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From Chiwan Park <chiwanp...@apache.org>
Subject Re: Flink on EMR Question
Date Wed, 06 Jan 2016 06:14:20 GMT

Thanks for answering me!

It is happy to hear the problem will be addressed. :)

About question 2, flink-runtime uses Apache Httpclient 4.2.6 and S3 file system api implemented
by Amazon uses 4.3.x. There are some API changes, so NoSuchMethodError exception occurs.

> On Jan 5, 2016, at 11:59 PM, Stephan Ewen <sewen@apache.org> wrote:
> Hi!
> Concerning (1) We have seen that a few times. The JVMs / Threads do sometimes not properly
exit in a graceful way, and YARN is not always able to kill the process (YARN bug). I am currently
working on a refactoring of the YARN resource manager (to allow to easy addition of other
frameworks) and have addressed this as part of that. Will be in the master in a bit.
> Concerning (2) Do you know which component in Flink uses the HTTP client?
> Greetings,
> Stephan
> On Tue, Jan 5, 2016 at 2:49 PM, Maximilian Bode <maximilian.bode@tngtech.com> wrote:
> Hi everyone,
> Regarding Q1, I believe I have witnessed a comparable phenomenon in a (3-node, non-EMR)
YARN cluster. After shutting down the yarn session via `stop`, one container seems to linger
around. `yarn application -list` is empty, whereas `bin/yarn-session.sh -q` lists the left-over
container. Also, there is still one application shown as ‚running‘ in Ambari’s YARN
pane under current applications. Then, after some time (order of a few minutes) it disappears
and the resources are available again.
> I have not tested this behavior extensibly so far. Noticeably, I was not able to reproduce
it by just starting a session and then ending it again right away without looking at the JobManager
web interface. Maybe this produces some kind of lag as far as YARN containers are concerned?
> Cheers,
> Max
> > Am 04.01.2016 um 12:52 schrieb Chiwan Park <chiwanpark@apache.org>:
> >
> > Hi All,
> >
> > I have some problems using Flink on Amazon EMR cluster.
> >
> > Q1. Sometimes, jobmanager container still exists after destroying yarn session by
pressing Ctrl+C. In that case, Flink YARN app seems exited correctly in YARN RM dashboard.
But there is a running container in the dashboard. From logs of the container, I realize that
the container is jobmanager.
> >
> > I cannot kill the container because there is no permission to restart YARN RM in
Amazon EMR. In my small Hadoop Cluster (w/3 nodes), the problem doesn’t appear.
> >
> > Q2. I tried to use S3 file system in Flink on EMR. But I can’t use it because
of version conflict of Apache Httpclient. In default, implementation of S3 file system in
EMR is `com.amazon.ws.emr.hadoop.fs.s3n.S3NativeFileSystem` which is linked with other version
of Apache Httpclient.
> >
> > As I wrote above, I cannot restart Hadoop cluster after modifying conf-site.xml
because of lack of permission. How can I solve this problem?
> >
> > Regards,
> > Chiwan Park
> >
> >

Chiwan Park

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