Managing the High Availability Service for Mirrorless Greenplum

This section provides guidance on how to manage the Greenplum high availability service, greenplum-postmaster. The greenplum-postmaster service monitors the primary segments of a Greenplum cluster to initiate automatic recovery if they become unavailable. This is required if running Greenplum without mirroring. Refer to About the Greenplum Architecture for more information about Greenplum primary segments and mirroring.

Prerequisites

Ensure that you have installed the greenplum-postmaster service. You may install the greenplum-postmaster service when you deploy a Greenplum cluster using the Greenplum Virtual Appliance, or by Installing the Greenplum High Availability Service if you deployed your cluster manually.

• If you deployed your cluster using the Greenplum Virtual Appliance, the greenplum-postmaster service is already enabled and running.

• If you deployed your cluster manually, the greenplum-postmaster service is not enabled by default. Follow Initializing the greenplum-postmaster Service to enable the service.

Validating the Greenplum Postmaster Service

Follow the steps below to check that the greenplum-postmaster service exists, is enabled, and is running:

• Log in to the master as gpadmin.
• To check if the service exists and is enabled on all hosts, run:

  gpssh -f hosts-all -e 'systemctl --user is-enabled greenplum-postmaster.service'
  

• To verify that the service is active and running on all hosts, run:

  gpssh -f hosts-all -e 'systemctl --user status greenplum-postmaster.service'
  

Managing the greenplum-postmaster Service

Follow the steps below to stop, start, and view the journal log of the greenplum-postmaster service:

• Log in to the master as gpadmin.
• To stop the greenplum-postmaster service, run:

  gpssh -f hosts-all -e 'systemctl --user stop greenplum-postmaster.service'
  

• To start the greenplum-postmaster service, run:

  gpssh -f hosts-all -e 'systemctl --user start greenplum-postmaster.service'
  

• To view the journal log, run:

  gpssh -f hosts-all -e 'journalctl --user-unit greenplum-postmaster.service'
  

Troubleshooting

You may encounter an error while accessing journal logs from the gpadmin user due to insufficient permissions.

$ journalctl --user-unit greenplum-postmaster.service
Hint: You are currently not seeing messages from the system.
      Users in the 'systemd-journal' group can see all messages. Pass -q to
      turn off this notice.
No journal files were opened due to insufficient permissions.

To resolve the above issue, log in to the master asroot and run the below command. It will add the gpadmin user to the systemd-journal group on all the hosts.

source /usr/local/greenplum-db/greenplum_path.sh
gpssh -f /home/gpadmin/hosts-all -e 'usermod -a -G systemd-journal gpadmin'

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