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Date: Sat, 2 Oct 2010 00:38:54 -0700 (PDT)
From: amit jaiswal <amit_jus@yahoo.com>
Subject: Re: BookKeeper newbie question
To: zookeeper-user@hadoop.apache.org
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Hi Flavio,=0A=0AI am using zookeeper 3.2.2. The documentation on apache =0A=
(http://hadoop.apache.org/zookeeper/docs/r3.3.0/bookkeeperStarted.html) ref=
ers =0Ato example that uses LedgerSequence class.=0A=0A=0ABasically I am tr=
ying to use BookKeeper / Hedwig and see if they can be used as =0Aa reliabl=
e message bus. Hedwig has only a video (http://vimeo.com/13282102) that =0A=
explains the system overview. But installation is non-trivial. I tried buil=
ding =0Afrom trunk, but trunk version is 3.4 and hedwig bundles zk 3.2 code=
 within =0Aitself. In short, was not able to build/install hedwig.=0A=0A1. =
Could you please give some pointers for hedwig. It seems that BookKeeper AP=
Is =0Aneed higher level abstraction which Hedwig can provide.=0A=0A2. How d=
oes bookkeeper handles zk session expiry? To be honest, zk itself should =
=0Acome up with a solution to recover from session expiry. Found this blog =
=0A: http://sna-projects.com/blog/2010/08/zookeeper-experience/ which actua=
lly =0Alists all the issues that I also faced while working with zk. =0A=0A=
3. Any comments on '=E2=80=9CLow Latency Message Bus With Scribe and HDFS=
=0A : http://sna-projects.com/blog/2010/09/scribe-and-hdfs/ and how that co=
mpares =0Ato BookKeeper / Hedwig?=0A=0A-regards=0AAmit=0A=0A=0A=0A=0A----- =
Original Message ----=0AFrom: Flavio Junqueira <fpj@yahoo-inc.com>=0ATo: "z=
ookeeper-user@hadoop.apache.org" <zookeeper-user@hadoop.apache.org>=0ASent:=
 Fri, 1 October, 2010 2:37:35 PM=0ASubject: Re: BookKeeper newbie question=
=0A=0AThanks for your questions, Amit.=0A=0AOn Sep 28, 2010, at 6:37 PM, am=
it jaiswal wrote:=0A=0A> Hi,=0A> =0A> I am experimenting with BookKeeper an=
d have a question on LedgerHandler class.=0A> The readEntries(firstEntry, l=
astEntry) method takes the indexes of first and=0A> last entries. Also, the=
 LedgerSequence object returned has method=0A> hasMoreElements().=0A=0AWhic=
h version are you using? I don't think we have LedgerSequence any longer.=
=0A=0A> =0A> Question:=0A> 1. How does a client knows the index of the last=
 entry? I was expecting =0Aclients=0A> to make a call like readEntries(0, I=
nteger.MAX_INT) and the hasMoreElements() =0A>to=0A> return false the momen=
t there are no more entries. Am I missing something in =0A>the=0A> way the =
API is supposed to be used?=0A> =0A=0AI believe you should use public long =
getLastAddConfirmed().=0A=0A=0A> 2. The LedgerSequence.hasMoreElements() re=
turns true (even if there are no =0Amore=0A> entries), and the nextEntry re=
turns null.=0A> =0A=0AreadEntries currently return Enumeration<LedgerEntry>=
, but I just noticed that =0Athe documentation is not correct, so I'll open=
 a jira to fix it.=0A=0A-Flavio