Re: dbmirror revisions

On Saturday August 16 2003 5:20, Bruce Momjian wrote:
> Ed, where are you on these dbmirror improvements?

My changes are complete as of late April, and I have not worked much on it
since. The changes are not in your CVS. Need to work with the dbmirror
author to see if that makes sense at this point.

Ed

> Ed L. wrote:
> > I've been modifying dbmirror and wanted to offer my changes to anyone
> > that cared to experiment, FWIW. My effort is ongoing, the docs aren't
> > perfect, I make no claims of production readiness, and testing of this
> > latest version has been minimal, so I strongly advise you to conduct
> > your own thorough testing before considering a production deployment.
> > That said, it's a significantly improved solution for our async
> > master-slave needs, with a few caveats below, and shouldn't be too hard
> > to setup.
> >
> > There are enough changes that I would hardly consider this a patch,
> > closer to an overhaul, since I've removed files, renamed others, and
> > added new files. Among the changes I've made so far:
> >
> > * Added script for easier setup of many tables/dbs/slaves;
> > * Added initial support for multiple master replicating distinct data
> > to a single slave;
> > * Added batching to minimize load on master and net traffic. You can
> > grab a configurable number of updates to replicate before hitting the
> > master again.
> >
> > * Added port specification;
> > * Wrapped all replication in transactions;
> > * Bulletproofed against downed master or slave;
> > * Started modularization of DB access layer, added some error
> > handling;
> > * Added a number of config vars for sync delays, etc;
> > * Eliminated bug in transaction ordering for replay. Updates
> > cannot be replicated in the order of the transactions (see archives for
> > discussion of why).
> >
> > * Eliminated need for clear_pending.pl by making dbmirror.pl
> > self-clearing;
> > * Collasped schema into 1 queue table for performance;
> > * Changed sequence ID column types to BIGINT for 64-bit
> > sequence; * Added reconnection handling for robustness;
> > * Added local tracking of last seq_id to help with recovery
> > robustness;
> > * Added master/slave compatibility checking;
> > * Enabled slave setup during production service so master does
> > not have to stop serving.
> > * Renamed tables to minimize namespace conflicts;
> > * Added lots of logging/debug messages;
> >
> > * Maybe a few other things I've forgotten...
> >
> >
> > AFAICS, there are still at least a few major drawbacks to this
> > approach:
> >
> > * DML statements are not replicated (same for eRServer, AFAIK).
> >
> > * SEQUENCE objects are not handled; nextval() will not be
> > replicated, so sequence objects (and serial columns) between master and
> > slave can easily get out of sync. I wonder if eRServer has this same
> > issue?
> >
> > * Mass updates/deletes/inserts of 5000 rows with a single SQL command
> > on the master will result in 5000 individual trigger-firings, and 5000
> > individual replication inserts on the slave. Rumor has it eRServer's
> > snapshot gets around this problem.
> >
> > The code is here:
> >
> > http://bluepolka.net/dbmirror/dbmirror-20030403-1605.tar.gz
> >
> > Ed
> >
> >
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