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From Ketan Gangatirkar <ke...@indeed.com>
Subject Re: observers in occasionally disconnected data centers
Date Wed, 18 May 2011 01:07:43 GMT
Hi.  Has there been any progress on this?  Thanks.

On Fri, May 6, 2011 at 11:32 AM, Patrick Hunt <phunt@apache.org> wrote:
> Mahadev is working with Giri to address. The jenkins folks are saying
> this is a machine administered by Yahoo and the issue needs to be
> address with them (their admins, but Mahadev/Giri are looking into it
> from our (zk) side).
>
> Patrick
>
> On Fri, May 6, 2011 at 4:33 AM, Ketan Gangatirkar <ketan@indeed.com> wrote:
>> Hi, Patrick.  Were you able to get any assistance from the hudson
>> admins?  Thanks.
>>
>> On Wed, May 4, 2011 at 12:53 PM, Patrick Hunt <phunt@apache.org> wrote:
>>> This is odd, it's failing in the c tests but for a weird reason:
>>>
>>> in:
>>> https://builds.apache.org/hudson/job/PreCommit-ZOOKEEPER-Build/247/artifact/trunk/build/tmp/zk.log
>>>
>>> it says:
>>> /grid/0/hudson/hudson-slave/workspace/PreCommit-ZOOKEEPER-Build/trunk/src/c/tests/zkServer.sh:
>>> line 115: java: command not found
>>>
>>> I'll ping the hudson admins and see if this is a known issue (also
>>> hudson is very slow today for some reason).
>>>
>>> Once that's addressed we should be good to go.
>>>
>>> Patrick
>>>
>>> On Wed, May 4, 2011 at 9:57 AM, Ketan Gangatirkar <ketan@indeed.com> wrote:
>>>> Got the patch formatted right and applying successfully, now I'll see
>>>> if I can figure out the unit test failure.
>>>>
>>>> On Wed, May 4, 2011 at 11:26 AM, Patrick Hunt <phunt@apache.org> wrote:
>>>>> Hi Ketan, the patch is failing to apply
>>>>> https://builds.apache.org/hudson/job/PreCommit-ZOOKEEPER-Build/246//console
>>>>>
>>>>> Looks like you used git, I usually do something like:
>>>>> git diff rev1..rev2 --no-prefix > ZOOKEEPER-784.patch
>>>>> can you give it another try?
>>>>>
>>>>> Patrick
>>>>>
>>>>> On Tue, May 3, 2011 at 6:42 PM, Ketan Gangatirkar <ketan@indeed.com>
wrote:
>>>>>> I have updated Sergey's patch to:
>>>>>>
>>>>>> * apply to current trunk
>>>>>> * incorporate one trivial output change he made to StatCommand in
>>>>>> NettyServerCnxn.java
>>>>>> * change log4j references to slf4j
>>>>>>
>>>>>> I have successfully run ant releaseaudit on the result.  The updated
>>>>>> patch is now attached to the issue:
>>>>>>
>>>>>> https://issues.apache.org/jira/browse/ZOOKEEPER-784
>>>>>>
>>>>>> I do *not* make any claim to have understood the contents of this
>>>>>> patch; all I did was synch everything and fix the obvious log4j/slf4j
>>>>>> change.  Now what?
>>>>>>
>>>>>>
>>>>>> On Tue, May 3, 2011 at 5:46 PM, Patrick Hunt <phunt@apache.org>
wrote:
>>>>>>> The core tests failed on last hudson, I just kicked off a patch
build,
>>>>>>> seems recent changes (logging?) have caused the patch to stop
>>>>>>> applying:
>>>>>>> https://hudson.apache.org/hudson/view/S-Z/view/ZooKeeper/job/PreCommit-ZOOKEEPER-Build/238/console
>>>>>>>
>>>>>>> Ketan would you like to try updating the patch and resubmit?
>>>>>>>
>>>>>>> Patrick
>>>>>>>
>>>>>>> On Tue, May 3, 2011 at 3:31 PM, Ketan Gangatirkar <ketan@indeed.com>
wrote:
