Upgrade Guide - Scylla 4.1 to 4.2 for Red Hat Enterprise Linux 7/8 or CentOS 7/8

This document is a step by step procedure for upgrading from Scylla 4.1 to Scylla 4.2, and rollback to 4.1 if required.

Applicable versions

This guide covers upgrading Scylla from the following versions: 4.1.x or later to Scylla version 4.2.y, on the following platforms:

  • Red Hat Enterprise Linux 7/8 or CentOS 7/8

Upgrade Procedure

Note

Execute the following commands one node at the time, moving to the next node only after the upgrade procedure completed successfully.

Upgrading your Scylla version is a rolling procedure that does not require a full cluster shutdown. For each of the nodes in the cluster, serially (i.e. one at a time), you will:

  • Check the cluster’s schema

  • Drain the node and backup the data

  • Backup the configuration file

  • Stop the Scylla service

  • Download and install new Scylla packages

  • Start the Scylla service

  • Validate that the upgrade was successful

Apply the following procedure serially on each node. Do not move to the next node before validating the node is up and running with the new version.

Once all the nodes have been upgraded to the new version 4.2, run a serial restart of all the nodes.

During the rolling upgrade, it is highly recommended:

  • Not to use new 4.2 features

  • Not to run administration functions, like repairs, refresh, rebuild or add or remove nodes. See here for suspending Scylla Manager (only available Scylla Enterprise) scheduled or running repairs.

  • Not to apply schema changes

Note

Before upgrading, make sure to use Scylla Monitoring 3.4 or newer, for the Dashboards.

Upgrade steps

Check the cluster schema

Make sure that all nodes have the schema synched prior to upgrade as any schema disagreement between the nodes causes the upgrade to fail.

nodetool describecluster

Drain node and backup the data

Before any major procedure, like an upgrade, it is highly recommended to backup all the data to an external device. In Scylla, backup is done using the nodetool snapshot command. For each node in the cluster, run the following command:

nodetool drain
nodetool snapshot

Take note of the directory name that nodetool gives you, and copy all the directories having this name under /var/lib/scylla to an external backup device.

When the upgrade is complete (for all nodes), remove the snapshot by running nodetool clearsnapshot -t <snapshot>, or you risk running out of disk space.

Backup configuration file

sudo cp -a /etc/scylla/scylla.yaml /etc/scylla/scylla.yaml.backup-src

Stop Scylla

sudo systemctl stop scylla-server
sudo service scylla-server stop
docker exec -it some-scylla supervisorctl stop scylla

(without stopping some-scylla container)

Download and install the new release

Before upgrading, check what Scylla version you are currently running with rpm -qa | grep scylla-server. You should use the same version as this version in case you want to rollback the upgrade. If you are not running a 4.1.x version, stop right here! This guide only covers 4.1.x to 4.2.y upgrades.

To upgrade:

  1. Update the Scylla rpm repo to 4.2

  2. Install the new Scylla version

sudo yum update scylla\* -y

Note

Alternator users upgrading from Scylla 4.0 to 4.1, need to set default isolation level

Start the node

sudo systemctl start scylla-server
sudo service scylla-server start
docker exec -it some-scylla supervisorctl start scylla

(with some-scylla container already running)

Validate

  1. Check cluster status with nodetool status and make sure all nodes, including the one you just upgraded, are in UN status.

  2. Use curl -X GET "http://localhost:10000/storage_service/scylla_release_version" to check the Scylla version. Validate that the version matches the one you upgraded to.

  3. Use journalctl _COMM=scylla to check there are no new errors in the log.

  4. Check again after two minutes, to validate no new issues are introduced.

Once you are sure the node upgrade was successful, move to the next node in the cluster.

Rollback Procedure

Note

Execute the following commands one node at the time, moving to the next node only after the rollback procedure completed successfully.

The following procedure describes a rollback from Scylla release 4.2.x to 4.1.y. Apply this procedure if an upgrade from 4.1 to 4.2 failed before completing on all nodes. Use this procedure only for the nodes that you upgraded to 4.2

Scylla rollback is a rolling procedure that does not require a full cluster shutdown. For each of the nodes rollback to 4.1, you will:

  • Drain the node and stop Scylla

  • Retrieve the old Scylla packages

  • Restore the configuration file

  • Reload the systemd configuration

  • Restart the Scylla service

  • Validate the rollback success

Apply the following procedure serially on each node. Do not move to the next node before validating the rollback was successful and that the node is up and running with the old version.

Rollback steps

Gracefully shutdown Scylla

  nodetool drain
.. include:: /rst_include/scylla-commands-stop-index.rst

Download and install the new release

  1. Remove the old repo file.

sudo rm -rf /etc/yum.repos.d/scylla.repo
  1. Update the Scylla rpm repo to 4.1

  2. Install

   sudo yum clean all
   sudo rm -rf /var/cache/yum
   sudo yum remove scylla\*tools-core
   sudo yum downgrade scylla\* -y
   sudo yum install scylla

Restore the configuration file

sudo rm -rf /etc/scylla/scylla.yaml
sudo cp -a /etc/scylla/scylla.yaml.backup-src| /etc/scylla/scylla.yaml

Restore system tables

Restore all tables of system and system_schema from previous snapshot, 4.2 uses a different set of system tables. Reference doc: Restore from a Backup and Incremental Backup

cd /var/lib/scylla/data/keyspace_name/table_name-UUID/snapshots/<snapshot_name>/
sudo cp -r * /var/lib/scylla/data/keyspace_name/table_name-UUID/
sudo chown -R scylla:scylla /var/lib/scylla/data/keyspace_name/table_name-UUID/

Reload systemd configuration

Require to reload the unit file if the systemd unit file is changed.

sudo systemctl daemon-reload

Start the node

sudo systemctl start scylla-server
sudo service scylla-server start
docker exec -it some-scylla supervisorctl start scylla

(with some-scylla container already running)

Validate

Check the upgrade instruction above for validation. Once you are sure the node rollback is successful, move to the next node in the cluster. Keep in mind that the version you want to see on your node is the old version, which you noted at the beginning of the procedure.