Denis, This is a subtle question. It looks like we have now a number of use-cases when persistent storage is required even for a pure in-memory mode. One of the use-cases is thin client authentication, the other is service grid configuration persistence.
Generally, I would agree that this is an expected behavior. However, this means that a user cannot simply start and stop nodes randomly anymore. Ignite start will require some sort of installation or work folder initialization (sort of initdb in postgres) which is ok for persistence-enabled modes, but I am not sure if this is expected for in-memory. Of course, we can run this initialization automatically, but it is not always a good idea. If we are ok to have this restrictions for in-memory mode, then service persistence makes sense. --AG 2018-04-11 22:36 GMT+03:00 Denis Magda <dma...@apache.org>: > Denis, > > I think that the service deployment state needs be persisted cluster-wide. > I guess that our meta-store is capable of doing so. Alex G., Vladimir, > could you confirm? > > As for the split-brain scenarios, I would put them aside for now because, > anyway, they have to be solved at lower levels (meta store, discovery, > etc.). > > Also, I heard that presently we store a service configuration in the system > cache that doesn't give us a way to deploy a new version of a service > without undeployment of the previous one. Will this issue be addressed by > the new deployment approach? > > -- > Denis > > On Wed, Apr 11, 2018 at 1:28 AM, Denis Mekhanikov <dmekhani...@gmail.com> > wrote: > > > Denis, > > > > Sounds reasonable. It's not clear, though, what should happen, if a > joining > > node has some services persisted, that are missing on other nodes. > > Should we deploy them? > > If we do so, it could lead to surprising behaviour. For example you could > > kill a node, undeploy a service, then bring back an old node, and it > would > > make the service resurrect. > > We could store some deployment counter along with the service > > configurations on all nodes, that would show how many times the service > > state has changed, i.e. it has been undeployed/redeployed. It should be > > kept for undeployed services as well to avoid situations like I > described. > > > > But it still leaves a possibility of incorrect behaviour, if there was a > > split-brain situation at some point. I don't think we should precess it > > somehow, though. If we choose to tackle it, it will overcomplicate things > > for a sake of a minor improvement. > > > > Denis > > > > вт, 10 апр. 2018 г. в 0:55, Valentin Kulichenko < > > valentin.kuliche...@gmail.com>: > > > > > I was responding to another Denis :) Agree with you on your point > though. > > > > > > -Val > > > > > > On Mon, Apr 9, 2018 at 2:48 PM, Denis Magda <dma...@apache.org> wrote: > > > > > > > Val, > > > > > > > > Guess we're talking about other situations. I'm bringing up the case > > > when a > > > > service was deployed dynamically and has to be brought up after a > full > > > > cluster restart w/o user intervention. To achieve this we need to > > persist > > > > the service's configuration somewhere. > > > > > > > > -- > > > > Denis > > > > > > > > On Mon, Apr 9, 2018 at 1:42 PM, Valentin Kulichenko < > > > > valentin.kuliche...@gmail.com> wrote: > > > > > > > > > Denis, > > > > > > > > > > EVT_CLASS_DEPLOYED should be fired every time a class is deployed > or > > > > > redeployed. If this doesn't happen in some cases, I believe this > > would > > > > be a > > > > > bug. I don't think we need to add any new events. > > > > > > > > > > -Val > > > > > > > > > > On Mon, Apr 9, 2018 at 10:50 AM, Denis Magda <dma...@apache.org> > > > wrote: > > > > > > > > > > > Denis, > > > > > > > > > > > > I would encourage us to persist a service configuration in the > meta > > > > store > > > > > > and have this capability enabled by default. That's essential for > > > > > services > > > > > > started dynamically. Moreover, we support similar behavior for > > > caches, > > > > > > indexes, and other DDL changes happened at runtime. > > > > > > > > > > > > -- > > > > > > Denis > > > > > > > > > > > > On Mon, Apr 9, 2018 at 9:34 AM, Denis Mekhanikov < > > > > dmekhani...