Maxim,
I am confused. We were talking about a custom Affinity Function.
As you noted, AffinityKeyMapper is deprecated, why do we add something
named "setPartitionAwarenessKeyMapper"?
Internal API approach is hacky.
IMO we should either develop a proper feature with a good public API, or
not add anything at all.
On Thu, Jul 7, 2022 at 6:34 PM Maxim Muzafarov <mmu...@apache.org> wrote:
> Folks,
>
>
> Thank you for your comments.
>
> First of all, I'd like to point out that if the cache is created with
> a custom affinity function or the legacy AffinityKeyMapper interface,
> the thin client should be able to provide only a `key-to-partition`
> mapping function to handle the case described above. The
> `partition-to-node` mappings the client will receive from a server
> node it connected to. This will simplify a bit the final solution.
>
> ==================
>
> I've checked your suggestions and it looks like both of them have some
> sufficient drawbacks:
>
> 1. Using SystemProperty looks really hacky and we are explicitly
> complicate a thin client configuration for an end user.
>
> 2. Extending the ClientCacheConfiguration is a very good and
> straightforward idea, however it doesn't fit the case described above.
> Caches previously created with custom affinity functions/key mappers
> already present in the cluster, so in this case we are forcing a user
> to store an additional ClientCacheConfiguration. This is not good. The
> cache.getOrCreate(cfg) method will also be used and fire in turn
> CACHE_GET_OR_CREATE_WITH_CONFIGURATION request which is not necessary
> here. For this case using cache.name(str) is only enough.
>
> ==================
>
> I propose the following two solutions that looks very promising:
>
> 3. Extending cache create methdos with a ClientCacheContext in the
> IgniteClient interface. This context will contain all additional cache
> attributes like custom cache affinity mappers that map cache keys to
> partitions if a custom affinity was used on the server side (note that
> all partition-to-node mappings will be received by thin client from a
> server node).
>
> interface IgniteClientEx extends IgniteClient {
> ClientCache<K, V> name(String name, ClientCacheContext cctx);
> ClientCache<K, V> getOrCreateCache(String name, ClientCacheContext
> cctx);
> ClientCache<K, V> getOrCreateCache(ClientCacheConfiguration cfg,
> ClientCacheContext cctx);
> }
>
> class ClientCacheContext {
> setPartitionAwarenessKeyMapper(ToIntBiFunction<Object, Integer>
> mapper);
> }
>
> 4. Use the same approach as the IgniteCache interface does for the
> same things - adding withPartitionAwarenessKeyMapper() to the
> interface. This method will allow to configure the thin client
> execution behaviour for the partition awareness feature by setting a
> custom cache key mapper.
>
> ==================
>
> I've used the 4-th solution due to it brings much less source code to
> the Apache Ignite codebase and looks a bit simpler to configure for a
> user. I've also move the withPartitionAwarenessKeyMapper() method to
> an internal API interface which still solves a user issue with the
> partition awareness, but also specifies that the custom mapping
> function and deprecated AffinityKeyMapper should not be used, in
> general.
>
> Please, take a look at my patch:
>
> https://issues.apache.org/jira/browse/IGNITE-17316
> https://github.com/apache/ignite/pull/10140/files
>
>
> On Fri, 1 Jul 2022 at 14:41, Pavel Tupitsyn <ptupit...@apache.org> wrote:
> >
> > I have no objections to extending the Thin Client configuration with a
> > pluggable Affinity Function.
> > Let's make it a normal Java setter though, system properties are hacky.
> > Especially when only some of the caches use custom affinity, as Maxim
> > mentioned.
> >
> > On Wed, Jun 29, 2022 at 7:20 PM Николай Ижиков <nizhi...@apache.org>
> wrote:
> >
> > > +1 to have ability to specify custom affinity for PA on thin client.
> > >
> > > It seems to me custom affinity is a rare use-case of Ignite API.
> > > Propose to have SystemProperty that can specify affinity implementation
> > > for a thin client.
> > >
> > >
> > > > 29 июня 2022 г., в 18:53, Maxim Muzafarov <mmu...@apache.org>
> > > написал(а):
> > > >
> > > > Igniters,
> > > >
> > > >
> > > > I've faced with a customer's cluster which has more than 150 nodes
> and
> > > > most for them are the thick-client nodes. Due to each thick-client is
> > > > a full-fledged cluster topology participant it affects the cluster
> > > > discovery machinery during the system operation and adding an
> > > > additional overhead for using/deploying a new nodes in Kubernetes
> > > > environment. However, the main thing from my point of view it
> prevents
> > > > updating the client side and server side components independently
> > > > (Apache Ignite doesn't support rolling upgrade).
> > > >
> > > > Accordingly to the assumptions above using thin clients become a
> > > > necessary. This looks even more attractive, since the thin client has
> > > > a fairly rich API over the past few releases.
> > > >
> > > >
> > > > The MAIN ISSUE here that blocks thin client usage is that for some of
> > > > cache groups a custom affinity function (and an AffinityKeyMapper)
> was
> > > > used which prevents enabling the Partition Awareness thin client
> > > > feature. Thus each cache request will have two hops.
> > > >
> > > > Of course, we can force users to migrate to a new API, but this
> > > > becomes more difficult when Apache Ignite is part of a much larger
> > > > architectural solution and thus it is doent' looks so friendly.
> > > >
> > > > The MAIN QUESTION here - does anyone know our users who have
> > > > encountered with the same issue? I want to solve such a problem once
> > > > and make all such users happy by implementing the general approach.
> > > >
> > > >
> > > > = Possible solutions =
> > > >
> > > >
> > > > 1. Making an affinity function pluggable (mapping calculations) on
> the
> > > > thin clients side. Currently the RendezvousAffinityFunction [1] is
> > > > only supported
> > > > for the partition awareness. A user's affinity function seems to be
> > > > the stateless function due to there is no machinery to transfer
> states
> > > > to the thin client.
> > > >
> > > > Pros - a general solution for all such cases;
> > > > Cons - unnecessary complexity, extending public API;
> > > >
> > > >
> > > > 2. Creating an Ignite extension which will extend the thin client API
> > > > thus a user will have a full control over a destination node to which
> > > > requests being sent.
> > > >
> > > > Pros - isolated solution, simple implementation;
> > > > Cons - hard to support spring-boot-thin-client etc. and other
> > > > extensions based on the thin client API;
> > > >
> > > >
> > > > Folks, please share your thoughts.
> > > >
> > > >
> > > > [1]
> > >
> https://github.com/apache/ignite/blob/master/modules/core/src/main/java/org/apache/ignite/internal/processors/platform/client/cache/ClientCachePartitionsRequest.java#L206
> > >
> > >
>
