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From Dmitriy Setrakyan <dsetrak...@apache.org>
Subject Re: API for asynchronous execution.
Date Thu, 14 Apr 2016 17:10:14 GMT
Do we have a coding example for this functionality somewhere? It would be
nice to review the changes from usability standpoint.

On Thu, Apr 14, 2016 at 3:58 AM, Nikolay Tikhonov <ntikhonov@gridgain.com>
wrote:

> We are close to completing IGNITE-2004 ticket.
> As part this ticket was made the following changes on public API
> - if callback has @IgniteAsyncCallback annotation then callback should be
> run asynchronously
> - these callbacks are executed in special pool (callback thread pool) which
> is configured by IgniteConfiguration.asyncCallbackThreadPoolSize
>
> Any comments on this?
>
> On Wed, Mar 30, 2016 at 12:45 PM, Yakov Zhdanov <yzhdanov@gridgain.com>
> wrote:
>
> > I think this approach works unless user does not initiate number of
> > concurrent cache operations greater than MSG_QUEUE_SIZE.  Where msg queue
> > size default is 1024, but still configurable.
> >
> > Thanks!
> > --
> > Yakov Zhdanov, Director R&D
> > *GridGain Systems*
> > www.gridgain.com
> >
> > 2016-03-30 11:44 GMT+03:00 Vladimir Ozerov <vozerov@gridgain.com>:
> >
> > > Does it mean that if cache update rate is greater than filter execution
> > > rate, then at some point we will stop reading messages from socket? If
> > yes,
> > > then it seems we still cannot execute cache operations:
> > > 1) Filter starts cache operation for a key. Current node is backup for
> > this
> > > key.
> > > 2) Cache message is sent to primary node
> > > 3) Primary sends message back to current node.
> > > 4) Message is never read because of backpressure. Cache operation and
> > > filter never complete.
> > >
> > > Am I missing something?
> > >
> > > On Wed, Mar 30, 2016 at 11:23 AM, Yakov Zhdanov <yzhdanov@apache.org>
> > > wrote:
> > >
> > > > Vladimir,
> > > >
> > > > Communication should stop reading from connection is there are too
> many
> > > > unprocessed messages. Sender will be blocked on putting message to
> > queue.
> > > >
> > > > --Yakov
> > > >
> > > > 2016-03-30 11:11 GMT+03:00 Vladimir Ozerov <vozerov@gridgain.com>:
> > > >
> > > > > Guys,
> > > > >
> > > > > Can you explain how backpressure control is implemented? What if
> > event
> > > > > arrival speed is greater than filter processing speed?
> > > > >
> > > > > On Wed, Mar 30, 2016 at 10:37 AM, Semyon Boikov <
> > sboikov@gridgain.com>
> > > > > wrote:
> > > > >
> > > > > > Andrey,
> > > > > >
> > > > > > I agree that current situation with threading in Ignite is very
> > > > > > inconvenient when user callbacks execute some non-trivial code.
> But
> > > > > > changing this to async dispatch is huge refactoring, even
> changing
> > > this
> > > > > > just for continuous queries callback is not so easy task.
> > > > > >
> > > > > > We can start with
> > https://issues.apache.org/jira/browse/IGNITE-2004,
> > > > and
> > > > > > if
> > > > > > more users complains arise we can think about changing others
> parts
> > > of
> > > > > > system.
> > > > > >
> > > > > > For now we need decisions for these points:
> > > > > > - how to specify that callback should be run asynchronously
> > (Nikolay
> > > > > > suggested marker interface IgniteAsyncCallback, or
> > > > @IgniteAsyncCallback)
> > > > > > - where these callbacks are executed, AFAIK Nikolay added special
> > > pool
> > > > > > which is configured in IgniteConfiguration (something like
> > > > > > IgniteConfiguration.asyncCallbackThreadPoolSize)
> > > > > >
> > > > > > Regards
> > > > > >
> > > > > >
> > > > > > On Tue, Mar 29, 2016 at 10:45 PM, Andrey Kornev <
> > > > > andrewkornev@hotmail.com>
> > > > > > wrote:
> > > > > >
> > > > > > > Vladimir, Igniters
> > > > > > >
> > > > > > > Here are my 2 cents.
> > > > > > >
> > > > > > > The current situation with threading when it comes to executing
> > > user
> > > > > > > callbacks -- the CQ filters (either local or remote), the
CQ
> > > > listeners,
> > > > > > the
> > > > > > > event listeners, the messaging listeners, the entry processors
> > > (did I
> > > > > > miss
> > > > > > > anything?) -- is pretty sad. The callbacks may get executed
on
> a
> > > > system
> > > > > > > pool's thread, public pool's, utility pool's, discovery
worker
> > > > thread,
> > > > > > > application thread, to name a few. It causes a lot of grief
and
> > > > > > suffering,
> > > > > > > hard-to-fix races, dead locks and other bugs.
> > > > > > >
> > > > > > > I guess it's always possible to come up with a more or
less
> > > > reasonable
> > > > > > > explanation to such predicament (which usually boils down
to
> "It
> > is
> > > > so
> > > > > > > because this is how it's implemented"), but I, as a user,
could
> > not
> > > > > care
> > > > > > > less. I want consistency. I want all my callbacks (including
> > Entry
> > > > > > > Processors!) to be executed on the public pool's threads,
to be
> > > > > precise.
> > > > > > > This is not the first time I complain about this, and I
really
> > > think
> > > > > it's
> > > > > > > time to fix this mess.
> > > > > > >
> > > > > > > For a good example of how to implement ordered async dispatch
> of
> > > > > > callbacks
> > > > > > > on large scale, one only needs to look at Akka (or Reactor
> > > > > > > https://github.com/reactor/reactor).  Coherence also managed
> to
> > > get
> > > > it
> > > > > > > right (in my opinion, that is).
> > > > > > >
> > > > > > > Regards
> > > > > > > Andrey
> > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

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