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From Nikolay Izhikov <nizhi...@apache.org>
Subject Re: {DISCUSSION] Cluster read-only mode.
Date Tue, 04 Jun 2019 10:52:03 GMT
Hello, Dmitriy.

I don't agree with you.

IEP should be written for any big changes in product.
We should have it for:

1. Following contributors.
2. History of decision making.
3. Easier documenting.

Without IEPs our product will become a total mess.

In the Apache Kafka one can't change any public API without KIP(Kafka improvement proposal).
I think it's a good practice.


В Вт, 04/06/2019 в 13:43 +0300, Dmitriy Pavlov пишет:
> Folks,
> 
> Sorry for offtopic. IEP is a good tool for case design is discussed before
> any implementation available. It is a good place to share the intent to do
> something and provide some details. It is a better place then mile-long
> emails.
> 
> For now, we have code and documentation later should be updated. I don't
> think we need to create IEP.
> 
> Sincerely,
> Dmitriy Pavlov
> 
> вт, 4 июн. 2019 г. в 12:16, Павлухин Иван <vololo100@gmail.com>:
> 
> > Sergey, Igniters,
> > 
> > Sorry if my question is not very smart.
> > 
> > I am trying to think about it from a perspective of a (newbie) user.
> > And from the first glance it is not clear how a read-only cluster is
> > different from a not active cluster? What is a fundamental difference
> > between them? Can we combine two modes into one? If not we will need a
> > clear explanation for a user.
> > 
> > пн, 3 июн. 2019 г. в 20:15, Maxim Muzafarov <maxmuzaf@gmail.com>:
> > > 
> > > 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
> > 
> > 
> > 
> > --
> > Best regards,
> > Ivan Pavlukhin
> > 

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