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Message from discussion Geographic Clusters connected by Gateway Nodes
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KTWalrus  
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 More options May 14 2012, 4:23 pm
From: KTWalrus <ktwal...@gmail.com>
Date: Mon, 14 May 2012 13:23:06 -0700 (PDT)
Local: Mon, May 14 2012 4:23 pm
Subject: Re: Geographic Clusters connected by Gateway Nodes
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BTW, the updates between Gateway nodes could be virtually synchronous
too, except that instead of an error back to the originator on failed
commit, the originating Gateway node could log the failed update to an
internal MySQL table so it could be manually examined, fixed, and re-
applied (if desired).  The update wouldn't be virtually synchronous
with the originating transaction since that would be committed to the
LAN Cluster before the Gateway node would initiate WAN replication.
But, individual clusters connected to the Gateway node would either be
all updated or none.

Also, I want to avoid using Oracle MySQL replication for anything
since I believe that if Oracle adds good star network replication,
they will not Open Source it (but keep it as a premium addon).
Percona Cluster looks like one project that is committed to Open
Source and I would like to choose it over any premium addon from
Oracle.

On May 14, 4:10 pm, KTWalrus <ktwal...@gmail.com> wrote:

> I thought MySQL replication is one-way?  So, I would have to designate
> two Gateway nodes in my 4 node cluster.  One would server for inbound
> updates and the other would serve for outbound updates.  And, for 3 or
> more clusters, I would need to setup a Gateway ring of replication.

> Percona Cluster uses a star network for replication and nodes handle
> both inbound and outbound updates.  I think it would be simpler if
> Percona Cluster supported Geographic Clusters as I described.  The
> Geographic Cluster could automatically handle failouts of clusters (as
> it does for LAN nodes) and auto-increments WAN wide instead of just
> LAN wide.  The Geographic Cluster would look just like a mega cluster
> with WAN links using optimized asynchronous replication and LAN links
> using virtually synchronous replication.  Otherwise, the entire
> cluster would look like one big efficient cluster.

> Really, the main feature that attracts me to Percona Cluster is the
> easy of setup and maintenance (handling failouts and joins) and the
> virtually synchronous feature is of lower priority to me.  A Percona
> Geographic Cluster that works just like a LAN Cluster, except that
> multiple Clusters may be semi-asynchronously connected for WAN
> updates, would be a fantastic option.

> On May 14, 3:35 pm, Alex Yurchenko <alexey.yurche...@codership.com>
> wrote:

> > Why don't you just use the regular asynchronous MySQL replication for
> > that? Any cluster node can serve as a "gateway", so provided you have
> > enough nodes you can theoretically have dedicated gateways for each
> > remote DC.

> > The thing is it won't be a Cluster anymore, as each DC will have its
> > own GTID, so it will be a group of loosely coupled clusters.

> > On 2012-05-14 21:40, KTWalrus wrote:

> > > I'm considering upgrading to Percona Cluster.  I will have 4 MySQL
> > > nodes in my local cluster.  When performance dictates that I need
> > > another node in the cluster, I'd like to colocate a new 4 node
> > > cluster
> > > in another DC (probably on the opposite coast from my first cluster).
> > > When I need yet more clusters, I want to locate it in another DC.

> > > I'm a bit worried that connecting my 4 node clusters to make 1 big
> > > Percona Cluster is going to kill performance.  As I understand it,
> > > Percona Clusters are only as fast to execute an update query as the
> > > slowest RTT between all nodes in the cluster.  The WAN links will
> > > naturally have the slowest RTT since they are geographically
> > > distributed (potentially crossing the entire continent).

> > > So, I'm wonder if Percona Cluster has or plans to have any
> > > enhancement
> > > to not make replicating changes between LAN clusters over WAN?

> > > If not, I suggest that 1 node in a cluster is the Gateway node for
> > > the
> > > cluster (accepting WAN to LAN and forwarding LAN to WAN updates).
> > > I'd think the current Master for the LAN cluster should automatically
> > > be the Gateway.

> > > Now, the updates within the LAN cluster should be virtually
> > > synchronous but asynchronous  between Gateways over the WAN.  Of
> > > couse, asynchronous updates should flow in both directions and be
> > > initiated as soon as the update is committed to the sending Gateway's
> > > node.

> > > The point is to not allow the replication time between clusters to
> > > affect a local cluster update time, but still keep the entire
> > > Geographic Cluster fairly in sync.  Also, this should save WAN
> > > bandwidth since the update only travels to and from Gateway nodes and
> > > not all nodes in the Geographic Cluster.


 
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