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Re: External replication proceeding



> I received your email and am re-posting to the maria developers list.
> It is truly amazing that maria developers are HAPPY with replication
> as it stands right now.
> binary logs, Single SLAVE reading from individual masters,
> bla-bla-bla.....

You are absolutely correct in that the classic replication mechanism with the binary log is by no means perfect, and in particular setup of a new slave can be a complete pest. That said, it was first implemented around 1999 and has served the web world extremely well. In fact, it was implemented on behalf of one particular client (non-recurring engineering).

In development, inevitably priorities have to be set.
As classic replication is a known entity for people, they can generally cope with its quirks.
So rather than seeing it as a "must fix immediately", it's regarded as a "it'd be nice to replace this, over time".

If it were to be designed and implemented today, particularly with the knowledge of how replication is getting used in the real world, and without any restrictions on budget/scope from a particular client, I'm sure it'd look very different - and no developer here would disagree with that basis analysis of the situation.

In practical terms, Galera is one possible replacement - I say possible, because it works differently and therefore does not cover all specific use cases of classic replication. It is unlikely that any single alternative can replace all use cases, so I'd envisage that classic replication will continue to be used even if most people move to another mechanism.
Galera can take care of most uses cases, and its implementation takes care of initialisation of new nodes and resynchronisation.

The people at Codership identified the problems, worked on a new architecture, and delivered the Galera code to MariaDB.
I am very impressed with their work and ongoing commitment.

I suggest you do take a look at what Galera does. Does it satisfy the requirements for replication that you set? Based on your own email where you listed your requirements, I'm suggesting that it might. If it needs improving, why not contribute to the Galera code?

Should you feel that something else is required after all, please go right ahead and create it - as you know MariaDB gladly accepts contributions. I look forward to seeing your code contributions.

Regards, Arjen.
(MariaDB captain)
Arjen Lentz, Exec.Director @ Open Query (http://openquery.com)
Australian peace of mind for your MySQL/MariaDB infrastructure.

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