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From Alex Plehanov <plehanov.a...@gmail.com>
Subject [DISCUSSION] Consistency across java thin/thick APIs
Date Fri, 21 Aug 2020 09:33:01 GMT
Hello, Igniters!

Since we touched on the subject of consistency across thin/thick APIs in
thread [1] I would like to continue the discussion here.

Currently, thick and thin APIs look similar but have no common parents. A
set of ClientCache methods is almost a subset of IgniteCache methods, but
these interfaces are fully independent. So we can't build common
abstraction which can work with ClientCache and IgniteCache without code
duplication. For example, we have ignite-spring-data module, to make it
thin-client compliant we should copy-paste all cache methods invocations.

It's impossible to make thin and thick interfaces absolutely identical and
we can't extend one from another since there thick and thin specific
methods needed, but we can move common methods to the parent interface. But
here is another problem: exceptions. Thick methods declared as throwing
IgniteException and IgniteCheckedException, but all thin-client interfaces
use ClientException. Without common exceptions for thin and thick clients,
we can't build common parent interface.

Currently, only a small amount of thick interfaces can be fully reused by
thin-client (Queries, IgniteBinary, ClusterNode)

Also, I would like to discuss JCache support by thin-client. We already use
some of JCache specification for thin-client, but not fully support JCache.
For example, we use Cache.Entry for queries and JCache expiration policies
in public thin-client API (also, some of JCache interfaces are used by the
internal implementation).

I've tried to implement POC for continuous queries for java thin client,
but without JCache support API looks weird. On the one hand, we should use
CacheEntryEventFilter (JCache interface) since it's required by the
server-side, on the other hand, we can't use CacheEntryUpdatedListener
since it requires CacheEntryEvent which requires an instance of Cache
(JCache interface), which doesn't exist on the thin-client side.

We have plans to change public API in Ignite 3.0, perhaps it makes sense to
make thick and thin API consistent. WDYT?
What about JCache support by thin-client in Ignite 3.0?
Please, share your thoughts.


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