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From Fabian Hueske <fhue...@gmail.com>
Subject Re: static/dynamic lookups in flink streaming
Date Thu, 22 Dec 2016 09:20:04 GMT
That approach should work as well.
The upcoming Flink 1.2.0 release will feature a function for asynchronous
operations, i.e., you can have multiple concurrent Redis requests, without
losing the fault tolerance guarantees.

Another alternative is to store the map in key-partitioned operator state
of a CoFlatMapFunction. One input is the stream with the IDs, the other
stream are the entries of the map which are inserted into the operator
This approach would require some initial buffering of the ID stream though.

Best, Fabian

2016-12-21 19:06 GMT+01:00 Meghashyam Sandeep V <vr1meghashyam@gmail.com>:

> Thanks for the solution Fab. My map would be substantially large. So I
> wouldn't want to replicate it in each operator. I will probably add a layer
> of redis cache adn use it in streaming process. Do you foresee any problems
> with that?
> Thanks,
> Sandeep
> On Wed, Dec 21, 2016 at 9:52 AM, Fabian Hueske <fhueske@gmail.com> wrote:
>> You could read the map from a file in the open method of a
>> RichMapFunction.
>> The open method is called before the first record is processed and can
>> put data into the operator state.
>> The downside of this approach is that the data is replicated in each
>> operator, i.e., each operator holds a full copy of the map.
>> On the other hand, you do not need to shuffle the data because each
>> parallel task can do the look-up.
>> If your <id, name> map is small, this would be the preferred approach.
>> Best, Fabian
>> 2016-12-21 18:46 GMT+01:00 Meghashyam Sandeep V <vr1meghashyam@gmail.com>
>> :
>>> As a follow up question, can we populate the operator state from an
>>> external source?
>>> My use case is as follows: I have a flink streaming process with Kafka
>>> as a source. I only have ids coming from kafka messages. My look ups
>>> (<id,name>) which is a static map come from a different source. I would
>>> like to use those lookups while applying operators on stream from Kafka.
>>> Thanks,
>>> Sandeep
>>> On Wed, Dec 21, 2016 at 6:17 AM, Fabian Hueske <fhueske@gmail.com>
>>> wrote:
>>>> OK, I see. Yes, you can do that with Flink. It's actually a very common
>>>> use case.
>>>> You can store the names in operator state and Flink takes care of
>>>> checkpointing the state and restoring it in case of a failure.
>>>> In fact, the operator state is persisted in the state backends you
>>>> mentioned before.
>>>> Best, Fabian
>>>> 2016-12-21 15:02 GMT+01:00 Meghashyam Sandeep V <
>>>> vr1meghashyam@gmail.com>:
>>>>> Hi Fabian,
>>>>> I meant look ups like IDs to names. For example if I have IDs coming
>>>>> through the stream and if I want to replace them with corresponding names
>>>>> stored in cache or somewhere within flink.
>>>>> Thanks,
>>>>> Sandeep
>>>>> On Dec 21, 2016 12:35 AM, "Fabian Hueske" <fhueske@gmail.com> wrote:
>>>>>> Hi Sandeep,
>>>>>> I'm sorry but I think I do not understand your question.
>>>>>> What do you mean by static or dynamic look ups? Do you want to access
>>>>>> an external data store and cache data?
>>>>>> Can you give a bit more detail about your use?
>>>>>> Best, Fabian
>>>>>> 2016-12-20 23:07 GMT+01:00 Meghashyam Sandeep V <
>>>>>> vr1meghashyam@gmail.com>:
>>>>>>> Hi there,
>>>>>>> I know that there are various state backends to persist state.
>>>>>>> there a similar way to persist static/dynamic look ups and use
them while
>>>>>>> streaming the data in Flink?
>>>>>>> Thanks,
>>>>>>> Sandeep

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