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From Vyacheslav Daradur <daradu...@gmail.com>
Subject Re: Support service on inactive cluster
Date Sat, 08 Dec 2018 16:24:14 GMT
Alexey,

If the question related only to Service Grid, I would say that it
shouldn't be difficult.

But there a lot of questions should be resolved before:
* public API is covered behind guards and user can't get services on
the inactive cluster (Ignite#services);
* service proxy's invocation processes via 'GridClosureProcessor', at
first sight, the processor does nothing on deactivation, so it
shouldn't be a problem (need deeper investigation);
* if service implementation based on Ignite's components, e.g. cache,
data-structures, streaming or something else, then it may become a
cause of unexpected behaviour.

I'd not like to allow end-users use of Service Grid after cluster
deactivation. But, if we are talking about internal service
implementation that means we know the possible pitfalls, then we are
able to introduce some flag to avoid the service cancellation on
cluster deactivation.

Regarding service's autostart, for both new and old implementations:
At current time services are not saved in metastore at node shutdown,
it means only statically configured services will be restored after
the restart.
It may be implemented in future.




On Sat, Dec 8, 2018 at 8:33 AM Alexey Kuznetsov <akuznetsov@apache.org> wrote:
>
> Denis,
>
> I'm thinking that we could have services that could do something useful
> even when cluster is deactivated.
> For example, I'm investigating how I can implement a Web Agent as a cluster
> singleton and I need that
> Web Agent should be always "on-line" and send telemetry to Web Console.
>
> Other users can also implement services that will do something useful even
> when cluster is deactivated.
>
> Make sense?
>
>
> On Sat, Dec 8, 2018 at 1:04 AM Denis Magda <dmagda@apache.org> wrote:
>
> > Alex,
> >
> > 1. Why do you need an operational service if the cluster is deactivated (no
> > changes to data are allowed, right)?
> >
> > 2. That should be covered in the existing EIP
> >
> > --
> > Denis
> >
> > On Fri, Dec 7, 2018 at 6:20 AM Alexey Kuznetsov <akuznetsov@apache.org>
> > wrote:
> >
> > > Igniters,
> > >
> > > I would like to discuss how we can support following features for
> > Service:
> > >
> > > 1) Made  services work on deactivated cluster. What we need for that?
> > >     Introduce some flag on service configuration?
> > >
> > > 2) Auto start service after full cluster restart if service was started
> > at
> > > runtime.
> > > Can we have also add some flag on service configuration?
> > >  And store such services the same way as we store user information for
> > > authentication in metastorage?
> > >
> > > What do yo think?
> > >
> > > I can create issues in JIRA if we agreed to support them.
> > >
> > > --
> > > Alexey Kuznetsov
> > >
> >
>
>
> --
> Alexey Kuznetsov



--
Best Regards, Vyacheslav D.

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