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Date: Wed, 30 May 2012 13:13:36 +0200
From: Ivan Kelly <ivank@apache.org>
To: bookkeeper-user@zookeeper.apache.org
Subject: Re: Is there any way to set a string name for a ledger and how to
 do checkpoint ?
Message-ID: <20120530111335.GA16393@moloch.vm.bytemark.co.uk>
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User-Agent: Mutt/1.5.20 (2009-06-14)

Hi Stone,

Currently the bookkeeper API only provides the primatives, and
developers need to add their own glue code on top of this. 

It may be worth your while to take a look at the WAL implementation we
did for HDFS[1]. This has "named" ledgers, and allow supports the
checkpointing. 

A "editlog" is a sequence of ledgers, which the journal manager
maintains in zookeeper. When a checkpoint is made, the current ledger
is closed, and a new one is created. HDFS maintains it's own
transaction ids so that it can removed old ledgers which are no longer
needed after checkpointing. 

We have been thinking about pulling out this abstract to make it
easier for general use, but not much progress has been made on this
yet. 

Regards
Ivan


[1] https://github.com/apache/hadoop-common/tree/trunk/hadoop-hdfs-project/hadoop-hdfs/src/contrib/bkjournal