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From Gwenhael Pasquiers <gwenhael.pasqui...@ericsson.com>
Subject RE: YARN High Availability
Date Mon, 23 Nov 2015 16:00:07 GMT
We are not yet using HA in our cluster instances.
But yes, we will have to change the zookeeper.path.root ☺

We package our jobs with their own config folder (we don’t rely on flink’s config folder);
we can put the maven project name into this property then they will have different values
☺


From: Till Rohrmann [mailto:trohrmann@apache.org]
Sent: lundi 23 novembre 2015 14:51
To: user@flink.apache.org
Subject: Re: YARN High Availability

The problem is the execution graph handle which is stored in ZooKeeper. You can manually remove
it via the ZooKeeper shell by simply deleting everything below your `recovery.zookeeper.path.root`
ZNode. But you should be sure that the cluster has been stopped before.

Do you start the different clusters with different `recovery.zookeeper.path.root` values?
If not, then you should run into troubles when running multiple clusters at the same time.
The reason is that then all clusters will think that they belong together.

Cheers,
Till

On Mon, Nov 23, 2015 at 2:15 PM, Gwenhael Pasquiers <gwenhael.pasquiers@ericsson.com<mailto:gwenhael.pasquiers@ericsson.com>>
wrote:
OK, I understand.

Maybe we are not really using flink as you intended. The way we are using it, one cluster
equals one job. That way we are sure to isolate the different jobs as much as possible and
in case of crashes / bugs / (etc) can completely kill one cluster without interfering with
the other jobs.

That future behavior seems good :-)

Instead of the manual flink commands, is there to manually delete those old jobs before launching
my job ? They probably are somewhere in hdfs, aren't they ?

B.R.


-----Original Message-----
From: Ufuk Celebi [mailto:uce@apache.org<mailto:uce@apache.org>]
Sent: lundi 23 novembre 2015 12:12
To: user@flink.apache.org<mailto:user@flink.apache.org>
Subject: Re: YARN High Availability

Hey Gwenhaël,

the restarting jobs are most likely old job submissions. They are not cleaned up when you
shut down the cluster, but only when they finish (either regular finish or after cancelling).

The workaround is to use the command line frontend:

bin/flink cancel JOBID

for each RESTARTING job. Sorry about the inconvenience!

We are in an active discussion about addressing this. The future behaviour will be that the
startup or shutdown of a cluster cleans up everything and an option to skip this step.

The reasoning for the initial solution (not removing anything) was to make sure that no jobs
are deleted by accident. But it looks like this is more confusing than helpful.

