Andreas:
On Wed, Apr 30, 2025 at 5:28 PM Andreas Stieger <andreas.stie...@gmx.de>
wrote:
> On 2025-04-30 17:07, Doug Robinson wrote:
>
> On Wed, Apr 30, 2025 at 10:25 AM Doug Robinson <doug.robin...@cirata.com>
> wrote:
>
>> On Wed, Apr 30, 2025 at 4:17 AM Andreas Stieger <andreas.stie...@gmx.de>
>> wrote:
>>
>>> WANdisco is not a typical Subversion server implementation. For
>>> synchronous multi-site replication (as opposed to svn sync which is
>>> asynchronous), it provides a proxy layer with a consensus protocol
>>> (think PAXOS, wsrep, raft).
>>
>>
> The WANdisco implementation is still asynchronous even though we try
> our hardest to make the replication occur absolutely as fast as possible.
> The PAXOS implementation is used to schedule the order of the repository
> updates. The updates then occur in that order at every site as soon as the
> data is available and the prior update has been applied.
>
> While a synchronous implementation might be great within a single data
> center, it comes with way too many problems for a world-wide WAN
> environment.
>
> Certainly, I should have been more clear with that I mean: In a
> multi-master replication setup you need consensus at a point when you want
> a candidate transaction to become a revision. If there is only such
> candidate ready, you can commit to both your global sequence and to the
> committing the client rather quickly. Not every other node may see it
> instantaneously, but would not be able to commit to another until they are
> caught up. I briefly played with the wsrep replication API between svn_fs
> layers to make a FLOSS version of that but never got beyond a prototype.
>
Cool! I can see you understand the details. I just needed folks (and the
historical
record comprised of this information) to understand that our implementation
is not
synchronous. It may seem like a minor point until you dig into the
ramifications.
Cheers.
Doug
--
*Doug Robinson* Senior Product Manager
P +1 925 396 1125
*E* doug.robin...@cirata.com
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