GTM_Standby_Configuration

(Draft)

What is GTM standby

GTM is Postgres-XC's central component which provides MVCC (multi-version concurrent control) information and sequence information to all the Postgres-XC transaction to implement single database view. Postgres-XC assumes that GTM is running and GTM crash leads to whole XC cluster crash. Because GTM provides tens of thousands of MVCC information per second, it is not practical to make static backup of GTM status used in the failover.

GTM standby usually runs on different server and backs up all the status change in GTM and maintains copy of GTM status for the failover. For the test or for your experience, GTM standby can run on the same server though. This page describes how to configure GTM standby and how it can be failed over when the master GTM crashes.

You should be familiar with GTM configuration. Plase visit [Real_Server_Configuration] and [Configure_Server_GTM] pages to learn this. All the configurations here are based upon these pages. Please note that GTM standby assumes Postgres-XC is configured with GTM proxy to handle GTM failover.

GTM standby configuration

Here, we're going to configure GTM standby as follows:

1. Server: runs on the server node04
2. Port: uses the port 20001
3. Nodename: gtm (same as Master GTM) --> Need to test of this is okay!!
4. Working directory: /home/postgresxc/pgxc/gtm
5. Master GM server: master GTM runs on the server node03 ([Real_Server_Configuration])
6. Master GTM server port: 20001

4 and 5 are taken from the fundamental configuration we've used in basic XC configuration.

To configure the above GTM standby, do as follows:

[main]$ ssh node04
[node04]$ initgtm -Z gtm -D /home/postgresxc/pgxc/gtm
[node04]$ cat >> /home/postgresxc/pgxc/gtm/gtm.conf