Re: Flink and factories?

[Sebastian Neef]

Hi,

wow, oh that's indeed a nice solution.

Your version still threw some errors:

> Caused by: org.apache.flink.api.common.InvalidProgramException: Object 
> factorytest.Config$1@5143c662 not serializable
> Caused by: java.io.NotSerializableException: factorytest.factory.PearFactory

I fixed this by adding "implements java.io.Serializable" to the
IDataFactory (and all other interfaces right away) - I hope that won't
backfire in the future.

Anyway, the problem seems solved. Yay and thank you!

Kind regards,
Sebastian

Re: Flink and factories?

[Chesnay Schepler]

The functions are serialized when env.execute() is being executed. The 
thing is, as i understand it, that your singleton is simply not part of 
the serialized function, so it doesn't actually matter when the function 
is serialized.


Storing the factory instance in the function shouldn't be too much work 
actually, the following code might do the trick already (changes in bold):


   DataSet processedData = this.getEnv().fromCollection(inputData).flatMap(new 
FlatMapFunction() {
*private final  factory =
   Config.getInstance().getFactory(); * 
   	@Override

public void flatMap(Integer integer, Collector collector) throws 
Exception {
if (integer % 2 == 0) {
collector.collect(*factory.newInstance()*);
}
}
   });

Regards,
Chesnay

On 19.10.2016 23:09, Sebastian Neef wrote:

Hi Chesnay,

thank you for looking into this!

Is there any way to tell Flink to (re)sync the changed classes and/or
tell it to distribute the serialized classes at a given point (e.g.
first on a env.execute() ) or so?

The thing is, that I'm working on a small framework which bases on
flink, so passing a configuration object to all functions/classes would
be overkill, I guess.

Thanks again and kind regards,
Sebastian

Re: Flink and factories?

[Sebastian Neef]

Hi Chesnay,

thank you for looking into this!

Is there any way to tell Flink to (re)sync the changed classes and/or
tell it to distribute the serialized classes at a given point (e.g.
first on a env.execute() ) or so?

The thing is, that I'm working on a small framework which bases on
flink, so passing a configuration object to all functions/classes would
be overkill, I guess.

Thanks again and kind regards,
Sebastian

Flink and factories?

[Sebastian Neef]

Hi,

I'm currently working with flink for my bachelor thesis and I'm running
into some odd issues with flink in regards to factories.

I've built a small "proof of concept" and the code can be found here:
https://gitlab.tubit.tu-berlin.de/gehaxelt/flink-factorytest

The idea is that a Config-singleton holds information or objects to use,
e.g. an AppleFactory (default) which implements a specific IDataFactory
interface. This AppleFactory is then used in a flatMap to create Apples
(objects which implement the IData interface):

> 
> System.out.println("Factory before processedData: " + 
> Config.getInstance().getFactory().getClass());
> DataSet processedData = 
> this.getEnv().fromCollection(inputData).flatMap(new FlatMapFunction IData>() {
> @Override
> public void flatMap(Integer integer, Collector collector) 
> throws Exception {
> if (integer % 2 == 0) {
> 
> collector.collect(Config.getInstance().getFactory().newInstance());
> }
> }
> });
>System.out.println("Factory after processedData: " + 
> Config.getInstance().getFactory().getClass());
> try {
> System.out.println("Class created: " + 
> processedData.collect().get(0).getClass());
> this.getDataHolder().setDataList(processedData.collect());
> } catch (Exception e) {
> e.printStackTrace();
> }


This happens in the "Config -> initData()" function. My Flink-Job looks
like this:

>   public static void main(String[] args) throws Exception {
> 
>   Config c = Config.getInstance(); //Use AppleFactory by default
> 
> //BOOM: Somehow flink ignores this?
> c.setFactory(new PearFactory());
> 
> c.initData();
> 
> DataSet data = 
> c.getEnv().fromCollection(c.getDataHolder().getDataList());

As you can see before the "c.initData()" call I set the factory to a
"PearFactory()" which will produce Pear-objects (also implementing the
IData interface).

Running the code will print the following text:

> Class created: class factorytest.Data.Apple

This, however, means that flink didn't catch (or ignored?) that the
factory has changed and still creates objects of type Apple.

Instead I'd expect the processedData.collect() list to contain
Pear-objects. What is even more confusing is that the two "Factory
before/after processedData" print statements correctly return the
PearFactory class.

What's the best way to fix this? Any tips/tricks/questions?

I guess that this issue is might be hard to explain in words, so I'd
really appreciate it if someone could have a look at the code and maybe
do an example run:

Job.java:
https://gitlab.tubit.tu-berlin.de/gehaxelt/flink-factorytest/blob/master/src/main/java/factorytest/Job.java

Config.java:
https://gitlab.tubit.tu-berlin.de/gehaxelt/flink-factorytest/blob/master/src/main/java/factorytest/Config.java

Example run:
https://gitlab.tubit.tu-berlin.de/gehaxelt/flink-factorytest/blob/master/EXAMPLE_RUN_OUTPUT.txt

Kind regards,
Sebastian Neef