postgres-xc-developers Mailing List for Postgres-XC (Page 2)

On Tue, Nov 1, 2011 at 1:25 AM, Michael Paquier
<mic...@gm...> wrote:
> Hi all,
>
> Please find attached a patch that adds a new option -C/--clusterfile
> allowing to specify a customized SQL file at initdb for node initialization
> with NODE DDL.
> The new option works as follows:
> initdb -C ./custom_file.sql -D datadir
> initdb --clusterfile ./custom_file.sql -D datadir
>
> Any comments are welcome.

I think we should slow down this line of development and re-think how
to do it without any SQL initialization file and find a better
solution. This is getting into the overall architecture of the system
and does not feel very clean to me. To be clear, I like the DDL
approach you advocate and the potential for flexibility it gives XC,
and that you put something together for it, but so far it seems to be
making things a bit unwieldy.

I prefer that we think about how to do this more cleanly in the
architecture and then develop supporting commands around that, before
we get too wedded to the current approach.

I will think about this some more, likely involving an abstraction
layer of (implicit) segments/partitions associated with nodes instead
of explicit named nodes directly.

Thanks,

Mason


> Regards,
> --
> Michael Paquier
> http://michael.otacoo.com
>
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Hi all,

Please find attached a patch the adds a keyword in CREATE/ALTER NODE to
identify the node-self.
Until now this was determined by the guc parameter pgxc_node_name.
The node DDL becomes with the extension for example:
CREATE NODE nodename WITH (SELF);
ALTER NODE nodename SET NOT SELF;

Also this patch adds deletes node registration for Coordinator, Datanode
and Proxy.
In current master pgxc_node_name is only necessary at early stages for
registration purposes so I think this makes sense.
It also simplifies the way nodes are added in the cluster.
However, those APIs are not completely deleted because GTM-Standby still
registers himself, so some feedback about this point would be nice.

Any comment is welcome.
Regards,
-- 
Michael Paquier
http://michael.otacoo.com

Hi all,

Please find attached a patch that adds a new option -C/--clusterfile
allowing to specify a customized SQL file at initdb for node initialization
with NODE DDL.
The new option works as follows:
initdb -C ./custom_file.sql -D datadir
initdb --clusterfile ./custom_file.sql -D datadir

Any comments are welcome.
Regards,
-- 
Michael Paquier
http://michael.otacoo.com

> I was not sure of the overall design, just trying to point out the
> theoretical danger, and again, because DDL was added for slaves, I was
> originally not sure if the intention was to allow them to retain their
> names and yet be able to be promoted. That is why I mentioned naming
> the partitions and using that order. Alternatively, perhaps one could
> use an internal id/OID behind the scenes for the partions, sort by
> that for determine hash & modulo buckets, and have a mapping of the
> partitions and node instances. Each master and standby should know
> what its partion id/oid is, perhaps returned at connection time when
> the connection comes from a coordinator.  This might do away with the
> node renaming issue.  Just something to mull over.  Or, maybe some
> standby naming convention will help. We should just think ahead a
> little bit about possible HA management scenarios for flexibility.
>
That's always good to remind there may be future issues in the future
regarding that.


> > Just about that....
> > The first meaning of registering nodes on GTM was to keep a track of all
> the
> > node information in the cluster.
> > But now that node names are the same and have to remain constant in the
> > cluster, is this really necessary?
> > Removing that will also allow to remove pgxc_node_name from guc params.
> > Then identifying a node self for Coordinator/Datanode could be done by
> > initdb with a SELF/NOT SELF keyword as an extension of CREATE DDL.
>
> Maybe it is a good idea. How would a node rename itself later then?
> ALTER NODE oldname RENAME newname? Then if it sees that its own name
> matches oldname, change itself to newname? Otherwise just update
> catalog info?
>
The initial thought was that a node could not rename itself at the current
state and that node names remain constant and consistant in the cluster.
That's why no SQL extensions have been made on this purpose yet.
In case a slave has to be changed to a former master, it should be renamed
to the old master though automatically.
Once again, one of the possible extensions would be to have a node
partition system as you mentioned inside pgxc_node for example.
-- 
Michael Paquier
http://michael.otacoo.com

>
> That worked, thank you.
>
That's good to know.
I will commit hopefully this week a patch to add an option in initdb to
specify a file that can be used instead of cluster_nodes.sql in share
folder.
Thanks,
-- 
Michael Paquier
http://michael.otacoo.com