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From Nick Dimiduk <ndimi...@apache.org>
Subject Re: OutputFormat vs SinkFunction
Date Mon, 08 Feb 2016 18:40:06 GMT
On Mon, Feb 8, 2016 at 9:51 AM, Maximilian Michels <mxm@apache.org> wrote:

> Changing the class hierarchy would break backwards-compatibility of the
> API. However, we could add another method to DataStream to easily use
> OutputFormats in streaming.

Indeed, that's why I suggested deprecating one and moving toward a
consolidated class hierarchy. It won't happen overnight, but this can be
managed pretty easily with some adapter code like this and some additional
overrides in the public APIs.

How did you write your adapter? I came up with the one below.

Our implementations are similar. This one is working fine with my test code.


On Mon, Feb 8, 2016 at 6:07 PM, Nick Dimiduk <ndimiduk@apache.org> wrote:
>> In my case, I have my application code that is calling addSink, for which
>> I'm writing a test that needs to use LocalCollectionOutputFormat. Having
>> two separate class hierarchies is not helpful, hence the adapter. Much of
>> this code already exists in the implementation of FileSinkFunction, so the
>> project already supports it in a limited way.
>> On Mon, Feb 8, 2016 at 4:16 AM, Maximilian Michels <mxm@apache.org>
>> wrote:
>>> Hi Nick,
>>> SinkFunction just implements user-defined functions on incoming
>>> elements. OutputFormat offers more lifecycle methods. Thus it is a
>>> more powerful interface. The OutputFormat originally comes from the
>>> batch API, whereas the SinkFunction originates from streaming. Those
>>> were more separate code paths in the past. Ultimately, it would make
>>> sense to have only the OutputFormat interface but I think we have to
>>> keep it to not break the API.
>>> If you need the lifecycle methods in streaming, there is
>>> RichSinkFunction, which implements OutputFormat and SinkFunction. In
>>> addition, it gives you access to the RuntimeContext. You can pass this
>>> directly to the "addSink(sinkFunction)" API method.
>>> Cheers,
>>> Max
>>> On Mon, Feb 8, 2016 at 7:14 AM, Nick Dimiduk <ndimiduk@apache.org>
>>> wrote:
>>> > Heya,
>>> >
>>> > Is there a plan to consolidate these two interfaces? They appear to
>>> provide
>>> > identical functionality, differing only in lifecycle management. I
>>> found
>>> > myself writing an adaptor so I can consume an OutputFormat where a
>>> > SinkFunction is expected; there's not much to it. This seems like code
>>> that
>>> > Flink should ship.
>>> >
>>> > Maybe one interface or the other can be deprecated for 1.0 API?
>>> >
>>> > Thanks,
>>> > Nick

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