[
https://issues.apache.org/jira/browse/S4-5?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13171944#comment-13171944
]
Leo Neumeyer commented on S4-5:
-------------------------------
I pushed a new version that seems to be working. I created a new Counter
example using the Fluent API. The maker class tries to infer all the required
info and if it cant, it exits with a message. The main ambiguity happens when a
PE has more than one stream field with the same EventType. In that case, the
user must provide the field name using the method withField(). Anyway,
implementing and debugging was quite a bit of work. Hope this is useful! The
Fluent API is completely independent and optional. Should be a good example for
others who may want to write a DSL. Doing a DSL in Java is quite cumbersome.
This is what the example looks like:
{code:title=S4 Fluent API|borderStyle=dashed}
@Override
public void configure() {
/* PE that prints counts to console. */
PEMaker printPE = addPE(PrintPE.class).asSingleton();
/* PEs that count events by user, gender, and age. */
PEMaker userCountPE = addPE(CounterPE.class);
userCountPE.addTrigger().fireOn(Event.class).ifInterval(100l,
TimeUnit.MILLISECONDS);
PEMaker genderCountPE = addPE(CounterPE.class);
genderCountPE.addTrigger().fireOn(Event.class).ifInterval(100l,
TimeUnit.MILLISECONDS);
PEMaker ageCountPE = addPE(CounterPE.class);
ageCountPE.addTrigger().fireOn(Event.class).ifInterval(100l,
TimeUnit.MILLISECONDS);
/* PE that generates random events. */
generateUserEventPE = addPE(GenerateUserEventPE.class).asSingleton();
generateUserEventPE.addTimer().withDuration(1, TimeUnit.MILLISECONDS);
/* Create the application graph. */
ageCountPE.emit(CountEvent.class).onKey(new
CountKeyFinder()).to(printPE);
genderCountPE.emit(CountEvent.class).onKey(new
CountKeyFinder()).to(printPE);
userCountPE.emit(CountEvent.class).onKey(new
CountKeyFinder()).to(printPE);
generateUserEventPE.emit(UserEvent.class).onKey(new
AgeKeyFinder()).to(ageCountPE);
generateUserEventPE.emit(UserEvent.class).onKey(new
GenderKeyFinder()).to(genderCountPE);
generateUserEventPE.emit(UserEvent.class).onKey(new
UserIDKeyFinder()).to(userCountPE);
}
{code}
I made a few additional changes:
* Removed the SingletonPE class because it was complicating the API. Instead I
added a method setSingleton() that creates an eagerly singleton in the app.
That is, the PE instance is created and initialized just before the app starts
and before events arrive.
* I improved initialization coordination.
* Started to use the Guava Precondition class because it makes the code
cleaner. Please look at ProcessingElement and use a similar pattern.
* Fixed some bugs.
> Prototype app builder
> ---------------------
>
> Key: S4-5
> URL: https://issues.apache.org/jira/browse/S4-5
> Project: Apache S4
> Issue Type: New Feature
> Affects Versions: 0.5
> Reporter: Leo Neumeyer
> Priority: Minor
> Fix For: 0.5
>
>
> Extend Guice AbstractModule to create a simple application builder layer. The
> idea is to evaluate if we can use Guice to do all the wiring including PEs
> and Streams and Apps.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
