Return-Path: X-Original-To: apmail-hadoop-hdfs-user-archive@minotaur.apache.org Delivered-To: apmail-hadoop-hdfs-user-archive@minotaur.apache.org Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by minotaur.apache.org (Postfix) with SMTP id 4196D101BE for ; Wed, 16 Oct 2013 05:17:10 +0000 (UTC) Received: (qmail 83645 invoked by uid 500); 16 Oct 2013 05:16:57 -0000 Delivered-To: apmail-hadoop-hdfs-user-archive@hadoop.apache.org Received: (qmail 83514 invoked by uid 500); 16 Oct 2013 05:16:55 -0000 Mailing-List: contact user-help@hadoop.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: user@hadoop.apache.org Delivered-To: mailing list user@hadoop.apache.org Received: (qmail 83477 invoked by uid 99); 16 Oct 2013 05:16:54 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 16 Oct 2013 05:16:54 +0000 X-ASF-Spam-Status: No, hits=1.5 required=5.0 tests=HTML_MESSAGE,RCVD_IN_DNSWL_LOW,SPF_PASS X-Spam-Check-By: apache.org Received-SPF: pass (athena.apache.org: domain of dechouxb@gmail.com designates 209.85.215.45 as permitted sender) Received: from [209.85.215.45] (HELO mail-la0-f45.google.com) (209.85.215.45) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 16 Oct 2013 05:16:50 +0000 Received: by mail-la0-f45.google.com with SMTP id eh20so164551lab.18 for ; Tue, 15 Oct 2013 22:16:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=9a17jQ7TzogTp3PtK2474t+E3ut3DHNbRUdy3kzi46c=; b=lkHxhHZ7SzKnAFDUxSvx/Tn0aHlEasQF8s8NtzSs4WTyh/4aULHR9dcv1+KvKjRn7V ixnssUGLLehehW8FBwojpcHMavfYq9Rnugi4ZHRr+5o2JdD6fCSrIpSOskw6YHM/BzQa phLpbtY61H2bseeG435F3dXZFoCFsXDv/QMLXhapa2YFecJ6odjWNISS+dfyw7Amiu8Z 6O57fPx8rLEA+V13luMa687cF/tGKGAbPguuE6WYYS4uSopbIJebAIt7Tjxneib7EBj9 hlpO3psoOHOkLTTuNkHx5yzfJiPp2LFeMEUJB/6ZVG1b65o63mKSKV3WMW4ayN51rfTi PeDw== MIME-Version: 1.0 X-Received: by 10.153.11.134 with SMTP id ei6mr38248lad.38.1381900588876; Tue, 15 Oct 2013 22:16:28 -0700 (PDT) Received: by 10.112.147.3 with HTTP; Tue, 15 Oct 2013 22:16:28 -0700 (PDT) In-Reply-To: References: Date: Wed, 16 Oct 2013 07:16:28 +0200 Message-ID: Subject: Re: high availability From: Bertrand Dechoux To: "user@hadoop.apache.org" Content-Type: multipart/alternative; boundary=001a113456eab70a5e04e8d4cd06 X-Virus-Checked: Checked by ClamAV on apache.org --001a113456eab70a5e04e8d4cd06 Content-Type: text/plain; charset=ISO-8859-1 http://blog.cloudera.com/blog/2012/10/quorum-based-journaling-in-cdh4-1/ Old version (4.1) but the principle is still the same. *No requirement for custom fencing configuration *- fencing methods such as STONITH require custom hardware; instead, we should rely only on software methods. Bertrand PS: But then the only true validation is by testing it. On Tue, Oct 15, 2013 at 10:59 PM, Jing Zhao wrote: > I think a real fencing is not required in case that you're using > QJM-based HA. If you are using ZKFC, a graceful fencing will first be > triggered in which ZKFC will send a RPC request to the original ANN to > make it standby. If the graceful fencing failed the configured fencing > will be used. In the worst case that your original ANN cannot > transition to standby state, QJM still has built-in single-writer > semantics (see https://issues.apache.org/jira/browse/HDFS-3862, > https://issues.apache.org/jira/browse/HDFS-4915). Thus you can set the > fence method to shell(/bin/true) (since in the current code the fence > configuration is still required). > > On Tue, Oct 15, 2013 at 12:11 PM, Koert Kuipers wrote: > > Jing, > > thanks for your answer. > > > > if hbase with high availability is the desired goal, is it recommended to > > remove sshfence? we do not plan to use hdfs for anything else. > > > > i understood that the only downside of no fencing is that the old > namenode > > could still be serving read requests. could this negatively impact hbase > > functionality, or worse, could it corrupt hbase somehow (not sure how > that > > would be...)