All,
The best solution I see so far is to add a new method to filters and interceptors for the NIO case. There are a couple of important advantages in doing this:
(1) The runtime time can inform a filter the processing mode (NIO or not) depending on which method is called
(2) Existing filters/interceptors can be extended for NIO and some of their logic re-used
(3) The parameter to these new methods (typically a context) can be custom crafted for NIO (thus avoiding strange runtime exceptions due to misuse).
This pattern could potentially be applied to readers/writers, but I haven’t really thought about that much —code re-usability there seems very useful too.
— Santiago
> On Mar 20, 2017, at 8:11 AM, Pavel Bucek <pavel.bucek_at_oracle.com> wrote:
>
> Yes, that's how I think about it. I do see backwards compatibility (even when it causes possible performance loss) as a must have.
>
> We had a discussion about FIlters and Interceptors with Santiago a there will need to be some changes, for example Interceptor is an interceptor of MessageBodyReader/Writer readFrom/writeTo, which are slightly different now, so we either need to introduce new interfaces or provide another way of doing what interceptor does.
>
> I don't have this in a shareable form yet, but please expect an update. Of course, any comments or suggestions are very welcomed (really, the whole non blocking support is not an easy task) ;)
>
> Best regards,
> Pavel
>
>
> On 19/03/2017 23:40, Sergey Beryozkin wrote:
>> Right, so the new API is for supporting NIO flows. People will have NIO
>> and not NIO centric services, JAX-RS 2.0 applications will not be
>> rewritten overnight to use NIO.
>> So, lets say we have a JAX-RS 2.0 LoggingFilter. Do you envisage it
>> continuing logging 2.1 service requests, wrapped if needed, so that the
>> users will not be forced to rewrite it just because a service
>> implementation decided to use NIO ?
>>
>> Thanks, Sergey
>>
>> On 16/03/17 14:00, Pavel Bucek wrote:
>>> I'm not sure whether I got what you really mean, but there shouldn't
>>> be a need for having LoggingFilter and NioLoggingFilter.
>>>
>>> Once non-blocking support is added and released, you'll just rewrite
>>> LoggingFilter to use new API. If there is any blocking filter in the
>>> chain, implementation would need to wrap Source/Sink/Processor into
>>> input/output stream(s).
>>>
>>> Pavel
>>>
>>> On 15/03/2017 16:43, Sergey Beryozkin wrote:
>>>> Sorry, meant to say having LoggingFilter and NioLoggingFilter etc
>>>> will not be ideal...
>>>>
>>>> Sergey
>>>> On 15/03/17 15:37, Sergey Beryozkin wrote:
>>>>> I guess if we have new NIO filters then we'd need to decide how the
>>>>> existing filters, example, Logging ones, would work alongside,
>>>>> asking users to write the filters which do the generic processing of
>>>>> input/output streams should still work even if the service code is
>>>>> optimized to do NIO ?
>>>>>
>>>>> Thanks, Sergey
>>>>> On 15/03/17 15:32, Sergey Beryozkin wrote:
>>>>>> Hi Santiago
>>>>>> On 15/03/17 13:06, Santiago Pericas-Geertsen wrote:
>>>>>>> Hi Sergey,
>>>>>>>
>>>>>>>>>> Please see
>>>>>>>>>> https://github.com/pavelbucek/jax-rs/blob/nio/examples/src/main/java/jaxrs/examples/nio/ServerSideProcessing.java
>>>>>>>>>> There are several methods added on Filters and interceptors,
>>>>>>>>>> which add the similar functionality as are added for resource
>>>>>>>>>> methods and Body Readers/Writers.
