flink-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Matt <dromitl...@gmail.com>
Subject Re: [BUG?] Cannot Load User Class on Local Environment
Date Thu, 27 Apr 2017 13:09:12 GMT
Hi Till,

Great! Do you know if it's planned to be included in v1.2.x or should we
wait for v1.3? I'll give it a try as soon as it's merged.

You're right about this approach launching a mini cluster on each Ignite
node. That is intentional, as described in my previous message on the list

The idea is to collocate Flink jobs on Ignite nodes, so each dataflow only
processes the elements stored on the local in-memory database. I get the
impression this should be much faster than randomly picking a Flink node
and sending all the data over the network.

Any insight on this?



On Thu, Apr 27, 2017 at 5:33 AM, Till Rohrmann <trohrmann@apache.org> wrote:

> I just copied my response because my other email address is not accepted
> on the user mailing list.
> Hi Matt,
> I think Stefan's analysis is correct. I have a PR open [1], where I fix
> the issue with the class loader.
> As a side note, by doing what you're doing, you will spawn on each Ignite
> node a new Flink mini cluster. These mini cluster won't communicate with
> each other and run independently. Is this what you intend to do?
> [1] https://github.com/apache/flink/pull/3781
> Cheers,
> Till
> On Wed, Apr 26, 2017 at 11:12 PM, Matt <dromitlabs@gmail.com> wrote:
>> Let's wait for Till then, I hope he can figure this out.
>> On Wed, Apr 26, 2017 at 11:03 AM, Stefan Richter <
>> s.richter@data-artisans.com> wrote:
>>> Ok, now the question is also about what classloaders Ignite is creating
>>> and how they are used, but the relevant code line in Flink is probably in
>>> FlinkMiniCluster.scala, line 538 (current master):
>>>  try {
>>>  JobClient.submitJobAndWait(
>>>    clientActorSystem,
>>>    configuration,
>>>    leaderRetrievalService,
>>>    jobGraph,
>>>    timeout,
>>>    printUpdates,
>>>    this.getClass.getClassLoader())
>>> } finally {
>>>    if(!useSingleActorSystem) {
>>>      // we have to shutdown the just created actor system
>>>      shutdownJobClientActorSystem(clientActorSystem)
>>>    }
>>>  }
>>> This is what is executed as part of executing a job through
>>> LocalEnvironment. As we can see, the classloader is set to the classloader
>>> of FlinkMiniCluster. Depending on the classloader structure inside Ignite,
>>> this classloader might not know your user code. What you could do is
>>> changing this line in a custom Flink build, changing line 538 for example
>>> to Thread.currentThread().getContextClassloader() and ensuring that the
>>> context classloader ins the runnable is a classloader that a) knows the
>>> user code and b) is a child of the classloader that knows the Ignite and
>>> Flink classes. Notice that this is not a general solution and should not
>>> become a general fix.
>>> I have heard that Till is about to change some things about local
>>> execution, so I included him in CC. Maybe he can provide additional hints
>>> how your use case might be better supported in the upcoming Flink 1.3.
>>> Best,
>>> Stefan
>>> Am 25.04.2017 um 22:50 schrieb Matt <dromitlabs@gmail.com>:
>>> I updated the code a little bit for clarity, now the line #56 mentioned
>>> in my previous message is line #25.
>>> In summary the error I'm getting is this:
>>> ---
>>> Caused by: org.apache.flink.streaming.runtime.tasks.StreamTaskException:
>>> Cannot load user class: com.test.Test
>>> ClassLoader info: URL ClassLoader:
>>> Class not resolvable through given classloader.
>>> ---
>>> But if I'm not wrong, after trying to load the class through
>>> URLClassLoader, Flink should try loading it with its parent ClassLoader,
>>> which should be the same ClassLoader that executed the environment, and it
>>> does have access to the class.
>>> Not sure what is wrong.
>>> On Tue, Apr 25, 2017 at 5:38 PM, Matt <dromitlabs@gmail.com> wrote:
>>>> Hi Stefan,
>>>> Check the code here: https://gist.github.com/
>>>> 17d82ee7dd921a0d649574a361cc017d , the output is at the bottom of the
>>>> page.
>>>> Here are the results of the additional tests you mentioned:
>>>> 1. I was able to instantiate an inner class (Test$Foo) inside the
>>>> Ignite closure, no problem with that
>>>> 2. I tried implementing SourceFunction and SinkFunction in Test itself,
>>>> I was able to instantiate the class inside the Ignite closure
>>>> 3. I'm not sure what you meant in this point, is it something like what
>>>> I tried in line #56?
>>>> Additionally, I tried implementing the SourceFunction and SinkFunction
>>>> in Test$Foo with the same result: it says "Cannot load user class:
>>>> com.test.Test$Foo"
>>>> Looks like Flink is not using the correct ClassLoader. Any idea?
>>>> Regards,
>>>> Matt
>>>> On Tue, Apr 25, 2017 at 7:00 AM, Stefan Richter <
>>>> s.richter@data-artisans.com> wrote:
>>>>> Hi,
>>>>> I would expect that the local environment picks up the class path from
>>>>> the code that launched it. So I think the question is what happens behind
>>>>> the scenes when you call ignite.compute().broadcast(runnable); .
>>>>> Which classes are shipped and how is the classpath build in the environment
>>>>> that runs the code. Your example is also not fully conclusive, because
>>>>> com.myproj.Test (which you can successfully instantiate) and
>>>>> com.myproj.Test$1$2 (which fails) are different classes, so maybe only
>>>>> outer class is shipped with the broadcast call. My theory is that not
>>>>> classes are shipped (e.g. inner classes), but only Test . You could try
>>>>> three things to analyze to problem a little more:
>>>>> 1) Create another inner class inside Test and try if you are still
>>>>> able to instantiate also this class via reflection.
>>>>> 2) Let Test class itself implement the map function (avoiding the
>>>>> usage of other/inner classes) and see if this works.
>>>>> 3) Check and set the thread’s context classloader inside the runnable
>>>>> to something that contains all required classes and see if this gets
>>>>> up by Flink.
>>>>> Best,
>>>>> Stefan
>>>>> Am 25.04.2017 um 07:27 schrieb Matt <dromitlabs@gmail.com>:
>>>>> Hi all,
>>>>> I'm trying to run Flink using a local environment, but on an Ignite
>>>>> node to achieve collocation (as mentioned in my previous message on this
>>>>> list).
>>>>> Have a look at the code in [1]. It's pretty simple, but I'm getting a
>>>>> "cannot load user class" error as shown in [2].
>>>>> If you check line #29 on the code, I'm able to create an instance of
>>>>> class Test, and it's the same context from which I'm creating the Flink
>>>>> job. Shouldn't it work provided I'm using a local environment?
>>>>> It would be really nice to be able to inject a ClassLoader into the
>>>>> chunk of code that creates the job. Is this currently possible?
>>>>> Any fix or workaround is appreciated!
>>>>> Best,
>>>>> Matt
>>>>> [1] https://gist.github.com/f248187b9638023b95ba8bd9d7f06215
>>>>> [2] https://gist.github.com/796ee05425535ece1736df7b1e884cce

View raw message