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From Denis Mekhanikov <dmekhani...@gmail.com>
Subject Re: Reference of local service.
Date Sun, 01 Mar 2020 21:32:56 GMT
Vladimir, Slava,

In general, I like the idea of abstracting the service deployment from its
usage, but there are some backward-compatibility considerations that won't
let us do so.

Or we can declare usage of services without interfaces incorrect


I don't think we can introduce a requirement for all services to have an
interface, unfortunately. Such change can potentially break existing code,
since such requirement doesn't exist currently.
Moreover, I don't see a way of implementing such a check. Are you going to
look just for any interface? What about Serializable? Will it do?

Usage of a proxy instead of service instances can lead to performance
degradation for local instances, which is another argument against such
change.

I think, it will make sense to make all service invocations work through a
proxy in Ignite 3.
For now though the best thing we can do is to calculate remote invocations
only, since all of them go through a proxy.
Another option is to provide a simple way for a user to account the service
invocations themselves.

What do you guys think?

Denis


вт, 25 февр. 2020 г. в 16:50, Vyacheslav Daradur <daradurvs@gmail.com>:

> It is not a change of public API from my point of view.
>
> Also, there is a check to allow getting proxy only for an interface, not
> implementation.
>
> Denis, what do you think?
>
>
> вт, 25 февр. 2020 г. в 16:28, Vladimir Steshin <vladsz83@gmail.com>:
>
>> Vyacheslav, this is exactly what I found. I'm doing [1] (metrics for
>> services) and realized I have to wrap local calls by a proxy. Is it a
>> change of public API and should come with major release only? Or we can
>> declare usage of services without interfaces incorrect?
>> [1] https://issues.apache.org/jira/browse/IGNITE-12464
>>
>> вт, 25 февр. 2020 г. в 16:17, Vyacheslav Daradur <daradurvs@gmail.com>:
>>
>>> {IgniteServices#service(String name)} returns direct reference in the
>>> current implementation.
>>>
>>> So, class casting should work for your example:
>>> ((MyServiceImpl)ignite.services().service(“myService”)).bar();
>>>
>>> It is safer to use an interface instead of an implementation, there is
>>> no guarantee that in future releases direct link will be returned, a
>>> service instance might be wrapped for monitoring for example.
>>>
>>>
>>> On Tue, Feb 25, 2020 at 4:09 PM Vladimir Steshin <vladsz83@gmail.com>
>>> wrote:
>>>
>>>> Vyacheslav, Hi.
>>>>
>>>> I see. But can we consider 'locally deployed service' is a proxy too,
>>>> not direct reference? What if I need to wrap it? This would be local
>>>> service working via proxy or null.
>>>>
>>>> вт, 25 февр. 2020 г. в 16:03, Vyacheslav Daradur <daradurvs@gmail.com>:
>>>>
>>>>> Hi, Vladimir
>>>>>
>>>>> The answer is in API docs: "Gets *locally deployed service* with
>>>>> specified name." [1]
>>>>>
>>>>> That means {IgniteServices#service(String name)} returns only locally
>>>>> deployed instance or null.
>>>>>
>>>>> {IgniteServices#serviceProxy(…)} returns proxy to call instances
>>>>> across the cluster. Might be used for load-balancing.
>>>>>
>>>>> [1]
>>>>> https://github.com/apache/ignite/blob/56975c266e7019f307bb9da42333a6db4e47365e/modules/core/src/main/java/org/apache/ignite/IgniteServices.java#L569
>>>>>
>>>>> On Tue, Feb 25, 2020 at 3:51 PM Vladimir Steshin <vladsz83@gmail.com>
>>>>> wrote:
>>>>>
>>>>>> Hello, Igniters.
>>>>>>
>>>>>> Previous e-mail was with wrong topic 'daradurvs@gmail.com' :)
>>>>>>
>>>>>> I got a question what exactly IgniteServices#service(String name)
is
>>>>>> supposed to return: reference to the object or a proxy for some reason
like
>>>>>> IgniteServices#serviceProxy(…)? Vyacheslav D., can you tell me
your opinion?
>>>>>>
>>>>>> public interface MyService {
>>>>>>
>>>>>>                public void foo();
>>>>>>
>>>>>> }
>>>>>>
>>>>>> public class MyServiceImpl implements Service, MyService {
>>>>>>
>>>>>>                @Override public void foo(){ … }
>>>>>>
>>>>>>                public void bar(){ … };
>>>>>>
>>>>>> }
>>>>>>
>>>>>>
>>>>>> // Is it required to support
>>>>>>
>>>>>> MyServiceImpl srvc = ignite.services().service(“myService”);
>>>>>>
>>>>>> srvc.foo();
>>>>>>
>>>>>> srvc.bar();
>>>>>>
>>>>>>
>>>>>>
>>>>>> // Or is the only correct way:
>>>>>>
>>>>>> MyService srvc = ignite.services().service(“myService”);
>>>>>>
>>>>>> srvc.foo();
>>>>>>
>>>>>>
>>>>>
>>>>> --
>>>>> Best Regards, Vyacheslav D.
>>>>>
>>>>
>>>
>>> --
>>> Best Regards, Vyacheslav D.
>>>
>> --
> Best Regards, Vyacheslav D.
>

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