea makes sense to me - a user can use rebalance future to wait for > > rebalance to finish. This will simplify the configuration even further. > > > > пн, 20 июл. 2020 г. в 21:27, Valentin Kulichenko < > > valentin.kuliche...@gmail.com>: > > > >> +1 for deprecating/removing NONE mode. > >> > >> Alexey, what do you think about the SYNC mode? In my experience, it does > >> not add much value as well. I would go as far as removing the > >> rebalancingMode parameter altogether (probably in 3.0). > >> > >> -Val > >> > >> On Mon, Jul 20, 2020 at 11:09 AM Ivan Pavlukhin <vololo...@gmail.com> > >> wrote: > >> > >> > Alexey, Igniters, > >> > > >> > Could you please outline motivation answering following questions? > >> > 1. Does this mode generally work correctly today? > >> > 2. Can this mode be useful at all? > >> > > >> > I can imagine that it might be useful in a transparent caching use > >> > case (if I did not misunderstand). > >> > > >> > 2020-07-20 20:39 GMT+03:00, Pavel Tupitsyn <ptupit...@apache.org>: > >> > > +1 > >> > > > >> > > More evidence: > >> > > > >> > > >> > https://stackoverflow.com/questions/62902640/apache-ignite-cacherebalancemode-is-not-respected-by-nodes > >> > > > >> > > On Mon, Jul 20, 2020 at 8:26 PM Alexey Goncharuk > >> > > <alexey.goncha...@gmail.com> > >> > > wrote: > >> > > > >> > >> Igniters, > >> > >> > >> > >> I would like to run the idea of deprecating and probably ignoring > >> > >> the > >> > >> NONE > >> > >> rebalance mode by the community. It's in the removal list for > Ignite > >> 3.0 > >> > >> [1], but it looks like it still confuses and creates issues for > >> > >> users > >> > >> [2]. > >> > >> > >> > >> What about deprecating it in one of the next releases and even > >> ignoring > >> > >> this constant in further releases, interpreting it as ASYNC, before > >> > >> Ignite > >> > >> 3.0? I find it hard to believe that any Ignite user actually has > >> > >> RebalanceMode.NONE set in their configuration due to its absolutely > >> > >> unpredictable behavior. > >> > >> > >> > >> Thanks for your thoughts, > >> > >> --AG > >> > >> > >> > >> [1] > >> > >> > >> > >> > >> > > >> > https://cwiki.apache.org/confluence/display/IGNITE/Apache+Ignite+3.0+Wishlist > >> > >> [2] > >> > >> > >> > >> > >> > > >> > http://apache-ignite-developers.2346864.n4.nabble.com/About-Rebalance-Mode-SYNC-amp-NONE-td47279.html > >> > >> > >> > > > >> > > >> > > >> > -- > >> > > >> > Best regards, > >> > Ivan Pavlukhin > >> > > >> > > > > > -- > > Best regards, > Ivan Pavlukhin > -- Best regards, Alexei Scherbakov
