Upgrading Apache Cassandra to DataStax Enterprise

Read and understand these instructions before upgrading. Carefully reviewing the planning and upgrade instructions can prevent errors and data loss. In addition, review the DataStax Enterprise release notes for the target upgrade version: 5.1 and 6.8.

Back up your Existing Installation

DataStax recommends backing up your data prior to any version upgrade.

A backup provides the ability to revert and restore all the data used in the previous version if necessary. For manual backup instructions, see Backing up a tarball installation or Backing up a package installation.

The general backup and restore operations are identical between Cassandra and DSE. Change the directory names and any DSE-specific commands as required.

Upgrade SSTables

Be certain to upgrade SSTables on your nodes both before and after upgrading. Failure to upgrade SSTables results in severe performance penalties and possible data loss.

Upgrade Restrictions and Limitations

Upgrade Paths

Upgrades are impacted by the version you are upgrading from and the version you are upgrading to. The greater the gap between the current version and the target version, the more complex the upgrade. Upgrades from earlier versions may require an interim upgrade to a required version:

Upgrade from Apache Cassandra®	Upgrade to DataStax Enterprise	Required interim version
Cassandra 3.0 and 3.11	DSE 6.0, 6.7 or DSE 6.8	DSE 5.1
Cassandra 3.0 and 3.11	DSE 5.1	Not required
Cassandra 3.0	DSE 5.0	Not required
Cassandra 2.1	DSE 5.0	DSE 4.8
Cassandra 2.0 and earlier		Cassandra 2.1

Upgrade from Apache Cassandra®

Upgrade to DataStax Enterprise

Required interim version

Cassandra 3.0 and 3.11

DSE 6.0, 6.7 or DSE 6.8

DSE 5.1

Cassandra 3.0 and 3.11

DSE 5.1

Not required

Cassandra 3.0

DSE 5.0

Not required

Cassandra 2.1

DSE 5.0

DSE 4.8

Cassandra 2.0 and earlier

Cassandra 2.1

Questions? Contact DataStax Support.

General Restrictions

Do not enable new features.
Do not run nodetool repair.
During the upgrade, do not bootstrap new nodes or decommission existing nodes.
Do not enable Change Data Capture (CDC) on a mixed-version cluster. Upgrade all nodes to DSE 5.1 or later before enabling CDC.
Complete the cluster-wide upgrade before the expiration of gc_grace_seconds (approximately 13 days) to ensure any repairs complete successfully.
Do not issue TRUNCATE or DDL related queries during the upgrade process.

Restrictions for Nodes using Security

Do not change security credentials or permissions until the upgrade is complete on all nodes.
If you are not already using Kerberos, do not set up Kerberos authentication before upgrading. First upgrade the cluster, and then set up Kerberos.

Driver Version Impacts

Be sure to check driver compatibility. Depending on the driver version, you might need to recompile your client application code.

DataStax drivers come in two types:

DataStax drivers for DataStax Enterprise (DSE) — for use by DSE 4.8 and later

DataStax drivers for Apache Cassandra® — for use by Apache Cassandra and DSE 4.7 and earlier

While the DataStax drivers for Apache Cassandra drivers can connect to DSE 5.0 and later clusters, DataStax strongly recommends upgrading to the DSE drivers. The DSE drivers provide functionality for all DataStax Enterprise (DSE) features.

During upgrades, you might experience driver-specific impact when clusters have mixed versions of drivers. If your cluster has mixed versions, the protocol version is negotiated with the first host to which the driver connects, although certain drivers, such as Java 4.x/2.x automatically select a protocol version that works across nodes. To avoid driver version incompatibility during upgrades, use one of these workarounds:

Protocol version: Set the protocol version explicitly in your application at start up. Switch to the Java driver to the new protocol version only after the upgrade is complete on all nodes in the cluster.
Initial contact points: Ensure that the list of initial contact points contains only hosts with the oldest DSE version or protocol version. For example, the initial contact points contain only protocol version 2.

For details on protocol version negotiation, see protocol versions with mixed clusters in the Java driver version you’re using, for example, Java driver.

Starting January 2020, you can use the same DataStax driver for Apache Cassandra (OSS) and DataStax Enterprise. DataStax has unified drivers to avoid user confusion and enhance the OSS drivers with some of the features in the DSE drivers. For more information, see the Better Drivers for Cassandra blog.

