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From: =?ISO-8859-1?Q?Andr=E9_Oriani?= <ra078686@students.ic.unicamp.br>
Date: Sat, 17 Jul 2010 21:02:24 -0300
Message-ID: <AANLkTikfzJlzzfCmfavAuLI6gkzvTAloDPz9cAZvcJCR@mail.gmail.com>
Subject: BookKeeper Doubts
To: zookeeper-user@hadoop.apache.org
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Hi,


I was not sure if I had understood the behavior of BookKeeper from
documentation. So I made  a little program, reproduced below, to see what
BookKeeper looks like in action. Assuming my code is correct ( you never
know  when your code has some nasty obvious bugs that only other person tha=
n
you can see ) , I could draw the follow conclusions:

1) Only the creator can add entries to a ledger, even though you can  open
the ledger, get a handle and call addEntry on it. No exception is thrown  i=
.
In other words, you cannot open a ledger for append.

2) Readers are able to see only the entries that were added to a ledger
until someone had opened it for reading. If you want to ensure  readers wil=
l
see all the entries, you must add all entries before any reader attempts to
read from the ledger.

Could someone please tell me if those conclusions are correct or if I am
mistaken? In the later case, could that person also tell me what is wrong ?

Thanks a lot for the attention and the patience with this BookKeeper newbie=
,
Andr=E9


package br.unicamp.zooexp.booexp;


import java.io.IOException;

import java.util.Enumeration;


import org.apache.bookkeeper.client.BKException;

import org.apache.bookkeeper.client.BookKeeper;

import org.apache.bookkeeper.client.LedgerEntry;

import org.apache.bookkeeper.client.LedgerHandle;

import org.apache.bookkeeper.client.BookKeeper.DigestType;

import org.apache.zookeeper.KeeperException;


public class BookTest {


    public static void main (String ... args) throws IOException,
InterruptedException, KeeperException, BKException{

        BookKeeper bk =3D new BookKeeper("127.0.0.1");

        LedgerHandle lh =3D bk.createLedger(DigestType.CRC32, "123"
.getBytes());

        long lh_id =3D lh.getId();

        lh.addEntry("Teste".getBytes());

        lh.addEntry("Test2".getBytes());

        System.out.printf("Got %d entries for lh\n"
,lh.getLastAddConfirmed()+1);


        lh.addEntry("Test3".getBytes());

        LedgerHandle lh1 =3D bk.openLedger(lh_id, DigestType.CRC32, "123"
.getBytes());

        System.out.printf("Got %d entries for lh1\n"
,lh1.getLastAddConfirmed()+1);

        lh.addEntry("Test4".getBytes());


        lh.addEntry("Test5".getBytes());

        lh.addEntry("Test6".getBytes());

        System.out.printf("Got %d entries for lh\n"
,lh.getLastAddConfirmed()+1);

        Enumeration<LedgerEntry> seq =3D lh.readEntries(0,
lh.getLastAddConfirmed());

        while (seq.hasMoreElements()){

            System.out.println(new String(seq.nextElement().getEntry()));

        }

        lh.close();


        lh1.addEntry("Test7".getBytes());

        lh1.addEntry("Test8".getBytes());


        System.out.printf("Got %d entries for lh1\n"
,lh1.getLastAddConfirmed()+1);


        seq =3D lh1.readEntries(0, lh1.getLastAddConfirmed());

        while (seq.hasMoreElements()){

            System.out.println(new String(seq.nextElement().getEntry()));

        }


        lh1.close();


        LedgerHandle lh2 =3D bk.openLedger(lh_id, DigestType.CRC32, "123"
.getBytes());

        lh2.addEntry("Test9".getBytes());


        System.out.printf("Got %d entries for lh2 \n"
,lh2.getLastAddConfirmed()+1);


        seq =3D lh2.readEntries(0, lh2.getLastAddConfirmed());

        while (seq.hasMoreElements()){

            System.out.println(new String(seq.nextElement().getEntry()));

        }


        bk.halt();


    }

}


Output:

Got 2 entries for lh

Got 3 entries for lh1

Got 6 entries for lh

Teste

Test2

Test3

Test4

Test5

Test6

Got 3 entries for lh1

Teste

Test2

Test3

Got 3 entries for lh2

Teste

Test2

Test3

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