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From Maxim Muzafarov <maxmu...@gmail.com>
Subject Re: {DISCUSSION] Cluster read-only mode.
Date Mon, 03 Jun 2019 17:14:59 GMT
Sergey,

Do we have an IEP for this feature?

What should happen when on an active cluster with put operations if we
receive a read-only state change request? How we guarantee that all
cache operations delivered (or not yet) to backups are not rejected by
applied read-only request? I haven't found such tests in your PR.

I've downloaded your branch and run some tests locally. I've tried
DataStreamer cache loads (allowOverwrite mode false) with a concurrent
cluster change state request to read-only mode and I've got strange
behaviour. My test scenario was:
1) Start DataStremer cache load;
2) change cluster to read-only state;
3) change state back to normal;

When the state has been changed to `read-only` I've flooded with a lot
of `Failed to perform cache operation (cluster is in read-only mode)`
errors, but when I've reverted the state back the DataStreamer
continue its load without any error. I think we should not allow such
behaviour. We should cancel the DataStreamer task or allow it to be
finished.

On Fri, 31 May 2019 at 13:00, Sergey Antonov <antonovsergey93@gmail.com> wrote:
>
> Hello, Zhenya, Maxim!
>
> Thank you for your replies!
>
> >> Should we also allow writes to the DistributedMetaStorage and if not why?
> Yes. DistributedMetastorage available for updates with enabled read-only
> mode. I added test about it to ClusterReadOnlyModeSelfTest
>
> >> What's the purpose for ignite-sys-cache updates still be available ?
> ignite-sys-cache is using in the different subcomponents, for example,
> security.
>
> чт, 30 мая 2019 г. в 20:30, Zhenya Stanilovsky <arzamas123@mail.ru.invalid>:
>
> > hi, Sergey.
> > What's the purpose for ignite-sys-cache updates still be available ?
> >
> > thanks !
> >
> > > Hello Igniters!
> > >
> > > I'm working on cluster read-only mode [1] feature. In this mode cluster
> > > will be available only for read operations, all data modification
> > > operations in user caches will be rejected
> > > with ClusterReadOnlyModeCheckedException. This feature could be helpfull
> > > for maintenance works (control.sh idle_verify/validate_indexes).
> > >
> > > A few points about cluster read-only mode:
> > > 1) Read-only mode could be enabled on active cluster only.
> > > 2) Read-only mode doens't store on PDS (i.e. after cluster restart
> > > enabled
> > > read-only mode will be forgotten)
> > > 3) Updates to ignite-sys-cache will be available with enabled read-only
> > > mode.
> > >
> > > More informartion about implementation you could find in PR [2].
> > >
> > > What do you think about this feature?
> > >
> > > [1] https://issues.apache.org/jira/browse/IGNITE-11256
> > > [2] https://github.com/apache/ignite/pull/6423
> >
>
>
> --
> BR, Sergey Antonov

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