Upgrade Nodes in this Order:

Upgrade nodes in this order:

In multiple datacenter clusters, upgrade every node in one datacenter before upgrading another datacenter.
Upgrade the seed nodes within a datacenter first.
DSE Analytics datacenters
1. For DSE Analytics nodes using DSE Hadoop, upgrade the Job Tracker node first. Then upgrade Hadoop nodes, followed by Spark nodes.
Transactional/DSE Graph datacenters
DSE Search nodes or datacenters

DataStax Enterprise and Apache Cassandra Configuration Files

DataStax Enterprise (DSE) configuration files
Configuration file	Installer-Services and package installations	Installer-No Services and tarball installations
dse	/etc/default/dse (systemd) or /etc/init.d/ (SystemV)	N/A Node type is set via command line flags.
dse-env.sh	/etc/dse/dse-env.sh	<installation_location>/bin/dse-env.sh
byoh-env.sh	/etc/dse/byoh-env.sh	<installation_location>/bin/byoh-env.sh
dse.yaml	/etc/dse/dse.yaml	<installation_location>/resources/dse/conf/dse.yaml
logback.xml	/etc/dse/cassandra/logback.xml	<installation_location>/resources/logback.xml
spark-env.sh	/etc/dse/spark/spark-env.sh	<installation_location>/resources/spark/conf/spark-env.sh
spark-defaults.conf	/etc/dse/spark/spark-defaults.conf	<installation_location>/resources/spark/conf/spark-defaults.conf

Cassandra configuration files
Configuration file	Installer-Services and package installations	Installer-No Services and tarball installations
cassandra.yaml	/etc/dse/cassandra/cassandra.yaml	<installation_location>/conf/cassandra.yaml
cassandra.in.sh	/usr/share/cassandra/cassandra.in.sh	<installation_location>/bin/cassandra.in.sh
cassandra-env.sh	/etc/dse/cassandra/cassandra-env.sh	<installation_location>/conf/cassandra-env.sh
cassandra-rackdc.properties	/etc/dse/cassandra/cassandra-rackdc.properties	<installation_location>/conf/cassandra-rackdc.properties
cassandra-topology.properties	/etc/dse/cassandra/cassandra-topology.properties	<installation_location>/conf/cassandra-topology.properties
jmxremote.password	/etc/cassandra/jmxremote.password	<installation_location>/conf/jmxremote.password

Tomcat server configuration file
Configuration file	Installer-Services and package installations	Installer-No Services and tarball installations
server.xml	/etc/dse/resources/tomcat/conf/server.xml	<installation_location>/resources/tomcat/conf/server.xml

Preparing to Upgrade

Follow these steps to prepare each node for the upgrade:

Familiarize yourself with the changes and features in the new release:
- DataStax Enterprise release notes for the target upgrade version: 5.1 or 6.8.
- General upgrade advice and Cassandra features in NEWS.txt. If you are upgrading from an earlier release, read NEWS.txt all the way back to your current version.
- Ensure that your version of Cassandra can be upgraded directly to the version of Cassandra that is used by DataStax Enterprise. See the Cassandra changes in CHANGES.txt.
Before upgrading, be sure that each node has adequate free disk space.

Determine current DSE data disk space usage:
```
sudo du -sh /var/lib/cassandra/data/
3.9G	/var/lib/cassandra/data/
```
Determine available disk space:
```
sudo df -hT /
Filesystem     Type  Size  Used Avail Use% Mounted on
/dev/sda1      ext4   59G   16G   41G  28% /
```
The required space depends on the compaction strategy. See Disk space.

Upgrade the SSTables on each node to ensure that all SSTables are on the current version:

nodetool upgradesstables

Failure to upgrade SSTables when required results in a significant performance impact and increased disk usage.

Use the --jobs option to set the number of SSTables that upgrade simultaneously. The default setting is 2, which minimizes impact on the cluster. Set to 0 to use all available compaction threads. DataStax recommends running the upgradesstables command on one node at a time or, when using racks, one rack at a time.

If the SSTables are already on the current version, the command returns immediately and no action is taken.

Verify the Java runtime version and upgrade to the recommended version.
```
java -version
openjdk version "1.8.0_222"
OpenJDK Runtime Environment (build 1.8.0_222-8u222-b10-1ubuntu1~18.04.1-b10)
OpenJDK 64-Bit Server VM (build 25.222-b10, mixed mode)
```
- Recommended: OpenJDK 8 (1.8.0_151 minimum)
  
  Recommendation changed due to the end of public updates for Oracle JRE/JDK 8. See Oracle Java SE Support Roadmap.
- Supported: Oracle Java SE 8 (JRE or JDK) (1.8.0_151 minimum)
  
  Although Oracle JRE/JDK 8 is supported, DataStax does more extensive testing on OpenJDK 8.
Run nodetool repair to ensure that data on each replica is consistent with data on other nodes:
```
nodetool repair -pr
```
Install the libaio package for optimal performance.

