I'm confortable with Scala, but for reasons outside my control, Java was
mandated for this project. We're using streams for another part of the
application, in a somewhat simpler scenario. This conversation has been
very helpful. The gems are these, I think:
a) Treat the refresh flow as normal program operation, not an exception
b) Encapsulate the refresh flow so that all of the timeout, scheduling,
retrying, and so on happens away from the components that actually use the
access tokens
c) Agents are useful as a mechanism for coordinating the distribution of
the refreshed tokens
d) Have the agents contain promises to prevent client code from using
expired tokens
I've now implemented the auto-refresh part without using streams. It's not
as elegant as yours, but it does the job. Thanks heaps, Lance. You've been
an enormous help.
On 13 August 2015 at 02:06, Lance Arlaus <lance.arl...@gmail.com> wrote:
> Oh, jeez. Yeah, that's entirely hideous.
>
> You know there's a cure for this disease. It's called Scala. However, side
> effects may include crawling compiles, awkward builds, and speaking
> optionally in futures :-)
>
> Seriously, if I'd known you were approaching this from Java, I'd advised
> against using Streams.
> You need the right language features and a good DSL to make this stuff
> accessible and maintainable (which the Akka guys have done a great job with
> so far, IMHO).
>
> You're right on about the Future contained in an Agent. That's the key
> interface between the two components (access and request). Like any
> software, as long as you get the interfaces right, the implementation
> should be swappable.
>
> Good luck!
>
>
> On Tuesday, August 11, 2015 at 10:32:57 AM UTC-4, David Pinn wrote:
>
>> Lance, I've been translating your autoRefresh method into Java.
>>
>> Kill. Me. Now.
>>
>> You wrote this:
>>
>> val auto = Sink(
>> Flow[(RefreshToken, Promise[AccessToken])],
>> Merge[(RefreshToken, Promise[AccessToken])](2),
>> request,
>> Unzip[RefreshToken, Promise[AccessToken]],
>> Zip[Future[RefreshResponse], Promise[AccessToken]],
>> Broadcast[(RefreshResponse, Promise[AccessToken])](3)
>> )((mat, _, _, _, _, _) => mat) {
>> implicit b => (initial, merge, request, unzip, zip, bcast) =>
>> ...
>> }
>>
>>
>>
>> ... which translates into Java 7 like this:
>>
>> Sink<Pair<RefreshToken, F.Promise<OAuth2Info>>, BoxedUnit> auto =
>> Sink.factory().create6(
>> Flow.<Pair<RefreshToken, F.Promise<OAuth2Info>>>create(),
>> Merge.<Pair<RefreshToken, F.Promise<OAuth2Info>>>create(2),
>> request,
>> Unzip.<RefreshToken, F.Promise<OAuth2Info>>create(),
>> Zip.<Future<RefreshResponse>, F.Promise<OAuth2Info>>create(),
>> Broadcast.<Pair<RefreshResponse, F.Promise<OAuth2Info>>>create(3
>> ),
>> new Function6<BoxedUnit, BoxedUnit, BoxedUnit, BoxedUnit,
>> BoxedUnit, BoxedUnit, BoxedUnit>() {
>> @Override
>> public BoxedUnit apply(BoxedUnit m1, BoxedUnit m2, BoxedUnit
>> m3, BoxedUnit m4, BoxedUnit m5, BoxedUnit m6) {
>> return m1;
>> }
>> },
>> new Function7<FlowGraph.Builder<BoxedUnit>,
>> FlowShape<Pair<RefreshToken, F.Promise<OAuth2Info>>, Pair<
>> RefreshToken, F.Promise<OAuth2Info>>>,
>> UniformFanInShape<Pair<RefreshToken, F.Promise<OAuth2Info>>,
>> Pair<RefreshToken, F.Promise<OAuth2Info>>>,
>> FlowShape<RefreshToken, F.Promise<RefreshResponse>>,
>> FanOutShape2<Pair<RefreshToken, F.Promise<OAuth2Info>>,
>> RefreshToken, F.Promise<OAuth2Info>>,
>> FanInShape2<Future<RefreshResponse>,
>>
>> ...
>
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