>>>>>>>> Thanks, Mahadev.  I had seen ZOOKEEPER-892 but not ZOOKEEPER-784.
 The
>>>>>>>> latter may be what we need.
>>>>>>>>
>>>>>>>> I read the comments attached to that issue.  The most recent
comment
>>>>>>>> was a Hudson CI message indicating that the tests against
the patch
>>>>>>>> failed.  I was not able to find out more as it appears that
the
>>>>>>>> configuration of the Apache Hudson has changed.  It appears
that the
>>>>>>>> patch was approved but not merged into trunk, and it's now
in limbo.
>>>>>>>> What is necessary to get that feature into the next release?
 I may be
>>>>>>>> able to assist, depending on what's involved.  Thank you.
>>>>>>>>
>>>>>>>>
>>>>>>>> On Tue, May 3, 2011 at 4:17 PM, Mahadev Konar <mahadev@apache.org>
wrote:
>>>>>>>>> Hi Ketan,
>>>>>>>>>  You are correct that observers need connection to quorum
as well.
>>>>>>>>> There have been quite a few discussions on multi colo
replication and
>>>>>>>>> read only mode of ZooKeeper.
>>>>>>>>>
>>>>>>>>> Here are the jiras for those:
>>>>>>>>>
>>>>>>>>> https://issues.apache.org/jira/browse/ZOOKEEPER-784
>>>>>>>>> and
>>>>>>>>> https://issues.apache.org/jira/browse/ZOOKEEPER-892
>>>>>>>>>
>>>>>>>>> These have been mostly targeted at exactly a use case
like yours.
>>>>>>>>> Please take a look and them and feel free to contribute/comment
on the
>>>>>>>>> jiras.
>>>>>>>>>
>>>>>>>>> --
>>>>>>>>> thanks
>>>>>>>>> mahadev
>>>>>>>>> @mahadevkonar
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Tue, May 3, 2011 at 2:07 PM, Ketan Gangatirkar <ketan@indeed.com>
wrote:
>>>>>>>>>> Hi.  We're considering ZooKeeper for coordinating
operations across
>>>>>>>>>> multiple data centers.  These data centers will
occasionally be
>>>>>>>>>> disconnected.  We were planning on using observers
in remote data
>>>>>>>>>> centers.  Our applications can survive being unable
to *write* to
>>>>>>>>>> ZooKeeper, but they do need to be able to read from
it, even if the
>>>>>>>>>> data were stale.
>>>>>>>>>>
>>>>>>>>>> On further examination, it looks like observers must
always be
>>>>>>>>>> connected to the quorum to function at all.  Is
this correct?  Does
>>>>>>>>>> anyone have suggestions for how to work around this
problem?  The
>>>>>>>>>> first thing that comes to mind is duplicating the
required data in
>>>>>>>>>> some other local data store and falling back on that
when the DC
>>>>>>>>>> becomes disconnected.  I imagine the disadvantages
of that are obvious
>>>>>>>>>> to everyone.  I hope someone can share some great
idea that allows me
>>>>>>>>>> to avoid that miserable fate.  Thanks.
>>>>>>>>>>
>>>>>>>>>> --
>>>>>>>>>> Ketan Gangatirkar
>>>>>>>>>> ketan@indeed.com
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>> Ketan Gangatirkar
>>>>>>>> ketan@indeed.com
>>>>>>>> Perishable Developer
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Ketan Gangatirkar
>>>>>> ketan@indeed.com
>>>>>> Perishable Developer
>>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Ketan Gangatirkar
>>>> ketan@indeed.com
>>>> Perishable Developer
>>>>
>>>
>>
>>
>>
>> --
>> Ketan Gangatirkar
>> ketan@indeed.com
>> Perishable Developer
>>
>



-- 
Ketan Gangatirkar
ketan@indeed.com
Perishable Developer

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