>>>>>>>>> The pattern used in filters and interceptors feels a bit
>>>>>>>>> strange, and perhaps not inline with the rest of the API. In
>>>>>>>>> particular,
>>>>>>>>>
>>>>>>>>> static class RequestInterceptor implements ReaderInterceptor {
>>>>>>>>> @Override
>>>>>>>>> public Object aroundReadFrom(ReaderInterceptorContext
>>>>>>>>> context) throws IOException, WebApplicationException {
>>>>>>>>>
>>>>>>>>> // we might need an Executor/ExecutorService when
>>>>>>>>> creating a processor
>>>>>>>>>
>>>>>>>>> context.addProcessor(PROCESSOR);
>>>>>>>>> return context.proceed();
>>>>>>>>> }
>>>>>>>>> }
>>>>>>>>>
>>>>>>>>> is not really filtering, but instead it is constructing a
>>>>>>>>> “flow” pipeline by adding one processor. I think this is
>>>>>>>>> because, even though we defined NIO readers/writers, we are
>>>>>>>>> trying to re-use the existing non-NIO filters and interceptors.
>>>>>>>> Can that (custom) PROCESSOR be added implicitly so that the user
>>>>>>>> do not have to write the boilerplate filters
>>>>>>> Possibly, but I’m not sure how would that fit with the rest of
>>>>>>> the API.
>>>>>>>
>>>>>>>>> If I need a NIO filter, why not define one directly (a type
>>>>>>>>> extending processor) and associate it with the NIO resource
>>>>>>>>> method as we do with normal filters? I see challenges doing this
>>>>>>>>> too, but it seems more natural to me.
>>>>>>>> Can you clarify please ? Having Nio filters in addition to all of
>>>>>>>> the existing filters/interceptors is indeed can become 'noisy’.
>>>>>>> NIO processing is very different from normal request processing.
>>>>>>> It just a feels a bit odd to call one of the existing filters or
>>>>>>> interceptors only for the purpose of “setting up” a flow pipeline
>>>>>>> (i.e., adding a processor). I think a filter/interceptor will be
>>>>>>> for NIO or it won’t.
>>>>>> I have to admit that now that I think about it I don't really
>>>>>> understand why NIO filters are needed ? We have new
>>>>>> NIOReader/Writer which are good.
>>>>>> What would dedicated NIO filters do in reality but adding the
>>>>>> custom processors ? Sorry, I thought I'd clarify before continuing
>>>>>> with either supporting or not supporting the introduction of NIP
>>>>>> specific filters :-)
>>>>>>
>>>>>>>> Would it make sense to have an annotation like
>>>>>>>> @Nio(MyProcessor.class) which would tell the runtime it would
>>>>>>>> need to add an interceptor which would exactly what Pavel
>>>>>>>> prototyped above ?
>>>>>>> Would that be on the resource method? We can, but that is not
>>>>>>> the way we associate filters/interceptors today: we define them
>>>>>>> globally or use name binding to associate them with resource methods.
>>>>>> I thought a bit more, @NIO annotation introducing is not a good
>>>>>> idea, Pavel mentioned that of course the custom Processors would
>>>>>> likely need the executors and other customizations, so it won't
>>>>>> help much.
>>>>>>
>>>>>> Thanks, Sergey
>>>>>>
>>>>>>> — Santiago
>>>>>>>
>>>>>>>>>> On 10/03/2017 18:16, Markus KARG wrote:
>>>>>>>>>>> Pavel,
>>>>>>>>>>> maybe I missed it, but is it planned to also provide a
>>>>>>>>>>> non-blocking replacement for the InputStream / OutputStream
>>>>>>>>>>> methods of Filters and other streaming components?
>>>>>>>>>>> Thanks
>>>>>>>>>>> -Markus
>>>>>>>>>>> From: Pavel Bucek [mailto:pavel.bucek_at_oracle.com]
>>>>>>>>>>> Sent: Dienstag, 7. März 2017 15:26
>>>>>>>>>>> To: jsr370-experts_at_jax-rs-spec.java.net
>>>>>>>>>>> Subject: NIO API review / request for feedback
>>>>>>>>>>> Dear EG members,
>>>>>>>>>>>
>>>>>>>>>>> please allow me to share the direction of what we are thinking
>>>>>>>>>>> about JAX-RS NIO support.
