.. |SCYLLA_NAME| replace:: ScyllaDB

.. |SRC_VERSION| replace:: 5.4
.. |NEW_VERSION| replace:: 5.5

.. |DEBIAN_SRC_REPO| replace:: Debian
.. _DEBIAN_SRC_REPO: https://www.scylladb.com/download/?platform=debian-10&version=scylla-5.2

.. |UBUNTU_SRC_REPO| replace:: Ubuntu
.. _UBUNTU_SRC_REPO: https://www.scylladb.com/download/?platform=ubuntu-20.04&version=scylla-5.2

.. |SCYLLA_DEB_SRC_REPO| replace:: ScyllaDB deb repo (|DEBIAN_SRC_REPO|_, |UBUNTU_SRC_REPO|_)

.. |SCYLLA_RPM_SRC_REPO| replace:: ScyllaDB rpm repo
.. _SCYLLA_RPM_SRC_REPO: https://www.scylladb.com/download/?platform=centos&version=scylla-5.2

.. |DEBIAN_NEW_REPO| replace:: Debian
.. _DEBIAN_NEW_REPO: https://www.scylladb.com/download/?platform=debian-10&version=scylla-5.4

.. |UBUNTU_NEW_REPO| replace:: Ubuntu
.. _UBUNTU_NEW_REPO: https://www.scylladb.com/download/?platform=ubuntu-20.04&version=scylla-5.4

.. |SCYLLA_DEB_NEW_REPO| replace:: ScyllaDB deb repo (|DEBIAN_NEW_REPO|_, |UBUNTU_NEW_REPO|_)

.. |SCYLLA_RPM_NEW_REPO| replace:: ScyllaDB rpm repo
.. _SCYLLA_RPM_NEW_REPO: https://www.scylladb.com/download/?platform=centos&version=scylla-5.4

.. |ROLLBACK| replace:: rollback
.. _ROLLBACK: ./#rollback-procedure

.. |SCYLLA_METRICS| replace:: Scylla Metrics Update - Scylla 5.2 to 5.4
.. _SCYLLA_METRICS: ../metric-update-5.2-to-5.4

=============================================================================
Upgrade |SCYLLA_NAME| from |SRC_VERSION| to |NEW_VERSION|
=============================================================================

This document is a step-by-step procedure for upgrading from |SCYLLA_NAME| |SRC_VERSION| 
to |SCYLLA_NAME| |NEW_VERSION|, and rollback to version |SRC_VERSION| if required.

This guide covers upgrading ScyllaDB on Red Hat Enterprise Linux (RHEL), CentOS, Debian, 
and Ubuntu. See :doc:`OS Support by Platform and Version </getting-started/os-support>` 
for information about supported versions.

It also applies when using ScyllaDB official image on EC2, GCP, or Azure.

Before You Upgrade ScyllaDB
==============================

**Upgrade Your Driver**

If you're using a :doc:`ScyllaDB driver </using-scylla/drivers/cql-drivers/index>`, 
upgrade the driver before you upgrade ScyllaDB. The latest two versions of each driver 
are supported.

**Upgrade ScyllaDB Monitoring Stack**

If you're using the ScyllaDB Monitoring Stack, verify that your Monitoring Stack 
version supports the ScyllaDB version to which you want to upgrade. See 
`ScyllaDB Monitoring Stack Support Matrix <https://monitoring.docs.scylladb.com/stable/reference/matrix.html>`_.
  
We recommend upgrading the Monitoring Stack to the latest version.

**Check Feature Updates**

See the ScyllaDB Release Notes for the latest updates. The Release Notes are published 
at the `ScyllaDB Community Forum <https://forum.scylladb.com/>`_.

.. note::
   
   In ScyllaDB 5.5, Raft-based consistent cluster management for new and existing 
   deployments is enabled by default and cannot be disabled.

