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From Patrick Hunt <ph...@apache.org>
Subject Re: observers in occasionally disconnected data centers
Date Wed, 04 May 2011 16:26:00 GMT
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
>

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