>>>>>>>>>>>
>>>>>>>>>>> As stated before, SSE wasn't the only place were Flow APIs
>>>>>>>>>>> should be utilized - NIO is another area where it can be
>>>>>>>>>>> utilized quite heavily. And that was mostly the main idea - to
>>>>>>>>>>> see where it does make sense to use that.
>>>>>>>>>>>
>>>>>>>>>>> Similarly to SSE, there is a plan to minimize / extract the
>>>>>>>>>>> Flow to different classes, but there should always be a clear
>>>>>>>>>>> path how to convert an instance into Flow.* (or
>>>>>>>>>>> org.reactivestreams.*) interfaces. It is not done yet, to keep
>>>>>>>>>>> things as clear as possible.
>>>>>>>>>>>
>>>>>>>>>>> One of the bigger concerns is backwards compatibility. There
>>>>>>>>>>> are interfaces, which do work directly with Input/Output
>>>>>>>>>>> stream, which is always a problem for reactive processing,
>>>>>>>>>>> since it is blocking by design. The specification will need to
>>>>>>>>>>> say something like "The runtime is non-blocking as long as the
>>>>>>>>>>> application code doesn't read from a provided InputStream or
>>>>>>>>>>> doesn't set an OutputStream."
>>>>>>>>>>>
>>>>>>>>>>> The motivation for doing this is to allow the JAX-RS apps to
>>>>>>>>>>> be non-blocking and reactive. JAX-RS 2.0 entity handling is
>>>>>>>>>>> designed around reading / producing Input / Output Stream,
>>>>>>>>>>> which is blocking by design. Non-blocking approach should
>>>>>>>>>>> result in higher throughput and better resource utilization of
>>>>>>>>>>> the server. Also, integration and coexistence with modern
>>>>>>>>>>> reactive frameworks should be possible to do without losing
>>>>>>>>>>> the advantage of having that framework (which was almost
>>>>>>>>>>> completely lost when dealing with blocking inputs/outputs).
>>>>>>>>>>>
>>>>>>>>>>> Let's jump into code snippets.
>>>>>>>>>>>
>>>>>>>>>>> Server - EX1 (byte handling):
>>>>>>>>>>>
>>>>>>>>>>> Snippet below shows how to process request entity body return
>>>>>>>>>>> response entity body, using Publisher<ByteBuffer> - no
>>>>>>>>>>> MessageBodyReader/Writer is involved. This can be used as a
>>>>>>>>>>> low-level integration point for other frameworks, which are
>>>>>>>>>>> also reactive and will do the processing, like
>>>>>>>>>>> serializing/deserializing (mapping) to some java type,
>>>>>>>>>>> filtering, etc. Returning a Publisher<ByteBuffer> is a
>>>>>>>>>>> reactive/nio alternative to javax.ws.rs.core.StreamingOutput,
>>>>>>>>>>> consuming an entity using Publisher<ByteBuffer> is a
>>>>>>>>>>> reactive/nio alternative to consuming entity as an InputStream.
>>>>>>>>>>>
>>>>>>>>>>> @POST
>>>>>>>>>>> @Path("/ex1")
>>>>>>>>>>> public Flow.Publisher<ByteBuffer>
>>>>>>>>>>> ex1(Flow.Publisher<ByteBuffer> entity) {
>>>>>>>>>>> Ex1Processor processor = new Ex1Processor();
>>>>>>>>>>> entity.subscribe(processor);
>>>>>>>>>>> return processor;
>>>>>>>>>>> }
>>>>>>>>>>> // ex1 processor
>>>>>>>>>>> public static class Ex1Processor implements
>>>>>>>>>>> Flow.Processor<ByteBuffer, ByteBuffer> {
>>>>>>>>>>> // ...
>>>>>>>>>>> }
>>>>>>>>>>> And there is already an issue, which is not clearly solved.
