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From Sergey Chugunov <sergey.chugu...@gmail.com>
Subject Re: Baseline auto-adjust`s discuss
Date Fri, 25 Jan 2019 12:17:35 GMT
Anton,

As I understand from the IEP document policy was supposed to support two
timeouts: soft and hard, so here you're proposing a bit simpler
functionality.

Just to clarify, do I understand correctly that this feature when enabled
will auto-adjust blt on each node join/node left event, and timeout is
necessary to protect us from blinking nodes?
So no complexities with taking into account number of alive backups or
something like that?

On Fri, Jan 25, 2019 at 1:11 PM Vladimir Ozerov <vozerov@gridgain.com>
wrote:

> Got it, makes sense.
>
> On Fri, Jan 25, 2019 at 11:06 AM Anton Kalashnikov <kaa.dev@yandex.ru>
> wrote:
>
> > Vladimir, thanks  for your notes, both of them looks good enough but I
> > have two different thoughts about it.
> >
> > I think I agree about enabling only one of manual/auto adjustment. It is
> > easier than current solution and in fact as extra feature  we can allow
> > user to force task to execute(if they doesn't want to wait until timeout
> > expired).
> > But about second one I don't sure that one parameters instead of two
> would
> > be more convenient. For example: in case when user changed timeout and
> then
> > disable auto-adjust after then when someone will want to enable it they
> > should know what value of timeout was before auto-adjust was disabled. I
> > think "negative value" pattern good choice for always usable parameters
> > like timeout of connection (ex. -1 equal to endless waiting) and so on,
> but
> > in our case we want to disable whole functionality rather than change
> > parameter value.
> >
> > --
> > Best regards,
> > Anton Kalashnikov
> >
> >
> > 24.01.2019, 22:03, "Vladimir Ozerov" <vozerov@gridgain.com>:
> > > Hi Anton,
> > >
> > > This is great feature, but I am a bit confused about automatic
> disabling
> > of
> > > a feature during manual baseline adjustment. This may lead to
> unpleasant
> > > situations when a user enabled auto-adjustment, then re-adjusted it
> > > manually somehow (e.g. from some previously created script) so that
> > > auto-adjustment disabling went unnoticed, then added more nodes hoping
> > that
> > > auto-baseline is still active, etc.
> > >
> > > Instead, I would rather make manual and auto adjustment mutually
> > exclusive
> > > - baseline cannot be adjusted manually when auto mode is set, and vice
> > > versa. If exception is thrown in that cases, administrators will always
> > > know current behavior of the system.
> > >
> > > As far as configuration, wouldn’t it be enough to have a single long
> > value
> > > as opposed to Boolean + long? Say, 0 - immediate auto adjustment,
> > negative
> > > - disabled, positive - auto adjustment after timeout.
> > >
> > > Thoughts?
> > >
> > > чт, 24 янв. 2019 г. в 18:33, Anton Kalashnikov <kaa.dev@yandex.ru>:
> > >
> > >>  Hello, Igniters!
> > >>
> > >>  Work on the Phase II of IEP-4 (Baseline topology) [1] has started. I
> > want
> > >>  to start to discuss of implementation of "Baseline auto-adjust" [2].
> > >>
> > >>  "Baseline auto-adjust" feature implements mechanism of auto-adjust
> > >>  baseline corresponding to current topology after event join/left was
> > >>  appeared. It is required because when a node left the grid and nobody
> > would
> > >>  change baseline manually it can lead to lost data(when some more
> nodes
> > left
> > >>  the grid on depends in backup factor) but permanent tracking of grid
> > is not
> > >>  always possible/desirible. Looks like in many cases auto-adjust
> > baseline
> > >>  after some timeout is very helpfull.
> > >>
> > >>  Distributed metastore[3](it is already done):
> > >>
> > >>  First of all it is required the ability to store configuration data
> > >>  consistently and cluster-wide. Ignite doesn't have any specific API
> for
> > >>  such configurations and we don't want to have many similar
> > implementations
> > >>  of the same feature in our code. After some thoughts is was proposed
> to
> > >>  implement it as some kind of distributed metastorage that gives the
> > ability
> > >>  to store any data in it.
> > >>  First implementation is based on existing local metastorage API for
> > >>  persistent clusters (in-memory clusters will store data in memory).
> > >>  Write/remove operation use Discovery SPI to send updates to the
> > cluster, it
> > >>  guarantees updates order and the fact that all existing (alive) nodes
> > have
> > >>  handled the update message. As a way to find out which node has the
> > latest
> > >>  data there is a "version" value of distributed metastorage, which is
> > >>  basically <number of all updates, hash of updates>. All updates
> history
> > >>  until some point in the past is stored along with the data, so when
> an
> > >>  outdated node connects to the cluster it will receive all the missing
> > data
> > >>  and apply it locally. If there's not enough history stored or joining
> > node
> > >>  is clear then it'll receive shapshot of distributed metastorage so
> > there
> > >>  won't be inconsistencies.
> > >>
> > >>  Baseline auto-adjust:
> > >>
> > >>  Main scenario:
> > >>          - There is grid with the baseline is equal to the current
> > topology
> > >>          - New node joins to grid or some node left(failed) the grid
> > >>          - New mechanism detects this event and it add task for
> changing
> > >>  baseline to queue with configured timeout
> > >>          - If new event are happened before baseline would be changed
> > task
> > >>  would be removed from queue and new task will be added
> > >>          - When timeout are expired the task would try to set new
> > baseline
> > >>  corresponded to current topology
> > >>
> > >>  First of all we need to add two parameters[4]:
> > >>          - baselineAutoAdjustEnabled - enable/disable "Baseline
> > >>  auto-adjust" feature.
> > >>          - baselineAutoAdjustTimeout - timeout after which baseline
> > should
> > >>  be changed.
> > >>
> > >>  This parameters are cluster wide and can be changed in real time
> > because
> > >>  it is based on "Distributed metastore". On first time this parameters
> > would
> > >>  be initiated by corresponded
> parameters(initBaselineAutoAdjustEnabled,
> > >>  initBaselineAutoAdjustTimeout) from "Ignite Configuration". Init
> value
> > >>  valid only before first changing of it after value would be changed
> it
> > is
> > >>  stored in "Distributed metastore".
> > >>
> > >>  Restrictions:
> > >>          - This mechanism handling events only on active grid
> > >>          - If baselineNodes != gridNodes on activate this feature
> would
> > be
> > >>  disabled
> > >>          - If lost partitions was detected this feature would be
> > disabled
> > >>          - If baseline was adjusted manually on baselineNodes !=
> > gridNodes
> > >>  this feature would be disabled
> > >>
> > >>  Draft implementation you can find here[5]. Feel free to ask more
> > details
> > >>  and make suggestions.
> > >>
> > >>  [1]
> > >>
> >
> https://cwiki.apache.org/confluence/display/IGNITE/IEP-4+Baseline+topology+for+caches
> > >>  [2] https://issues.apache.org/jira/browse/IGNITE-8571
> > >>  [3] https://issues.apache.org/jira/browse/IGNITE-10640
> > >>  [4] https://issues.apache.org/jira/browse/IGNITE-8573
> > >>  [5] https://github.com/apache/ignite/pull/5907
> > >>
> > >>  --
> > >>  Best regards,
> > >>  Anton Kalashnikov
> >
>

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