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From Alexandr Kuramshin <ein.nsk...@gmail.com>
Subject Re: Add ability to enable and disable rebalancing per-node
Date Thu, 11 May 2017 07:12:32 GMT
to Nick,

could you please describe in more detail the use of DataStreamer (do you
use StreamReceiver)?

It seems that you've unnecessary care about synchronous service startup and
cache rebalance. Service should start quickly after node has joined the
topology, and will process all the data has been collected by local
partitions the moments before. You may use rebalance delay to minimize the
amount of collected data before the service has been be started.

But if your service depends on external resources (another service),
managing rebalance won't help you because external resource may get
unavailable even after your service gets started and rebalance has occur.
You can't unrebalance partitions in such the case. In addition, if some
event-cache should be supplied with other caches (storing additional data
for service processing), there is always the gap between rebalancing
partition of first and the last cache containing collocated data. I think
you should not worry about additional network calls while rebalancing in

to Sasha,

I think we need configuration property enablePartitionExchange (in addition
to MBean flag) to have an ability to disable partition exchange at node

2017-05-06 2:51 GMT+07:00 npordash <nickpordash@gmail.com>:

> I can outline a use-case I have which may help define requirements for this
> task. For context, I was originally going to try and address the below
> use-case by disabling automatic rebalancing on a per-cache basis and use a
> cluster-wide task to orchestrate manual rebalancing; however, this issue
> sounds like it may provide a better approach.
> I have caches setup for the sole purpose of routing data to nodes via a
> Data
> Streamer. The logic in the streamer is simply to access a plugin on the
> data
> node which exposes a processing pipeline and runs the received cache
> entries
> through it. The data in this case is monitoring related and there is one
> cache (or logical stream) per data type (f.e. logs, events, metrics).
> The pipeline is composed of N services which are deployed as node
> singletons
> and have a service filter which targets a particular cache. These services
> can be deployed and un-deployed as processing requirements change or bugs
> are fixed without requiring clients to know or care about it.
> The catch here is that when nodes are added I don't want map partitions to
> rebalance to a new node until I know all of the necessary services are
> running, otherwise we may have a small window where data is processed
> through a pipeline that isn't completely initialized yet which would result
> in a data quality issue. Alternatively, I could have the pipeline raise an
> error which would cause the streamer to retry, but I'd like this to be
> handled more gracefully, if possible.
> In addition, it will probably be the case were these caches eventually have
> node filters so that we can isolate resources for these streams across
> different computes. This means that, for example, if we add a node only for
> metrics then deferring rebalancing should ideally only impact caches that
> would get assigned to that node.
> Going even further... so far we've talked about one cache which is used
> just
> for streaming, but at least one of the services would create its own set of
> caches as an in-memory storage layer which maintains an inverted index and
> time series data for elements coming through the stream. The storage caches
> in this case would only exist on nodes where the stream cache is and most
> of
> the write activity to these caches would be local since they would use the
> same affinity as the stream cache (if most writes were remote this wouldn't
> scale well). So... these caches would need to rebalance at the same time in
> order to minimize the possibility of additional network calls.
> The main concern I have is how to avoid the race condition of another node
> joining the topology _after_ it has been determined rebalancing should
> happen, but _before_ rebalancing is triggered. If this is controlled on a
> per-node (+cache) basis - as the ticket describes - it's probably a
> non-issue, but it's definitely an issue if it's only on a per-cache basis.
> -Nick
> --
> View this message in context: http://apache-ignite-
> developers.2346864.n4.nabble.com/Add-ability-to-enable-and-
> disable-rebalancing-per-node-tp17494p17529.html
> Sent from the Apache Ignite Developers mailing list archive at Nabble.com.

Alexandr Kuramshin

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