>>>>>>>>>>>
>>>>>>>>>>> Returning a Publisher instance from the resource method does
>>>>>>>>>>> put some constraints on the Publisher itself - it needs to
>>>>>>>>>>> cache all events which will be emitted prior subscription of
>>>>>>>>>>> the jax-rs implementation Subscriber instance (which is the
>>>>>>>>>>> only way how to get the data from a Publisher).
>>>>>>>>>>>
>>>>>>>>>>> This can be solved by stating that request entity publisher
>>>>>>>>>>> won't produce any events until the resource method is invoked
>>>>>>>>>>> and the implementation Subscriber subscribed to the returned
>>>>>>>>>>> response entity publisher. Or the resource method can return
>>>>>>>>>>> Consumer<Flow.Subscriber<ByteBuffer>>, which would effectively
>>>>>>>>>>> grant control of the implementation subscription process. Any
>>>>>>>>>>> comments or suggestions welcomed [ref Q1].
>>>>>>>>>>>
>>>>>>>>>>> Server - EX2 (consuming stream of pojos):
>>>>>>>>>>>
>>>>>>>>>>> The next example should be slightly more straightforward. It
>>>>>>>>>>> shows how to process a Publisher of custom type, in this case
>>>>>>>>>>> called "POJO".
>>>>>>>>>>>
>>>>>>>>>>> The only limitation or rule here would be that the subscriber
>>>>>>>>>>> for the request entity must be subscribed before the resource
>>>>>>>>>>> method "ex2" invocation ends.
>>>>>>>>>>>
>>>>>>>>>>> New interface is introduced here - NioBodyReader. It has
>>>>>>>>>>> exactly the same responsibility as good old MessageBodyReader,
>>>>>>>>>>> but without using a blocking OutputStream to write the entity.
>>>>>>>>>>> Note that the "core" type is the Publisher<ByteBuffer>, which
>>>>>>>>>>> is in this case mapped (or converted) into Publisher of POJOs.
>>>>>>>>>>>
>>>>>>>>>>> @POST
>>>>>>>>>>> @Path("/ex2")
>>>>>>>>>>> @Consumes(MediaType.APPLICATION_JSON)
>>>>>>>>>>> public void ex2(Flow.Publisher<POJO> entity,
>>>>>>>>>>> @Suspended AsyncResponse response) {
>>>>>>>>>>> // TODO: introduce a helper or modify AsyncResponse to
>>>>>>>>>>> support this pattern directly?
>>>>>>>>>>> entity.subscribe(
>>>>>>>>>>> // POJO subscriber - consumer
>>>>>>>>>>> new Flow.Subscriber<POJO>() {
>>>>>>>>>>> @Override
>>>>>>>>>>> public void onSubscribe(Flow.Subscription
>>>>>>>>>>> subscription) {
>>>>>>>>>>> // ...
>>>>>>>>>>> }
>>>>>>>>>>> @Override
>>>>>>>>>>> public void onNext(POJO item) {
>>>>>>>>>>> // ...
>>>>>>>>>>> }
>>>>>>>>>>> @Override
>>>>>>>>>>> public void onError(Throwable throwable) {
>>>>>>>>>>> response.resume(throwable);
>>>>>>>>>>> }
>>>>>>>>>>> @Override
>>>>>>>>>>> public void onComplete() {
>>>>>>>>>>> response.resume(Response.ok().build());
>>>>>>>>>>> }
>>>>>>>>>>> }
>>>>>>>>>>> );
>>>>>>>>>>> }
>>>>>>>>>>> @Provider
>>>>>>>>>>> @Consumes(MediaType.APPLICATION_JSON)
>>>>>>>>>>> public static class Ex2NioBodyReader implements
>>>>>>>>>>> NioBodyReader<POJO> {
>>>>>>>>>>> @Override
>>>>>>>>>>> public boolean isReadable(Class<?> type, Type
>>>>>>>>>>> genericType, Annotation[] annotations, MediaType mediaType) {
>>>>>>>>>>> return true;
>>>>>>>>>>> }
>>>>>>>>>>> @Override
>>>>>>>>>>> public Flow.Publisher<POJO>
>>>>>>>>>>> readFrom(Flow.Publisher<ByteBuffer> entity,
>>>>>>>>>>> Class<POJO> type,
>>>>>>>>>>> Type genericType,
>>>>>>>>>>> Annotation[] annotations,
>>>>>>>>>>> MediaType mediaType,
>>>>>>>>>>> MultivaluedMap<String, String> httpHeaders) {
>>>>>>>>>>> Ex2MappingProcessor mappingProcessor = new
>>>>>>>>>>> Ex2MappingProcessor();
>>>>>>>>>>> entity.subscribe(mappingProcessor);
>>>>>>>>>>> return mappingProcessor;
>>>>>>>>>>> }
>>>>>>>>>>> }
>>>>>>>>>>> // mapping Publisher<ByteBuffer> to Publisher<POJO>
>>>>>>>>>>> // ByteBuffers are expected to contain JSON (indicated by
>>>>>>>>>>> @Consumes on the resource method and NioBodyReader).