Upgrade Procedure
=================

A ScyllaDB upgrade is a rolling procedure that does **not** require full cluster shutdown.
For each of the nodes in the cluster, serially (i.e., one node at a time), you will:

* Check that the cluster's schema is synchronized
* Drain the node and backup the data
* Backup the configuration file
* Stop ScyllaDB
* Download and install new ScyllaDB packages
* Start ScyllaDB
* Validate that the upgrade was successful

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

**During** the rolling upgrade, it is highly recommended:

* Not to use the new |NEW_VERSION| features.
* Not to run administration functions, such as repairs, refresh, rebuild, or add 
  or remove nodes. See `sctool <https://manager.docs.scylladb.com/stable/sctool/>`_ 
  for suspending ScyllaDB Manager (only available for ScyllaDB Enterprise) scheduled 
  or running repairs.
* Not to apply schema changes.

**After** the upgrade, you may need to :ref:`verify <validate-raft-setup-enabled-default>` 
that Raft was successfully initiated in your cluster. This step only applies 
if you manually disabled the ``consistent_cluster_management`` option before
upgrading to version 5.4.

Upgrade Steps
=============

Check the cluster schema
-------------------------

Make sure that all nodes have the schema synchronized before the upgrade. The upgrade 
procedure will fail if there is a schema disagreement between nodes.

.. code:: sh

   nodetool describecluster

Drain the nodes and backup data
-----------------------------------

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

.. code:: sh

   nodetool drain
   nodetool snapshot

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

When the upgrade is completed on all nodes, remove the snapshot with the 
``nodetool clearsnapshot -t <snapshot>`` command to prevent running out of space.

Backup the configuration file
------------------------------

Back up the ``scylla.yaml`` configuration file and the ScyllaDB packages
in case you need to rollback the upgrade.

.. tabs::

   .. group-tab:: Debian/Ubuntu

      .. code:: sh
         
         sudo cp -a /etc/scylla/scylla.yaml /etc/scylla/scylla.yaml.backup
         sudo cp /etc/apt/sources.list.d/scylla.list ~/scylla.list-backup

   .. group-tab:: RHEL/CentOS

      .. code:: sh
         
         sudo cp -a /etc/scylla/scylla.yaml /etc/scylla/scylla.yaml.backup
         sudo cp /etc/yum.repos.d/scylla.repo ~/scylla.repo-backup


Gracefully stop the node
------------------------

.. code:: sh

   sudo service scylla-server stop

Download and install the new release
------------------------------------

Before upgrading, check what version you are running now using ``scylla --version``. 
You should take note of the current version in case you want to |ROLLBACK|_ the upgrade.

.. tabs::

   .. group-tab:: Debian/Ubuntu

        **To upgrade ScyllaDB:**

        #. Update the |SCYLLA_DEB_NEW_REPO| to |NEW_VERSION|.

        #. Install the new ScyllaDB version:

            .. code-block:: console

               sudo apt-get clean all
               sudo apt-get update
               sudo apt-get dist-upgrade scylla


        Answer ‘y’ to the first two questions.

   .. group-tab:: RHEL/CentOS

        **To upgrade ScyllaDB:**

        #. Update the |SCYLLA_RPM_NEW_REPO|_  to |NEW_VERSION|.
        #. Install the new ScyllaDB version:

            .. code:: sh

               sudo yum clean all
               sudo yum update scylla\* -y

.. note::

   If you are running a ScyllaDB official image (for EC2 AMI, GCP, or Azure), 
   you need to:
   
    * Download and install the new ScyllaDB release for Ubuntu; see 
      the Debian/Ubuntu tab above for instructions.
    * Update underlying OS packages.

   See :doc:`Upgrade ScyllaDB Image </upgrade/ami-upgrade>` for details.


Start the node
--------------

.. code:: sh

   sudo service scylla-server start

Validate
--------

#. Check cluster status with ``nodetool status`` and make sure **all** nodes, including 
   the one you just upgraded, are in ``UN`` status.
#. Use ``curl -X GET "http://localhost:10000/storage_service/scylla_release_version"`` 
   to check the ScyllaDB version. Validate that the version matches the one you upgraded to.
#. Check scylla-server log (by ``journalctl _COMM=scylla``) and ``/var/log/syslog`` to 
   validate there are no new errors in the log.
#. 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.

See |Scylla_METRICS|_ for more information.

After Upgrading Every Node
===============================

Skip this step if you upgraded from 5.2 to 5.4 with default settings

This section only applies if you manually disabled the ``consistent_cluster_management`` 
option before upgrading from version 5.2. to 5.4.

