By looking at the suggested 5.0 examples I was able to get an
AsyncServerExchangeHandler subclass to play nicely with Kotlin coroutines
on the AsyncDataProducer side of things, i.e. minimizing produce() polling
and avoiding buffering.
I haven't been as successful with throttling calls on the AsyncDataConsumer
side, i.e. consume() calls keep being made even though the capacity window
has gone negative. I think this might be the expected behavior because of
this comment in AbstractHttp1StreamDuplexer:
// At present the consumer can be forced to consume data
// over its declared capacity in order to avoid having
// unprocessed message body content stuck in the session
// input buffer
Does that refer to just the case where the capacity starts positive but
data exceeding the capacity is delivered to consume()? Or does it refer to
the behavior I see, which is that capacity updates (or the lack of them)
don't seem to have any effect for HTTP/1.1?
I've also tried running the Http1IntegrationTest.testSlowResponseConsumer()
test, substituting this line to trigger updateCapacity() calls:
client.start(Http1Config.custom().setBufferSize(256).setInitialWindowSize(32).build());
By adding the small initial window, I can see the capacityWindow going more
and more negative on each consume() call with all the data buffered before
the test code completes its first sleep.
I don't have a specific use case for a slow consumer, just want to know if
I'm misunderstanding something.
Thanks!
Roy
On Fri, Sep 6, 2019 at 10:15 AM Roy Hashimoto <roy.hashim...@gmail.com>
wrote:
> Those are good leads, I'll pursue them.
>
> Thanks!
> Roy
>
> On Fri, Sep 6, 2019 at 9:57 AM Oleg Kalnichevski <ol...@apache.org> wrote:
>
>> On Fri, 2019-09-06 at 09:43 -0700, Ryan Schmitt wrote:
>> > Have you looked at the reactive extensions for HttpCore5? They
>> > demonstrate
>> > how to implement AsyncEntityProducer/AsyncDataProducer with support
>> > for
>> > backpressure (or you can just use the Reactive Streams API instead):
>> >
>> >
>>
>> https://github.com/apache/httpcomponents-core/tree/master/httpcore5-reactive/src/main/java/org/apache/hc/core5/reactive
>> >
>> >
>>
>> Just a bit of background. In 5.0 one can no longer assume that one
>> message exchange has exclusive ownership of the underlying connection.
>> Multiplexed message exchanges in HTTP/2 and piplelined message
>> exchanges in HTTP/1.1 must not block other concurrent exchanges.
>> Message changes however can update their current capacity via
>> `CapacityChannel`. Reactive extensions is a great example and also an
>> alternative to the native APIs per Ryan's recommendation.
>>
>> If you prefer the native APIs you can take a look at the classic I/O
>> adaptors that essentially emulate the classic blocking i/o on top of
>> the new async APIs [1] or HTTP/1.1 integration tests [2] that have a
>> number of 'slow' consumer / producer test cases.
>>
>> Cheers
>>
>> Oleg
>>
>> [1]
>> https://github.com/apache/httpcomponents-core/tree/master/httpcore5/src/main/java/org/apache/hc/core5/http/nio/support/classic
>> [2]
>> https://github.com/apache/httpcomponents-core/blob/master/httpcore5-testing/src/test/java/org/apache/hc/core5/testing/nio/Http1IntegrationTest.java
>>
>>
>> > On Fri, Sep 6, 2019 at 9:33 AM Roy Hashimoto <roy.hashim...@gmail.com
>> > >
>> > wrote:
>> >
>> > > I'm playing with asynchronous handlers in HttpCore 5, and I'd like
>> > > to have
>> > > an AsyncEntityProducer write data at its own (slow) rate like in
>> > > this old
>> > > thread <
>> > > https://marc.info/?l=httpclient-commons-dev&m=134928851229305&w=2
>> > > > .
>> > >
>> > > Writing to the DataStreamChannel whenever I want - outside the
>> > > scope of a
>> > > produce() method call - works fine, but I notice that produce() is
>> > > being
>> > > called every 5-6 milliseconds which ideally I would like to
>> > > eliminate or
>> > > reduce.
>> > >
>> > > The answer in the old thread was to use IOControl.suspendOutput()
>> > > and
>> > > IOControl.requestOutput(), but this class appears no longer to be
>> > > in
>> > > HttpCore 5. I see that there is a DataStreamChannel.requestOutput()
>> > > but I
>> > > haven't figured out what suspension call that should be paired
>> > > with. I have
>> > > tried simply returning 0 from my AsyncEntityProducer.available()
>> > > override,
>> > > but that doesn't seem to be it.
>> > >
>> > > Is there a new way to suspend/resume output in HttpCore 5?
>> > >
>> > > Thanks!
>> > > Roy
>> > >
>> > > Kotlin source here
>> > > <
>> > > https://gist.github.com/rhashimoto/1f5501d3b5d2aa95251fe12f4f0be250
>> > > >.
>> > >
>>
>>
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