Re: [Postgres-xc-developers] What is best choice to set up a PGXC HA environment?

[Masaki H. <his...@la...>]

Hi, Julian, 

> > I am thinking 3 choices as below:
> >
> > 1. Pacemaker and Corosync.
> > I have little experience on Linux HA, so one week passed, I even can
> > not install them successfully, including
Pacemaker/Corosync/crmsh/resouce
> agent.
> > There are some website mentioned Pacemaker/corosync can help PGXC to
> > build a HA infrastructure, but I can not find a comprehensive guide to
> > do it. There are much more commponents in PGXC than PG, I think I
> > should learn how to build it based on PG first.
> 
> I know separate XC project to provide Pacemaker/Corosync resource
> agent for XC.   Please let me push them to provide info.

We are planning to release resource agent for pacemaker/heartbeat within a
few months.
Basic idea is to manage pairs of Master-Slave for Datanode, Coordinator and
GTM at each server by pacemaker.
Hopefully this could be one of the solution to HA feature at XC.

> > 2. Zookeeper
> > It seems that Zookeeper has the ability to build a HA solution for
> > PGXC, which have the similar function with Pacemaker, but I have to
> > develop the heartbeat function for Zookeeper to
> > start/stop/monitor/failover PGXC. And I do not know if my understand is
> right.
> 
> Sorry, I'm not familiar with Zookeeper.
>
> > 3. PGXC support HA internally.
> > Because the table of pgxc_nodes in coordinator already have some
> > information about the cluster, it can be enhanced to save the
> > Master/Slave relations, it is replicated between all coordinators,
> > then it can used as a CRM(Cluster Resource Management, as Pacemaker)
> compoment.
> > And the coordinator will connect to datanode/gtm/other coordinator in
> > its regular work, so the heartbeat function exists natually. Even when
> > the database is in the spare time, the coordinator can send a simple
> > query as "select 1+1" to datanodes as the heartbeat ticks.
> > What need to do is that, the coordinator will start a new process when
> > starting, the new process will act as a heartbeat /resouce_agent to
> > monitor the cluster status, and restart/failover once one commponent
fails.

How about monitoring coordinator and GTM? Do you have any idea?

> > As my initial understanding, Choice 3 is better than Choice 2 which is
> > better than Choice 1. But for the development effort, the order is
> > reversed, Choice 1 is easy achieved based on current existing codes.

What do we mean by better?
My requirement is as follows : 

Availability :
 - Shorten Failure detection
 - Shorten downtime at Failover / Switchover

Node management usability : 
 - We can manage Slave node as well as Master node into XC Cluster
 - Enables node monitoring and management at psql
 - No need to install / configure external tools : pacemaker / colosync 

What else?

Regards,

Hisada

> > I am very appreciated that you can share your advice with me.
> 
> Yes, I do agree with this solution.   I'd like to have this as a part
> of XC release 1.3.



> PGXC internal HA should be integrated with other monitoring feature such
as
> server hardware, power and network.
> 
> It will be exciting to begin this discussion in this mailing list.
> 
> Regards;
> ---
> Koichi Suzuki
> 
> >
> > Thanks
> > Julian
> >
> >
> >
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