Can we actually avoid any public API changes and do the following:
When a feature flag is present and there is a custom affinity function on
the server, send back the class name (or binary type id, if possible) of
the affinity function?
Then simply instantiate it on the client and call `partition(Object key)`
on it?
On Thu, Jul 7, 2022 at 8:32 PM Maxim Muzafarov <mmu...@apache.org> wrote:
> Pavel,
>
> Here is my thoughts.
>
> As I mentioned before, we will need only the
> AffinityFunction#partition(Object key) method for calculation on the
> client side due to all the partition-to-node mappings will be
> requested asynchronously from a server node how it is happening now
> for cache groups with the default affinity function. Thus setting the
> AffinityFunction looks on the client side redundant and it can be
> transformed to a simple ToInFunction<Object> interface.
>
> public interface ToIntFunction<Object> {
> int applyAsInt(Object key);
> }
>
> Another point that I'd like also to mention is that the cache already
> created in a cluster, so it will be better to eliminate the duplicate
> affinity function configuration (setting the number of partitions). It
> is fully possible to receive the number of partitions from a server
> node (the same way as it currently happening). Thus instead of the
> ToInFunction<Object> interface it will be better to use
> ToInBiFunction<Object, Integer>.
>
> public interface ToIntBiFunction<Object, Integer> {
> int applyAsInt(Object key, Integer parts);
> }
>
>
> I agree with you that "setPartitionAwarenessKeyMapper" may be is not
> good naming here, we can rename it and move it to the public API, of
> course.
>
> On Thu, 7 Jul 2022 at 20:06, Pavel Tupitsyn <ptupit...@apache.org> wrote:
> >
> > 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
> > > > >
> > > > >
> > >
>