.. _validate-raft-setup-enabled-default:

Validate Raft Setup
-------------------------

Enabling Raft causes the ScyllaDB cluster to start an internal Raft 
initialization procedure as soon as every node is upgraded to the new version. 
The goal of that procedure is to initialize data structures used by the Raft 
algorithm to consistently manage cluster-wide metadata, such as table schemas.

Assuming you performed the rolling upgrade procedure correctly (in particular, 
ensuring that the schema is synchronized on every step), and if there are no 
problems with cluster connectivity, that internal procedure should take a few 
seconds to finish. However, the procedure requires full cluster availability.
If one of the nodes fails before the procedure finishes (for example, due to 
a hardware problem), the process may get stuck, which may prevent schema or 
topology changes in your cluster.

Therefore, following the rolling upgrade, you must verify that the internal 
Raft initialization procedure has finished successfully by checking the logs 
of every ScyllaDB node. If the process gets stuck, manual intervention is 
required.

Refer to the 
:ref:`Verifying that the internal Raft upgrade procedure finished successfully <verify-raft-procedure>` 
section for instructions on verifying that the procedure was successful and 
proceeding if it gets stuck.


Rollback Procedure
==================

.. include:: /upgrade/_common/warning_rollback.rst

The following procedure describes a rollback from |SCYLLA_NAME| |NEW_VERSION|.x to 
|SRC_VERSION|.y. Apply this procedure if an upgrade from |SRC_VERSION| to 
|NEW_VERSION| fails before completing on all nodes. 
Use this procedure only for nodes you upgraded to |NEW_VERSION|.

.. warning::

   The rollback procedure can be applied **only** if some nodes have not been 
   upgraded to |NEW_VERSION| yet.As soon as the last node in the rolling upgrade 
   procedure is started with |NEW_VERSION|, rollback becomes impossible. At that 
   point, the only way to restore a cluster to |SRC_VERSION| is by restoring it 
   from backup.

ScyllaDB rollback is a rolling procedure that does **not** require full cluster shutdown.

For each of the nodes you rollback to |SRC_VERSION|, serially (i.e., one node 
at a time), you will:

* Drain the node and stop Scylla
* Retrieve the old ScyllaDB packages
* Restore the configuration file
* Reload systemd configuration
* Restart ScyllaDB
* Validate the rollback success

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

Rollback Steps
==============
Drain and gracefully stop the node
----------------------------------

.. code:: sh

   nodetool drain
   nodetool snapshot
   sudo service scylla-server stop

Restore and install the old release
------------------------------------

.. tabs::

   .. group-tab:: Debian/Ubuntu

        #. Restore the |SRC_VERSION| packages backed up during the upgrade.

            .. code:: sh

               sudo cp ~/scylla.list-backup /etc/apt/sources.list.d/scylla.list
               sudo chown root.root /etc/apt/sources.list.d/scylla.list
               sudo chmod 644 /etc/apt/sources.list.d/scylla.list

        #. Install:

            .. code-block::

               sudo apt-get update
               sudo apt-get remove scylla\* -y
               sudo apt-get install scylla

        Answer ‘y’ to the first two questions.

   .. group-tab:: RHEL/CentOS

        #. Restore the |SRC_VERSION| packages backed up during the upgrade procedure.

            .. code:: sh

               sudo cp ~/scylla.repo-backup /etc/yum.repos.d/scylla.repo
               sudo chown root.root /etc/yum.repos.d/scylla.repo
               sudo chmod 644 /etc/yum.repos.d/scylla.repo

        #. Install:

            .. code:: console

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

Restore the configuration file
------------------------------
.. code:: sh

   sudo rm -rf /etc/scylla/scylla.yaml
   sudo cp /etc/scylla/scylla.yaml-backup /etc/scylla/scylla.yaml

Reload systemd configuration
----------------------------

You must reload the unit file if the systemd unit file is changed.

.. code:: sh

   sudo systemctl daemon-reload

Start the node
--------------

.. code:: sh

   sudo service scylla-server start

Validate
--------
Check the upgrade instructions above for validation. Once you are sure the node 
rollback is successful, move to the next node in the cluster.