@gmail.com> > > > > > > wrote: > > > > > > > > > > > > > Another question, that I would like to discuss is whether > > services > > > > > should > > > > > > > be preserved on cluster restarts. > > > > > > > > > > > > > > Currently it depends on persistence configuration. If > persistence > > > for > > > > > any > > > > > > > data region is enabled, then services will be persisted as > well. > > > This > > > > > is > > > > > > a > > > > > > > pretty strange way of configuring this behaviour. > > > > > > > I'm not sure, if anybody relies on this functionality right > now. > > > > Should > > > > > > we > > > > > > > support it at all? If yes, should we make it configurable? > > > > > > > > > > > > > > Denis > > > > > > > > > > > > > > пн, 9 апр. 2018 г. в 19:27, Denis Mekhanikov < > > > dmekhani...@gmail.com > > > > >: > > > > > > > > > > > > > > > Val, > > > > > > > > > > > > > > > > Sounds reasonable. I just think, that user should have some > way > > > to > > > > > > know, > > > > > > > > that new version of a service class was deployed. > > > > > > > > One way to do it is to listen to *EVT_CLASS_DEPLOYED. *I'm > not > > > > sure, > > > > > > > > whether it is triggered on class redeployment, though. If > not, > > > then > > > > > > > another > > > > > > > > event type should be added. > > > > > > > > > > > > > > > > I don't think, that a lot of people will implement their own > > > > > > > > *DeploymentSpi*-s, so we should make work with > > *UriDeploymentSpi* > > > > as > > > > > > > > comfortable as possible. > > > > > > > > > > > > > > > > Denis > > > > > > > > > > > > > > > > пт, 6 апр. 2018 г. в 23:40, Valentin Kulichenko < > > > > > > > > valentin.kuliche...@gmail.com>: > > > > > > > > > > > > > > > >> Yes, the class deployment itself has to be explicit. I.e., > > there > > > > has > > > > > > to > > > > > > > be > > > > > > > >> a manual step where user updates the class, and the exact > step > > > > > > required > > > > > > > >> would depend on DeploymentSpi implementation. But then > Ignite > > > > takes > > > > > > care > > > > > > > >> of > > > > > > > >> everything else - service redeployment and restart is > > automatic. > > > > > > > >> > > > > > > > >> Dmitriy Pavlov, all this is going to be disabled if > > > DeploymentSpi > > > > is > > > > > > not > > > > > > > >> configured. In this case service class definitions have to > be > > > > > deployed > > > > > > > on > > > > > > > >> local classpath and can't be updated in runtime. Just like > it > > > > works > > > > > > > right > > > > > > > >> now. > > > > > > > >> > > > > > > > >> -Val > > > > > > > >> > > > > > > > >> On Fri, Apr 6, 2018 at 10:20 AM, Dmitriy Setrakyan < > > > > > > > dsetrak...@apache.org > > > > > > > >> > > > > > > > > >> wrote: > > > > > > > >> > > > > > > > >> > On Fri, Apr 6, 2018 at 9:13 AM, Dmitry Pavlov < > > > > > > dpavlov....@gmail.com> > > > > > > > >> > wrote: > > > > > > > >> > > > > > > > > >> > > Hi Igniters, > > > > > > > >> > > > > > > > > > >> > > I like automatic redeploy which can be disabled by > config > > if > > > > > user > > > > > > > >> wants > > > > > > > >> > to > > > > > > > >> > > control this process. What do you think? > > > > > > > >> > > > > > > > > > >> > > > > > > > > >> > I do not think we should have anything automatic when it > > comes > > > > to > > > > > > > >> > deployment, everything should be explicit. However, if we > > use > > > > the > > > > > > > >> > deployment SPI, then a user should be able to do "hot" > > > redeploy, > > > > > > > where a > > > > > > > >> > new service will be deployed if the user drops an updated > > jar. > > > > > > > >> > > > > > > > > >> > We should not create anything new here. Ignite already > has a > > > > > > > deployment > > > > > > > >> SPI > > > > > > > >> > and it already works in a certain way. Let's not change > it. > > > > > > > >> > > > > > > > > >> > D. > > > > > > > >> > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
