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From "Tzu-Li (Gordon) Tai" <tzuli...@apache.org>
Subject Re: is flink' states functionality futile?
Date Wed, 26 Jul 2017 02:44:01 GMT
<https://ci.apache.org/projects/flink/flink-docs-release-1.3/dev/stream/state.html>  
it's a program that sinks messages only after enough items accumulated in 
the buffe
Yes, that’s another important aspect of how Flink’s checkpointing is used to achieve at-least-once
/ exactly-once delivery to external systems.

For more details on how this works, I recommend taking at the docs here [1].


Now, assume I'm not bothered of recovering failures and only want the 
simplest way to implement a program that remembers data from the last run in 
the stream

By “the last run in the stream”, you mean the history of the stream so far, correct?
If that’s the case, and you don’t care about losing state on failures and don’t care
about at-least-once / exactly-once, then yes you don’t have to use the managed state APIs
in Flink.
You can just have ordinary fields to achieve this since Flink’s streaming operators are
basically long-running processes that continuously process events in the stream and manipulates
its state.

Cheers,
Gordon

On 23 July 2017 at 10:28:37 PM, ziv (zivmeri@gmail.com) wrote:

Ok, Let me see if I understand you correctly.  
You actually state that flink' states functionality is introduced only to  
handle recovering from failures.  
Let's take the example given in 1.3 documentary -  
https://ci.apache.org/projects/flink/flink-docs-release-1.3/dev/stream/state.html  
<https://ci.apache.org/projects/flink/flink-docs-release-1.3/dev/stream/state.html>
 
it's a program that sinks messages only after enough items accumulated in  
the buffer.  
Now, assume I'm not bothered of recovering failures and only want the  
simplest way to implement a program that remembers data from the last run in  
the stream, then, according to you, I may not use none of the elements  
associated with flink' states -  
ListState  
snapshotState  
initializeState  
restoreState  
and the program still functions correctly?  





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