>>>>>>>>>>> public static class Ex2MappingProcessor implements
>>>>>>>>>>> Flow.Subscriber<ByteBuffer>, Flow.Publisher<POJO> {
>>>>>>>>>>> // ...
>>>>>>>>>>> }
>>>>>>>>>>> Same issue as [Q1] is valid for this as well - same solution
>>>>>>>>>>> will need to be applied for "readFrom" method.
>>>>>>>>>>> Another issue is about what should be passed to "isReadable"
>>>>>>>>>>> method as "type" parameter. I'm not exactly sure whether we
>>>>>>>>>>> can safely obtain generic type of a parameter from the
>>>>>>>>>>> resource method (public void ex2(Flow.Publisher< POJO> entity,
>>>>>>>>>>> ..)). Any comments/suggestions welcomed [ref Q2].
>>>>>>>>>>>
>>>>>>>>>>> Note that using @Suspended shouldn't be enforced here; it
>>>>>>>>>>> should be possible to return a Response directly and still be
>>>>>>>>>>> able to consume the requestentity.
>>>>>>>>>>>
>>>>>>>>>>> Server - EX3 (producing list of POJOs):
>>>>>>>>>>>
>>>>>>>>>>> The last (for now) example shows how we can produce and write
>>>>>>>>>>> POJOs. Resource method doesn't take any parameters and
>>>>>>>>>>> provides a Publisher of POJO objects, which will be converted
>>>>>>>>>>> to JSON in NioBodyWriter. NioBodyReader is a reactive
>>>>>>>>>>> alternative to MessageBodyReader from older version of the
>>>>>>>>>>> specification.
>>>>>>>>>>>
>>>>>>>>>>> @GET
>>>>>>>>>>> @Path("/ex3")
>>>>>>>>>>> @Produces(MediaType.APPLICATION_JSON)
>>>>>>>>>>> public Flow.Publisher<POJO> ex3() {
>>>>>>>>>>> Flow.Publisher<POJO> pojoPublisher = null;
>>>>>>>>>>> // source of the POJO "stream" can be anything -
>>>>>>>>>>> database call, client call to
>>>>>>>>>>> // another service, ...
>>>>>>>>>>> //
>>>>>>>>>>> // DB
>>>>>>>>>>> // .getEmployees(department) //
>>>>>>>>>>> StreamPublisher<EmployeeDbModel> -- reactive stream
>>>>>>>>>>> // .map((Function<EmployeeDbModel,
>>>>>>>>>>> EmployeeToReturn>) employeeDbModel -> {
>>>>>>>>>>> // // ...
