debian-mirror-gitlab/doc/topics/autodevops/upgrading_postgresql.md

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Upgrading PostgreSQL for Auto DevOps (FREE)

Auto DevOps provides an in-cluster PostgreSQL database for your application.

The version of the chart used to provision PostgreSQL:

• Is 0.7.1 in GitLab 12.8 and earlier.
• Can be set to from 0.7.1 to 8.2.1 in GitLab 12.9 and later.

GitLab encourages users to migrate their database to the newer PostgreSQL chart.

This guide provides instructions on how to migrate your PostgreSQL database, which involves:

1. Taking a database dump of your data.
2. Installing a new PostgreSQL database using the newer version 8.2.1 of the chart and removing the old PostgreSQL installation.
3. Restoring the database dump into the new PostgreSQL.

Prerequisites

1. Install kubectl.
2. Ensure that you can access your Kubernetes cluster using kubectl. This varies based on Kubernetes providers.
3. Prepare for downtime. The steps below include taking the application offline so that the in-cluster database does not get modified after the database dump is created.
4. Ensure you have not set POSTGRES_ENABLED to false, as this setting deletes any existing channel 1 database. For more information, see Detected an existing PostgreSQL database.

NOTE: If you have configured Auto DevOps to have staging, consider trying out the backup and restore steps on staging first, or trying this out on a review app.

Take your application offline

If required, take your application offline to prevent the database from being modified after the database dump is created.

1. Get the Kubernetes namespace for the environment. It typically looks like <project-name>-<project-id>-<environment>. In our example, the namespace is called minimal-ruby-app-4349298-production.

   $ kubectl get ns
   
   NAME                                                  STATUS   AGE
   minimal-ruby-app-4349298-production                   Active   7d14h
   

2. For ease of use, export the namespace name:

   export APP_NAMESPACE=minimal-ruby-app-4349298-production
   

3. Get the deployment name for your application with the following command. In our example, the deployment name is production.

   $ kubectl get deployment --namespace "$APP_NAMESPACE"
   NAME                  READY   UP-TO-DATE   AVAILABLE   AGE
   production            2/2     2            2           7d21h
   production-postgres   1/1     1            1           7d21h
   

4. To prevent the database from being modified, set replicas to 0 for the deployment with the following command. We use the deployment name from the previous step (deployments/<DEPLOYMENT_NAME>).

   $ kubectl scale --replicas=0 deployments/production --namespace "$APP_NAMESPACE"
   deployment.extensions/production scaled
   

5. You must also set replicas to zero for workers if you have any.

Backup

1. Get the service name for PostgreSQL. The name of the service should end with -postgres. In our example the service name is production-postgres.

   $ kubectl get svc --namespace "$APP_NAMESPACE"
   NAME                     TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)    AGE
   production-auto-deploy   ClusterIP   10.30.13.90   <none>        5000/TCP   7d14h
   production-postgres      ClusterIP   10.30.4.57    <none>        5432/TCP   7d14h
   

2. Get the pod name for PostgreSQL with the following command. In our example, the pod name is production-postgres-5db86568d7-qxlxv.

   $ kubectl get pod --namespace "$APP_NAMESPACE" -l app=production-postgres
   NAME                                   READY   STATUS    RESTARTS   AGE
   production-postgres-5db86568d7-qxlxv   1/1     Running   0          7d14h
   

3. Connect to the pod with:

   kubectl exec -it production-postgres-5db86568d7-qxlxv --namespace "$APP_NAMESPACE" bash
   

4. Once, connected, create a dump file with the following command.

   • SERVICE_NAME is the service name obtained in a previous step.

   • USERNAME is the username you have configured for PostgreSQL. The default is user.

   • DATABASE_NAME is usually the environment name.

   • When prompted for the database password, the default is testing-password.

   ## Format is:
   # pg_dump -h SERVICE_NAME -U USERNAME DATABASE_NAME > /tmp/backup.sql
   
   pg_dump -h production-postgres -U user production > /tmp/backup.sql
   

5. Once the backup dump is complete, exit the Kubernetes exec process with Control-D or exit.

6. Download the dump file with the following command:

   kubectl cp --namespace "$APP_NAMESPACE" production-postgres-5db86568d7-qxlxv:/tmp/backup.sql backup.sql
   

Retain persistent volumes

By default the persistent volumes used to store the underlying data for PostgreSQL is marked as Delete when the pods and pod claims that use the volume is deleted.

This is significant as, when you opt into the newer 8.2.1 PostgreSQL, the older 0.7.1 PostgreSQL is deleted causing the persistent volumes to be deleted as well.

