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Re: Question regarding rescale api


Hi Mingliang,

Aljoscha is right. At the moment Flink does not support to spread out tasks across all TaskManagers. This is a feature which we still need to add. Until then, you need to set the parallelism to the number of available slots in order to guarantee that all TaskManagers are equally used.

Cheers,
Till

On Mon, Dec 10, 2018 at 3:18 PM Aljoscha Krettek <aljoscha@xxxxxxxxxx> wrote:
Hi,

I think with how currently the assignment of tasks to slots works there is no way of ensuring that the source tasks are evenly spread to the TaskManagers (TaskExecutors). The rescale() API is from a time where scheduling worked a bit different in Flink, I'm afraid.

I'm cc'ing Till, who might know more about scheduling.

Best,
Aljoscha


On 10. Dec 2018, at 13:02, 祁明良 <mqi@xxxxxxxxxxxxxxx> wrote:


Hi Aljoscha,

Seems you are the committer of rescale api, any help about this question?

Best,
Mingliang


发件人: 祁明良
发送时间: 2018年12月9日 18:20
收件人: user@xxxxxxxxxxxxxxxx
主题: Question regarding rescale api
 
Hi All,

I see the rescale api allow us to somehow redistribute element locally, but is it possible to make the upstream operator distributed evenly on task managers?
For example I have 10 task managers each with 10 slots. The application reads data from Kafka topic with 20 partitions, then rescale it to full parallelism. To me it seems that the 20 slots needed to read from Kafka won’t distributed evenly on 10 task managers, which means further rescale still needs to shuffle data over network.


Best,
Mingliang

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