>>>>>>>>>>> // });
>>>>>>>>>>> return pojoPublisher;
>>>>>>>>>>> }
>>>>>>>>>>> @Provider
>>>>>>>>>>> @Produces(MediaType.APPLICATION_JSON)
>>>>>>>>>>> public static class Ex3NioBodyWriter implements
>>>>>>>>>>> NioBodyWriter<POJO> {
>>>>>>>>>>> @Override
>>>>>>>>>>> public boolean isWriteable(Class<?> type, Type
>>>>>>>>>>> genericType, Annotation[] annotations, MediaType mediaType) {
>>>>>>>>>>> return true;
>>>>>>>>>>> }
>>>>>>>>>>> @Override
>>>>>>>>>>> public void writeTo(Flow.Publisher<POJO>
>>>>>>>>>>> entityObjectPublisher,
>>>>>>>>>>> Flow.Subscriber<ByteBuffer> subscriber,
>>>>>>>>>>> Class<?> type,
>>>>>>>>>>> Type genericType,
>>>>>>>>>>> Annotation[] annotations,
>>>>>>>>>>> MediaType mediaType,
>>>>>>>>>>> MultivaluedMap<String, Object>
>>>>>>>>>>> httpHeaders) {
>>>>>>>>>>> // map Publisher<POJO> to Publisher<ByteBuffer> and
>>>>>>>>>>> subscribe Flow.Subscriber<ByteBuffer> to it.
>>>>>>>>>>> }
>>>>>>>>>>> }
>>>>>>>>>>> Resource method is minimalistic, [Q1] applies here as well.
>>>>>>>>>>>
>>>>>>>>>>> The example introduces NioBodyWriter and its isWriteable
>>>>>>>>>>> method does have [Q2], similarly to NioBodyReader. #writeTo
>>>>>>>>>>> doesn't have any issues - [Q1] is mitigated there because the
>>>>>>>>>>> implementation passes a supplier to the implementation - there
>>>>>>>>>>> doesn't need to be anything returned. Something similar might
>>>>>>>>>>> be able to do for NioBodyWriter as well.
>>>>>>>>>>>
>>>>>>>>>>> Comment to writing multiple POJO instances:
>>>>>>>>>>> https://github.com/pavelbucek/jax-rs/blob/bfc5b3d6caecab2f6304f92ac7b44a7ad6a5fdff/jaxrs-api/src/main/java/javax/ws/rs/ext/NioBodyWriter.java#L82
>>>>>>>>>>>
>>>>>>>>>>> Important point to mention is that even when producing
>>>>>>>>>>> multiple instances, the intention here is still to return the
>>>>>>>>>>> single HTTP response.
>>>>>>>>>>>
>>>>>>>>>>> ===
>>>>>>>>>>>
>>>>>>>>>>> We have more, but this email is already too long - I will post
>>>>>>>>>>> more after there is some feedback on the presented concepts
>>>>>>>>>>> and issues. Please let us know if this format is OK or if
>>>>>>>>>>> you'd prefer something else - I guess I could do a screencast,
>>>>>>>>>>> hangout or something similar.
>>>>>>>>>>>
>>>>>>>>>>> Source links:
>>>>>>>>>>>
>>>>>>>>>>> - complete server example:
>>>>>>>>>>> https://github.com/pavelbucek/jax-rs/blob/bfc5b3d6caecab2f6304f92ac7b44a7ad6a5fdff/examples/src/main/java/jaxrs/examples/nio/NioResource.java
>>>>>>>>>>> - client (to be discussed):
>>>>>>>>>>> https://github.com/pavelbucek/jax-rs/blob/bfc5b3d6caecab2f6304f92ac7b44a7ad6a5fdff/examples/src/main/java/jaxrs/examples/nio/NioClient.java
>>>>>>>>>>> - server side processing (including interceptors):
>>>>>>>>>>> https://github.com/pavelbucek/jax-rs/blob/bfc5b3d6caecab2f6304f92ac7b44a7ad6a5fdff/examples/src/main/java/jaxrs/examples/nio/ServerSideProcessing.java
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> (Not including direct link to individual examples, since we
>>>>>>>>>>> will continue working on them...)
>>>>>>>>>>>
>>>>>>>>>>> Looking forward to your feedback!
>>>>>>>>>>>
>>>>>>>>>>> Thanks and regards,
>>>>>>>>>>> Pavel & Santiago
>>>>>>
>