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From Donald Szeto <don...@apache.org>
Subject Re: Eventserver API in an Engine?
Date Wed, 28 Jun 2017 23:27:19 GMT
Hey Mars,

Thanks for the suggestion and I agree with your point on the metadata part.
Essentially I think the app and channel concept should be instead logically
grouped together with event, not metadata.

I think in some advanced use cases, event storage should not even be a hard
requirement as engine templates can source data differently. In the long
run, it might be cleaner to have event server (and all relevant concepts
such as its API, access keys, apps, etc) as a separable package, that is by
default turned on, embedded to engine server. Advanced users can either
make it standalone or even turn it off completely.

I imagine this kind of refactoring would echo Pat's proposal on making a
clean and separate engine and metadata management system down the road.

Regards,
Donald

On Wed, Jun 28, 2017 at 3:29 PM Mars Hall <mars@heroku.com> wrote:

> One of the ongoing challenges we face with PredictionIO is the separation
> of Engine & Eventserver APIs. This separation leads to several problems:
>
> 1. Deploying a complete PredictionIO app requires multiple processes, each
> with its own network listener
> 2. Eventserver & Engine must be configured to share exactly the same
> storage backends (same `pio-env.sh`)
> 3. Confusion between "Eventserver" (an optional REST API) & "event
> storage" (a required database)
>
> These challenges are exacerbated by the fact that PredictionIO's docs &
> `pio app` CLI make it appear that sharing an Eventserver between Engines is
> a good idea. I recently filed a JIRA issue about this topic. TL;DR sharing
> an eventserver between engines with different Meta Storage config will
> cause data corruption:
>   https://issues.apache.org/jira/browse/PIO-96
>
>
> I believe a lot of these issues could be alleviated with one change to
> PredictionIO core:
>
> By default, expose the Eventserver API from the `pio deploy` Engine
> process, so that it is not necessary to deploy a second Eventserver-only
> process. Separate `pio eventserver` could still be optional if you need the
> separation of concerns for scalability.
>
>
> I'd love to hear what you folks think. I will file a JIRA enhancement
> issue if this seems like an acceptable approach.
>
> *Mars Hall
> Customer Facing Architect
> Salesforce Platform / Heroku
> San Francisco, California
>
>

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