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From ziv <ziv.m...@elbitsystems.com>
Subject RE: is flink' states functionality futile?
Date Wed, 26 Jul 2017 05:28:05 GMT
Hi, what is the reference you wanted to link in [1]?

From: Tzu-Li (Gordon) Tai [via Apache Flink Mailing List archive.] [mailto:ml+s1008284n18936h39@n3.nabble.com]
Sent: 26 July 2017 05:44
To: Meri Ziv
Subject: Re: is flink' states functionality futile?

<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 ([hidden email]</user/SendEmail.jtp?type=node&node=18936&i=0>)
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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