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From "Mike Accola" <macc...@us.ibm.com>
Subject Re: Class Cache
Date Tue, 01 Aug 2017 22:15:07 GMT
Thank you to those of you who replied.

I can't really explain why, but yesterday afternoon, out of the blue, this 
problem disappeared.  Everything was working fine for a while.  Until some 
different strange behavior came up this afternoon.  I don't believe any 
code changes I made should affect this.

I suspect this is all related to some kind of caching somewhere somehow.

I was already putting mylib2.jar into flink's lib directory.  I was doing 
this because mylib2.jar has some native methods and I had had better luck 
loading these.

Now I am running into a problem where my application runs successfully.  I 
then turn around and run the same application a 2nd time (it should get 
exact same results). Except this 2nd time I get a ClassNotFoundException 
for one of the classes in mylib2.jar.  I've temporarily taken references 
to the class that uses the native library out of the code just to rule out 
that this is related to any native loading problems.  If I do 
stop-local.sh and start-local.sh, I get the same result:  works the first 
time I run, but get the ClassNotFoundException the 2nd time.

I am running flink 1.3.0 on linux (RHEL 6.8). I am not using yarn.  Just 
plain, out of the box local mode.

Is it possible that the cache in this blob server is getting corrupted? Is 
there a way to tell?  Is there a way to disable the blob server?

Any other ideas on things to look at?

From:   Ufuk Celebi <uce@apache.org>
To:     dev@flink.apache.org
Date:   07/31/2017 04:13 PM
Subject:        Re: Class Cache

Hey Mike!

Thanks for the detailed information about your setup. I'm also puzzled
by this...

(1) Which version of Flink are you using? We recently merged some
changes to the JAR distribution components, which might cause this
(although I think that's unlikely).

(2) As a temporary work around you could try putting mylib2.jar into
the /lib folder and not pulling it in via --classpath. After doing
this you would need to stop/start the cluster and resubmit the job.

– Ufuk

On Mon, Jul 31, 2017 at 10:17 PM, Stephan Ewen <sewen@apache.org> wrote:
> Hi Mike!
> Flink does in fact cache jar files in the "blob server". But these are
> cached subject to the following conditions:
>   - No caching across "sessions", meaning start/stop of the
> cluster/jobmanager. If you run the per-job-yarn setup, the job does not
> cache anything.
>   - Files are cached under a content hash, meaning as soon as the 
> changes, the artifact is not reused. So if you actually change the jar
> file, no caching should happen.
> I cannot really explain what you are observing and have never seen that
> myself...
> Stephan
> On Mon, Jul 31, 2017 at 9:00 PM, Mike Accola <maccola@us.ibm.com> wrote:
>> No, I did not explicitly  create an uber-jar.  The mylib1.jar is very
>> light. It only contains my main application class (including
>> ProcessFunction).
>> I have been specifying --classpath option on my flink run command to 
>> in the mylib2.jar .
>> Plus, I have been rebuilding mylib1.jar frequently just to be safe and 
>> hasn't made a difference.
>> Mike Accola
>> maccola@us.ibm.com
>> From:   Eron Wright <eronwright@gmail.com>
>> To:     dev@flink.apache.org
>> Date:   07/31/2017 01:47 PM
>> Subject:        Re: Class Cache
>> A Flink program is typically packaged as an 'uber-jar' containing its
>> dependencies.  The Flink quickstart project illustrates this (see the 
>> of the shading plugin in pom.xml).   Based on your description, the
>> classes
>> of mylib2.jar were copied into mylib1.jar when the latter was built. 
>> rebuilding mylib1.jar to effect the change.
>> -Eron
>> On Mon, Jul 31, 2017 at 11:18 AM, Mike Accola <maccola@us.ibm.com> 
>> > Are classes cached somewhere in flink?  I am running in a very basic,
>> > local environment on Linux (start_local.sh).  I've somehow gotten my
>> > environment into a strange state that I don't understand.  I feel 
like I
>> > am overlooking something simple, but I've checked everything I can 
>> > of.
>> >
>> > My main flink application with a ProcessFunction is embedded in
>> > mylib1.jar.  Within my ProcessFunction I use another class that is
>> > embedded in mylib2.jar.
>> >
>> > When I made changes to function in mylib2.jar and rebuilt the jar, I
>> > realized the changes weren't taking affect.  In fact, I then delete
>> > mylib2.jar entirely and my application still worked.  I can't figure 
>> > where my application is picking up the function contained in 
>> I
>> > have checked any temp directories, library paths, etc.  I have
>> repeatedly
>> > stopped/started my flink environment just to be safe.
>> >
>> > I tried adding -verbose:class to env.java.opts.  It output a lot of
>> class
>> > loading info to the stdout log, but there were no references to my 
>> > in mylib2.jar.
>> >
>> > This has to be caching this code somehow whether it is in flink or in
>> the
>> > jvm.  Any ideas what could be happening or how to debug this further?
>> >
>> > Thanks
>> >
>> >
>> >

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