Return-Path: X-Original-To: apmail-zookeeper-user-archive@www.apache.org Delivered-To: apmail-zookeeper-user-archive@www.apache.org Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by minotaur.apache.org (Postfix) with SMTP id D2EFF775 for ; Wed, 4 May 2011 16:58:09 +0000 (UTC) Received: (qmail 29853 invoked by uid 500); 4 May 2011 16:58:09 -0000 Delivered-To: apmail-zookeeper-user-archive@zookeeper.apache.org Received: (qmail 29720 invoked by uid 500); 4 May 2011 16:58:09 -0000 Mailing-List: contact user-help@zookeeper.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: user@zookeeper.apache.org Delivered-To: mailing list user@zookeeper.apache.org Received: (qmail 29712 invoked by uid 99); 4 May 2011 16:58:09 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 04 May 2011 16:58:09 +0000 X-ASF-Spam-Status: No, hits=-0.7 required=5.0 tests=RCVD_IN_DNSWL_LOW,SPF_PASS X-Spam-Check-By: apache.org Received-SPF: pass (athena.apache.org: domain of ketan@indeed.com designates 209.85.213.170 as permitted sender) Received: from [209.85.213.170] (HELO mail-yx0-f170.google.com) (209.85.213.170) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 04 May 2011 16:58:04 +0000 Received: by yxi11 with SMTP id 11so649770yxi.15 for ; Wed, 04 May 2011 09:57:43 -0700 (PDT) MIME-Version: 1.0 Received: by 10.91.39.9 with SMTP id r9mr1274256agj.84.1304528262111; Wed, 04 May 2011 09:57:42 -0700 (PDT) Received: by 10.90.70.10 with HTTP; Wed, 4 May 2011 09:57:42 -0700 (PDT) In-Reply-To: References: Date: Wed, 4 May 2011 11:57:42 -0500 Message-ID: Subject: Re: observers in occasionally disconnected data centers From: Ketan Gangatirkar To: user@zookeeper.apache.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable 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 wrote: > Hi Ketan, the patch is failing to apply > https://builds.apache.org/hudson/job/PreCommit-ZOOKEEPER-Build/246//conso= le > > 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 wrot= e: >> 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. =A0The 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. =A0Now what? >> >> >> On Tue, May 3, 2011 at 5:46 PM, Patrick Hunt 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 wr= ote: >>>> Thanks, Mahadev. =A0I had seen ZOOKEEPER-892 but not ZOOKEEPER-784. = =A0The >>>> latter may be what we need. >>>> >>>> I read the comments attached to that issue. =A0The most recent comment >>>> was a Hudson CI message indicating that the tests against the patch >>>> failed. =A0I was not able to find out more as it appears that the >>>> configuration of the Apache Hudson has changed. =A0It 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? =A0I may = be >>>> able to assist, depending on what's involved. =A0Thank you. >>>> >>>> >>>> On Tue, May 3, 2011 at 4:17 PM, Mahadev Konar wro= te: >>>>> Hi Ketan, >>>>> =A0You 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 th= e >>>>> jiras. >>>>> >>>>> -- >>>>> thanks >>>>> mahadev >>>>> @mahadevkonar >>>>> >>>>> >>>>> >>>>> On Tue, May 3, 2011 at 2:07 PM, Ketan Gangatirkar = wrote: >>>>>> Hi. =A0We're considering ZooKeeper for coordinating operations acros= s >>>>>> multiple data centers. =A0These data centers will occasionally be >>>>>> disconnected. =A0We were planning on using observers in remote data >>>>>> centers. =A0Our 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. =A0Is this correct? =A0D= oes >>>>>> anyone have suggestions for how to work around this problem? =A0The >>>>>> 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. =A0I imagine the disadvantages of that are obv= ious >>>>>> to everyone. =A0I hope someone can share some great idea that allows= me >>>>>> to avoid that miserable fate. =A0Thanks. >>>>>> >>>>>> -- >>>>>> Ketan Gangatirkar >>>>>> ketan@indeed.com >>>>>> >>>>> >>>> >>>> >>>> >>>> -- >>>> Ketan Gangatirkar >>>> ketan@indeed.com >>>> Perishable Developer >>>> >>> >> >> >> >> -- >> Ketan Gangatirkar >> ketan@indeed.com >> Perishable Developer >> > --=20 Ketan Gangatirkar ketan@indeed.com Perishable Developer