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From Emmanuel Lecharny <>
Subject Re: [DRS] Changelog improvements
Date Mon, 26 Jan 2009 10:27:24 GMT
Hi David,

> I'm not sure exactly what the requirements here are but a couple of existing
> projects that might provide a usable journal/log:
> objectweb howl is a transaction log, basically its designed to write
> "prepare" entries that have some data and "commit" entries that say the data
> is no longer relevant.  I imagine you could write the ldif entry as the
> "prepare" record and some indication of all replicas being up-to-date as the
> "commit" entry.

That's something we might check, as it may alleviate the burden of
writing our own wheel...

> activemq has quite a few journal/log schemes.  I think that they are mostly
> using kaha.  I'm don't understand all the features but think that it would
> do everything you need.  IIUC typically the messages themselves are written
> to one "database" and for each subscription an index entry is written to a
> related reference database.  As the acks come in for the subscriptions the
> index entries are removed and after all deliveries have happened the main
> entry is removed.

Another project to look at.

> I imagine you could implement the whole replication scheme using activemq
> embedded brokers on each server but this might not be the most performant
> implementation.

Regarding activeMQ, atm, nothing has been decided. We thought about
using a JMS system to manage replication, as it offrs a reliable
asynchronous system to communicate between servers. We have to go a
bit further in the requirements, nothing is really stabilized atm.
Emmanuel L├ęcharny

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