? > > > > thanks! koert > > > > > > > > On Tue, Oct 15, 2013 at 12:38 AM, Jing Zhao > wrote: > >> > >> "it is unclear to me if the transition in this case is also rapid but > >> the fencing takes long while the new namenode is already active, or if > >> in this period i am stuck without an active namenode." > >> > >> The standby->active transition will get stuck in this period, i.e., > >> the NN can only become active after fencing the old active NN. During > >> this period since the only NN is in standby state which cannot handle > >> usual R/W operations and just throws StandbyException, hbase region > >> server may kill itself in some cases I guess. > >> > >> I think you can remove sshfence from the configuration if you are > >> using QJM-based HA. > >> > >> On Fri, Oct 11, 2013 at 4:51 PM, Koert Kuipers > wrote: > >> > i have been playing with high availability using journalnodes and 2 > >> > masters > >> > both running namenode and hbase master. > >> > > >> > when i kill the namenode and hbase-master processes on the active > >> > master, > >> > the failover is perfect. hbase never stops and a running map-reduce > jobs > >> > keeps going. this is impressive! > >> > > >> > however when instead of killing the proceses i kill the entire active > >> > master > >> > machine, the transactions is less smooth and can take a long time, at > >> > least > >> > it seems this way in the logs. this is because ssh fencing fails but > >> > keeps > >> > trying. my fencing is configured as: > >> > > >> > > >> > dfs.ha.fencing.methods > >> > > >> > sshfence > >> > shell(/bin/true) > >> > > >> > true > >> > > >> > > >> > it is unclear to me if the transition in this case is also rapid but > the > >> > fencing takes long while the new namenode is already active, or if in > >> > this > >> > period i am stuck without an active namenode. it is hard to accurately > >> > test > >> > this in my setup. > >> > is this supposed to take this long? is HDFS writable in this period? > and > >> > is > >> > hbase supposed to survive this long transition? > >> > > >> > thanks! koert > >> > >> -- > >> CONFIDENTIALITY NOTICE > >> NOTICE: This message is intended for the use of the individual or entity > >> to > >> which it is addressed and may contain information that is confidential, > >> privileged and exempt from disclosure under applicable law. If the > reader > >> of this message is not the intended recipient, you are hereby notified > >> that > >> any printing, copying, dissemination, distribution, disclosure or > >> forwarding of this communication is strictly prohibited. If you have > >> received this communication in error, please contact the sender > >> immediately > >> and delete it from your system. Thank You. > > > > > > -- > CONFIDENTIALITY NOTICE > NOTICE: This message is intended for the use of the individual or entity to > which it is addressed and may contain information that is confidential, > privileged and exempt from disclosure under applicable law. If the reader > of this message is not the intended recipient, you are hereby notified that > any printing, copying, dissemination, distribution, disclosure or > forwarding of this communication is strictly prohibited. If you have > received this communication in error, please contact the sender immediately > and delete it from your system. Thank You. > -- Bertrand Dechoux --001a113456eab70a5e04e8d4cd06 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable

Old version (4.1) but the pr= inciple is still the same.

No requirement for custom fencing configuration=A0- fencing meth= ods such as STONITH=A0= require custom hardware; instead, we should rely only on software methods.<= br>

Bertrand
PS: But then the only true validation= is by testing it.

On Tue, Oct 15, 2013 at 10:59 PM, Jing Zhao <jing@hortonworks.com= > wrote:
I think a real fencing is not required in case that you're using
QJM-based HA. If you are using ZKFC, a graceful fencing will first be
triggered in which ZKFC will send a RPC request to the original ANN to
make it standby. If the graceful fencing failed the configured fencing
will be used. In the worst case that your original ANN cannot
transition to standby state, QJM still has built-in single-writer
semantics (see https://issues.apache.org/jira/browse/HDFS-3862,
https://issues.apache.org/jira/browse/HDFS-4915). Thus you can set t= he
fence method to shell(/bin/true) (since in the current code the fence
configuration is still required).

On Tue, Oct 15, 2013 at 12:11 PM, Koert Kuipers <koert@tresata.com> wrote:
> Jing,
> thanks for your answer.
>
> if hbase with high availability is the desired goal, is it recommended= to
> remove sshfence? we do not plan to use hdfs for anything else.
>
> i understood that the only downside of no fencing is that the old name= node
> could still be serving read requests. could this negatively impact hba= se
> functionality, or worse, could it corrupt hbase somehow (not sure how = that
> would be...)?
>
> thanks! koert
>
>
>
> On Tue, Oct 15, 2013 at 12:38 AM, Jing Zhao <jing@hortonworks.com> wrote:
>>
>> "it is unclear to me if the transition in this case is also r= apid but
>> the fencing takes long while the new namenode is already active, o= r if
>> in this period i am stuck without an active namenode."
>>
>> The standby->active transition will get stuck in this period, i= .e.,
>> the NN can only become active after fencing the old active NN. Dur= ing
>> this period since the only NN is in standby state which cannot han= dle
>> usual R/W operations and just throws StandbyException, hbase regio= n
>> server may kill itself in some cases I guess.
>>
>> I think you can remove sshfence from the configuration if you are<= br> >> using QJM-based HA.
>>
>> On Fri, Oct 11, 2013 at 4:51 PM, Koert Kuipers <koert@tresata.com> wrote:
>> > i have been playing with high availability using journalnodes= and 2
>> > masters
>> > both running namenode and hbase master.
>> >
>> > when i kill the namenode and hbase-master processes on the ac= tive
>> > master,
>> > the failover is perfect. hbase never stops and a running map-= reduce jobs
>> > keeps going. this is impressive!
>> >
>> > however when instead of killing the proceses i kill the entir= e active
>> > master
>> > machine, the transactions is less smooth and can take a long = time, at
>> > least
>> > it seems this way in the logs. this is because ssh fencing fa= ils but
>> > keeps
>> > trying. my fencing is configured as:
>> >
>> > =A0<property>
>> > =A0 =A0 <name>dfs.ha.fencing.methods</name>
>> > =A0 =A0 <value>
>> > =A0 =A0 =A0 sshfence
>> > =A0 =A0 =A0 shell(/bin/true)
>> > =A0 =A0 </value>
>> > =A0 =A0 <final>true</final>
>> > =A0 </property>
>> >
>> > it is unclear to me if the transition in this case is also ra= pid but the
>> > fencing takes long while the new namenode is already active, = or if in
>> > this
>> > period i am stuck without an active namenode. it is hard to a= ccurately
>> > test
>> > this in my setup.
>> > is this supposed to take this long? is HDFS writable in this = period? and
>> > is
>> > hbase supposed to survive this long transition?
>> >
>> > thanks! koert
>>
>> --
>> CONFIDENTIALITY NOTICE
>> NOTICE: This message is intended for the use of the individual or = entity
>> to
>> which it is addressed and may contain information that is confiden= tial,
>> privileged and exempt from disclosure under applicable law. If the= reader
>> of this message is not the intended recipient, you are hereby noti= fied
>> that
>> any printing, copying, dissemination, distribution, disclosure or<= br> >> forwarding of this communication is strictly prohibited. If you ha= ve
>> received this communication in error, please contact the sender >> immediately
>> and delete it from your system. Thank You.
>
>

--
CONFIDENTIALITY NOTICE
NOTICE: This message is intended for the use of the individual or entity to=
which it is addressed and may contain information that is confidential,
privileged and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, you are hereby notified that=
any printing, copying, dissemination, distribution, disclosure or
forwarding of this communication is strictly prohibited. If you have
received this communication in error, please contact the sender immediately=
and delete it from your system. Thank You.



--
Bertrand De= choux
--001a113456eab70a5e04e8d4cd06--