Re: Stopping a job

M Singh Mon, 08 Jun 2020 22:37:18 -0700

 Thanks Kostas, Arvid, and Senthil for your help.
    On Monday, June 8, 2020, 12:47:56 PM EDT, Senthil Kumar 
<senthi...@vmware.com> wrote:  
 
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I am just stating this for completeness.
 
  
 
When a job is cancelled, Flink sends an Interrupt signal to the Thread running 
the Source.run method
 
  
 
For some reason (unknown to me), this does not happen when a Stop command is 
issued.
 
  
 
We ran into some minor issues because of said behavior.
 
  
 
From: Kostas Kloudas <kklou...@gmail.com>
Date: Monday, June 8, 2020 at 2:35 AM
To: Arvid Heise <ar...@ververica.com>
Cc: M Singh <mans2si...@yahoo.com>, User-Flink <user@flink.apache.org>
Subject: Re: Stopping a job
 
  
 
What Arvid said is correct. 
 
The only thing I have to add is that "stop" allows also exactly-once sinks to 
push out their buffered data to their final destination (e.g. Filesystem). In 
other words, it takes into account side-effects, so it guarantees exactly-once 
end-to-end, assuming that you are using exactly-once sources and sinks. Cancel 
with savepoint on the other hand did not necessarily and committing 
side-effects is was following a "best-effort" approach.
 
  
 
For more information you can check [1].
 
  
 
Cheers,
 
Kostas 
 
  
 
[1] https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=103090212
 
  
 
On Mon, Jun 8, 2020 at 10:23 AM Arvid Heise <ar...@ververica.com> wrote:

It was before I joined the dev team, so the following are kind of speculative:

The concept of stoppable functions never really took off as it was a bit of a
clumsy approach. There is no fundamental difference between stopping and
cancelling on (sub)task level. Indeed if you look in the twitter source of 1.6
[1], cancel() and stop() are doing the exact same thing. I'd assume that this
is probably true for all sources.

So what is the difference between cancel and stop then? It's more the way on
how you terminate the whole DAG. On cancelling, you cancel() on all tasks more
or less simultaneously. If you want to stop, it's more a fine-grain cancel,
where you stop first the sources and then let the tasks close themselves when
all upstream tasks are done. Just before closing the tasks, you also take a
snapshot. Thus, the difference should not be visible in user code but only in
the Flink code itself (task/checkpoint coordinator)

So for your question:

1. No, as on task level stop() and cancel() are the same thing on UDF level.

2. Yes, stop will be more graceful and creates a snapshot. [2]

3. Not that I am aware of. In the whole flink code base, there are no more (see
javadoc). You could of course check if there are some in Bahir. But it
shouldn't really matter. There is no huge difference between stopping and
cancelling if you wait for a checkpoint to finish.

4. Okay you answered your second question ;) Yes cancel with savepoint = stop
now to make it easier for new users.

[1]
https://github.com/apache/flink/blob/release-1.6/flink-connectors/flink-connector-twitter/src/main/java/org/apache/flink/streaming/connectors/twitter/TwitterSource.java#L180-L190

[2] https://ci.apache.org/projects/flink/flink-docs-release-1.10/ops/cli.html

On Sun, Jun 7, 2020 at 1:04 AM M Singh <mans2si...@yahoo.com> wrote:

Hi Arvid:

Thanks for the links.

A few questions:

1. Is there any particular interface in 1.9+ that identifies the source as
stoppable ?

2. Is there any distinction b/w stop and cancel in 1.9+ ?

3. Is there any list of sources which are documented as stoppable besides the
one listed in your SO link ?

4. In 1.9+ there is flink stop command and a flink cancel command.
(https://ci.apache.org/projects/flink/flink-docs-stable/ops/cli.html#stop). So
it appears that flink stop will take a savepoint and the call cancel, and
cancel will just cancel the job (looks like cancel with savepoint is deprecated
in 1.10).

Thanks again for your help.

On Saturday, June 6, 2020, 02:18:57 PM EDT, Arvid Heise <ar...@ververica.com>
wrote:

Yes, it seems as if FlinkKinesisConsumer does not implement it.

Here are the links to the respective javadoc [1] and code [2]. Note that in
later releases (1.9+) this interface has been removed. Stop is now implemented
through a cancel() on source level.

In general, I don't think that in a Kinesis to Kinesis use case, stop is needed
anyways, since there is no additional consistency expected over a normal cancel.

[1]https://ci.apache.org/projects/flink/flink-docs-release-1.6/api/java/org/apache/flink/api/common/functions/StoppableFunction.html

[2]https://github.com/apache/flink/blob/release-1.6/flink-core/src/main/java/org/apache/flink/api/common/functions/StoppableFunction.java

On Sat, Jun 6, 2020 at 8:03 PM M Singh <mans2si...@yahoo.com> wrote:

Hi Arvid:

I check the link and it indicates that only Storm SpoutSource, TwitterSource
and NifiSource support stop.

Does this mean that FlinkKinesisConsumer is not stoppable ?

Also, can you please point me to the Stoppable interface mentioned in the link
? I found the following but am not sure if TwitterSource implements it :

https://github.com/apache/flink/blob/8674b69964eae50cad024f2c5caf92a71bf21a09/flink-runtime/src/main/java/org/apache/flink/runtime/rpc/StartStoppable.java

Thanks

On Friday, June 5, 2020, 02:48:49 PM EDT, Arvid Heise <ar...@ververica.com>
wrote:

Hi,

could you check if this SO thread [1] helps you already?

[1]https://stackoverflow.com/questions/53735318/flink-how-to-solve-error-this-job-is-not-stoppable

On Thu, Jun 4, 2020 at 7:43 PM M Singh <mans2si...@yahoo.com> wrote:

Hi:

I am running a job which consumes data from Kinesis and send data to another
Kinesis queue. I am using an older version of Flink (1.6), and when I try to
stop the job I get an exception

Caused by: java.util.concurrent.ExecutionException:
org.apache.flink.runtime.rest.util.RestClientException: [Job termination (STOP)
failed: This job is not stoppable.]

I wanted to find out what is a stoppable job and it possible to make a job
stoppable if is reading/writing to kinesis ?

Thanks

Arvid Heise| Senior Java Developer

JoinFlink Forward - The Apache Flink Conference

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Arvid Heise| Senior Java Developer

JoinFlink Forward - The Apache Flink Conference

Stream Processing | Event Driven | Real Time

VervericaGmbH | Invalidenstrasse 115, 10115 Berlin, Germany

Ververica GmbH
Registered at Amtsgericht Charlottenburg: HRB 158244 B
Managing Directors: Timothy Alexander Steinert, Yip Park Tung Jason, Ji (Toni)
Cheng

Arvid Heise| Senior Java Developer

JoinFlink Forward - The Apache Flink Conference

Stream Processing | Event Driven | Real Time

VervericaGmbH | Invalidenstrasse 115, 10115 Berlin, Germany

Ververica GmbH
Registered at Amtsgericht Charlottenburg: HRB 158244 B
Managing Directors: Timothy Alexander Steinert, Yip Park Tung Jason, Ji (Toni)
Cheng

Re: Stopping a job

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