Re: [DISCUSS] New API for setting up observers.

[Keith Turner <ke...@deenlo.com>]

I made this change and its up for review.

https://github.com/apache/incubator-fluo/pull/817

On Thu, Feb 23, 2017 at 5:36 PM, Keith Turner <ke...@deenlo.com> wrote:
> The current way observers are set up in Fluo requires specifying a
> class for each observers in configuration.  This is cumbersome and
> prevents using lambdas and anonymous inner classes.  It also makes it
> hard to follow what a Fluo Application is doing.  This cumbersome way
> of setting things up propagates forward into higher level constructs
> in Fluo Recipes making them also cumbersome to use.
>
> I think it would be much simpler if the user only had to specify one
> factory class in configuration that created all observers.  This
> factory would be free to pair a lambda with a column for an observer.
> Observed columns would no longer be tightly coupled with a specific
> class.  I am thinking the factory would look something like the
> following.
>
> interface ObserversFactory {
>   Map<ObservedColumn, Observer> getObservers(SimpleConfiguration
> applicationConfig);
> }
>
> A user would implement this interface with a class that creates all of
> their observers.
>
> class UserObserversFactory implements ObserversFactory {
>   Map<ObservedColumn, Observer> getObservers(SimpleConfiguration appConfig) {
>     //all of users observers are setup here in code, which is much
> easier to follow than current way of configuring each observer class
> individually.
>      HashMap observers = ...;
>      observers.put(col1, tx,row,col -> ....); //an observer that's a lambda
>      ExportQueue.addObserver(observers, appConfig, "queueId", exports
> -> ....);  //using a lambda to handle exports...
>   }
> }
>
> The user would configure Fluo to use the above observer factory.
>
> I am thinking of trying to implement this for 1.1, but wanted to see
> if anyone had any input before I started.  If it seems to work well, I
> was thinking of deprecating the current way of configuring observers.
> I would update webindex and fluo recipes in parallel to evaluate the
> changes.