– Ufuk

> On 23 Nov 2015, at 11:45, Gwenhael Pasquiers <gwenhael.pasquiers@ericsson.com<mailto:gwenhael.pasquiers@ericsson.com>>
wrote:
>
> Hi again !
>
> On the same topic I'm still trying to start my streaming job with HA.
> The HA part seems to be more or less OK (I killed the JobManager and it came back), however
I have an issue with the TaskManagers.
> I configured my job to have only one TaskManager and 1 slot that does [source=>map=>sink].
> The issue I'm encountering is that other instances of my job appear and are in the RESTARTING
status since there is only one task slot.
>
> Do you know of this, or have an idea of where to look in order to understand what's happening
?
>
> B.R.
>
> Gwenhaël PASQUIERS
>
> -----Original Message-----
> From: Maximilian Michels [mailto:mxm@apache.org<mailto:mxm@apache.org>]
> Sent: jeudi 19 novembre 2015 13:36
> To: user@flink.apache.org<mailto:user@flink.apache.org>
> Subject: Re: YARN High Availability
>
> The docs have been updated.
>
> On Thu, Nov 19, 2015 at 12:36 PM, Ufuk Celebi <uce@apache.org<mailto:uce@apache.org>>
wrote:
>> I’ve added a note about this to the docs and asked Max to trigger a new build of
them.
>>
>> Regarding Aljoscha’s idea: I like it. It is essentially a shortcut for configuring
the root path.
>>
>> In any case, it is orthogonal to Till’s proposals. That one we need to address
as well (see FLINK-2929). The motivation for the current behaviour was to be rather defensive
when removing state in order to not loose data accidentally. But it can be confusing, indeed.
>>
>> – Ufuk
>>
>>> On 19 Nov 2015, at 12:08, Till Rohrmann <trohrmann@apache.org<mailto:trohrmann@apache.org>>
wrote:
>>>
>>> You mean an additional start-up parameter for the `start-cluster.sh` script for
the HA case? That could work.
>>>
>>> On Thu, Nov 19, 2015 at 11:54 AM, Aljoscha Krettek <aljoscha@apache.org<mailto:aljoscha@apache.org>>
wrote:
>>> Maybe we could add a user parameter to specify a cluster name that is used to
make the paths unique.
>>>
>>>
>>> On Thu, Nov 19, 2015, 11:24 Till Rohrmann <trohrmann@apache.org<mailto:trohrmann@apache.org>>
wrote:
>>> I agree that this would make the configuration easier. However, it entails also
that the user has to retrieve the randomized path from the logs if he wants to restart jobs
after the cluster has crashed or intentionally restarted. Furthermore, the system won't be
able to clean up old checkpoint and job handles in case that the cluster stop was intentional.
>>>
>>> Thus, the question is how do we define the behaviour in order to retrieve handles
and to clean up old handles so that ZooKeeper won't be cluttered with old handles?
>>>
>>> There are basically two modes:
>>>
>>> 1. Keep state handles when shutting down the cluster. Provide a mean to define
a fixed path when starting the cluster and also a mean to purge old state handles. Furthermore,
add a shutdown mode where the handles under the current path are directly removed. This mode
would guarantee to always have the state handles available if not explicitly told differently.
However, the downside is that ZooKeeper will be cluttered most certainly.
>>>
>>> 2. Remove the state handles when shutting down the cluster. Provide a shutdown
mode where we keep the state handles. This will keep ZooKeeper clean but will give you also
the possibility to keep a checkpoint around if necessary. However, the user is more likely
to lose his state when shutting down the cluster.
>>>
>>> On Thu, Nov 19, 2015 at 10:55 AM, Robert Metzger <rmetzger@apache.org<mailto:rmetzger@apache.org>>
wrote:
>>> I agree with Aljoscha. Many companies install Flink (and its config) in a central
directory and users share that installation.
>>>
>>> On Thu, Nov 19, 2015 at 10:45 AM, Aljoscha Krettek <aljoscha@apache.org<mailto:aljoscha@apache.org>>
wrote:
>>> I think we should find a way to randomize the paths where the HA stuff stores
data. If users don’t realize that they store data in the same paths this could lead to problems.
>>>
>>>> On 19 Nov 2015, at 08:50, Till Rohrmann <trohrmann@apache.org<mailto:trohrmann@apache.org>>
wrote:
>>>>
>>>> Hi Gwenhaël,
>>>>
>>>> good to hear that you could resolve the problem.
>>>>
>>>> When you run multiple HA flink jobs in the same cluster, then you don’t
have to adjust the configuration of Flink. It should work out of the box.
>>>>
>>>> However, if you run multiple HA Flink cluster, then you have to set for each
cluster a distinct ZooKeeper root path via the option recovery.zookeeper.path.root in the
Flink configuraiton. This is necessary because otherwise all JobManagers (the ones of the
different clusters) will compete for a single leadership. Furthermore, all TaskManagers will
only see the one and only leader and connect to it. The reason is that the TaskManagers will
look up their leader at a ZNode below the ZooKeeper root path.
>>>>
>>>> If you have other questions then don’t hesitate asking me.
>>>>
>>>> Cheers,
>>>> Till
>>>>
>>>>
>>>> On Wed, Nov 18, 2015 at 6:37 PM, Gwenhael Pasquiers <gwenhael.pasquiers@ericsson.com<mailto:gwenhael.pasquiers@ericsson.com>>
wrote:
>>>> Nevermind,
>>>>
>>>>
>>>>
>>>> Looking at the logs I saw that it was having issues trying to connect to
ZK.
>>>>
>>>> To make I short is had the wrong port.
>>>>
>>>>
>>>>
>>>> It is now starting.
>>>>
>>>>
>>>>
>>>> Tomorrow I’ll try to kill some JobManagers *evil*.
>>>>
>>>>
>>>>
>>>> Another question : if I have multiple HA flink jobs, are there some points
to check in order to be sure that they won’t collide on hdfs or ZK ?
>>>>
>>>>
>>>>
>>>> B.R.
>>>>
>>>>
>>>>
>>>> Gwenhaël PASQUIERS
>>>>
>>>>
>>>>
>>>> From: Till Rohrmann [mailto:till.rohrmann@gmail.com<mailto:till.rohrmann@gmail.com>]
>>>> Sent: mercredi 18 novembre 2015 18:01
>>>> To: user@flink.apache.org<mailto:user@flink.apache.org>
>>>> Subject: Re: YARN High Availability
>>>>
>>>>
>>>>
>>>> Hi Gwenhaël,
>>>>
>>>>
>>>>
>>>> do you have access to the yarn logs?
>>>>
>>>>
>>>>
>>>> Cheers,
>>>>
>>>> Till
>>>>
>>>>
>>>>
>>>> On Wed, Nov 18, 2015 at 5:55 PM, Gwenhael Pasquiers <gwenhael.pasquiers@ericsson.com<mailto:gwenhael.pasquiers@ericsson.com>>
wrote:
>>>>
>>>> Hello,
>>>>
>>>>
>>>>
>>>> We’re trying to set up high availability using an existing zookeeper quorum
already running in our Cloudera cluster.
>>>>
>>>>
>>>>
>>>> So, as per the doc we’ve changed the max attempt in yarn’s config as
well as the flink.yaml.
>>>>
>>>>
>>>>
>>>> recovery.mode: zookeeper
>>>>
>>>> recovery.zookeeper.quorum: host1:3181,host2:3181,host3:3181
>>>>
>>>> state.backend: filesystem
>>>>
>>>> state.backend.fs.checkpointdir: hdfs:///flink/checkpoints
>>>>
>>>> recovery.zookeeper.storageDir: hdfs:///flink/recovery/
>>>>
>>>> yarn.application-attempts: 1000
>>>>
>>>>
>>>>
>>>> Everything is ok as long as recovery.mode is commented.
>>>>
>>>> As soon as I uncomment recovery.mode the deployment on yarn is stuck on :
>>>>
>>>>
>>>>
>>>> “Deploying cluster, current state ACCEPTED”.
>>>>
>>>> “Deployment took more than 60 seconds….”
>>>>
>>>> Every second.
>>>>
>>>>
>>>>
>>>> And I have more than enough resources available on my yarn cluster.
>>>>
>>>>
>>>>
>>>> Do you have any idea of what could cause this, and/or what logs I should
look for in order to understand ?
>>>>
>>>>
>>>>
>>>> B.R.
>>>>
>>>>
>>>>
>>>> Gwenhaël PASQUIERS
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
> <unwanted_jobs.jpg>

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