RHEL platforms:
```
sudo yum install libaio
```
Debian:
```
sudo apt-get install libaio1
```

Back up any customized configuration files since they may be overwritten with default values during installation of the new version.

If you backed up your installation using the instructions in Backing up a tarball installation or Backing up a package installation, your original configuration files are included in the archive.

Upgrade Steps

Follow these steps on each node in the recommended order. The upgrade process requires upgrading and restarting one node at a time.

These steps are performed in your upgraded version and use DSE 5.1 documentation.

Flush the commit log of the current installation:
```
nodetool drain
```
Stop the node. (Cassandra: 2.1, 2.2, 3.0)
Uninstall Cassandra.

If you installed Cassandra from packages in APT or RPM repositories, you must remove the packages before setting up and installing DSE.
- For packages installed from APT repositories:
  sudo apt-get autoremove "dsc*" "cassandra*" "apache-cassandra*"
  This action shuts down Cassandra if it is still running.
- For packages installed from Yum repositories:
  sudo yum remove "dsc*" "cassandra*" "apache-cassandra*"
  The old Cassandra configuration file might be renamed to cassandra.yaml.rpmsave. For example:
  warning: /etc/cassandra/default.conf/cassandra.yaml saved as /etc/cassandra/default.conf/cassandra.yaml.rpmsave
- If Cassandra was installed with a binary tarball, issue:
  ps auwx | grep cassandra
  sudo kill cassandra_pid
  Then remove the Cassandra installation directory.
Install DSE using the appropriate instructions: 5.1 | 6.8.

To configure the new product version:

Compare changes in the new configuration files with the backup configuration files after the upgrade but before restarting, remove deprecated settings, and update any new settings if required.

You must use the new configuration files that are generated from the upgrade installation. Copy any parameters needed from your old configuration files into these new files.

Do not replace the newly-generated configuration files with the old files.

Use the DSE yaml_diff tool to compare backup YAML files with the upgraded YAML files:

cd /usr/share/dse/tools/yamls

./yaml_diff path/to/yaml-file-old path/to/yaml-file-new
...

CHANGES
=========
authenticator:
- AllowAllAuthenticator
+ com.datastax.bdp.cassandra.auth.DseAuthenticator

authorizer:
- AllowAllAuthorizer
+ com.datastax.bdp.cassandra.auth.DseAuthorizer

roles_validity_in_ms:
- 2000
+ 120000
...

If upgrading from Cassandra 3.11.2 or later, comment out the following parameters in cassandra.yaml if they exist:
- enable_materialized_views
- enable_sasi_indexes
  
  See configuration for the location of Cassandra configuration files.
Start the node using the appropriate method: 5.1 | 6.8.

Verify that the upgraded datacenter names match the datacenter names in the keyspace schema definition:

Get the node’s datacenter name:

nodetool status | grep "Datacenter"
Datacenter: datacenter-name

Verify that the node’s datacenter name matches the datacenter name for a keyspace:

cqlsh --execute "DESCRIBE KEYSPACE keyspace-name;" | grep "replication"
CREATE KEYSPACE keyspace-name WITH replication = {'class': 'NetworkTopologyStrategy, 'datacenter-name': '3'};

Review the logs for warnings, errors, and exceptions:
```
grep -w 'WARNING\|ERROR\|exception' /var/log/cassandra/*.log
```
Warnings, errors, and exceptions are frequently found in the logs when starting an upgraded node. Some of these log entries are informational to help you execute specific upgrade-related steps. If you find unexpected warnings, errors, or exceptions, contact DataStax Support.

Non-standard log locations are configured in dse-env.sh.
Run nodetool repair:
```
bin/nodetool repair -pr
```
Be sure to run nodetool repair on each node in the datacenter.
Repeat the upgrade process on each node in the cluster following the recommended order.

After the entire cluster upgrade is complete: upgrade the SSTables on one node at a time or, when using racks, one rack at a time.

Failure to upgrade SSTables when required results in a significant performance impact and increased disk usage and possible data loss. Upgrading is not complete until the SSTables are upgraded.

nodetool upgradesstables

You can run the upgradesstables command before all the nodes are upgraded as long as you run the command on only one node at a time, or when using racks, one rack at a time. Running upgradesstables on too many nodes at once degrades performance.

Upgrading Apache Cassandra to DataStax Enterprise

Back up your Existing Installation

Upgrade SSTables

Upgrade Restrictions and Limitations

Upgrade Paths

General Restrictions

Restrictions for Nodes using Security

Driver Version Impacts

Upgrade Nodes in this Order:

DataStax Enterprise and Apache Cassandra Configuration Files

Preparing to Upgrade

Upgrade Steps

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