To expand a Greenplum cluster, you first use the Greenplum Operator to apply an updated Greenplum cluster configuration that increases the number of segments. The Greenplum Operator automatically creates the new segment pods in Kubernetes and starts a job to run gpexpand and initialize the new segments. You can optionally run manual commands to redistribute data to the new segments, and to remove the gpexpand schema that is created during the expansion process.
Note: You cannot resize a cluster to use a lower number of segments; you must delete and re-create the cluster to reduce the number of segments.
Follow these steps to expand a VMware Tanzu Greenplum cluster on Kubernetes:
Go to the workspace subdirectory where you unpacked the VMware Tanzu Greenplum distribution, or to the directory where you created your Greenplum cluster deployment manifest. For example:
$ cd ./greenplum-for-kubernetes-*/workspace
Edit the manifest file that you used to deploy your Greenplum cluster. Edit the file to increase the primarySegmentCount value. This example increases the number of segments defined in the default Greenplum deployment (my-gp-instance.yaml) to 6:
primarySegmentCount: 6
After modifying the file, use kubectl to apply the change. For example:
$ kubectl apply -f my-gp-instance.yaml
greenplumcluster.greenplum.pivotal.io/my-greenplum configured
Execute watch kubectl get all and wait until the new Greenplum pods reach the Running state:. Also observe the progress of the expansion job (job.batch/my-greenplum-gpexpand-job) and wait for it to complete:
$ watch kubectl get all
NAME READY STATUS RESTARTS AGE
pod/greenplum-operator-6ff95b6b79-kq9vr 1/1 Running 0 60m
pod/master-0 1/1 Running 0 43m
pod/my-greenplum-gpexpand-job-52g4q 1/1 Running 0 30s
pod/segment-a-0 1/1 Running 0 43m
pod/segment-a-1 1/1 Running 0 31s
pod/segment-a-2 1/1 Running 0 31s
pod/segment-a-3 1/1 Running 0 31s
pod/segment-a-4 1/1 Running 0 31s
pod/segment-a-5 1/1 Running 0 31s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/agent ClusterIP None <none> 22/TCP 43m
service/greenplum LoadBalancer 10.102.131.136 <pending> 5432:32753/TCP 43m
service/greenplum-validating-webhook-service-6ff95b6b79-kq9vr ClusterIP 10.106.60.103 <none> 443/TCP 60m
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 64m
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/greenplum-operator 1/1 1 1 60m
NAME DESIRED CURRENT READY AGE
replicaset.apps/greenplum-operator-6ff95b6b79 1 1 1 60m
NAME READY AGE
statefulset.apps/master 1/1 43m
statefulset.apps/segment-a 6/6 43m
NAME COMPLETIONS DURATION AGE
job.batch/my-greenplum-gpexpand-job 0/1 30s 30s
NAME STATUS AGE
greenplumcluster.greenplum.pivotal.io/my-greenplum Running 43m
In the unlikely case that the update fails, the Greenplum cluster's status will be UpdateFailed. Should that occur, investigate the logs (for example, kubectl logs pod/my-greenplum-gpexpand-job-52g4q) to see what happened, address the underlying problem, and use kubectl to re-apply the change.
The expansion process is complete after all pods' expansion jobs are marked Complete, and job.batch/my-greenplum-gpexpand-job, shows 1/1 Completions. At that point, you can either use the cluster with the new segment resources as-is, or continue with the optional steps below to redistribute data to the new segment pods and/or remove the expansion schema.
(Optional.) If you want to redistribute existing data to use the new segment pods, perform these steps:
Open a bash shell to the Greenplum master pod:
$ kubectl exec -it master-0 -- bash
gpadmin@master-0:~$
Execute the gpexpand command with the -d or -e options to specify the maximum duration or end time after which redistribution stops, respectively. Also include -D gpadmin to indicate that the expansion schema is stored in the gpadmin database. For example, to redistribute tables for a maximum of 10 hours, enter:
$ gpexpand -d 10:00:00
20200513:19:20:32:002601 gpexpand:master-0:gpadmin-[INFO]:-local Greenplum Version: 'postgres (Greenplum Database) 6.8.0 build commit:a21de286045072d8d1df64fa48752b7dfac8c1b7'
20200513:19:20:32:002601 gpexpand:master-0:gpadmin-[INFO]:-master Greenplum Version: 'PostgreSQL 9.4.24 (Greenplum Database 6.8.0 build commit:a21de286045072d8d1df64fa48752b7dfac8c1b7) on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu 7.5. 0-3ubuntu1~18.04) 7.5.0, 64-bit compiled on Apr 30 2020 00:14:35'
20200513:19:20:32:002601 gpexpand:master-0:gpadmin-[INFO]:-Querying gpexpand schema for current expansion state
20200513:19:20:32:002601 gpexpand:master-0:gpadmin-[INFO]:-Expanding gpadmin.madlib.migrationhistory
20200513:19:20:32:002601 gpexpand:master-0:gpadmin-[INFO]:-Finished expanding gpadmin.madlib.migrationhistory
20200513:19:20:37:002601 gpexpand:master-0:gpadmin-[INFO]:-EXPANSION COMPLETED SUCCESSFULLY
20200513:19:20:37:002601 gpexpand:master-0:gpadmin-[INFO]:-Exiting...
If you do not specify the -d or -e options, redistribution is performed until all tables in the expansion schema are redistributed. If you specify a duration or end time and redistribution stops before all tables are redistributed, you can continue redistributing tables at a later time.
(Optional.) Remove the expansion schema if you have finished redistributing tables to the new segments, or if you never intend to redistribute tables to the new segments.
Note: You must remove the expansion schema before you can expand the Greenplum cluster again.
Open a bash shell to the Greenplum master pod:
$ kubectl exec -it master-0 bash
gpadmin@master-0:~$
Execute the gpexpand command with the -c option, and enter y when prompted to delete the expansion schema:
$ gpexpand -c
20200513:19:22:19:002637 gpexpand:master-0:gpadmin-[INFO]:-local Greenplum Version: 'postgres (Greenplum Database) 6.8.0 build commit:a21de286045072d8d1df64fa48752b7dfac8c1b7'
20200513:19:22:19:002637 gpexpand:master-0:gpadmin-[INFO]:-master Greenplum Version: 'PostgreSQL 9.4.24 (Greenplum Database 6.8.0 build commit:a21de286045072d8d1df64fa48752b7dfac8c1b7) on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu 7.5. 0-3ubuntu1~18.04) 7.5.0, 64-bit compiled on Apr 30 2020 00:14:35'
20200513:19:22:19:002637 gpexpand:master-0:gpadmin-[INFO]:-Querying gpexpand schema for current expansion state
Do you want to dump the gpexpand.status_detail table to file? Yy|Nn (default=Y):
> y
20200513:19:22:33:002637 gpexpand:master-0:gpadmin-[INFO]:-Dumping gpexpand.status_detail to /greenplum/data-1/gpexpand.status_detail
20200513:19:22:33:002637 gpexpand:master-0:gpadmin-[INFO]:-Removing gpexpand schema
20200513:19:22:33:002637 gpexpand:master-0:gpadmin-[INFO]:-Cleanup Finished. exiting...