You can verify this by using the following command:

$ kubectl get pv
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                                                     STORAGECLASS   REASON   AGE
pvc-0da80c08-5239-11ea-9c8d-42010a8e0096   8Gi        RWO            Delete           Bound    minimal-ruby-app-4349298-staging/staging-postgres         standard                7d22h
pvc-9085e3d3-5239-11ea-9c8d-42010a8e0096   8Gi        RWO            Delete           Bound    minimal-ruby-app-4349298-production/production-postgres   standard                7d22h

To retain the persistent volume, even when the older 0.7.1 PostgreSQL is deleted, we can change the retention policy to Retain. In this example, we find the persistent volume names by looking at the claims names. As we are interested in keeping the volumes for the staging and production of the minimal-ruby-app-4349298 application, the volume names here are pvc-0da80c08-5239-11ea-9c8d-42010a8e0096 and pvc-9085e3d3-5239-11ea-9c8d-42010a8e0096:

$ kubectl patch pv  pvc-0da80c08-5239-11ea-9c8d-42010a8e0096 -p '{"spec":{"persistentVolumeReclaimPolicy":"Retain"}}'
persistentvolume/pvc-0da80c08-5239-11ea-9c8d-42010a8e0096 patched
$ kubectl patch pv  pvc-9085e3d3-5239-11ea-9c8d-42010a8e0096 -p '{"spec":{"persistentVolumeReclaimPolicy":"Retain"}}'
persistentvolume/pvc-9085e3d3-5239-11ea-9c8d-42010a8e0096 patched
$ kubectl get pv
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                                                     STORAGECLASS   REASON   AGE
pvc-0da80c08-5239-11ea-9c8d-42010a8e0096   8Gi        RWO            Retain           Bound    minimal-ruby-app-4349298-staging/staging-postgres         standard                7d22h
pvc-9085e3d3-5239-11ea-9c8d-42010a8e0096   8Gi        RWO            Retain           Bound    minimal-ruby-app-4349298-production/production-postgres   standard                7d22h

Install new PostgreSQL

WARNING: Using the newer version of PostgreSQL deletes the older 0.7.1 PostgreSQL. To prevent the underlying data from being deleted, you can choose to retain the persistent volume.

NOTE: You can also scope the AUTO_DEVOPS_POSTGRES_CHANNEL, AUTO_DEVOPS_POSTGRES_DELETE_V1 and POSTGRES_VERSION variables to specific environments, e.g. staging.

1. Set AUTO_DEVOPS_POSTGRES_CHANNEL to 2. This opts into using the newer 8.2.1-based PostgreSQL, and removes the older 0.7.1-based PostgreSQL.
2. Set AUTO_DEVOPS_POSTGRES_DELETE_V1 to a non-empty value. This flag is a safeguard to prevent accidental deletion of databases.
3. If you have a POSTGRES_VERSION set, make sure it is set to 9.6.16 or higher. This is the minimum PostgreSQL version supported by Auto DevOps. See also the list of tags available.
4. Set PRODUCTION_REPLICAS to 0. For other environments, use REPLICAS with an environment scope.
5. If you have set the DB_INITIALIZE or DB_MIGRATE variables, either remove the variables, or rename the variables temporarily to XDB_INITIALIZE or the XDB_MIGRATE to effectively disable them.
6. Run a new CI pipeline for the branch. In this case, we run a new CI pipeline for master.
7. After the pipeline is successful, your application is upgraded with the new PostgreSQL installed. Zero replicas exist at this time, so no traffic is served for your application (to prevent new data from coming in).

Restore

1. Get the pod name for the new PostgreSQL, in our example, the pod name is production-postgresql-0:

   $ kubectl get pod --namespace "$APP_NAMESPACE" -l app=postgresql
   NAME                      READY   STATUS    RESTARTS   AGE
   production-postgresql-0   1/1     Running   0          19m
   

2. Copy the dump file from the backup steps to the pod:

   kubectl cp --namespace "$APP_NAMESPACE" backup.sql production-postgresql-0:/tmp/backup.sql
   

3. Connect to the pod:

   kubectl exec -it production-postgresql-0 --namespace "$APP_NAMESPACE" bash
   

4. Once connected to the pod, run the following command to restore the database.

   • When asked for the database password, the default is testing-password.
   • USERNAME is the username you have configured for PostgreSQL. The default is user.
   • DATABASE_NAME is usually the environment name.

   ## Format is:
   # psql -U USERNAME -d DATABASE_NAME < /tmp/backup.sql
   
   psql -U user -d production < /tmp/backup.sql
   

5. You can now check that your data restored correctly after the restore is complete. You can perform spot checks of your data by using the psql.

Reinstate your application

Once you are satisfied the database has been restored, run the following steps to reinstate your application:

1. Restore the DB_INITIALIZE and DB_MIGRATE variables, if previously removed or disabled.
2. Restore the PRODUCTION_REPLICAS or REPLICAS variable to its original value.
3. Run a new CI pipeline for the branch. In this case, we run a new CI pipeline for master. After the pipeline is successful, your application should be serving traffic as before.