From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 27 Sep 2018 12:04:46 +0300 From: Vladimir Davydov Subject: Re: [tarantool-patches] Re: [PATCH rfc] schema: add possibility to find and throw away dead replicas Message-ID: <20180927090446.i7gf22lqtzkvykal@esperanza> References: <20180921182503.14027-1-arkholga@tarantool.org> <20180926144658.dru6pw44e33nnnpi@esperanza> <20a60b35-1615-4b26-c0f6-032530ac3b1b@tarantool.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20a60b35-1615-4b26-c0f6-032530ac3b1b@tarantool.org> To: Olga Arkhangelskaia Cc: tarantool-patches@freelists.org, georgy@tarantool.org List-ID: On Thu, Sep 27, 2018 at 10:37:57AM +0300, Olga Arkhangelskaia wrote: > > > 26/09/2018 17:46, Vladimir Davydov пишет: > > On Fri, Sep 21, 2018 at 09:25:03PM +0300, Olga Arkhangelskaia wrote: > > > Adds possibility to get list of alive replicas in a replicaset, > > > prune from box.space_cluster those who is not considered as alive, > > > and if one has doubts see state of replicaset. > > > > > > Replica is considered alive if it is just added, its status after > > > timeout period is not stopped or disconnected. However it it has both > > > roles (master and replica) we consider such instance dead only if its > > > upstream and downstream status is stopped or disconnected. > > > > > > If replica is considered dead we can prune its uuid from _cluster space. > > > If one not sure if the replica is dead or is there is any activity on it > > > it is possible to list replicas with its role, status and lsn > > > statistics. > > > > > > If you have some ideas how else we can/should decide whether replica is dead > > > please share. > > > > > > Closes #3110 > > > --- > > > > > > https://github.com/tarantool/tarantool/issues/3110 > > > https://github.com/tarantool/tarantool/tree/OKriw/gh-3110-prune-dead-replica-from-replicaset-1.10 > > A documentation request with the new API description is missing. > > Tests don't pass on Travis CI. > > > > Regarding the code: > > > > 1. Why do you add a function that lists *alive* replicas? The issue > > author didn't ask for that. He asked for a script that would delete > > dead replicas from the _cluster system space. We might want to add a > > function that would list *dead* replicas so that he/she could check > > what replicas would be deleted (aka "dry run"), but it doesn't make > > sense to list alive replicas. > It is easy to change, but as I understood we need to throw away replica. How does it contradict what I said? > > > > 2. Dead replica detection is utterly ridiculuous: the functions sleeps > > for the given amount of time and then deletes inactive replicas. > > As a user, I'd want to have an ability to delete replicas that have > > been inactive for, say, a day. Does this mean that I have to wait > > for a whole day before this function completes? Obviously, no. > > I guess tarantool core should keep track of the time each replica > > was active > > So we need changes in core code? About lastt time of activity, what do you > mean? Lasn change, vclock, status? Real time when the replica was last active. > If replica is dead for long perion of time we can see its status. And as I > undestand we have heartbeat to monitor the connecion, so if there is > problems with it - we see status. Disconnected status only means that the replica is not available right now. We want to delete replicas that haven't been active for the specified amount of time, say a day or even a week. BTW, forgot to mention: this function should probably be defined in box.ctl. > > last time so that the function would work instantly. > > The time should probably be persisted so that restarts wouldn't > > affect the way the function works. >